Study On The Atmospheric Carbon And Nitrogen Deposition In Danjiangkou Reservoir Area

With the rapid economic development and the continuous improvement of energy consumption,more and more pollutants are discharged into the atmosphere.Atmospheric deposition is an important part in the material exchange of the atmosphere,water and soil.The study of atmospheric deposition has always been one of the important research contents in the field of ecology and environment.In this study,the Danjiangkou reservoir area is selected as the research object,and three monitoring points were set up in the Danjiangkou reservoir area from 2019 to 2020.Collect atmospheric wet deposition samples,analyze and determine relevant indicators,and study the characteristics of atmospheric wet deposition in the Danjiangkou reservoir area.So as to provide corresponding practical experience and data support for the study of atmospheric deposition characteristics in related areas.The main conclusions of this research are as follows:（1）The concentration of active nitrogen in Danjiangkou reservoir area is on the high side.There are differences in nitrogen concentration in different months,and the main order is winter>spring>autumn>summer.Rainfall is the main factor affecting the concentration of various forms of nitrogen,and has a significant negative correlation（p<0.05）.The total flux of nitrogen deposition in the two years showed a trend of Qushou(39.17 kg hm^-2)>Xichuan(34.43 kg hm^-2)>Madeng(24.44 kg hm^-2).Nitrogen in Madeng and Qushou mainly comes from agricultural sources.Nitrogen in Xichuan is more significantly affected by human activities.（2）Phosphorus deposition in the Danjiangkou reservoir area is at a relatively low level.Compared with nitrogen deposition,phosphorus deposition has less impact on the water quality of the reservoir area.The monthly average concentration of phosphorus deposition showed a trend of Madeng(0.05 mg L^-1)>Xichuan(0.04 mg L^-1)>Qushou(0.03 mg L^-1).The total flux of phosphorus deposition showed a trend of Xichuan(0.54 kg hm^-2)>Madeng(0.50 kg hm^-2)>Qushou(0.47 kg hm^-2).Rainfall is the main factor affecting the flux of phosphorus deposition,There is a significant positive correlation between phosphorus deposition flux and rainfall.（p<0.05）.Summer is the main period of phosphorus deposition in the Danjiangkou reservoir area,accounting for more than 50%.（3）The concentration of inorganic ions in the Danjiangkou reservoir area is at a medium level.The total ion concentration of Cl^-,SO₄^2-,Ca²⁺,Mg²⁺,K⁺,and Na⁺showed a trend of Xichuan(367.12μeq L^-1)>Madeng(241.42μeq L^-1)>Qushou(207.82μeq L^-1).SO₄^2-,Ca²⁺and Cl^-are the three main inorganic ions in the Danjiangkou reservoir area.SO₄^2-is mainly derived from human activities.Ca²⁺has obvious characteristics of crustal origin.Biomass combustion accounts for a large proportion of Cl^-sources,followed by marine sources.K⁺mostly comes from the land-sourced dust and biomass combustion.Na⁺mainly comes from marine sources.Mg²⁺mainly comes from non-marine sources.（4）Through the EEM-PARAFAC analysis model,the rainwater DOM in the Danjiangkou reservoir area has identified four components.Two are UV-like humus components C1 and C2,and two are protein-like components C3 and C4.The largest percentage of protein components in Mating annual rainfall is 56%,and the largest percentages of UV-like humus components in Xichuan and Qushou are 57%and 54%,respectively.Fluorescence parameter results show that the DOM in the rainwater in the Danjiangkou reservoir area has significant endogenous characteristics,low degree of humification,strong autogenic characteristics,and high microbial activity.（5）The relative concentration of DOM a300 in the Danjiangkou reservoir area show a trend of Madeng(5.78 m^-1)>Xichuan(5.15 m^-1)>Qushou(4.93 m^-1).Rainfall also affects the relative concentration of DOM.RDA analysis of DOM spectral characteristic parameters and water quality indicators shows that EC,DTN and DOC have the highest interpretation of DOM spectral characteristic parameters in Madeng.NO₃^--N,DTN,SO₄^2-have the highest interpretation of the DOM spectral characteristic parameters in Xichuan.SO₄^2-,DOC,and DTN have the highest interpretation of the DOM spectral characteristic parameters in Qushou.