Water and sediment chemistry of Lake Pumayum Co,South Tibet,China: implications for interpreting sediment carbonate |
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Authors: | Jianting Ju Li-ping Zhu Junbo Wang Manping Xie Xiaolin Zhen Yong Wang Ping Peng |
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Institution: | (1) Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 100085 Beijing, China;(2) Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101 Beijing, China;(3) Science in China Press, 100717 Beijing, China |
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Abstract: | 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. |
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