Variation characteristics and source analysis of nitrogen and phosphorus in shallow groundwater in a typical agricultural area of the Hetao Irrigation District
[Objective]Hetao Irrigation Area is an important grain production base in China.The shallow groundwater in the area has decreased in recent years,and the agricultural non-point source pollution might be the main influencing factor.In order to effectively improve the regional water environment quality,it is of great significance to accurately grasp the pollution status and changing trends of shallow groundwater.[Methods]Atypical agricultural area in the Wuyuan County of Bayannur City was select-ed as the study area,and the characteristics and sources of nitrogen and phosphorus in shallow groundwater in the study area were systematically studied by analyzing the morphological features and hydration group classification of shallow groundwater.[Results]The shallow groundwater in the study area is neutral to weakly alkaline,and belongs to the brackish water.The domi-nant cationic and anionic ions in water are Na+and HCO3-,respectively.The chemical type of groundwater water is HCO3-Na,and the composition of groundwater is greatly influenced by evaporation and concentration.The average concentrations of TN and TP in shallow groundwater were 3.24 mg/L and 0.11 mg/L,respectively,which are higher than those in surface water in dit-ches.The average proportion of inorganic nitrogen in total nitrogen was 76.6％,the average proportion of nitrate nitrogen was 69.4％,and the average proportion of inorganic phosphorus and organic phosphorus in total phosphorus was 28.9％and 71.1％,respectively.The peak value of nitrogen and phosphorus concentration occurred before spring irrigation,and the groundwater ni-trogen and phosphorus concentration showed a downward trend after spring irrigation and autumn irrigation,and increased first and then decreased after summer irrigation.[Conclusion]The variability of nitrogen and phosphorus in shallow groundwater in the Hetao irrigation area shows clear seasonal variability,with high concentrations of total nitrogen in the water and relatively low concentrations of total phosphorus.The source of TN is influenced by human activity alone,while the source of TP is affected by both human activities and mineral dissolution.
groundwaternitrogen and phosphorushydrochemical componentswater qualitypollution characteristicsprinci-ple component analysissource analysisHetao Irrigation Area
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