Spatial variation of TDS in Lake Dari under ice-covered-non-ice-covered conditions and its influencing factors
Total dissolved solids(TDS)is one of the key tracers for water cycle processes.Especially in cold and arid regions,lakes experience both periods of icebound in winter and concentrated atmospheric precipitation inputs in summer,which leads to the chemistry characteristics that the TDS contents at different depths of lake correspond to the different recharge sources.Based on this,in this paper,a total of 324 lake water(ice)and other samples were continuously collected from 2018 to 2020,targeting Dali Lake in Inner Mongolia,to systematically analyze the characteristics of the changes in lake TDS content,and to explore the effects of the differences in the recharge sources on the changes in TDS under the ice-covered-non-ice-covered state in conjunction with the changes in the stable isotopes of hydrogen and oxygen(δD and δ18O).The results showed that:1)In icebound period,the lower TDS content(mean～213mg/L)in ice corresponded to the most enrichedδD and δ18O values in the ice body(～-24.25‰ and-1.22‰),whereas the water body had a relatively high TDS content(mean～483mg/L)with relatively impoverished δD and δ18O values(～-33.56‰ and-2.35‰).In the non-icebound period,the TDS content decreased with a water depth decreased slightly,whileδD and δ18O values(mean values-32.375‰ and-2.09‰)were more enriched than in winter waters.In particular,the d-excess values of the water were significantly negative in summer,indicating that recharge from atmospheric precipitation and other sources increased.2)Although the process of TDS,δD and δ18O values in Lake Dari water samples was similar,the correlation between TDS and isotope values in surface water was lower in the non-icebound period and higher in the icebound period due to the"freeze concentration"effect,while the correlation between TDS and isotope values in bottom water was higher in the deep water(water depth＞7.0 m)due to the difference in groundwater recharge process in different depths,which resulted in a higher correlation between TDS and isotope values in deep water(water depth＞7.0m).The correlation between TDS and isotope values in surface water was lower in the non-icebound period and higher in the icebound period due to the influence of"freeze concentration",while the correlation between TDS and isotope values in the deep water(water depth＞7.0m)was higher in whole year due to the influence of the groundwater recharge process at different depths in the bottom water.In particular,the changes in TDS content in Lake Dari showed a significant inverse relationship with d-excess values,indicating the influence of evaporation and atmospheric precipitation on the hydrochemical characteristics of the lake,and further indicating that the changes in TDS content are influenced by hydrological cycle processes.
total dissolved solids(TDS)hydrogen and oxygen isotopesrecharge sourcesicebound periodDali Lake
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