Hydrogen And Oxygen Isotope Interpretation Of The Effect Of Lake Water Evaporation On Water Environment In Dongping Lake

As the most widely used tracers in isotope hydrology,²H and ¹⁸O have been widely used in the study of lake water cycle,lake evaporation and retention time,and the source of water pollutants,etc.It has become an important research method to solve the problem of lake water environment.Based on the collection of relevant data,field investigation and laboratory experiments,the temporal and spatial distribution characteristics of hydrogen and oxygen isotopes and hydrochemistry in Dongping Lake region were analyzed by using hydrogen and oxygen stable isotope technique.The relationship between ²H and ¹⁸O of Dongping Lake and its hydrochemistry was discussed,and the hydrochemical composition and variation characteristics of Dongping Lake and its source rivers?Dawen River and Liuchang River?were clarified.The effects of river-lake evaporation in different months on lake water environment were revealed,which provided theoretical basis for the study of lake hydrologic process and water environment and maintained the environmental health of Dongping Lake.It is of practical significance to ensure the sustainability of water resources utilization.The results show that:?1?The water chemical content of Dongping Lake has obvious spatial and temporal difference characteristics.The dominant anions and cation in the hydrochemical composition are SO₄^2-and Ca²⁺,Na⁺,respectively.The content of SO₄^2-and Na⁺was the highest in June and low in October.The content of Ca²⁺was high in October and low in April.And the nutrients show different temporal characteristics.In June,the release of nitrogen and phosphorus during putrefaction of Potamogeton crispus resulted in a higher content of TN and TP in the lake area.The highest water temperature in August was beneficial to the degradation of organic pollutants,but the rainfall brought the surface organic matter into the lake,which made the COD content higher.In spatial distribution,the content of TDS increased from southeast to northwest in April,June and August.But in October,the trend of increasing gradually from the center to the north and south.Affected by the replenishment of the Daqing River,the nutrient salts?TN,TP and COD?in the lake area in October showed a decreasing trend from southeast to northwest.However,in August,the lake area TN affected by rainfall is low in the center and high around the lake.?2?The spatial and temporal characteristics of?D and?¹⁸O in Dongping Lake are significant.The slope and intercept of the lake evaporation line in the study area are smaller than that of the atmospheric swath.The value of?D and?¹⁸O in the lake area is affected by the mutual balance of rainfall and evaporation.The results show that the values of?D and?¹⁸O were higher in June and lower in October.The?D and?¹⁸O values in August were second only to June.The slope of the evaporation line affected by the humidity is the largest in August,and its non-equilibrium dynamic fractional distillation is small,thus affecting the relatively small concentration of the?D and?¹⁸O in the lake water.In spatial distribution,the spatial variation of?D and?¹⁸O is consistent.Except for August,?D and?¹⁸O are enriched gradually from south to north with the direction of lake water movement,but in August they are affected by rainfall and atmospheric humidity.The distribution characteristics of?D and?¹⁸O are lower all around.?3?Evaporation affects the water chemical content of some lakes to a certain extent.The negative deuterium surplus can reflect the evaporation and fractionation of water body.There are different degrees of evaporation fractionation in Dongping Lake all year round,and the evaporation fractionation in June is stronger.It can be seen from the response of hydrochemistry to evaporation fractionation that the temperature and COD show significant positive correlation with?¹⁸O,?D and negative correlation with deuterium surplus?d?in June when evaporation fractionation is strong.The results show that chemical oxygen demand is affected by evaporation fractionation to a certain extent,which is related to temperature.The other ions were not affected by evaporation,except CO₃^2-.In August,there was a significant negative correlation between total nitrogen and?¹⁸O,?D,and a significant positive correlation between TDS,salinity,conductivity and?¹⁸O,?D,indicating that the total salinity of lake water was strongly influenced by evaporation.The total nitrogen in the lake is mainly affected by the recharge source and man-made activities.In other months,K,Na,HCO₃^-and pH were also affected by evaporation and recharge sources.