| Atmospheric deposition is an important source of pollutants in land and aquatic environments.The harmful substances in the deposition not only affect the ecological environment,but also endanger human health.In this paper,8 dust sampling points were evenly distributed in the typical coking base of about 100 km2,and each sample was placed in parallel with 2 sampling barrels.In a full year of April 9,2015-April 9,2016,it was divided into three periods including spring-summer,summer-autumn,winter-spring(as the representative of the dust,rainy season and heating period respectively).A total of 48 dust samples were collected in the 3 period,and the dry weight of the deposition samples was measured with an analytical balance of 1/10000.Then,the corresponding atmospheric deposition fluxes were calculated.By using ArcGIS software and inverse distance weighted interpolation,the spatial distribution of dust deposition flux was obtained.Based on the location and spatial distribution of pollution sources interpreted with the 2 m remote sensing image interpretation,prevailing wind direction and other meteorological data,this paper discussed the temporal and spatial characteristics and causes of regional atmospheric deposition.The main conclusions of this study are as follow:(1)We conducted color synthesis with 2 m HD remote sensing image downloaded from Map World,and corrected image by geometric calibration with Xi’an 80 coordinate road and other vector map.By visual interpretation with computer screen,and the field inspection and verify we got 14 coking enterprises and 42 coal washing plant in the study area,a total of 56 polluting enterprises.The interpretation mark of the coal washing plant:The middle of a large black area has small isolated rectangular plants.Most plants are sky blue.In addition,we could see a strip of ribbon on the image.The interpretation mark of the coking plant:Large black areas were on the image,which were plants,mixed with white or blue buildings and facilities.In the plant of the coking plant,there are columnar chimneys with small diameter in top and big diameter in bottom.There are white dense smoke in the upper part of some working corporate chimney.And more importantly,strip coke ovens were arranged in parallel,like a dressing texture.(2)According to the upper area of the collecting bucket,the weight of collected deposition and the actual sampling days of each sampling period,this author calculated deposition flux at 8 different sampling points in the study area,and dust deposition fluxes in 3 different periods.Then this author conducted spatial interpolation to deposition flux of the study area with IDW interpolation by ArcGIS.Through cross validation method and by comparing the interpolation results of different interpolation parameters,the optimal parameters of IDW interpolation w of deposition flux as obtained:Power exponents of spring-summer,summer-autumn,heating seasons and the annual deposition flux were 1.Deposition flux’s search direction was eight-direction search in summer-autumn,and the search direction of the data in other three periods was non-directional search.The search points of winter-spring and the annual deposition flux were 3,and those in heating seasons as well as summer-autumn was 7.(3)During April 9,2015-April 9,2016,average deposition flux of 8 samples in spring-summer,summer-autumn,and heating duration was 0.588 g/(m2 · d),0.343 g/(m2 · d)g/(m 2·d)and 0.303 g/(m 2·d)respectively.The overall characteristics of the deposition flux in the study area with seasonal changes were as follows:The as the deposition flux of the spring-summer(dust season)>the deposition flux of summer-autumn(rainy season)>the deposition flux of heating period(winter and early spring).2 sampling points,No.2 and No.3,were slightly abnormal in 8 sampling points:The deposition flux of the heating period,respectively,compared with the deposition flux of the 2 points were 0.05 g/(m2·d)and 0.0028 g/(m2·d)higher,but the difference is small.(4)In the study area,the spatial distribution of deposition flux in different periods is obvious,higher in the center central and lower around the center.During Spring-summer,autumn-summer and heating period,deposition flux with the biggest changesappearedin the areas surrounding the connection of No.6 and No.7 sampling points,the connection of No.7 and No.8 sampling point,andthe connection of No.3 and No.5 sampling points.The dust deposition flux is high in the vicinity of No.7 sampling point and No.3 sampling point,whilethe dust deposition flux distribution is low mainly in the vicinity of No.5 and No.8 sampling points.(5)During the study period,the prevailing wind direction in the study area was SW(18.31%),followed by SSW(13.9%).The prevailing wind direction in the study area was the same as the prevailing wind direction calculated from the wind direction data of the study area(1981-2008).The scope of the study area was small,and the deposition flux in the short distance of the prevailing wind direction surrounding some samples were obviously different.So prevailing wind direction had a certain influence on the distribution of visible deposition flux,but the impact area was limited.The deposition in the study area mainly came from local pollution sources.In the middle of the study area,the distribution of pollution points was dense,consistent with the deposition flux in the study area,which is high in the middle and low in the surrounding areas. |
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