Hydrogeochemistry of high-altitude lake: a case study of the Chandra Tal, Western Himalaya, India

Abstract

Major ion chemistry of lake water provides important information about the sources of dissolved ions, weathering, and hydrogeochemical processes as well as anthropogenic activities taking place in the lake environment. Surface water samples were collected from 23 different locations of the Chandra Tal (Lake) situated in the Western Himalaya and analyzed for 12 different physicochemical parameters for understanding hydrogeochemistry of the study area. The average value of pH in the lake water was measured to be 8.1, showing alkaline nature. HCO3− was the most dominant anion and Ca2+ and Mg2+ were major cations in the Chandra Tal water. The high ratios of (Ca2+ + Mg2+)/TZ+ (total cations), (Ca2+ + Mg2+)/(Na+ + K+), Ca2+/Na+, Mg2+/Na+, and HCO3−/Na+ show the dominancy of carbonate weathering as a major source of dissolved ions in the lake water of the study area. On the other hand, equivalent ratios of Na+/Cl− and K+/Cl− are significantly higher than the sea aerosol indicating relatively minor contribution of these ions from atmospheric fallout to the chemical composition of the Chandra Tal water. The carbon dioxide partial pressure (Pco2) of the lake water (10–2.9 atm) was significantly higher than Pco2 value of the atmosphere (10–3.5 atm), showing disequilibrium with respect to the atmosphere and open system weathering in the catchment. The correlation and R-mode principal component analysis indicate that Chandra Tal water chemistry is mainly controlled by weathering processes such as carbonate and silicate weathering, oxidation of pyrite, dissolution of sulphate minerals along with small contribution from atmospheric precipitation, and anthropogenic activities.