Particle Size Distribution And Pollution Characteristics Of Water-soluble Ions In Atmospheric Particulates In Jiangbei New District, Nanjing

To characterize the day-night variation and size distributions of water-soluble ions of PM in 2018 and 2019.The date of this article were collected with TH-150C Samlper and MOUDI-14 Impact Sampler.The chemical composition of atmospheric particles was determined by ion chromatography.The pollution characteristics and size distribution of water-soluble ions in atmospheric particles were one of the most important properties of atmospheric particulate matter,the differences in concentration,components and pollution sources of size-fragmented PM were studied.The main listed are as follow:(1)The mass concentrations of TSP,PM_1.8and PM_0.56in summer in Nanjing Jiangbei New Area were higher than that in autumn,contrary to PM_0.1,the proportion of fine particles in autumn was higher than that in summer.Size distribution of the PM mass concentration in summer and atumn were three peaks,the main peak at 0.18?0.56?m in summer,the main peak at 0.32?0.56?m in autumn.The correlation between meteorological elements and sizes distribution of PM showed that the coarse and fine particles were negatively correlated with temperature and relative humidity in summer.(2)The average mass concentration of water-soluble ions was(59.01?30.75)?g·m^-3in winter.The average mass concentration of water-soluble ions at daytime was higher than that at the nighttime.The ratio of NO₃^-and NH₄⁺concentration to total ion concentrations was higher at night,while SO₄^2-and Cl^-were higher during daytime.SO₄^2-,NO₃^-and NH₄⁺(SNA)was the dominant components of water-soluble ions of PM_2.5,the mass concentration of SNA in polluted days was higher than that in clean days.The ratio of anion-cation balance(AE/CE)were more than 1,indicating that the PM_2.5was acidic.NO₃^-and SO₄^2-were the most abundant water-soluble ions of size-fragmented PM in summer and autumn,which were concentrated in PM_0.56and PM_1.8,respectively.NO₃^-and SO₄^2-were mainly distributed in the0.32?0.56?m fine particle segment in summer,and the distribution type is unimodal.In autumn,they mainly exist in the 0.32?0.56?m and 1.8?3.2?m particle size segments,and the distribution type is bimodal.(3)There was a significant linear correlation between NH₄⁺with NO₃^-and SO₄^2-,indicated that it was mainly in the form of NH₄NO₃and(NH₄)₂SO₄in PM_2.5in winter.The PMF source apportionment indicated that the water-soluble ions of PM_2.5mainly derived from motor vehicle emissions,fossil fuel combustion,biomass burning and dust in Nanjing Jiangbei New Area.The mean value of the nitrogen oxidation rate(NOR)in summer and autumn were 0.11 and 0.19,respectively,which were less than 0.1 in PM_0.1.The mean value of the sulfur oxidation rate(SOR)were 0.25 and 0.48,which all particle sizes were greater than 0.1,indicating that there was a high secondary aerosol transformation rate of nitrogen and sulfur,and it was higher in autumn than in summer.The result of PCA on water-soluble ions showed that PM_0.1mainly emitted by vehicle emissions,fossil fuel combustion,dust and industry in summer and in autumn PM_0.1mainly emitted by vehicle emissions,dust and industry.