Major Ion Geochemistry of Nam Co Lake and its Sources, Tibetan Plateau

Abstract

The major cations and anions from lake water samples and its sources, including glacier snow, precipitation, stream, and swamp water in the Nam Co basin, central Tibetan Plateau, were studied. The concentrations of the major ions varied significantly in the five environmental matrices. Generally, the mean concentrations of most ions are in the order of lake water [ swamp water [ stream water [ precipitation [ snow. Rock weathering is the dominant process controlling the chemical compositions of the stream and swamp waters, with carbonate weathering being the primary source of the dissolved ions. The Nam Co lake water is characterized by high Na + concentration and extremely low Ca 2+ concentration relative to other ions, resulting from evapoconcentration and chemical precipitation within the lake. Comparison with the water chemistry of other lakes over the Tibetan Plateau indicated that Nam Co is located in a transition area between non-saline lakes and highly saline lakes. The relatively low concentration of total dissolved solids is possibly due to the abundant inflow of glacial meltwater and relatively high annual precipitation.

Comparisons between the chemical compositions of lake water, inflowing river water, and lake sediment in Nam Co, central Tibetan Plateau, China and their controlling mechanisms

“…HCO 3 − concentration in lake water was not measured but can be estimated based on pH, and then solving for the balance between cations and anions (e.g., Mitamura et al, 2003;Murakami et al, 2007;Li et al, 2007b;Zhang et al, 2008;Ju et al, 2010). An average pH of 8.7 was used based on a water column profile taken in 70 m of water ( Fig.…”

“…Ca 2+ and HCO 3 − were the dominant cation and anion, respectively, in precipitation (Li et al, 2007b). Concentrations of most ions, decreased from lake water, to swamp water, stream water, precipitation, and to snow (Zhang et al, 2008). These studies, while important, did not address issues related to water and sediment chemistry.…”

Spatial-temporal patterns of major ion chemistry and its controlling factors in the Manasarovar Basin, Tibet

“…Limited by the severe natural conditions, the studies that aim to understand the water chemistry of inland lakes in the Tibetan Plateau are still at a basic stage of investigation. They are mostly focused on areas with convenient traffic, which are heavily disturbed by human activities, such as Lake Qinghai (Xiao et al, 2012;Xu et al, 2010), Lake Nam Co Zhang et al, 2008), Lake Yamzhog Yumco (Sun et al, 2013;Zhang et al, 2012), and Lake Pumayum Co Zhu et al, 2010). These studies showed that there are large variations among the ion compositions of the inland lakes on the plateau.…”

Sub-surface water contribution to recession flow in a mountain headwater stream system based on single monitoring campaign

“…Observed δ 18 O and δ 2 H values of water showed differential isotopic enrichment of input water sources that we attribute to early snowmelt and glacier meltwater based on data positioning relative to a regional LMWL (Kendall and McDonnell, ; Liu et al ., ). Relatively lower solute concentrations that were found in water samples collected from the McDonald Creek compared to other studies are likely due to dilution from meltwater that dominated streamflow at the time of sampling (Cook et al ., ; Zhang et al ., ; Yang et al ., ). The dominance of Ca ++ , Mg ++ , and SO 4 −− reflects the general carbonate lithology of the watershed (Ross, ; Whipple, ).…”