water analysis research articles

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• Published: 21 January 2016

Drinking water quality assessment and its effects on residents health in Wondo genet campus, Ethiopia

• Yirdaw Meride 1 &
• Bamlaku Ayenew 1  

Environmental Systems Research volume  5 , Article number:  1 ( 2016 ) Cite this article

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Water is a vital resource for human survival. Safe drinking water is a basic need for good health, and it is also a basic right of humans. The aim of this study was to analysis drinking water quality and its effect on communities residents of Wondo Genet.

The mean turbidity value obtained for Wondo Genet Campus is (0.98 NTU), and the average temperature was approximately 28.49 °C. The mean total dissolved solids concentration was found to be 118.19 mg/l, and EC value in Wondo Genet Campus was 192.14 μS/cm. The chloride mean value of this drinking water was 53.7 mg/l, and concentration of sulfate mean value was 0.33 mg/l. In the study areas magnesium ranges from 10.42–17.05 mg/l and the mean value of magnesium in water is 13.67 mg/l. The concentration of calcium ranges from 2.16–7.31 mg/l with an average value of 5.0 mg/l. In study areas, an average value of sodium was 31.23 mg/1and potassium is with an average value of 23.14 mg/1. Water samples collected from Wondo Genet Campus were analyzed for total coliform bacteria and ranged from 1 to 4/100 ml with an average value of 0.78 colony/100 ml.

On the basis of findings, it was concluded that drinking water of the study areas was that all physico–chemical parameters. All the Campus drinking water sampling sites were consistent with World Health Organization standard for drinking water (WHO).

Safe drinking water is a basic need for good health, and it is also a basic right of humans. Fresh water is already a limiting resource in many parts of the world. In the next century, it will become even more limiting due to increased population, urbanization, and climate change (Jackson et al. 2001 ).

Drinking water quality is a relative term that relates the composition of water with effects of natural processes and human activities. Deterioration of drinking water quality arises from introduction of chemical compounds into the water supply system through leaks and cross connection (Napacho and Manyele 2010 ).

Access to safe drinking water and sanitation is a global concern. However, developing countries, like Ethiopia, have suffered from a lack of access to safe drinking water from improved sources and to adequate sanitation services (WHO 2006 ). As a result, people are still dependent on unprotected water sources such as rivers, streams, springs and hand dug wells. Since these sources are open, they are highly susceptible to flood and birds, animals and human contamination (Messeret 2012 ).

The quality of water is affected by an increase in anthropogenic activities and any pollution either physical or chemical causes changes to the quality of the receiving water body (Aremu et al. 2011 ). Chemical contaminants occur in drinking water throughout the world which could possibly threaten human health. In addition, most sources are found near gullies where open field defecation is common and flood-washed wastes affect the quality of water (Messeret 2012 ).

The World Health Organization estimated that up to 80 % of all sicknesses and diseases in the world are caused by inadequate sanitation, polluted water or unavailability of water (WHO 1997 ). A review of 28 studies carried out by the World Bank gives the evidence that incidence of certain water borne, water washed, and water based and water sanitation associated diseases are related to the quality and quantity of water and sanitation available to users (Abebe 1986 ).

In Ethiopia over 60 % of the communicable diseases are due to poor environmental health conditions arising from unsafe and inadequate water supply and poor hygienic and sanitation practices (MOH 2011 ). About 80 % of the rural and 20 % of urban population have no access to safe water. Three-fourth of the health problems of children in the country are communicable diseases arising from the environment, specially water and sanitation. Forty-six percent of less than 5 years mortality is due to diarrhea in which water related diseases occupy a high proportion. The Ministry of Health, Ethiopia estimated 6000 children die each day from diarrhea and dehydration (MOH 2011 ).

There is no study that was conducted to prove the quality water in Wondo Genet Campus. Therefore, this study is conducted at Wondo Genet Campus to check drinking water quality and to suggest appropriate water treated mechanism.

Results and discussions

The turbidity of water depends on the quantity of solid matter present in the suspended state. It is a measure of light emitting properties of water and the test is used to indicate the quality of waste discharge with respect to colloidal matter. The mean turbidity value obtained for Wondo Genet Campus (0.98 NTU) is lower than the WHO recommended value of 5.00 NTU.

Temperature

The average temperature of water samples of the study area was 28.49 °C and in the range of 28–29 °C. Temperature in this study was found within permissible limit of WHO (30 °C). Ezeribe et al. ( 2012 ) reports similar result (29 °C) of well water in Nigeria.

Total dissolved solids (TDS)

Water has the ability to dissolve a wide range of inorganic and some organic minerals or salts such as potassium, calcium, sodium, bicarbonates, chlorides, magnesium, sulfates etc. These minerals produced un-wanted taste and diluted color in appearance of water. This is the important parameter for the use of water. The water with high TDS value indicates that water is highly mineralized. Desirable limit for TDS is 500 mg/l and maximum limit is 1000 mg/l which prescribed for drinking purpose. The concentration of TDS in present study was observed in the range of 114.7 and 121.2 mg/l. The mean total dissolved solids concentration in Wondo Genet campus was found to be 118.19 mg/l, and it is within the limit of WHO standards. Similar value was reported by Soylak et al. ( 2001 ), drinking water of turkey. High values of TDS in ground water are generally not harmful to human beings, but high concentration of these may affect persons who are suffering from kidney and heart diseases. Water containing high solid may cause laxative or constipation effects. According to Sasikaran et al. ( 2012 ).

Electrical conductivity (EC)

Pure water is not a good conductor of electric current rather’s a good insulator. Increase in ions concentration enhances the electrical conductivity of water. Generally, the amount of dissolved solids in water determines the electrical conductivity. Electrical conductivity (EC) actually measures the ionic process of a solution that enables it to transmit current. According to WHO standards, EC value should not exceeded 400 μS/cm. The current investigation indicated that EC value was 179.3–20 μS/cm with an average value of 192.14 μS/cm. Similar value was reported by Soylak et al. ( 2001 ) drinking water of turkey. These results clearly indicate that water in the study area was not considerably ionized and has the lower level of ionic concentration activity due to small dissolve solids (Table 1 ).

PH of water

PH is an important parameter in evaluating the acid–base balance of water. It is also the indicator of acidic or alkaline condition of water status. WHO has recommended maximum permissible limit of pH from 6.5 to 8.5. The current investigation ranges were 6.52–6.83 which are in the range of WHO standards. The overall result indicates that the Wondo Genet College water source is within the desirable and suitable range. Basically, the pH is determined by the amount of dissolved carbon dioxide (CO 2 ), which forms carbonic acid in water. Present investigation was similar with reports made by other researchers’ study (Edimeh et al. 2011 ; Aremu et al. 2011 ).

Chloride (Cl)

Chloride is mainly obtained from the dissolution of salts of hydrochloric acid as table salt (NaCl), NaCO 2 and added through industrial waste, sewage, sea water etc. Surface water bodies often have low concentration of chlorides as compare to ground water. It has key importance for metabolism activity in human body and other main physiological processes. High chloride concentration damages metallic pipes and structure, as well as harms growing plants. According to WHO standards, concentration of chloride should not exceed 250 mg/l. In the study areas, the chloride value ranges from 3–4.4 mg/l in Wondo Genet Campus, and the mean value of this drinking water was 3.7 mg/l. Similar value was reported by Soylak et al. ( 2001 ) drinking water of Turkey.

Sulfate mainly is derived from the dissolution of salts of sulfuric acid and abundantly found in almost all water bodies. High concentration of sulfate may be due to oxidation of pyrite and mine drainage etc. Sulfate concentration in natural water ranges from a few to a several 100 mg/liter, but no major negative impact of sulfate on human health is reported. The WHO has established 250 mg/l as the highest desirable limit of sulfate in drinking water. In study area, concentration of sulfate ranges from 0–3 mg/l in Wondo Genet Campus, and the mean value of SO 4 was 0.33 mg/l. The results exhibit that concentration of sulfate in Wondo Genet campus was lower than the standard limit and it may not be harmful for human health.

Magnesium (Mg)

Magnesium is the 8th most abundant element on earth crust and natural constituent of water. It is an essential for proper functioning of living organisms and found in minerals like dolomite, magnetite etc. Human body contains about 25 g of magnesium (60 % in bones and 40 % in muscles and tissues). According to WHO standards, the permissible range of magnesium in water should be 50 mg/l. In the study areas magnesium was ranges from 10.42 to 17.05 mg/l in Wondo Genet Campus and the mean value of magnesium in water is 13.67 mg/l. Similar value was reported by Soylak et al. ( 2001 ) drinking water of Turkey. The results exhibit that concentration of magnesium in Wondo Genet College was lower than the standard limit of WHO.

Calcium (Ca)

Calcium is 5th most abundant element on the earth crust and is very important for human cell physiology and bones. About 95 % of calcium in human body stored in bones and teeth. The high deficiency of calcium in humans may caused rickets, poor blood clotting, bones fracture etc. and the exceeding limit of calcium produced cardiovascular diseases. According to WHO ( 2011 ) standards, its permissible range in drinking water is 75 mg/l. In the study areas, results show that the concentration of calcium ranges from 2.16 to 7.31 mg/l in Wondo Genet campus with an average value of 5.08 mg/l.

Sodium (Na)

Sodium is a silver white metallic element and found in less quantity in water. Proper quantity of sodium in human body prevents many fatal diseases like kidney damages, hypertension, headache etc. In most of the countries, majority of water supply bears less than 20 mg/l, while in some countries the sodium quantity in water exceeded from 250 mg/l (WHO 1984 ). According to WHO standards, concentration of sodium in drinking water is 200 mg/1. In the study areas, the finding shows that sodium concentration ranges from 28.54 to 34.19 mg/1 at Wondo Genet campus with an average value of 31.23.

Potassium (k)

Potassium is silver white alkali which is highly reactive with water. Potassium is necessary for living organism functioning hence found in all human and animal tissues particularly in plants cells. The total potassium amount in human body lies between 110 and 140 g. It is vital for human body functions like heart protection, regulation of blood pressure, protein dissolution, muscle contraction, nerve stimulus etc. Potassium is deficient in rare but may led to depression, muscle weakness, heart rhythm disorder etc. According to WHO standards the permissible limit of potassium is 12 mg/1. Results show that the concentration of potassium in study areas ranges from 20.83 to 27.51 mg/1. Wondo Genet College with an average value of 23.14 mg/1. Present investigation was similar with reports made by other researchers’ study (Edimeh et al. 2011 ; Aremu et al. 2011 ). These results did not meet the WHO standards and may become diseases associated from potassium extreme surpassed.

Nitrate (NO 3 )

Nitrate one of the most important diseases causing parameters of water quality particularly blue baby syndrome in infants. The sources of nitrate are nitrogen cycle, industrial waste, nitrogenous fertilizers etc. The WHO allows maximum permissible limit of nitrate 5 mg/l in drinking water. In study areas, results more clear that the concentration of nitrate ranges from 1.42 to 4.97 mg/l in Wondo Genet campus with an average value of 2.67 mg/l. These results indicate that the quantity of nitrate in the study site is acceptable in Wondo Genet campus (Table 2 ).

Bacterial contamination

The total coliform group has been selected as the primary indicator bacteria for the presence of disease causing organisms in drinking water. It is a primary indicator of suitability of water for consumption. If large numbers of coliforms are found in water, there is a high probability that other pathogenic bacteria or organisms exist. The WHO and Ethiopian drinking water guidelines require the absence of total coliform in public drinking water supplies.

In this study, all sampling sites were not detected of faecal coliform bacteria. Figure  1 shows the mean values of total coliform bacteria in drinking water collected from the study area. All drinking water samples collected from Wondo Genet Campus were analyzed for total coliform bacteria and ranged from 1 to 4/100 ml with an average value of 0.78 colony/100 ml. In Wondo Genet College, the starting point of drinking water sources (Dam1), the second (Dam2) and Dam3 samples showed the presence of total coliform bacteria (Fig.  1 ). According to WHO ( 2011 ) risk associated in Wondo Genet campus drinking water is low risk (1–10 count/100 ml).

The mean values of total coliform bacteria in drinking water

According to the study all water sampling sites in Wondo Genet campus were meet world health organization standards and Ethiopia drinking water guideline. Figure  2 indicated that mean value of the study sites were under the limit of WHO standards.

Comparison of water quality parameters of drinking water of Wondo Genet campus with WHO and Ethiopia standards

Effect of water quality for residence health’s

Diseases related to contamination of drinking-water constitute a major burden on human health. Interventions to improve the quality of drinking-water provide significant benefits to health. Water is essential to sustain life, and a satisfactory (adequate, safe and accessible) supply must be available to all (Ayenew 2004 ).

Improving access to safe drinking-water can result in tangible benefits to health. Every effort should be made to achieve a drinking-water quality as safe as practicable. The great majority of evident water-related health problems are the result of microbial (bacteriological, viral, protozoan or other biological) contamination (Ayenew 2004 ).

Excessive amount of physical, chemical and biological parameters accumulated in drinking water sources, leads to affect human health. As discussed in the result, all Wondo Genet drinking water sources are under limit of WHO and Ethiopian guideline standards. Therefore, the present study was found the drinking water safe and no residence health impacts.

On the basis of findings, it was concluded that drinking water of the study areas was that all physico–chemical parameters in all the College drinking water sampling sites, and they were consistent with World Health Organization standard for drinking water (WHO). The samples were analyzed for intended water quality parameters following internationally recognized and well established analytical techniques.

It is evident that all the values of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), SO 4 , and NO 3 fall under the permissible limit and there were no toxicity problem. Water samples showed no extreme variations in the concentrations of cations and anions. In addition, bacteriological determination of water from College drinking water sources was carried out to be sure if the water was safe for drinking and other domestic application. The study revealed that all the College water sampling sites were not contained fecal coliforms except the three water sampling sites had total coliforms.

The study was conducted in Wondo Genet College of Forestry and Natural Resources campus, which is located in north eastern direction from the town of Hawassa and about 263 km south of Addis Ababa (Fig.  3 ). It lies between 38°37′ and 38°42′ East longitude and 7°02′ and 7°07′ north latitude. Landscape of the study area varies with an altitude ranging between 1600 and 2580 meters above sea level. Landscape of the study area varies with an altitude ranging between 1600 and 2580 meters above sea level.

Map of study area

The study area is categorized under Dega (cold) agro-ecological zone at the upper part and Woina Dega (temperate) agro-ecological zone at the lower part of the area. The rainfall distribution of the study area is bi-modal, where short rain falls during spring and the major rain comes in summer and stays for the first two months of the autumn season. The annual temperature and rainfall range from 17 to 19 °C and from 700 to 1400 mm, respectively (Wondo Genet office of Agriculture 2011).

Methodology

Water samples were taken at ten locations of Wondo Genet campus drinking water sources. Three water samples were taken at each water caching locations. Ten (10) water samples were collected from different locations of the Wondo Genet campus. Sampling sites for water were selected purposely which represents the entire water bodies.

Instead of this study small dam indicates the starting point of Wondo Genet campus drinking water sources rather than large dams constructed for other purpose. Taps were operated or run for at least 5 min prior to sampling to ensure collection of a representative sample (temperature and electrical conductivity were monitored to verify this). Each sample’s physico–chemical properties of water were measured in the field using portable meters (electrical conductivity, pH and temperature) at the time of sampling. Water samples were placed in clean containers provided by the analytical laboratory (glass and acid-washed polyethylene for heavy metals) and immediately placed on ice. Nitric acid was used to preserve samples for metals analysis.

Analysis of water samples

Determination of ph.

The pH of the water samples was determined using the Hanna microprocessor pH meter. It was standardized with a buffer solution of pH range between 4 and 9.

Measurement of temperature

This was carried out at the site of sample collection using a mobile thermometer. This was done by dipping the thermometer into the sample and recording the stable reading.

Determination of conductivity

This was done using a Jenway conductivity meter. The probe was dipped into the container of the samples until a stable reading will be obtained and recorded.

Determination of total dissolved solids (TDS)

This was measured using Gravimetric Method: A portion of water was filtered out and 10 ml of the filtrate measured into a pre-weighed evaporating dish. Filtrate water samples were dried in an oven at a temperature of 103 to 105 °C for \(2\frac{1}{2}\)  h. The dish was transferred into a desiccators and allowed cool to room temperature and were weighed.

In this formula, A stands for the weight of the evaporating dish + filtrate, and B stands for the weight of the evaporating dish on its own Mahmud et al. ( 2014 ).

Chemical analysis

Chloride concentration was determined using titrimetric methods. The chloride content was determined by argentometric method. The samples were titrated with standard silver nitrate using potassium chromate indicator. Calcium ions concentrations were determined using EDTA titrimetric method. Sulphate ions concentration was determined using colorimetric method.

Microorganism analysis

In the membrane filtration method, a 100 ml water sample was vacuumed through a filter using a small hand pump. After filtration, the bacteria remain on the filter paper was placed in a Petri dish with a nutrient solution (also known as culture media, broth or agar). The Petri dishes were placed in an incubator at a specific temperature and time which can vary according the type of indicator bacteria and culture media (e.g. total coliforms were incubated at 35 °C and fecal coliforms were incubated at 44.5 °C with some types of culture media). After incubation, the bacteria colonies were seen with the naked eye or using a magnifying glass. The size and color of the colonies depends on the type of bacteria and culture media were used.

Statically analysis

All data generated was analyzed statistically by calculating the mean and compare the mean value with the acceptable standards. Data collected was statistically analyzed using Statistical Package for Social Sciences (SPSS 20).

Abbreviations

ethylene dinitrilo tetra acetic acid

Minstor of Health

nephelometric turbidity units

total dissolved solid

World Health Organization

Abebe L (1986) Hygienic water quality; its relation to health and the testing aspects in tropical conditions. Department of Civil Engineering, University of Tempere, Finland

Aremu MO et al (2011) Physicochemical characteristics of stream, well and borehole water sources in Eggon, Nasarawa State, Nigeria. J Chem Soc Nigeria 36(1):131–136

Google Scholar  

Ayenew T (2004) Environmental implications of changes in the levels of lakes in the Ethiopian Rift since 1970. Reg Environ Chang 4:192–204

Article   Google Scholar  

Edimeh et al (2011) Physico-chemical parameters and some Heavy metals content of rivers Inachalo and Niger in Idah, Kogi State. J Chem Soc Nigeria 36(1):95–101

Ezeribe AL et al (2012) Physico-chemical properties of well water samples from some villages in Nigeria with cases of stained and mottle teeth. Sci World J 7(1):1–13

Jackson et al (2001) Water in changing world, Issues in Ecology. Ecol Soc Am, Washington, pp 1–16

Mahmud et al (2014) Surface water quality of Chittagong University campus, Bangladesh. J Environ Sci 8:2319-2399

Messeret B (2012) Assessment of drinking water quality and determinants of household potable water consumption in Simada district, ethiopia

MOH (2011) Knowledge, attitude and practice of water supply, environmental sanitation and hygiene practice in selected worked as of Ethiopia

Napacho A, Manyele V (2010) Quality assessment of drinking water in Temeke district (Part II): characterization of chemical parameters. Af J Environ Sci Technol 4(11):775–789

Sasikaran S et al (2012) Physical, chemical and microbial analysis of bottled drinking water. J Ceylon Medical 57(3):111–116

Soylak et al (2002) Chemical analysis of drinking water samples from Yozgat, Turkey. Polish J Environ Stud 11(2):151–156

WHO (1984) Guideline for drinking water quality. Health Criteria Support Inf 2:63–315

World Health Organization (1997) Basic Environmental Health, Geneva

World Health Organization (2004) Guidelines for drinking-water quality. World Health Organization, Geneva

World Health Organization (2006) In water, sanitation and health world health organization

WHO (2011) Guidelines for drinking-water quality, 4th edn. Geneva, Switzerland

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Authors’ contributions

YM: participated in designing the research idea, field data collection, data analysis, interpretation and report writing; BA: participated in field data collection, interpretation and report writing. Both authors read and approved the final manuscript.

Authors’ information

Yirdaw Meride: Lecturer at Hawassa University, Wondo Genet College of Forestry and Natural Resources. He teaches and undertakes research on solid waste, carbon sequestration and water quality. He has published three articles mainly in international journals. Bamlaku Ayenew: Lecturer at Hawassa University, Wondo Genet College of Forestry and Natural Resources. He teaches and undertakes research on Natural Resource Economics. He has published three article with previous author and other colleagues.

Acknowledgements

Hawassa University, Wondo Genet College of Forestry and Natural Resources provided financial support for field data collection and water laboratory analysis. The authors thank anonymous reviewers for constructive comments.

Competing interests

The authors declare that they have no competing interests.

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Meride, Y., Ayenew, B. Drinking water quality assessment and its effects on residents health in Wondo genet campus, Ethiopia. Environ Syst Res 5 , 1 (2016). https://doi.org/10.1186/s40068-016-0053-6

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Received : 01 September 2015

Accepted : 06 January 2016

Published : 21 January 2016

DOI : https://doi.org/10.1186/s40068-016-0053-6

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Data availability

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to their containing information that could compromise the privacy of research participants.

Acikel S, Ekmekci M (2016) Hydrochemical characterization of Pamukkale travertines, Denizli, Turkey, for remediative measures. Environ Earth Sci 75(22):1456–1457. https://doi.org/10.1007/s12665-016-6258-1

Article   CAS   Google Scholar  

Akin M (2009) A quantitative weathering classification system for yellow travertines. Environ Earth Sci 61(1):47–61. https://doi.org/10.1007/s12665-009-0319-7

Article   Google Scholar  

Altunel E (2019) D. A. F Pamukkale travertines: A natural and cultural monument in the World heritage list. Landscapes and Landforms of Turkey. 219–229. https://doi.org/10.1007/978-3-030-03515-0_8

Bare IJ, Horvatin IN, Roller Lutz Z (2011) Spatial and seasonal variations in the stable C isotope composition of dissolved inorganic carbon and in physico-chemical water parameters in the Plitvice Lakes system. Isotopes in Environmental. Health Stud 47(3):316–329. https://doi.org/10.1080/10256016.2011.596625

Cao J, Guo J, Yang G (2009) Evolutionary trend of the Huanglong Travertine in Songpan. Acta Geologica Sichuan 29(S2):222–228. https://doi.org/10.3969/j.issn.1006-0995.2009.z1.042 (in Chinese with English Abstract)

Capezzuoli E, Gandin A, Pedley M (2014) Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: the state of the art. Sedimentology 61(1):1–21. https://doi.org/10.1111/sed.12075

Chen X, Zhou X (1988) A study on isotopes of karst water and travertine deposits at the Huanglong scenic spot. Carsologica Sinica 176:233–240

Google Scholar  

Cukurluoglu S (2017) Sources of trace elements in wet deposition in Pamukkale, Denizli, western Turkey. Environ Forensics 18(1):83–99. https://doi.org/10.1080/15275922.2016.1263899

Dang Z, Ren J, An C (2019) Effect of Ms 7.0 earthquake on travertine landscapes and hydrochmistry of Jiuzhaigou core scenic spots. Carsologica Sinica 38(02):186–192. https://doi.org/10.11932/karst20190204 (in Chinese with English Abstract)

Davenport ML, Nicholson SE (1993) On the relation between rainfall and the normalized difference Vegetation Index for diverse vegetation types in East Africa. Int J Remote Sens 14(12):2369–2389. https://doi.org/10.1080/01431169308954042

DeWitt JD, Boston KM, Alessi MA, Chirico PG (2022) Quantifying and visualizing 32 years of agricultural land use change in Kabul, Afghanistan. J Maps 18(2):352–361. https://doi.org/10.1080/17445647.2022.2063079

Dong F, Dai Q, Jiang Z, Chen X, Xu R, Zhang Q, An D, Li Q, Zhang T, Andelka P (2023) Travertine/tufa resource conservation and sustainable development call for a world-wide initiative. Appl Geochem 148:105505. https://doi.org/10.1016/j.apgeochem.2022.105505 (in Chinese with English Abstract)

Dove PM, Hochella MF (1992) Calcite precipitation mechanisms and inhibition by orthophosphate: in situ observations by scanning force Microscopy. Geochim Cosmochim Acta 57(3):705–714. https://doi.org/10.1016/0016-7037(93)90381-6

Drysdale RN, Taylor MP, Ihlenfeld C (2002) Factors controlling the chemical evolution of travertine-depositing rivers of the Barkly karst, northern Australia. Hydrol Process 16(15):2941–2962. https://doi.org/10.1002/hyp.1078

Elmetwalli AH, Tyler AN, Moghanm FS, Alamri SA, M, Eid EM, Elsayed S (2021) Integration of Radiometric Ground-Based Data and High-Resolution QuickBird Imagery with Multivariate modeling to Estimate Maize traits in the Nile Delta of Egypt. Sensors 21(11):3915. https://doi.org/10.3390/s21113915

Feng Y, Wang S, Zhao M, Zhou L (2022) Monitoring of Land Desertification Changes in Urat Front Banner from 2010 to 2020 based on remote Sensing Data. Water 14(11):1777. https://doi.org/10.3390/w14111777

Ford TD, Pedley HM (1996) A review of tufa and travertine deposits of the world. Earth Sci Rev 41(3–4):117–175. https://doi.org/10.1016/S0012-8252(96)00030-X

Fouke BW (2011) Hot-spring systems Geobiology: abiotic and biotic influences on travertine formation at Mammoth Hot Springs, Yellowstone National Park, USA. Sedimentology 58(1):170–219. https://doi.org/10.1111/j.1365-3091.2010.01209.x

Gao W, Zhang J, Zhang W, Sun D, Guo J, Zhao S, Zeng Y, Liu X (2023) Hydrochemical characteristics and driving factors of travertine deposition in Huanglong, Sichuan, SW, China. Water Sci Technol 87(5):1232–1249. https://doi.org/10.2166/wst.2023.048

Goldscheider N, Chen Z, Auler AS, Bakalowicz M, Veni G (2020) Global distribution of carbonate rocks and karst water resources. Hydrogeol J 28(5):1–17. https://doi.org/10.1007/s10040-020-02139-5

Gu J, Fan X (2009) Assessment of travertine evolution in Jiuzhaighou-Huanglong area using grey system model. 566–573

Gu Y, Du J, Tang Y, Qiao X, Deng G (2013) Challenges for sustainable tourism at the Jiuzhaigou World Natural Heritage site in western China. Nat Resour Forum 37(2):103–112. https://doi.org/10.1111/1477-8947.12015

Gutman G, Ignatov A (1998) The derivation of the green vegetation fraction from NOAA/AVHRR data for use in numerical weather prediction models. Int J Remote Sens 19(8):1533–1543. https://doi.org/10.1080/014311698215333

Heritage UW (2019) 47th Anniversary of the World Heritage Convention [EB/OL].2020. http://whc.unesco.org/en/news/2056

Hu W, Chen Z (2024) Characteristics of Flood season precipitation over the Past Century in the Min River Headwater Region. J Yangtze River Sci Res Inst. 1–7. (in Chinese with English Abstract)

Huang H, Song T, Yan D, An D, Min S, Dang Z, Dai Q (2020) Study on the spatial variation characteristics of hydrochemistry in the surface water system of Huanglong Ravine,Sichuan Province. Industrial Minerals Process 49(08):43–47. https://doi.org/10.16283/j.cnki.hgkwyjg.2020.08.011 (in Chinese with English Abstract)

Jaber HS, Shareef MA, Merzah ZF (2022) Object-based approaches for land use-land cover classification using high resolution quick bird satellite imagery (a case study: Kerbela, Iraq). Geodesy Cartography 48(2):85–91. https://doi.org/10.3846/gac.2022.14453

Kang X (2009) Two temples, three religions, and a Tourist attraction. Mod China 35(3):227–255. https://doi.org/10.1177/0097700408329600

Kubiak Wójcicka K, Piątkowski K, Juśkiewicz WW (2021) Lake surface changes of the Osa River catchment, (northern Poland), 1900–2010. J Maps 17(2):18–29. https://doi.org/10.1080/17445647.2020.1857856

Li M, Wu B, Cai L (2007) Tourism development of World Heritage sites in China: a geographic perspective. Tour Manag 29(2):308–319. https://doi.org/10.1016/j.tourman.2007.03.013

LI Y, Tian Y, Li Y (2011) Tufa algae and biological karstification at Huanglong, Sichuan. Carsologica Sinica 30(1):86–92. https://doi.org/10.3969/j.issn.1001-4810.2011.01.014 (in Chinese with English Abstract)

Li X, Hijazi I, Xu M, Lv H, Meouche RE (2016) Implementing two methods in GIS software for indoor routing: an empirical study. Multimedia Tools Appl 75(24):17449–17464. https://doi.org/10.1007/s11042-015-3156-6

Liang K, Hu X, Li S, Huang C, Tang Y (2014) Anthropogenic Effect on Deposition Dynamics of Lake Sediments Based on 137 Cs and 210 Pb ex Techniques in Jiuzhaigou National Nature Reserve,China. Chinese Geographical Science 24(2). 180–190. https://doi.org/CNKI:SUN:ZDKX.0.2014-02-004

Liu Z, Yuan D, He S (1997) Stable Carbon Isotope Geochemical and Hydrochemical features in the system of Carbonate-H 2 O-CO 2 and their implication-evidence from several typical Karst areas of China. Acta Geologica Sinica - Engl Ed 71(4):446–454. https://doi.org/10.1111/j.1755-6724.1997.tb00383.x

Liu Z, Yuan D, He S (2000) Geochemical features of the geothermal CO 2 -watercarbonate rock system and analysis on its CO 2 sources: examples from Huanglong Ravine and Kangding, Sichuan, and Xiage, Zhongdian, Yunnan. Science in China 43, 569–576. https://doi.org/CNKI:SUN:JDXG.0.2000-06-001

Liu Z, Sun H, Lu B, Liu X, Ye W, Zeng C (2010) Wet-dry seasonal variations of hydrochemistry and carbonate precipitation rates in a travertine-depositing canal at Baishuitai, Yunnan, SW China: implications for the formation of biannual laminae in travertine and for climatic reconstruction. Chem Geol 273(3):258–266. https://doi.org/10.1016/j.chemgeo.2010.02.027

Liu Z, Svensson U, Dreybrodt W, Yuan D, Buhmann D (2011) Hydrodynamic control of inorganic calcite precipitation in Huanglong Ravine, China: field measurements and theoretical prediction of deposition rates. Geochem Cosmochem acta 59(15):3087–3097. https://doi.org/10.1016/0016-7037(95)00198-9

Liu X, Sun D, Cao N, Yuan N, Huang H, Tian C, Zhang Q, Tang S, Li D, Zhou D, Dong F (2021) Study on the structure of multi-layer water circulation system in the corescenic spot of Huanglong. Carsologica Sinica 40(01):19–33. https://doi.org/10.11932/karst20210103 (in Chinese with English Abstract)

Liu C, Zhang X, Wang T, Chen G, Zhu K, Wang Q, Wang J (2022) Detection of vegetation coverage changes in the Yellow River Basin from 2003 to 2020. Ecol Ind 138:108818

Lugli S, Tang Y, Reghizzi M, Xue Q, Schreiber BC, Deng G (2017) Seasonal Pattern in the high-elevation Fluvial Travertine from the Jiuzhaigou National Nature Reserve, Sichuan, Southwestern China. J Sediment Res 87(3):253–271. https://doi.org/10.2110/jsr.2017.14

Maja R, Josip R, Igor R, Andrijana B (2021) Hydrological System of the Plitvice Lakes—Trends and changes in water levels, inflows, and losses. Hydrology 8(4):174. https://doi.org/10.3390/hydrology8040174

Min S, Dai Q, Cui J, Li Q, Dang Z, Luo Y, Dong F (2021) Study on degradation characteristics and restoration and conservation materials of travertine marble dam,Huanglong. Carsologica Sinica 40(01):99–104. https://doi.org/10.11932/karst20210110 (in Chinese with English Abstract)

Mohamed E (2023) A spatiotemporal transferable image fusion technique for GeoEye-1 satellite imagery. Aerosp Syst 6(2):1–18. https://doi.org/10.1007/s42401-023-00208-7

Nicholson SE, Farrar TJ (1994) The influence of soil type on the relationships between NDVI, rainfall, and soil moisture in semiarid Botswana. I. NDVI response to rainfall. Remote Sens Environ 50(2):107–120. https://doi.org/10.1016/0034-4257(94)90038-8

Pedley HM (1990) Classification and environmental models of cool freshwater tufas. Sed Geol 68(1–2). https://doi.org/10.1016/0037-0738(90)90124-C

Pedley M (2010) Tufas and travertines of the Mediterranean region: a testing ground for freshwater carbonate concepts and developments. Sedimentology 56(1):221–246. https://doi.org/10.1111/j.1365-3091.2008.01012.x

Pentecost A (2005) Travertine: Berlin:Springer Science. Business Media

Pentecost A, Viles H (1994) A review and reassessment of Travertine classification. Geographie Phys Et Quaternaire 48(3):305–314. https://doi.org/10.7202/033011arCopiedAn error has occurred

Piao S, Fang J, Zhou L, Guo Q, Henderson M, Ji W, Li Y, Tao S (2003) Interannual variations of monthly and seasonal normalized difference vegetation index (NDVI) in China from 1982 to 1999. J Geophys Research: Atmos 108(D14). https://doi.org/10.1029/2002JD002848

PlenkovićMoraj A, Horvatinčić N, Primchabdija B (2002) Periphyton and its role in tufa deposition in karstic waters (Plitvice Lakes, Croatia). Biol - Sect Bot 57(4):423–431. https://doi.org/10.1152/ajpcell.00402.2010

Qiao X, Du J, Lugi S, Ren J, Xiao W, Chen P, Tang Y (2016) Are climate warming and enhanced atmospheric deposition of sulfur and nitrogen threatening tufa landscapes in Jiuzhaigou National Nature Reserve, Sichuan, China? Sci Total Environ 562:724–731. https://doi.org/10.1016/j.scitotenv.2016.04.073

Qiao X, Du J, H Kota S, Ying Q, Xiao W, Tang Y (2018) Wet deposition of sulfur and nitrogen in Jiuzhaigou National Nature Reserve, Sichuan, China during 2015–2016: possible effects from regional emission reduction and local tourist activities. Environ Pollut 233(FEB):267–277. https://doi.org/10.1016/j.envpol.2017.08.041

Qiu S, Wang F, Dong F (2021) Sedimentary evolution of the Dawan travertines and their geological environmental significance. Huanglong China Depositional Record 8(1):251–265. https://doi.org/10.1002/dep2.165

Reddy MM (1977) Crystallization of calcium carbonate in the presence of trace concentrations of phosphorus-containing anions: I. Inhibition by phosphate and glycerophosphate ions at pH 8.8 and 25℃. J Cryst Growth 41(2):287–295. https://doi.org/10.1016/0022-0248(77)90057-4

Ricketts JW, Ma L, Wagler AE, Garcia VH (2019) Global travertine deposition modulated by oscillations in climate. J Quat Sci 34(7):558–568. https://doi.org/10.1002/jqs.3144

SGMBGST (2001) 1:50,000 Ecological Geology Map and report of Huanglong. Beijing: Geological Publishing House. 1-109. (in Chinese with English Abstract)

Sironić A, Barešić J, Horvatinčić N, Brozinčević A, Vurnek M, Kapelj S (2017) Changes in the geochemical parameters of karst lakes over the past three decades – the case of Plitvice Lakes, Croatia. Appl Geochem 78:18–22. https://doi.org/10.1016/j.apgeochem.2016.11.013

Stow D, Daeschner S, Hope A, Douglas D, Petersen A, Myneni R, Zhou L, Oechel W (2003) Variability of the seasonally Integrated Normalized Difference Vegetation Index across the North Slope of Alaska in the 1990s. Int J Remote Sens 24(5):1111–1117. https://doi.org/10.1080/0143116021000020144

Sun H, Liu Z, Liu X (1996) Seasonal variations in delta 13 C and delta 18 O of travertine. Geochimica et cosmochimica actas a 74. 1016–1029. https://doi.org/10.1016/j.gca.2009.11.008

Tang S, Zhang Q, Tai Y, An D, Wang X (2016) Investigation and analysis on the Dynamic Change of Water Quantity for through years in the Huanglong Scenic Valley. Environ Sustainable Dev 41(04):209–210. https://doi.org/10.19758/j.cnki.issn1673-288x.2016.04.058 (in Chinese with English Abstract)

Thenkabail Prasad M Michael (2015) Advantage of hyperspectral EO-1 Hyperion over multispectral IKONOS, GeoEye-1, WorldView-2, Landsat ETM plus, and MODIS vegetation indices in crop biomass estimation. Isprs J Photogrammetry Remote Sens 108:205–218. https://doi.org/10.1016/j.isprsjprs.2015.08.001

Wan X, Yang J, Cheng W, Luo L, An D, Tang S, Tai Y (2010) Headwater origin analysis in the Huanglong scenic spot, Sichuan, China. J Chengdu Univ Technology(Social Sciences) 37(01):91–95. https://doi.org/10.3969/j.issn.1671-9727.2010.01.014 (in Chinese with English Abstract)

Wang H, Liu Z (2010) Hydrochemical Variations of the Huanglong Spring-Fed Travertine-Depositing Stream in the Huanglong Ravine, Sichuan, SW China, a World Natural Heritage Site. Springer Berlin Heidelberg. 381–386. https://doi.org/10.1007/978-3-642-12486-0_59

Wang H, Liu Z, Zeng C, Liu X, Sun H, An D, Tang S, Zhang Q (2009) Hydrochemical variations of Huanglong Spring and the stream in Huanglong Ravine,Sichuan Province. Geochimica 38(3):307–314. https://doi.org/10.1016/S1874-8651(10)60080-4 (in Chinese with English Abstract)

Wang H, Liu Z, Zhang J, Sun H, Wang X (2010) Spatial and temporal hydrochemical variations of the spring-fed travertine-depositing stream in the Huanglong Ravine, Sichuan, SW China. Acta Carsologica / Karsoslovni Zbornik 39(2):247–259. https://doi.org/10.3986/ac.v39i2.97

Wang H, Liu Z, Yan H (2014) Contrasts in variations of the carbon and oxygen isotopic composition of travertines formed in pools and a ramp stream at Huanglong Ravine, China: implications for paleoclimatic interpretations. Geochim et Cosmochim Acta: J Geochemical Soc Meteoritical Soc 125:34–38. https://doi.org/10.1016/j.gca.2013.10.001

Xie J, Gary S, Xu W, Chen J, Ren H, An D, Brad G (2017) Fungi as architects of the Rimstone dams in Huanglong, NSD, Sichuan, China. Microb Ecol 73(1):29–38. https://doi.org/10.1007/s00248-016-0841-6

Yang J, Wan X, XI B (2004) Characteristics and formation of the travertine funnels in the Jiuzhaigou-Huanglong area. Hydrogeol Eng Geol 31(02):90–93. https://doi.org/10.3969/j.issn.1000-3665.2004.02.022

Yuan H, Nie K, Xu X (2021) Relationship between tourism number and air quality by carbon footprint measurement: a case study of Jiuzhaigou scenic area. Environ Sci Pollut Res 28(16):20894–20902. https://doi.org/10.1007/s11356-020-12068-1

Zhang T (2022) Study on The Behavior of Travertine Deposition Under Hydrodynamic Force in Huanglong, Sichuan, SouthWest University of Science and Technology. (in Chinese with English Abstract)

Zhang J, Tang S (2015) Study on cause of Surface Water Flow R eduction at Huanglong scenic spot. WORLD SCI-TECH R D 37(06):688–691. https://doi.org/10.16507/j.issn.1006-6055.2015.06.012 . (in Chinese with English Abstract)

Zhang J, Wang H, Liu Z, An D, Dreybrodt W (2012) Spatial-temporal variations of travertine deposition rates and their controlling factors in Huanglong Ravine, China - a world’s heritage site. Appl Geochem: J Int Assoc Geochem Cosmochem 27(1):211–222. https://doi.org/10.1016/j.apgeochem.2011.10.005

Zhang Z, Zhang B, Li L, Yang Z (2015) Weathering rate of stone of Confucius Temple Hall in Quzhou, Zhejiang Province, China-Part II: reasons for weathering asymmetry. 373–380

Zhang M, Wang J, Li S (2019) Tempospatial changes and main anthropogenic influence factors of vegetation fractional coverage in a large-scale opencast coal mine area from 1992 to 2015. J Clean Prod 232:940–952. SEP.20 https://doi.org/10.1016/j.jclepro.2019.05.334

Zhao B, Wang Y, Luo Y, Li J, Zhang X, Shen T (2018) Landslides and dam damage resulting from the Jiuzhaigou earthquake (8 August 2017), Sichuan, China. Royal Soc Open Sci 5(3):171418. https://doi.org/10.1098/rsos.171418

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This work was supported by the National Natural Science Foundation of China (grant no.41973053); the Open Fund of State Key Laboratory of Earthquake Dynamics, Institute of Geology, Seismological Bureau of China (grant no. LED2019B05); the Sichuan Province Overseas HighEnd Talent Introduction Project (grant no. 22RCYJ0060); the Open Fund of Key Laboratory of Mountain Disasters and Surface Processes of China Academy of Sciences (grant no. 19zd3105); the Open Fund of State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences (grant no. SKLLQG1620); the Open Fund of Guangxi Key Science and Technology Innovation Base on Karst Dynamics (grant no. KDL&Guangxi202302).

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ZJ. Z and FD. W wrote the main manuscriptZJ. Z carried out the statistical sorting and screening of the collected data, and compiled the modification and confirmation of Figs.  1 and 2 and other related mapsS. T and QM. Z provided water volume data for the study area of HuanglongYY. Z, XQ. Z and FQ. D provide relevant suggestions and feasible suggestionsWY. H and JH. L wrote Figs.  3 , 7 , 9 , 11 , 12 and 13 , and 14 GQ. H summarized and made all the tables in the articleS. C and ·SW. J wrote Figs.  4 , 5 , 6 and 8 , and 10 LP. J provided some chapter information and assisted in revising the articleAll the authors reviewed the manuscript.

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Zhou, Z., Wang, F., Zhu, Y. et al. Analysis of the factors causing degradation and changes in the colourful pool area of the Huanglong travertine in Sichuan Province, China. Carbonates Evaporites 39 , 58 (2024). https://doi.org/10.1007/s13146-024-00971-4

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What the data says about Americans’ views of climate change

A recent report from the United Nations’ Intergovernmental Panel on Climate Change has underscored the need for international action to avoid increasingly severe climate impacts in the years to come. Steps outlined in the report, and by climate experts, include major reductions in greenhouse gas emissions from sectors such as energy production and transportation.

But how do Americans feel about climate change, and what steps do they think the United States should take to address it? Here are eight charts that illustrate Americans’ views on the issue, based on recent Pew Research Center surveys.

Pew Research Center published this collection of survey findings as part of its ongoing work to understand attitudes about climate change and energy issues. The most recent survey was conducted May 30-June 4, 2023, among 10,329 U.S. adults. Earlier findings have been previously published, and methodological information, including the sample sizes and field dates, can be found by following the links in the text.

Everyone who took part in the June 2023 survey is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way, nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories. Read more about the ATP’s methodology .

Here are the questions used for this analysis , along with responses, and its methodology .

A majority of Americans support prioritizing the development of renewable energy sources. Two-thirds of U.S. adults say the country should prioritize developing renewable energy sources, such as wind and solar, over expanding the production of oil, coal and natural gas, according to a survey conducted in June 2023.

In a previous Center survey conducted in 2022, nearly the same share of Americans (69%) favored the U.S. taking steps to become carbon neutral by 2050 , a goal outlined by President Joe Biden at the outset of his administration. Carbon neutrality means releasing no more carbon dioxide into the atmosphere than is removed.

Nine-in-ten Democrats and Democratic-leaning independents say the U.S. should prioritize developing alternative energy sources to address America’s energy supply. Among Republicans and Republican leaners, 42% support developing alternative energy sources, while 58% say the country should prioritize expanding exploration and production of oil, coal and natural gas.

There are important differences by age within the GOP. Two-thirds of Republicans under age 30 (67%) prioritize the development of alternative energy sources. By contrast, 75% of Republicans ages 65 and older prioritize expanding the production of oil, coal and natural gas.

Americans are reluctant to phase out fossil fuels altogether, but younger adults are more open to it. Overall, about three-in-ten adults (31%) say the U.S. should completely phase out oil, coal and natural gas. More than twice as many (68%) say the country should use a mix of energy sources, including fossil fuels and renewables.

While the public is generally reluctant to phase out fossil fuels altogether, younger adults are more supportive of this idea. Among Americans ages 18 to 29, 48% say the U.S. should exclusively use renewables, compared with 52% who say the U.S. should use a mix of energy sources, including fossil fuels.

There are age differences within both political parties on this question. Among Democrats and Democratic leaners, 58% of those ages 18 to 29 favor phasing out fossil fuels entirely, compared with 42% of Democrats 65 and older. Republicans of all age groups back continuing to use a mix of energy sources, including oil, coal and natural gas. However, about three-in-ten (29%) Republicans ages 18 to 29 say the U.S. should phase out fossil fuels altogether, compared with fewer than one-in-ten Republicans 50 and older.

There are multiple potential routes to carbon neutrality in the U.S. All involve major reductions to carbon emissions in sectors such as energy and transportation by increasing the use of things like wind and solar power and electric vehicles. There are also ways to potentially remove carbon from the atmosphere and store it, such as capturing it directly from the air or using trees and algae to facilitate carbon sequestration.

The public supports the federal government incentivizing wind and solar energy production. In many sectors, including energy and transportation, federal incentives and regulations significantly influence investment and development.

Two-thirds of Americans think the federal government should encourage domestic production of wind and solar power. Just 7% say the government should discourage this, while 26% think it should neither encourage nor discourage it.

Views are more mixed on how the federal government should approach other activities that would reduce carbon emissions. On balance, more Americans think the government should encourage than discourage the use of electric vehicles and nuclear power production, though sizable shares say it should not exert an influence either way.

When it comes to oil and gas drilling, Americans’ views are also closely divided: 34% think the government should encourage drilling, while 30% say it should discourage this and 35% say it should do neither. Coal mining is the one activity included in the survey where public sentiment is negative on balance: More say the federal government should discourage than encourage coal mining (39% vs. 21%), while 39% say it should do neither.

Americans see room for multiple actors – including corporations and the federal government – to do more to address the impacts of climate change. Two-thirds of adults say large businesses and corporations are doing too little to reduce the effects of climate change. Far fewer say they are doing about the right amount (21%) or too much (10%).

Majorities also say their state elected officials (58%) and the energy industry (55%) are doing too little to address climate change, according to a March 2023 survey.

In a separate Center survey conducted in June 2023, a similar share of Americans (56%) said the federal government should do more to reduce the effects of global climate change.

When it comes to their own efforts, about half of Americans (51%) think they are doing about the right amount as an individual to help reduce the effects of climate change, according to the March 2023 survey. However, about four-in-ten (43%) say they are doing too little.

Democrats and Republicans have grown further apart over the last decade in their assessments of the threat posed by climate change. Overall, a majority of U.S. adults (54%) describe climate change as a major threat to the country’s well-being. This share is down slightly from 2020 but remains higher than in the early 2010s.

Nearly eight-in-ten Democrats (78%) describe climate change as a major threat to the country’s well-being, up from about six-in-ten (58%) a decade ago. By contrast, about one-in-four Republicans (23%) consider climate change a major threat, a share that’s almost identical to 10 years ago.

Concern over climate change has also risen internationally, as shown by separate Pew Research Center polling across 19 countries in 2022. People in many advanced economies express higher levels of concern than Americans . For instance, 81% of French adults and 73% of Germans describe climate change as a major threat.

Climate change is a lower priority for Americans than other national issues. While a majority of adults view climate change as a major threat, it is a lower priority than issues such as strengthening the economy and reducing health care costs.

Overall, 37% of Americans say addressing climate change should be a top priority for the president and Congress in 2023, and another 34% say it’s an important but lower priority. This ranks climate change 17th out of 21 national issues included in a Center survey from January.

As with views of the threat that climate change poses, there’s a striking contrast between how Republicans and Democrats prioritize the issue. For Democrats, it falls in the top half of priority issues, and 59% call it a top priority. By comparison, among Republicans, it ranks second to last, and just 13% describe it as a top priority.

Our analyses have found that partisan gaps on climate change are often widest on questions – such as this one – that measure the salience or importance of the issue. The gaps are more modest when it comes to some specific climate policies. For example, majorities of Republicans and Democrats alike say they would favor a proposal to provide a tax credit to businesses for developing technologies for carbon capture and storage.

Perceptions of local climate impacts vary by Americans’ political affiliation and whether they believe that climate change is a serious problem. A majority of Americans (61%) say that global climate change is affecting their local community either a great deal or some. About four-in-ten (39%) see little or no impact in their own community.

The perception that the effects of climate change are happening close to home is one factor that could drive public concern and calls for action on the issue. But perceptions are tied more strongly to people’s beliefs about climate change – and their partisan affiliation – than to local conditions.

For example, Americans living in the Pacific region – California, Washington, Oregon, Hawaii and Alaska – are more likely than those in other areas of the country to say that climate change is having a great deal of impact locally. But only Democrats in the Pacific region are more likely to say they are seeing effects of climate change where they live. Republicans in this region are no more likely than Republicans in other areas to say that climate change is affecting their local community.

Our previous surveys show that nearly all Democrats believe climate change is at least a somewhat serious problem, and a large majority believe that humans play a role in it. Republicans are much less likely to hold these beliefs, but views within the GOP do vary significantly by age and ideology. Younger Republicans and those who describe their views as moderate or liberal are much more likely than older and more conservative Republicans to describe climate change as at least a somewhat serious problem and to say human activity plays a role.

Democrats are also more likely than Republicans to report experiencing extreme weather events in their area over the past year – such as intense storms and floods, long periods of hot weather or droughts – and to see these events as connected with climate change.

About three-quarters of Americans support U.S. participation in international efforts to reduce the effects of climate change. Americans offer broad support for international engagement on climate change: 74% say they support U.S. participation in international efforts to reduce the effects of climate change.

Still, there’s little consensus on how current U.S. efforts stack up against those of other large economies. About one-in-three Americans (36%) think the U.S. is doing more than other large economies to reduce the effects of global climate change, while 30% say the U.S. is doing less than other large economies and 32% think it is doing about as much as others. The U.S. is the second-largest carbon dioxide emitter , contributing about 13.5% of the global total.

When asked what they think the right balance of responsibility is, a majority of Americans (56%) say the U.S. should do about as much as other large economies to reduce the effects of climate change, while 27% think it should do more than others.

A previous Center survey found that while Americans favor international cooperation on climate change in general terms, their support has its limits. In January 2022 , 59% of Americans said that the U.S. does not have a responsibility to provide financial assistance to developing countries to help them build renewable energy sources.

In recent years, the UN conference on climate change has grappled with how wealthier nations should assist developing countries in dealing with climate change. The most recent convening in fall 2022, known as COP27, established a “loss and damage” fund for vulnerable countries impacted by climate change.

Note: This is an update of a post originally published April 22, 2022. Here are the questions used for this analysis , along with responses, and its methodology .

• Climate, Energy & Environment
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How Republicans view climate change and energy issues

How americans view future harms from climate change in their community and around the u.s., americans continue to have doubts about climate scientists’ understanding of climate change, growing share of americans favor more nuclear power, why some americans do not see urgency on climate change, most popular.

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Water Intake, Water Balance, and the Elusive Daily Water Requirement

Lawrence e. armstrong.

1 University of Connecticut, Human Performance Laboratory and Department of Nutritional Sciences, Storrs CT 06269-1110, USA; [email protected]

Evan C. Johnson

2 University of Wyoming, Human Integrated Physiology Laboratory, Division of Kinesiology and Health, Laramie, WY 82071, USA

Water is essential for metabolism, substrate transport across membranes, cellular homeostasis, temperature regulation, and circulatory function. Although nutritional and physiological research teams and professional organizations have described the daily total water intakes (TWI, L/24h) and Adequate Intakes (AI) of children, women, and men, there is no widespread consensus regarding the human water requirements of different demographic groups. These requirements remain undefined because of the dynamic complexity inherent in the human water regulatory network, which involves the central nervous system and several organ systems, as well as large inter-individual differences. The present review analyzes published evidence that is relevant to these issues and presents a novel approach to assessing the daily water requirements of individuals in all sex and life-stage groups, as an alternative to AI values based on survey data. This empirical method focuses on the intensity of a specific neuroendocrine response (e.g., plasma arginine vasopressin (AVP) concentration) employed by the brain to regulate total body water volume and concentration. We consider this autonomically-controlled neuroendocrine response to be an inherent hydration biomarker and one means by which the brain maintains good health and optimal function. We also propose that this individualized method defines the elusive state of euhydration (i.e., water balance) and distinguishes it from hypohydration. Using plasma AVP concentration to analyze multiple published data sets that included both men and women, we determined that a mild neuroendocrine defense of body water commences when TWI is ˂1.8 L/24h, that 19–71% of adults in various countries consume less than this TWI each day, and consuming less than the 24-h water AI may influence the risk of dysfunctional metabolism and chronic diseases.

1. Introduction

Individuals with a normal P OSM (e.g., 285–295 mOsm/kg) may be considered to be normally hydrated without regard to daily total water intake (TWI; [ 1 ]) or urinary biomarkers [ 2 ] because the brain actively regulates both total body water volume (within 0.5% day-to-day; [ 3 ]) and blood concentration (within a normal P OSM range of 285–295 mOsm/kg; [ 4 ]) across a wide range of TWI (women, 1.3–6.1; men, 1.7–7.9 L/24h; [ 5 , 6 ]). Thus, an individual with suboptimal water intake may be evaluated to be euhydrated due to the defense of P OSM through reduced urine production and other compensatory responses. However, there is no widespread consensus regarding a definition of euhydration. For example, the 2004 U.S. National Academy of Medicine (NAM) publication, which presented dietary reference intakes for water [ 6 ], included a lengthy review of water balance studies and water needs (i.e., using the stable isotope of water D 2 O) of children and adults ( Table 1 ). However, this report concluded that: (a) individual water requirements can vary greatly on a day-to-day basis because of differences in physical activity, climates, and dietary contents; and (b) there is no single daily water requirement for a given person. As a result, Adequate Intake (AI) volumes for water (i.e., which are not daily water requirements) were developed from median TWI values in the NHANES III survey database [ 5 ]. The 2010 European Food Safety Authority (EFSA) panel utilized a different approach when developing dietary reference intakes [ 7 ]. Water AI values for various life-stage groups ( Table 1 ) were derived from three factors: observed intakes of European population groups, desirable urine osmolality values, and desirable TWI volumes per unit of dietary energy (Kcal) consumed. Similar to the NAM report (above), however, the EFSA report stated that a single water intake cannot meet the needs of everyone in any population group because the individual need for water is related to caloric consumption, the concentrating-diluting capacities of the kidneys, and water losses via excretion and secretion. This report defined the minimum water requirement in general terms as the amount of water that equals water losses and prevents adverse effects of insufficient water such as dehydration.

Comparison of recommended Adequate Intakes a for water, published by European and American health organizations.

a Adequate Intakes represent an amount that should meet the needs of almost everyone in a specific life-stage group who is healthy, consumes an average diet, and performs moderate levels of physical activity [ 6 , 7 ]; b , values refer to total water intake (TWI = plain water + beverages + food moisture).

Neither the NAM nor the EFSA document presented a method to assess the human water requirement of individuals, or (b) neuroendocrine data to support daily AI values for water. However, it is widely accepted that the brain constantly acts to preserve homeostasis via neuroendocrine responses which defend set points of body water volume and concentration [ 8 ]. In contrast to the methods used in the NAM and EFSA reports, we propose that minimal/baseline fluid-electrolyte regulatory responses by the brain signal body water balance (i.e., euhydration), and that increased neuroendocrine responses (e.g., plasma AVP levels) represent the threshold at which the brain begins to defend body water volume and concentration (i.e., hypohydration). This is important because no measurement or biomarker has previously been proposed to define a state of euhydration (i.e., often defined loosely as normal total body water or water balance). Furthermore, we propose that neuroendocrine thresholds, in conjunction with TWI measurements, can reveal the water intake requirement of individuals in a specific life-stage group when the turnover of body water (e.g., intake versus loss) is relatively constant (i.e., no large activity-induced sweat loss), an average diet is consumed, and ample water is available to support ad libitum drinking. Sedentary adults whose free-living daily activities include working in an air-conditioned office and consuming a typical Western diet represent an example of such a group. We propose this individualized physiological measurement of neuroendocrine responses as a methodological alternative to AI values ( Table 1 ).

Thus, the primary purpose of the present manuscript is not to modify current AIs but rather to provide novel additional perspectives regarding 24-h TWI, euhydration, and human water requirements. We have analyzed the relationship between 24-h TWI values and their corresponding plasma AVP levels from multiple research studies, and identified a plasma AVP concentration that approximates the neuroendocrine response threshold for water regulation in free-living adults. Interestingly, this AVP threshold is exceeded when 24-h TWI is ˂1.8 L/24h. The second purpose of the present manuscript is to increase awareness of the importance of daily water intake, because a considerable percentage of individuals in industrialized countries consume less than the 24-h water AI that is recommended for their life stage. Evidence for this purpose exists in a growing body of recent epidemiological studies that report statistically significant relationships between chronic low daily water consumption and disease states or metabolic dysfunction.

Because methods and terminology vary across publications, we emphasize the following important definitions. The term water in beverages refers to water + water in all other fluids (e.g., juice, tea, coffee, milk). The term total water intake refers to water + water in beverages + food moisture (e.g., fruit, soup). Distinct from the term dehydration (i.e., the process of losing water), the term hypohydration is presently defined as a steady-state condition of reduced total body water.

2. Representative Research Evidence

As shown in Table 2 , a variety of methods and theoretical approaches have influenced our present understanding and theories regarding human water intake, euhydration, hypohydration, and water requirements. The range of measured or calculated variables includes dietary macronutrients, 24-h TWI (defined above), biomarkers of hydration status, water volumes (i.e., consumed, metabolized, excreted, turnover), and fluid-electrolyte regulating hormones. Not all these methods (column 1, Table 2 ) have contributed in meaningful ways to organizational recommendations regarding the daily water intake required for good health ( Table 1 ). For example, the NAM recommendations [ 6 ] include consideration of large non-renal water losses via sweating, during labor or physical activity. This is a primary reason why 24-h TWI recommendations from European and U.S. organizations differ by 1.1–1.3 L/24h, in specific life stage and sex categories ( Table 1 ). Table 3 describes eight components of 24-h water balance, shown as the headings for columns 2-9. All these components interact with each other in a network that includes the central nervous system (CNS), oropharyngeal region, gastrointestinal tract, kidneys, neuroendocrine system, cardiovascular system, skin, and respiratory organs; feedback from one organ system affects all others, directly and/or indirectly. The components of 24-h water balance in Table 3 have contributed to international recommendations regarding the daily water intake required for good health ( Table 1 ). For example, the NAM recommendations [ 6 ] assimilated all water balance components in Table 3 , and the recommendations of the EFSA (2010) [ 7 ] emphasized both desirable urine osmolality values and the observed TWI of specific groups.

Investigational and theoretical approaches to assess human water intake, euhydration, hypohydration, and water requirements.

a , minimum urine volume corresponds to the urine volume necessary to excrete urine solutes at maximum urine osmolality (defined as 1400 mOsm/kg); b , free urine volume is a precursor to the modern concept of free water reserve (see Table 1 ); c , free water reserve is calculated statistically as the virtual water volume that could be additionally reabsorbed at maximum osmolality, in all but 2% to 3% of healthy subjects at a specific life stage and sex; d , collection of a 24-h urine sample, determination of urine volume and osmolality, and calculation of obligatory and free water volumes allow for the determination of individual 24-h hydration status, determined using statistical confidence intervals (Manz and Wentz, 2005 [ 11 ]); e , e.g., meal timing and contents, physical activity; f , LD and HD were defined slightly differently in each study (LD range, 1.0–1.6; HD range, 2.4–3.3 L/24h); g , adequate water intake is not a requirement, but rather the TWI that meets the needs of almost everyone in a specific life stage and sex group, to prevent deleterious effects of dehydration (i.e., metabolic and functional abnormalities); h , the DLW method is theoretically based on the differential turnover kinetics of the stable isotopes of oxygen ( 18 O) and hydrogen ( 2 H). After drinking a known mass of DLW ( 2 H 2 18 O), 2 H is eliminated from body water as H 2 O whereas 18 O is eliminated as H 2 O and CO 2 (Racette et al., 1994 [ 49 ]). The accumulation of a stable isotope of water ( 2 H 2 O) in plasma, saliva, urine, or sweat determines the rate of water movement throughout the body. i , AVP is difficult to measure because of its brief half-life, whereas plasma copeptin is relatively stable and its concentration is strongly correlated to that of AVP. Abbreviations: AI, adequate intake; AVP, arginine vasopressin; DLW, doubly labeled water; HCT, hematocrit; HD, individuals who habitually consume a high daily water volume; LD, individuals who habitually consume a low daily water volume; M B , body mass; NRWL, non-renal water loss as eccrine sweat, transdermal, respiratory and stool water; S OSM , salivary osmolality; SR, sweat rate measured as M B change; TBW, total body water; TWI, total water intake = (plain water + water in beverages + food moisture); T OSM , tear osmolality; FC, fluid consumed during a defined time period; BHI, beverage hydration index, relative to water;%∆PV, percent change of plasma volume; TPP, total plasma protein; U COL , urine color [ 50 ]; U FUV , free urine volume; U FWR , free water reserve; U OSM , urine osmolality; U TOT , total excreted osmolar load; U SG , urine specific gravity; U VM , minimal urine volume; U VOL , urine volume; U MAX, maximal urine osmolality produced by the kidneys;.

Dietary, physiological, metabolic, and behavioral components of human 24-h water balance.

a , TWI, total water intake = (plain water + water in beverages + food moisture); b , water generated during substrate oxidation; c , greatly influenced by diet composition; d , in a 24-h sample; e , NRWL includes eccrine sweat, transdermal, respiratory and stool water losses; f , FWR = (24-h urine volume, L/day) − (obligatory urine volume, L/day). The latter term is the water volume necessary to excrete the 24-h solute load, hypothetically calculated as (830 mOsm/kg) − (3–4 mOsm/kg per year > 20 years of age) [ 1 ]. Hydration status is inadequate if FWR is negative. Abbreviations: TBW, total body water; NES, neuroendocrine system (central nervous system + hormones); ECV, extracellular volume; ICV, intracellular volume; MRCA, maximal renal concentrating ability; CNS, central nervous system (brain + spinal cord); GI, gastrointestinal organs; GE, Germany; FR, France; USA, United States of America.

A review of the hundreds of publications that contributed to our understanding of human water intake, euhydration, hypohydration, and water requirements is beyond the scope of this manuscript. However, the mean values ( Table 3 ), measured variables, and reference citations ( Table 2 and Table 3 ), although not exhaustive, represent the nature and types of meaningful available evidence regarding human water needs.

3. Why are Human Water Requirements Elusive?

To maintain normal physiological functions (e.g.., blood pressure, pH, internal body temperature) and optimal health, and to deliver essential substances (e.g., oxygen, water, glucose, sodium, potassium) to cells, the CNS and neuroendocrine hormones act constantly to preserve internal homeostasis via a complex network of many organ and neural systems. Figure 1 presents several CNS-regulated variables which are relevant to body water balance. Each of these variables is simultaneously: (a) maintained (i.e., within the circulatory system or fluid compartments of the body) at a specific set point (e.g., a threshold beyond which the intensity of neuroendocrine responses increases ); and (b) constantly changing throughout the human life span in response to water and food intake, urine production, and non-renal water losses. Because of these fluctuations, human body water regulation is also dynamic. Therefore, we utilize the phrase dynamic complexity to refer to a constantly changing, vastly integrated regulatory mechanism [ 56 ]. This dynamic complexity is amplified by interconnected fluid compartments (i.e., intracellular, interstitial, extracellular, circulatory), organ systems ( Table 3 ), neural plasticity (i.e., adaptations), and interactions of the physical processes (i.e., osmotic and oncotic pressure, simple diffusion, active transport) which govern water and electrolyte movements throughout the body.

Variables that are regulated as part of body water homeostasis.

This dynamic complexity ( Table 3 , Figure 1 ) represents the primary reason why the daily water requirements of humans have not been determined to this date ( Table 1 ). We provide the following evidence in support of this statement:

• The relative influence of physiological processes which maintain water balance ( Table 3 ) varies with different life scenarios. During sedentary daily activities in a mild environment, renal responses and thirst are the primary homeostatic regulators. During continuous-intermittent labor, or prolonged exercise at low intensities (5–18h duration), renal responses and thirst have minor-to-large effects on water regulation, whereas sweat loss presents the foremost challenge to homeostasis [ 56 ].

Frequency distribution of the habitual total water intake (TWI, 5-d mean values, n = 120) of healthy, college-aged women ( n = 120). Reprinted with permission (Johnson et al., 2016 [ 13 ]).

• The 24-h human water requirement varies with anthropomorphic characteristics, especially body mass. Large individuals require a greater daily TWI than small individuals [ 6 ].
• The daily water requirement of any life-stage group is influenced by dietary sodium, protein and total solute load, due to individual dietary preferences as well as traditional regional-cultural foods. For example, large differences of mean urine osmolality (U OSM ) have been reported for residents of Germany (860 mOsm/kg) and Poland (392 mOsm/kg). These differences are influenced by unique regional customs involving beverages (i.e., water, beer, wine) and food items [ 1 ] and the moisture content of solid foods; the latter factor varies among countries and demographic groups: the United States, 20–35% [ 2 , 51 , 58 , 59 ]; Germany, 27% [ 10 ]; the United Kingdom, 24–28%; and France, 35–38% [ 14 ].
• The principle that both water and beverages contribute to rehydration and the maintenance of body water has been fundamental in publications involving large populations [ 11 , 25 ], TWI differences in various countries [ 14 , 15 ], habitual low and high TWI consumers [ 16 , 17 ], water AI recommendations [ 6 , 7 ], the health effects of beverage consumption [ 60 ], young versus older adults [ 61 ], 12-h or 24-h water restriction [ 62 , 63 ], and experimental interventions which control and modify daily total water intake and beverage types [ 13 , 17 , 36 , 64 ]. However, small differences exist in the percentage of water retained (4-h post consumption), primarily due to beverage osmolality and the content of sodium chloride, protein, and/or energy [ 36 , 37 ].
• Intracellular water volume (~28 L in a 70 kg male) is considerably larger than extracellular water volume (~14 L) [ 65 ]. No hydration assessment technique measures intracellular water content or concentration directly [ 27 ].
• Although some authorities consider plasma osmolality (P OSM ) to be the best index of euhydration and hypohydration [ 2 , 6 ], P OSM does not assess whole-body hydration validly in all settings, especially when TBW, water intake, and water loss are fluctuating [ 66 ]. Furthermore, P OSM may not reflect widely accepted physiologic principles, as shown by decreased P OSM (6 out of 39 subjects) after losing 3–8% of body mass via sweating [ 67 ], and increased P OSM at rest (4 out of 30 values) 60 min after ingesting 500 ml of water [ 68 ]. These findings likely result from the large between- and within-subject variance that exists in P OSM measurements [ 56 ].

Plasma osmotic threshold a for plasma AVP increase.

a , refers to the plasma osmolality (i.e., determined statistically or graphically) at which plasma AVP concentration rises from baseline; b , mean (range or 95% confidence interval); c , data derived from a figure.

Research findings that illustrate the dynamic complexity of AVP, a peptide hormone produced in the hypothalamus a .

a , compiled from: [ 69 , 72 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 ].

Plasma osmotic threshold a for appearance of the thirst sensation.

a , refers to the plasma osmolality (i.e., determined statistically or graphically) at which thirst is first perceived; b , mean (range or 95% confidence interval); Abbreviations: IV HS , intravenous hypertonic saline; IV I , intravenous isotonic saline.

• Older adults (>65 years) experience reduced thirst and water intake, reduced maximal renal concentrating ability, greater plasma AVP concentration during water restriction, and reduced ability to excrete a water load when compared to younger adults [ 61 , 88 , 89 ]. Although the osmotic threshold for thirst apparently does not change during the aging process [ 88 , 90 ], older adults have a reduced autonomic baroreceptor capability to sense a depletion of blood volume [ 89 , 91 ]. In addition, older adults demonstrate changes in water satiation that hinder the ability to hydrate following an osmotic challenge. This deficiency has been linked to changes in cerebral blood flow and/or altered activation of the anterior midcingulate cortex area within the brain [ 92 ]. Thus, aging appears to be responsible for large between-subject variances (i.e., of the variables in Table 3 ) across age groups, which make it difficult to determine a universal water requirement for children, adults, and the elderly ( Table 1 ).

The preceding points of evidence exemplify the difficulties which the National Academy of Medicine, USA, and the European Food Safety Authority faced and which prompted them to establish Adequate Intakes (AI), which are not Recommended Dietary Allowances (requiring a higher level of evidence) or water requirements ( Table 1 ). The NAM assumed the TWI AI volumes to be adequate, based on observed or experimentally determined approximations or estimates of water intake by a group of apparently healthy people [ 6 ]. The EFSA determined AIs on the basis of population statistics, utilizing calculated ‘free water reserve’ (ml/24h) [ 12 ]; this quantity is defined as the difference between the measured urine volume (ml/24h) and the calculated urine volume necessary to excrete all urine solutes (i.e., obligatory urine volume, mOsm/24-h) at the group mean value of maximum U OSM [ 1 , 11 ]. Furthermore, both the NAM and EFSA noted that AI values for water apply only to moderate environmental temperatures and moderate physical activity levels, because non-renal water losses via sweating (see column 8 in Table 3 ) can exceed 8.0 L/24h when exercise-heat stress is extreme [ 7 ].

4. A Proposed Method to Assess Daily Water Requirements

We now propose a novel approach to the assessment of the daily water requirement of individuals in all life stages, which was not employed during the development of water AI values ( Table 1 ). This method focuses on the thresholds and intensity of responses within the brain and neuroendocrine system (i.e., autonomic nerves and endocrine organs that release hormones to regulate water and electrolyte balance). Figure 3 provides a graphic representation of this technique. The central dashed line represents the set point (threshold) for each of the five regulated variables listed within the central rectangle; Table 4 and Table 6 present set point values for a plasma AVP increase and the appearance of thirst. The regions to the left and right of the set point represent a water or sodium deficit, and water or sodium excess, respectively; the zones farthest to the left and right of the set point represent the greatest perturbations of each regulated variable due to change forces (e.g., dehydration, drinking, large dietary osmotic load). The block arrows to the left and right of the set point illustrate neuroendocrine responses which move each regulated variable toward the set point in an effort to restore altered homeostasis; examples include release of AVP, angiotension II, aldosterone, atrial natriuretic peptide, as well as blood vessel constriction or dilation, increased thirst, and water consumption (i.e., sensory and behavioral effects that are influenced by endocrine responses). The strongest neuroendocrine responses occur at the far left and far right of the threshold (labeled with the words deficit and excess). If all fluid-electrolyte regulatory variables are at or near the set point (or if all neuroendocrine responses are minimal), a state of euhydration exists because the brain is activating no compensatory responses; in contrast, when responses counteract water loss a state of dehydration or hypohydration exists. Measuring the intensity of neuroendocrine responses and identifying when set points have been exceeded allow for quantitative comparisons of values during controlled laboratory experiments. Alternatively, the area under the curve (i.e., response intensity plotted versus response duration) could be measured.

A proposed schematic of a method to assess human daily water requirements by measuring the intensity of neuroendocrine responses that are employed by the brain to defend homeostasis of body water volume and concentration. These responses and thresholds are inherent hydration biomarkers, and the means by which the brain maintains good health and optimal function. Abbreviations: AVP, arginine vasopressin; ANG II, angiotensin II; ALD, aldosterone; ANP, atrial naturietic peptide.

Figure 4 illustrates this approach to assessing individual daily water needs. In normal subjects, the increase in plasma AVP (panel A) is stimulated primarily by increased P OSM . Increasing P OSM signifies increasing perturbation of homeostasis; whereas an increasing plasma AVP concentration represents an increased intensity of neuroendocrine response and indicates that the brain is regulating body water via the kidneys. Thus, the data in the upper right quadrants of panel A and panel B correspond to intense neuroendocrine responses and a rigorous defense of total body water; the data in the lower left quadrants correspond to minimal-to-moderate defense of total body water.

The relationship of plasma osmolality to plasma AVP (panel A), and the relationship of plasma AVP to urine osmolality (panel B). Reprinted with copyright from Robertson et al. [ 71 ]. Plasma was collected during recumbent rest in three states of water balance: ad libitum fluid intake, following an acute water load (20 ml/kg), and after acute periods of fluid restriction. The data represent healthy adults and patients with diverse types of polyuria (i.e., abnormally large urine volume and frequency). Dashed lines represent the sensitivity limit of the plasma AVP assay.

In normal adults, an increased intensity of neuroendocrine response (i.e., which defends the volume and concentration of total body water) results in decreased urine volume and increased urine osmolality, secondary to increased plasma AVP ( Figure 4 , panel B). As such, urinary variables (e.g., osmolality, specific gravity, 24-h urine volume) have been identified as valid hydration biomarkers in studies involving free-living pregnant women, nonpregnant women, and men [ 16 , 18 , 38 , 39 , 57 ]. Central, autonomically-controlled changes of plasma AVP concentration (i.e., at the border of euhydration and mild hypohydration; Figure 3 ) also act to maintain optimal health and functions in normal persons. In turn, AVP may be a prognostic indicator of various disease states ( Table 7 ), including ischemic stroke, myocardial infarction, pneumonia, certain types of cancer, and septic shock [ 93 , 94 , 95 ].

Effects of 12-h and 24-h water restriction a on plasma osmolality and AVP concentration.

a , diets included no water or beverages and dry food items; b , nonpregnant women; c , 24-h total water intake was not measured; d , body mass loss was 1.8–1.9% of the baseline value; Abbreviations: AVP, arginine vasopressin; EU, euhydrated; WR, water restriction.

In terms of the water requirements of normal individuals, determining the intensity of the body’s defense of total body water and tonicity (e.g., measuring changes of plasma AVP or regulated variables) provides a laboratory method to assess the intensity of homeostatic responses and the response thresholds which the brain employs. Once identified, these measurements could be compared to experimentally-controlled TWI volumes to determine the minimum 24-h TWI that generally elicits no neuroendocrine response above resting baseline levels (i.e., thereby representing euhydration or normal water balance). This method for assessing 24-h water balance also can be applied to the TWI of free-living adults. For example, in recent years several research teams have compared the physiological responses of habitual low-volume drinkers (LOW) to those of habitual high-volume drinkers (HIGH) [ 16 , 17 , 18 , 51 ]. Figure 5 depicts plasma the AVP concentrations of free-living LOW and HIGH during one morning laboratory visit on each of 8 days. The TWI levels of LOW ( n = 14 ♀) and HIGH ( n = 14 ♀) are described in the figure legend. The experimental design involved 3 d of baseline observations, 4 d of modified water intake (during which LOW consumed the TWI which HIGH habitually consumed, and vice versa), and 1 d of ad libitum water intake. The morning plasma AVP levels in Figure 5 were similar (LOW, 1.4–1.5 pg/ml; HIGH, 1.1–1.3 pg/ml) when both groups were consuming a similar high TWI (LOW, 3.5 L/24h; HIGH, 3.2 L/24h). Considering the plasma AVP threshold which indicates an obvious neuroendocrine response (~2.0 pg/ml [ 78 ]; Figure 4 ), LOW were above this threshold when consuming a TWI volume of 1.6–1.7 L/24h whereas HIGH were above this 2.0 pg/ml AVP threshold only when their TWI was modified to 2.0 L/24h on days 4–7. We interpret these data to mean that the brain did not attempt to conserve water when TWI was ≥3.2 L/24h, and that the water requirement of these healthy young women existed between 1.6 and 3.2 L/24h. Similar plasma AVP concentrations have been published in a study of LOW (TWI, 0.74 L/24h) and HIGH (TWI, 2.70 L/24h) by Perrier and colleagues [ 16 ]. Furthermore, a plasma AVP threshold ˂2.0 pg/ml corresponds closely with the euhydrated baseline values shown in Table 7 (1.0–1.8 pg/ml), as observed in four groups of men and women. However, when these test subjects underwent water restriction for 12h and 24h, a stronger neuroendocrine response was observed (i.e., representing hypohydration) as plasma AVP levels of 2.9–3.5 pg/ml in young adults and 8.3 pg/ml in older adults. In one Table 7 experiment [ 63 ], participants (5 ♂ & 3 ♀, 26–50 years) rehydrated with tap water (10 ml/kg, 620–870 ml) after a 24-h water restriction; 60 min after this water consumption, the average plasma AVP decreased from 3.3 to 1.5 pg/ml, suggesting that subjects had reached a state of euhydration.

Morning plasma AVP concentrations of habitual high-volume drinkers (HIGH, 3.2 ± 0.6 L/24h, n = 14♀) and low-volume drinkers (LOW, 1.6 L/24h, n = 14♀) during ad libitum baseline (3 days), modified water intake (4 days; HIGH, 2.0 ± 0.2 and LOW, 3.5 ± 0.1 L/24h), and ad libitum recovery (1 day; HIGH, 3.2 ± 0.9 and LOW, 1.7 ± 0.5 L/24h). Different experimental phases are separated by vertical dotted lines. a, within-group significant difference from the 3-d baseline mean ( p < 0.001). Reprinted with permission from Johnson et al., (2016) [ 13 ].

Utilizing a plasma AVP threshold of ˂2.0 pg/ml, this method could be employed to: (a) define and distinguish states of euhydration and hypohydration; and (b) evaluate the neuroendocrine response changes which occur with advanced age ( Table 7 ; [ 61 , 88 , 91 , 96 ]) or any factor that potentiates the release of AVP into the circulation. Although a plasma AVP concentration is useful because it represents the sum of all factors that influence pituitary AVP release ( Table 5 ) and AVP turnover in the circulation, we acknowledge that other hormonal/neurological biomarkers (e.g., angiotensin II, aldosterone) also play a role in water homeostasis. In addition, cases of over-hydration likely represent a limitation of this method. Excess body water may reduce plasma AVP to a level below the sensitivity of present-day technologies (i.e., most immunoassays detect AVP to ≥0.5 pg/ml; [ 69 ], making it difficult to distinguish over-hydrated states from a normal euhydrated state (1.0–1.8 pg/ml; Table 7 ). One final limitation of this method is the circadian variation in AVP secretion. It would be imperative for any investigation utilizing this proposed method to ensure blood sampling at similar times if successive samples were taken as it has been demonstrated that AVP is both an outcome and input related to suprachiasmatic nucleus activity [ 97 ].

Plasma AVP concentration was selected as the primary outcome variable of this method because previous TWI investigations have also published AVP with no copeptin measurements. However, AVP has a short half-life and is difficult to isolate/analyze [ 69 , 98 ], whereas copeptin is stable at room temperature and is recognized as a diagnostic biomarker for various diseases [ 99 , 100 ]. Furthermore, several studies have reported a strong correlation between plasma AVP and copeptin levels in healthy individuals [ 98 , 101 ] and patients [ 102 , 103 ] across a wide range of P OSM . Thus, it is very likely that copeptin will be measured in future investigations of neuroendocrine response intensity.

Currently, copeptin is just beginning to be used in clinical settings during randomized control trials evaluating changes in water intake and disease [ 104 , 105 ]. Clinical settings are ideal because copeptin measurement, although less prone to errors compared to AVP, still requires specialized and expensive equipment (i.e., B·R·A·H·M·S KRYPTOR random-access immunoassay analyzer, ThermoFisher Scientific). Copeptin is also utilized in hospital settings for the evaluation of heart failure [ 106 ]. Therefore, many researchers in the clinical setting already have access to copeptin analysis equipment. It is hoped that in the coming years this type of equipment will become a mainstay within hydratrion physiology laboratories, or advances in assay techniques will make copeptin quantification more accessible for all levels of researchers.

To our knowledge, only one study has assessed changes of plasma copeptin concentrations in normal adults during water restriction [ 107 ]. Resting euhydrated plasma copeptin values (i.e., representing no neuroendocrine response by the brain to conserve water) were 18.5 ± 6.8 pg/ml (4.6 ± 1.7 pmol/L; 8 ♀, 8 ♂) at baseline, and increased to 37.0 ± 20.9 pg/ml (9.2 ± 5.2 pmol/L) after a 28-h water restriction period that induced a 1.7% body mass loss. To determine a plasma copeptin threshold similar to the plasma AVP threshold of 2.0 pg/ml (see above), additional experiments similar to those in Table 7 are required.

5. Neuroendocrine Responses across a Range of TWIs

Figure 6 provides evidence regarding the daily water requirement of humans. Compiling a range of data from six studies that reported 22 different observation days [ 10 , 13 , 16 , 18 , 54 , 64 ], we plotted the relationships between TWI and the primary brain-regulated variable (P OSM ), the neuroendocrine response (plasma AVP) to changes of P OSM , and the resulting changes in urine volume and concentration. The R 2 value for each relationship describes the amount of variance in the four variables that is explained by TWI values. Clearly, P OSM is not strongly related to TWI ( R 2 = 0.18, p < 0.05) because blood concentration is regulated by the brain within a narrow normal limit [ 4 ], across a wide range of TWI [ 6 ]; as reported in previous publications [ 16 , 18 ], P OSM does not serve as a valid indicator of either TWI or water requirement in free-living adults. This fact opposes the theory that all individuals with normal P OSM levels are similar [ 2 , 108 ], even if their 24-h TWI is low.

Urine volume (U VOL ), plasma osmolality (P OSM ), urine osmolality (U OSM , 24h), and plasma AVP plotted against daily total water intake. EFSA and NAM water Adequate Intakes are shown as the vertical shaded column. AVP concentrations associated with water restriction (WR) and baseline resting total water intake (B) ( Table 7 ) appear as horizontal shaded rows. All data points are group mean values (SD not shown) from investigations that measured TWI.

The relationship between TWI and urine osmolality in Figure 6 appears to be moderately strong ( R 2 = 0.56, p < 0.001), but not very strong because of the simultaneous influence of dietary osmolar load on U OSM . In contrast, the relationship between TWI and urine volume is very strong ( R 2 = 0.94, p < 0.001). However, plasma AVP concentration is the only variable in Figure 6 that directly represents the intensity of neuroendocrine responses across a wide range of TWI (0.7–6.8 L/24h). As such, this relationship ( R 2 = 0.88) provides evidence of the TWI volume that is required to maintain water and electrolyte homeostasis. Recalling that a plasma AVP concentration of ≥2.0 pg/ml indicates an obvious neuroendocrine response by the brain ([ 78 ]; Figure 4 ), and that the normal resting level (shaded zone labeled WR) of plasma AVP lies below 2.0 pg/ml, the line of best fit for the relationship between TWI and plasma AVP in Figure 6 shows that a plasma AVP concentration of 2.0 pg/ml is equivalent to a TWI of 1.8 L/24h. Approximately 40% of young healthy college-aged women in the USA ( Figure 2 ), 19–24% of men and women in Great Britain [ 109 ], and 68–71% of men and women in Spain [ 110 ] consume less than this volume of water each day. In Figure 6 , a TWI of 1.8 L/24h is equivalent to a urine volume of ~1400 mL/24h and a 24-h urine osmolality of ~770 mOsm/kg. Furthermore, a TWI of 1.8 L/24h is similar to the much-debated recommendation to drink “8 × 8” each day, which refers to consuming eight 8 oz glasses of water (1.89 L/24h) [ 108 , 111 ], and to the recommended daily AI of water for women (2.0 L/24h, Table 1 ) established by the European Food Safety Authority [ 7 ]. The two vertical shaded zones in Figure 6 display the EFSA and NAM daily water AI ranges for men and women; all of these AI correspond to plasma AVP levels <2.0 pg/ml and a minimal/baseline neuroendocrine defense of total body water and tonicity ( Table 7 ). The daily water AI range of the NAM corresponds to plasma AVP levels well below 2.0 pg/ml, likely because the NAM proposed that human water requirements should not be based on a “minimal” intake [ 6 ], as this might eventually lead to a deficit and possible adverse performance and health consequences [ 2 ].

Figure 6 also depicts plasma AVP levels during the four 12-h and 24-h water restriction experiments (see the horizontal shaded zone labeled WR) that are described in Table 7 . At the end of these water restriction periods, group mean plasma AVP concentrations ranged from 2.9–3.5 pg/ml, representing a mild-to-moderate neuroendocrine response ( Figure 3 and Figure 4 ). Interestingly, this range of concentrations (representing hypohydration of approximately 1% of body mass) is similar to the plasma AVP levels reported for individuals who habitually consume a low daily TWI of 0.7 L/24h (2.4 pg/ml; [ 16 ]), 1.0 L/24h (2.5–3.6 pg/ml; [ 54 ]), and 1.6 L/24h (2.5–2.9 pg/ml; Figure 5 ; [ 13 ]). This suggests that women who consume a TWI of 0.7–1.6 L/24h (i.e., ~20–30% of young healthy women; Figure 2 )—well below the AI recommended by EFSA and NAM ( Table 1 )—experience a chronic mild-to-moderate neuroendocrine defense of total body water. This observation is significant because numerous investigations and letters to the editor have proposed that chronically elevated plasma AVP and angiotensin II levels may be related to negative health outcomes (e.g., cardiovascular disease, obesity, diabetes, cancer morbidity and mortality) [ 69 , 96 , 112 ] as well as the progression of disease states (e.g., salt-sensitive hypertension, chronic kidney disease, and diabetic nephropathy [ 113 ]). Other investigators have: (a) utilized plasma copeptin concentrations (i.e., part of the molecular pre-prohormone of AVP) to detect myocardial ischemia and other diseases ( Figure 4 ; [ 8 , 69 , 114 ]); and (b) supported the use of AVP receptor antagonists to treat specific cardiovascular pathologies, suggesting dysfunctional body water regulation [ 115 , 116 ]. A 6-week study, involving 82 healthy adults (50% ♀) in three TWI groups (1.43, 1.83, and 2.42 L/24h), provided promising evidence (i.e., increasing the daily TWI of the two LOW groups to match 2.42 L/24h) of reduced circulating copeptin levels [ 19 ]. This study suggests that the reduction of plasma AVP via increased TWI offers a safe, cost-effective, and easy-to-implement primary preventive intervention that should be evaluated in large future clinical trials [ 117 ].

6. Evidence for a Role of 24-h TWI in Reducing Disease Risk

As noted above, a surprising number of adults in developed countries do not meet water AI recommendations ( Table 1 ). This fact is significant in terms of long-term health outcomes because a growing body of epidemiological evidence shows that chronically elevated plasma AVP ( likely due to an insufficient daily TWI) is related to cardiovascular, obesity and cancer morbidity and mortality, as well as the regulation of glucose metabolism. Unfortunately, controlled, randomized clinical trials (spanning multiple years or decades), which focus on the relationship between chronic low water volume intake and development of diseases, do not exist for three reasons [ 118 ]. First, lengthy controlled studies suffer from participant attrition and noncompliance because it is difficult for any person to maintain a constant hydration state or 24-h TWI across years of life. Second, multiple personal characteristics, dietary habits, or lifestyle behaviors may concurrently encourage disease development. Third, because of the large number of confounding dietary, behavioral, and genetic factors related to the development of the above diseases, the number of subjects required for adequately-powered statistical analyses which isolate the effects of water is large and the research is costly. Therefore, researchers must focus on the mechanisms that regulate body water ( Figure 1 and Figure 4 ) to investigate potential relationships between chronic low TWI and the development of diseases.

Recent epidemiological studies ( n = 3000–4000 Scandinavian adults) have reported statistically significant associations between high plasma AVP (or its surrogates, including low daily TWI, low urine flow rate, high P OSM , or copeptin) [ 69 ] and the incidence of type 2 diabetes, metabolic syndrome, end-stage renal disease, cardiovascular disease, and premature death [ 117 , 119 , 120 , 121 , 122 ]. Furthermore, during the past 25 years, several observational studies have reported that increased daily TWI reduces the risk of kidney stone formation and stone recurrence [ 118 , 123 , 124 , 125 , 126 , 127 , 128 ] preserves kidney function in chronic kidney disease [ 129 ], and retards cyst growth in polycystic kidney disease [ 130 ]. If these findings are supported by future controlled intervention studies, it is possible that increased daily water consumption will be recognized as a safe, cost-effective, simple primary preventive intervention for some kidney diseases [ 117 , 131 ]. However, establishing such relationships will be challenging (i.e., for the reasons noted in the preceding paragraph) [ 118 ], and will likely be specific to each type of kidney disease/dysfunction. For example, at least one recent randomized clinical trial found no benefit of coaching chronic kidney disease patients to increase their 24-h TWI, even though coaching resulted in a 24-h urine volume that was +0.6 L/day greater than an uncoached control group ( p < 0.001) [ 104 ]. Thus, because epidemiological and observational studies do not allow for cause-and-effect inferences, randomized clinical trials and experimental studies employing animal models are needed to further evaluate mechanisms such as the contribution of AVP to renal, cardiovascular, and metabolic disorders [ 113 ].

7. AVP Influences Glucose Metabolism

The first observations regarding the association between “pituitary extract” and antidiuresis occurred more than a century ago [ 132 ], after which AVP synthesis and its mechanistic description became the subjects of the 1955 Nobel Prize in Chemistry [ 133 ]. Two decades later, medical professionals hypothesized that the excess water loss (i.e., polyuria) observed in people with type 2 diabetes mellitus resulted from decreased secretion of AVP. Contrary to their inclination, researchers testing this hypothesis observed that the plasma AVP concentration was markedly elevated in hyperglycemic patients [ 134 ]. These researchers, along with many during subsequent decades, hypothesized that increased plasma AVP was an ineffective effort to conserve water in the face of an overwhelming solute diuresis caused by glucose in urine (i.e., glucosuria). To our knowledge, this theory persisted until 2010, when epidemiological findings reversed the relationship between AVP and glucose regulation, from one of result to cause [ 135 ]. Based on an apparent dose-response relationship between copeptin and severity of the metabolic syndrome [ 136 ], the important work of Enhörning and colleagues [ 135 ] described a significant positive association between the baseline plasma copeptin concentration of healthy adults and their odds of developing impaired fasting glucose and/or diabetes during the five-year observation period. Shortly thereafter, it was confirmed that an inverse relationship existed between self-reported water intake and the development of hyperglycemia, during a nine-year longitudinal surveillance study [ 137 ]. These two investigations were theoretically connected by the fact that AVP is secreted in response to high plasma osmolality (i.e., low water intake) and acts via V2 receptors in renal nephrons, increasing translocation of the aquaporin 2 channel and facilitating increased water reabsorption [ 138 ]. Thus, chronically low water intake is associated with elevated plasma AVP [ 16 ], both of which predict the development of impaired glucose regulation.

Historically, low daily water intake, in the absence of symptoms and outside of athletic pursuits, has been considered to be innocuous because theoretically it was balanced by increased AVP secretion, enhanced renal water reabsorption, increased water consumption, and maintenance of water balance [ 108 ]. However, the examination of cellular receptors sensitive to AVP yielded insights into possible mechanisms responsible for the above results. Distinct from V2 membrane receptors, V1a receptors are expressed in the kidney, liver, vascular smooth muscle, blood platelets, and brain [ 69 ]. In the liver, V1a stimulation by AVP initiates calcium signaling reactions which increase glycogenolysis and blood glucose, directly in hepatocytes and indirectly via vasoconstriction-mediated ischemia [ 139 ]. Indeed, multiple animal investigations and human genetic studies have described the role of V1a receptors in glucose regulation and dysfunction [ 140 , 141 , 142 ].

Independently, V1b receptors are concentrated within the hypothalamic-pituitary-adrenocortical (HPA) axis, where they enhance ACTH and cortisol release, and the physiological effects of CRH, when stimulated by AVP. The downstream effect of increased plasma glucocorticoids is increased hepatic gluconeogenesis and decreased insulin sensitivity [ 143 ]. The role of AVP in glucocorticoid release is supported by observational data which show that individuals who consume low daily TWI exhibit increased plasma concentrations of both AVP and cortisol [ 16 ]. Additionally, men with type 2 diabetes exhibited deteriorated glucose control and increased plasma cortisol following three days of water restriction [ 144 ]. Thus, mounting evidence suggests that a link exists between AVP and glucose regulation. Our understanding of this relationship will expand in coming years.

Despite numerous efforts to define a state of euhydration and determine the daily water requirements of children, men, women, and older adults, no empirical research provides definitive answers and no universal consensus exists. The dynamic complexity of the water regulatory network, and inter-individual differences, are the primary reasons why widespread consensus regarding the daily water requirements has not been reached to this date. In the preceding paragraphs, we have proposed a novel experimental approach that offers an alternative to water AI survey data and the potential to determine 24-h water requirements of individuals. This approach involves the assessment of the intensity of neuroendocrine responses during euhydration and following experimental perturbations of essential regulated variables. Although future researchers may choose a different regulated variable, we focused on plasma AVP as the primary hydration biomarker to determine the intensity of neuroendocrine responses to a range of TWIs ( Figure 6 ). A plasma AVP concentration < 2.0 pg/ml represents a baseline euhydrated state (i.e., the brain is not attempting to conserve water), whereas plasma AVP ≥2.0 pg/ml indicates dehydration or hypohydration because the brain is acting to conserve water ([ 78 ]; Figure 4 ). These concentrations provide a previously unpublished definition of each term. Our examination of data from multiple research studies ( Figure 6 ) demonstrates that a plasma AVP concentration of 2.0 pg/ml is equivalent to a TWI of 1.8 L/24h. Observational studies demonstrate that 19–71% of adults in various countries consume this volume of water or less each day [ 13 , 109 , 110 ]. This is significant because increasing evidence shows that chronically elevated plasma AVP (likely due to an insufficient daily TWI) could contribute to a number of negative health outcomes. A TWI of 1.8 L/24h also questions the theory that all individuals with normal P OSM levels are similar [ 2 , 108 ], even if their 24-h TWI is low. Fortunately, the chronic reduction of plasma AVP by consuming a daily TWI that maintains plasma AVP <2.0 pg/ml suggests a safe, cost-effective, and easy-to-implement primary preventive intervention that can be evaluated in future long-term clinical trials.

Acknowledgments

The authors would like to thank Professor Ivan Tack, M.D., Ph.D., Toulouse School of Medicine, Toulouse, France for sharing insights regarding the central regulation of renal function and Hillary Yoder, M.S. for providing clerical assistance with the production of the manuscript.

Author Contributions

L.E.A. and E.C.J. worked together on the generation, editing, table design and figure creation for this manuscript.

Conflicts of Interest

Lawrence Armstrong has previously served as a Scientific Advisory Board member, paid consultant, and has received research funding from Danone Nutricia Research, France. He presently serves as a member of the Board of Trustees, Drinking Water Research Foundation, Alexandria, VA and is also a paid consultant to the Foundation. Evan Johnson has previously received funding for research investigations from Danone Nutricia Research, France, and served as a paid consultant to Dr. Armstrong during the preparation of this paper for the Drinking Water Research Foundation, Alexandria, VA, USA.

ORIGINAL RESEARCH article

Simulation of thermal field in mass concrete with cooling pipes based on the isogeometric analysis method provisionally accepted.

• 1 College of Mechanics and Materials, Hohai University, China
• 2 Hohai University, China

The final, formatted version of the article will be published soon.

As water pipe cooling system is widely applied to controlling temperature in mass concrete structures, the precise simulation of the temperature field in mass concrete with cooling pipes embedded is meaningful. This paper presents an isogeometric analysis (IGA) with NURBS for heat transfer in mass concrete with consideration of the cooling pipe. The proposed method not only achieves the same level of accuracy with fewer nodes, but also eliminates the time-consuming process of mesh in the traditional FEM method. The coarsest parameter space which depicts small pipe and large concrete precisely is constructed to create an efficient model for numerical computation. In addition, the unique k-refinement in IGA is supposed to be the most appropriate encryption mechanism, and the knot insertion vector for effective refinement is calculated by considering the characteristics of temperature gradient distribution around the cooling pipes. Besides, different calculation parameter has been discussed to show the stability and flexibility of the IGA. The obtained numerical results demonstrate the accuracy and efficiency of the proposed scheme in the simulation of transient temperature fields in concrete structures with cooling systems.

Keywords: isogeometric analysis, Mass concrete, Cooling pipe system, Temperature field, heat transfer, Temperature gradient

Received: 15 Nov 2023; Accepted: 22 Apr 2024.

Copyright: © 2024 Li, Chen and Zhu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Qingwen Li, College of Mechanics and Materials, Hohai University, Nanjing, China

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