Tracing The Source Of Nitrogen Pollution In Bang Lake By Stable Isotope

In this study,the ion concentration and stable isotope of nitrate(δ¹⁵N,δ¹⁸O)were determined to analysis nitrate contributions:the organic carbon,nitrogen concentration and stable isotope(δ¹⁵N,δ¹³C)to determine the main source of organic matter in sediments.in order to provide a scientific basis for the environmental manager of Bang Lake.We got some conclusions:（1）The average water temperature of Bang lake is 16.5℃,and the water temperature in dry season is significantly lower than that in wet season;The p H value of the water b ody changed little,with an average of 6.7,showing weak acidity as a whole;value in dry season was significantly higher than that in wet season,with an average of 8.7 mg/L;TDS in dry season is higher than that in wet season,which belongs to the range of fresh water.（2）In dry season,the water body of Bang lake is SO₄·HCO₃—Ca;The surface water in wet season is HCO₃—Ca;The deep water body is HCO₃—Ca·Na water in wet season.In dry season,K⁺、Ca²⁺、Na⁺、Mg²⁺、SO₄^2-、HCO₃^-and other water-soluble ions in Bang lake may mainly come from the dissolution of silicate and carbonate rocks.In wet season,K⁺、Ca²⁺、Na⁺、Mg²⁺、SO₄^2-、HCO₃^-and other water-soluble ions are not only related to the dissolution of silicate and carbonate rocks,but also affected by human activities.（3）In dry season,the organic matter in the sediments of Bang Lake may mainly come from soil organic matter and plankton,while in wet season,the organic matter in the sediments of Bang Lake may mainly come from soil organic matter and plankton,and a small part from aquatic vascular plants.（4）According to the nitrogen and oxygen isotopes of nitrate in Bang Lake,the nitrate in Bang Lake may mainly come from atmospheric precipitation and NH₄⁺in precipitation and fertilizer in dry season,and a small part from soil organic nitrogen.In wet season,the nitrate in Bang Lake mainly comes from soil organic nitrogen and NH₄⁺in precipitation and fertilizer,and a small part from atmospheric precipitation,There may be nitrification in Bang Lake,but no denitrification.（5）The source analysis results of the SIAR model show that the nitrate in Bang water body in the dry season mainly comes from precipitation and NH₄⁺（55.3%）in fertilizers and atmospheric deposition（26.3%）,which account for more than 80%;and the wet season Nitrate in the water body mainly comes from precipitation and NH4+in fertilizers（surface water:59.1%,deep water:65.2%）and soil organic nitrogen（surface water:24.6%,deep water 23.5%）,which account for more than 83%.