Water and sediment chemistry of Lake Pumayum Co, South Tibet, China: implications for interpreting sediment carbonate
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A combination of water and sediment chemistry was used to investigate carbonate production and preservation in Lake Pumayum Co (altitude 5,030 m a.s.l.), south Tibet, China. We compared the chemical composition of lake water in various parts of the lake with that of input rivers and found that the loss of Ca2+ results from calcite sedimentation induced by evaporation and biogenic precipitation. This is supported by evaporation data from the catchment and δ18O measurements on water. Results suggest that CaCO3 is the predominant carbonate in this lake. There is a positive correlation in the sediments among concentrations of total inorganic carbon (TIC), Ca, total organic carbon (TOC), and total nitrogen, confirming that most carbonates in sediment are endogenic. The Jiaqu River is the largest inflow to Lake Pumayum Co and has a strong influence on both lake water chemistry and sediment composition. The river and lake bathymetry influence carbonate sedimentation by affecting water flow velocity and growing conditions for macrophytes. Different carbon contents and relationships between TIC and TOC in the two long cores from different depths in the lake reveal that hypolimnetic conditions also influence carbonate precipitation and preservation.
KeywordsCarbonate Lake sediments Tibetan Plateau Water chemistry Spatial distribution Lake Pumayum Co
This study was supported by the National Natural Science Foundation of China (Grants No. 40871099), the National Basic Research Program of China (Grant No. 2005CB422002), and the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX2-YW-146-4). The authors thank two anonymous reviewers for the encouragement and constructive remarks. We also thank Ms. Margaret Joyner and Dr. Mark Brenner for help with improvement of the language. Thanks are also given to J. Gao, D. M Qu, and S. P. Gao from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, for their great help with laboratory work.
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