Controls on Gosaikunda Lake Chemistry within Langtang National Park in High Himalaya, Nepal

摘要

Surface water samples and lake bed sediments were collected and analyzed from Gosaikunda Lake within Langtang National Park (28°05'N, 85°25'E; 4380 m a.s.l.) in the central Himalayan region of Nepal during fall 2011. The major cations and anions in equivalents were present in the following order: ?and , respectively. Sulfide oxidation coupled with carbonate dissolution and aluminosilicate dissolution appeared to be the dominant geochemical processes determining lake water dissolved ions. Sulfate concentration was much higher than the alkalinity which is in contrast to glacier meltwater within the same landscape. Alkalinity primarily as bicarbonate contributes 88.6% to the total dissolved inorganic carbon (DIC) followed by carbon dioxide (CO2) and carbonate (CO3) in surface water samples. Organic carbon contributes 0.3% to 5.4% to the sediments and the organic matter is predominantly of aquatic origin. The lake is under saturated with carbon dioxide and the average partial pressure of carbon dioxide (pCO2) appeared quite low (43.4 μatm). Overall, natural biogeochemical processes regulate the chemical species within the lake ecosystem. The lake is oligotrophic, however, nutrients and dissolved organic carbon (DOC) concentrations are enhanced at the near shore sites close to the tracking trail.