Study On Atmospheric Nitrogen Wet Deposition In The Hinterland Of The Three Gorges Reservoir Area

Atmospheric nitrogen?N?deposition,an important component in the global N cycle,has increased sharply in recent decades in China.Although these N inputs to ecosystems can increase food production and stimulate plant growth,excessive N has caused a cascade of detrimental effects on natural ecosystems and humans,including the acidification of soils and waters,negative impacts on the buffering capacity of soil,a loss of biological diversity,and risks to human health.At the same time,N deposition can influence the balance of greenhouse gases.Based on the conditions,it is imperative to carry out the research of atmospheric N deposition.The Three Gorges Reservoir Area is the focal point of the barrier of ecological environment and the construction of western ecological environment in the middle and upper reaches of the Yangtse River,many researches paid attention to its changes of atmospheric environment.Although it is the region of immigration in the Hinterland of the Three Gorges Reservoir,it is also the sensitive region of ecological environment,meanwhile,its ecological environmenz were affected by natural factors and anthropogenic activities,therefore systematic research on atmospheric N deposition and acid rain are not only helpful for us to make full use of environmental nutrients,but also provide basic data for environmental monitoring and assessment,and it can perfect atmospheric environment evaluations,ecological systems N resources management and evaluation,it is imperative to carry it out.In this paper,we used automated precipitaion and dust monitoring instrument of model APS-3A,long-term experiment to monitor the atmospheric N wet deposition,about 2 years'samples were collected in Wanzhou?urban?and Gaoyang?suburb?the characteristics of N wet deposition and precipitaion acidity and so on were analysed.The main results were as follows:1.During the moniroring period?from July 2014 to May 2016?,precipitation monthly mean pH value in Wanzhou was 5.47,and the rate of acid rain in Wanzhou account for 40.850m.annual mean rainfall was 1079.7 mm·a-,the annual mean deposition fluxes among dissolved inorganic N?DIN?,ammonium N?NH--O?and nitrate N?NO--N?were 12.40,8.18 and 4.22 kg N·nm^-2·a-1,respectively.The mean ratio of N2H--N/NO2--N was 1.79.2.Precipitation monthly mean pH value in Gaoyang was 5.49,and the rate of acid rain in Gaoyang account for 33.93%,annual mean rainfall was 832.8 mm · a-1,the annual mean deposition fluxes among DIN,NH₄^--N and NO2--N were 6.40,4.05 and 2.35 kg N · hm^-2· a-1,respectively.The mean ratio of NH4+-N/NO2--N was 1.61.3.The comparisions among this study and some parts of China,the concentrations of three kinds of inorganic N in the two sites were lower than those in the suburb of Chongqing?Shapingba area?,the outer suburb?Beibei Xiema field?and the forest zone?Fairy Mountain National Forest Park?,which were higher than that of Haibei and Nvingchi,which were less affected by human activities,the three kinds of inorganic N deposition fluxes of the two monitoring sites were lower than those same pattern of land surface.we concluded that the annual mean concentrations of NH41--N,NO₃^--N and DIN were middle levels;as a whole,atmospheric N wet deposition was affected by anthropogenic activity relatively significantly.The annual mean deposition fluxes among NH₄^--N,NO₃^--N and DIN between Wanzhou and Gaoyang were in a lower level,but they were affected by human activity relatively seriously.4.Based on the analysis of the backward trajectories of the precipitation of the two monitoring sites,it is found that the precipitation air masses were mainly from the northwest and southwest,and the precipitation was affected by the continental air masses.