Characteristics Of Atmospheric Subsidence And Its Effect On Water Quality In Danjiangkou Reservoir Area

Danjiangkou reservoir was taken as the object to study the characteristics of atmospheric wet deposition and its influence on the water quality of it.In August 2017 to December 2018in Xichuan county Laogou village?agroforestry area?respectively,Xichuan Madeng town?traffic?,Xichuan county?district?and Qushou?water?,and other four kinds of main ecological zones set up four monitoring stations,and to the continuous monitoring of atmospheric nitrogen wet sedimentation,the Danjiangkou library different biome spatial and temporal variation characteristics and source of inorganic nitrogen atmospheric wet deposition has carried on the preliminary analysis,and the influence of the atmospheric wet deposition inorganic nitrogen for reservoir water quality was evaluated.In addition,three-dimensional fluorescence combined with parallel factor analysis eems-parafac method was used to study the fluorescence components and sources of wet deposition in the reservoir area,providing a theoretical basis for the determination of the source of atmospheric deposition pollutants and their impact on water quality in Danjiangkou reservoir area.The main results are as follows:?1?The ammonium,nitrate and total inorganic nitrogen contents of Laogou Village,Xichuan Madeng Town,Xichuan County and Qu shou of the four monitoring points of Danjiangkou Reservoir are respectively 0.186⁷.79 mgN·L^-1(mean value is 1.66 mgN·L^-1),0.14 to 6.8 mgN·L^-1(mean value 1.28 mgN·L^-1),0.51 to 13.63 mgN·L^-1(mean value 3.01mgN·L^-1).In terms of seasonal changes,the highest concentration in autumn is followed by winter and lowest in summer.?2?The settlement flux of the Laogou Village monitoring point representing the agro-ecological zone in the Danjiangkou reservoir area is the lowest(16.43 mgN·L^-1),which is lower than the sedimentation flux of the monitoring point of Madeng Town representing the transportation area(16.93 mgN·L^-1)It is the monitoring point of xichuan County(25.53mgN·L^-1)in the commercial area,and the sedimentation flux of the Qu shou monitoring point representing the water area is the highest(29.68 kgN·hm^-2),which has approached and exceeded the critical point of ecosystem nitrogen deposition saturation 25 kgN·hm^-2,this indicates that atmospheric nitrogen wet deposition will bring a large nitrogen input to the water quality in the reservoir area.The deposition flux of inorganic nitrogen in the reservoir area has obvious monthly variation characteristics.The highest deposition appears in May,and the lowest in December,with a difference of 400 times.The wet deposition fluxes of ammonium nitrogen,nitrate nitrogen and inorganic nitrogen in the reservoir area all show the seasonal distribution pattern of spring>summer>winter>autumn.Generally speaking,the flux of ammonium nitrogen in most months is obviously higher than that of nitrate nitrogen,which indicates that the atmospheric inorganic nitrogen agricultural emission sources in the reservoir area are dominant.Precipitation is the most critical factor affecting the wet deposition of inorganic nitrogen.The deposition fluxes of ammonium nitrogen,nitrate nitrogen and total inorganic nitrogen in the wet season?from April to September?are 2.77,6.05 and 4.2 times of those in the dry season?from October to march?respectively,indicating that April to September is the main period of nitrogen deposition in the reservoir area.?3?The PARAFAC model was used to accurately identify the organic matter fluorescence components in the study area.There were significant differences in the concentrations of the organic fluorescent components C1?C2?C3 and C4.The proportion of tyrosine is the largest,accounting for 48%?mean?of the whole,followed by proteinoids?tryptophan?accounting for about 24%,humic substances accounting for 18%,and fulvic acid.Class substances account for 10%.This indicated that natural sources accounted for 72%,while man-made sources only accounted for 28%.