Atmospheric Nitrogen And Phosphorus Deposition Characteristics And Source Analysis Of Reservoir In Sand Source Areas

With the rapid industrial development and the impact of human agricultural activities,a large amount of nitrogen and phosphorus nutrients have been released into the atmosphere.Meanwhile,dust disasters have occurred frequently in our country.The reservoir in the sand source area has an ecological vulnerability.In order to study the characteristics and sources of atmospheric subsidence of the reservoir in the sand source area,to find out the impact of atmospheric subsidence on the ecological environment of the reservoir area,this study conducted continuous observation of atmospheric subsidence and reservoir water in the study area of Dahekou Reservoir from April 2021 to April 2022and conducted measurement and analysis of chemical indexes of atmospheric subsidence.The sources of nitrogen and phosphorus nutrients are analyzed,and the research conclusions are as follows:（1）The annual storage of atmospheric nitrogen and phosphorus deposition in the study area were 35.77 t/a and 4.17 t/a,respectively.Atmospheric nitrogen and phosphorus deposition were 26.79 t/a and 3.87 t/a,respectively.The rainy season provides a great input of phosphorus,and the precipitation events have a great influence on the input of nitrogen and phosphorus.The characteristics of the water environment in the reservoir are generally good.Both atmospheric sedimentation and surface runoff are important sources of nutrient load in the reservoir.Nitrogen load generated by atmospheric sedimentation is 1.76 times of runoff,which is the main source of nitrogen in the reservoir;phosphorus load generated by runoff is 1.28 times of atmospheric,which is the main source of phosphorus in the reservoir.The atmospheric nitrogen deposition load is mainly concentrated in spring and summer,and the phosphorus deposition load is mainly concentrated in summer.The seasonal variation of runoff nitrogen load was not obvious,while the phosphorus load showed a higher performance in summer,autumn and winter.（2）Nitrogen wet deposition fluxes were mainly ammonia nitrogen and nitric nitrogen in spring,autumn and winter,and ammonia nitrogen,nitric nitrogen and organic nitrogen in summer.Both inorganic phosphorus and organic phosphorus are important components of phosphorus wet deposition,and inorganic phosphorus contributes more.According to the correlation characteristics of morphological nitrogen and phosphorus,the concentrations of total phosphorus and inorganic phosphorus were positively correlated with rainfall,while inorganic nitrogen and rainfall were both negatively correlated.Precipitation intensity had a positive effect on the washing effect of organic nitrogen and inorganic phosphorus.The wet sedimentation is only weakly acidic in autumn,and its effect on acidification is not obvious.In spring and autumn,the atmospheric precipitation pollution was more serious,and from winter to spring,the precipitation gradually changed from sulfuric acid type to nitric acid type.Dry deposition was affected by sandy weather and agricultural activities in spring.The total nitrogen and phosphorus deposition fluxes of dry deposition were higher in spring and summer,but lower in autumn and winter.（3）HYSPLIT simulation shows that the annual air mass in the study area is mainly from the northwest and west direction of Mongolia,and the precipitation is mainly due to the upper cold vortex.Only under a few extreme weather conditions,the air mass will migrate from the south or east in a small range,extending from the single northwest to central and northeast China.（4）According to the PMF model,the main sources of wet deposition can be divided into the following four categories:coal source,dust source,agricultural source and atmospheric transmission source.The main source of nutrients is agricultural source,while a small part of NO₃^-comes from coal burning and sand dust.The main source of NH₄⁺is agricultural source,while dust and coal are also important sources.The main source of DON is atmospheric transport.The main sources of DIP and DOP are dust and atmospheric transport.