| To investigate the pollution characteristics and sources of water-soluble ions and heavy metal elements in atmospheric fine particles of Hangzhou,this study sets up two sampling points to collect atmospheric fine particles?multi-stage sampler was used for the water-soluble ions?in Hangzhou,one is located in a residential area near the industrial district and the other is in a commercial and residential area.The water-soluble ions were analysed by IC and the heavy metal elements were analysed by ICP-MS.During the sampling period,the annual average concentrations of PM2.5 at S1and S2 were 87.70±39.42?g·m-3 and 81.96±40.31?g·m-3,respectively.The seasonal change of PM2.5 concentrations was winter>autumn>spring>summer,autumn and winter were the main period which haze frequently occurred.The ratio of daily average concentration of PM2.5 exceeding national standard at two sites was up to 66.4%,and the annual average concentration of PM2.5 was two times more than national standard.The results showed that water-soluble ion was an important component of PM2.5,and the annual average mass concentration of 9 water-soluble ions was 46.63?g·m-3,which accounted for 54.97%of PM2.5.The dominant ions,including Cl-,NO3-,SO42-and NH4+,exhibited a significant seasonal variation in mass concentrations,with the order of winter>autumn>spring>summer.Mass concentration ratio of NO3-and SO42-indicated that the pollution of NO3-was getting worse.The values of sulfur oxidation rate and nitrogen oxidation rate indicated that the secondary particles existed obviously in the atmosphere of Hangzhou and the ratio of the second conversion of SO2 was larger than that of NO2.The factor analysis indicated that secondary aerosol,road dust,building dust and industrial emission were the main sources of PM2.5 in Hangzhou during the sampling period.The analysis of thirteen-stage particles indicated that atmospheric particles in 0.4001.600?m represented a significant share in all sizes of the particles.Cl-,NO3-,SO42-and NH4+and K+were mainly distributed in the fine particles,Ca2+was mainly distributed in the coarse particles.According to the analysis of water-soluble ions in PM1.0,PM1.0-2.5,PM2.5-10,the water-soluble ions in atmospheric particles in winter of Hangzhou were mainly distributed in ultrafine particle PM1.0.The annual average mass concentration of 9 heavy metal elements accounted for3.36%of PM2.5.And the annual average mass concentration of heavy metal elements was in the order of Fe>Al>Zn>Pb>Mn>Cu>Cr>Ni>Cd.There was little difference between two sampling sites about the annual average mass concentration of heavy metal elements,indicating that heavy metal pollution of PM2.5 in Hangzhou had no obvious spatial variations.Different heavy metal elements had different seasonal variation rules.The enrichment factor values of Cr,Ni,Cu,Zn,Cd,Pb were all above ten,indicating that human activity was the main sources of heavy metal elements,and the influence of soil dust was small.The potential ecological risk index showed that the ecological damage degree of Pb,Cd in PM2.5 was extremely strong.The geo-accumulation index indicated that the pollution level of Zn,Cd,Pb in PM2.5 was highest,which belong to the level of serious pollution.Among these elements,the pollution index of Cd was especially high,and special attention should be paid to it in the future research. |
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