Characteristics Of Water-soluble Ions In Dry And Wet Deposition In Taiyuan

Atmospheric dry and wet deposition was an important way of removing from atmosphere for particulate and gaseous pollutants,which played an important role in the migration and cycle of pollutants in the ecosystem.Taiyuan is one of the heavily industrialized cities in China, and the emission load of dust and sulfur dioxide took the first place in China.In this study, dry and wet deposition samples were collected from November 2014 to November 2015 in Taiyuan, and pH value and electricity conductivity in wet depositions samples and major water-soluble ions(WSIs) (F?Cl-?NO3-?SO42-?Na+?NH4+?K+?Mg2+? Ca2+) in dry and wet deposition samples were analyzed.Firstly, the chemical compositions and deposition fluxes of WSIs were reported, and then the distribution of WSIs in dry and wet deposition were estimated by the WSI level and deposition flux.In the end, the emission source were discussed by correlation analysis and diagnostic ratios analysis. The results were of great significance to understand the removal ways of atmospheric pollutants by dry and wet deposition and provided scientific evidence for the pollution control and environmental policy-making in Taiyuan.The major conclusions were as follows:(1) The total WSIs in the dry deposition samples were in the range of 1444.99—10390.72 ?g·g-1, with the mean level of 6124.61 ?g·g-1. The results showed that SO42-(3376.82 ?g·g-1),Ca2+(837.43 ?g·g-1), Cl- (827.55 ?g·g-1) and NO3- (586.40 ?g·g-1) were major ions in dry deposition, contributing 92% of the total ions concentration in the dry deposition in Taiyuan.(2) The total WSIs in the wet deposition samples were in the range of 324.08—3357.02 ?eq·L-1, with the mean level of 767.36 ?eq·L-1. The results showed that Ca2+(217.73 ?eq·L-1), SO42- (208.15 ?eq·L-1), NH4+(171.53 ueq·L-1) and NO3- (77.41 ?eq·L-1) were major ions in wet deposition, contributing 87% of the total ions concentration in the wet deposition in Taiyuan.(3) The dry and wet deposition fluxes of WSIs were in the range of 18.96—256.87 mg·(m2·d)-1, with the mean level of 146.16 mg·(m2·d)-1.Dry deposition fluxes of WSIs varied from 18.96 to 52.85 mg·(m2·d)-1 and wet deposition fluxes of WSIs varied from 143.54 to 230.61 mg·(m2·d)-1. Compared with dry deposition, wet deposition was the main way for WSIs removing from the atmosphere in Taiyuan.(4) The total dry and wet deposition fluxes of S were 1.21 t·km-2·a-1, with 0.22 t·km-2·a-1in the dry deposition and 0.99 t·km-2·a-1 in the wet deposition in Taiyuan. The fluxes for the total dry and wet deposition of N were 1.20 t·km-2·a-1, with 0.14 t·km-2·a-1 in the dry deposition and 1.06 t·km-2·a-1 in the wet deposition in Taiyuan.(5) Based on the correlation analysis and diagnostic ratios analysis, coal burning,vehicle exhaust and soil particles were three main sources of WSIs in dry and wet deposition in Taiyuan.