STUDY ON SEASONAL VARIATION OF WATER-SOLUBLE IONS IN PM2.5 OF MAIN URBAN AREA IN HENGYANG, CHINA

In order to explore the characteristics and sources of PM2.5 and water-soluble ion pollution in Hengyang City, PM2.5 samples were collected in January, April, July, and September 2019. Mass concentration of PM2.5 he measured by gravimetry and 9 water-soluble ionic components, such as NH4+, K+, Na+, Mg2+, Ca-(2+) and F-, Cl-, SO42-, NO3-, by ion chromatography, and then carried out concentration characteristics, pH, secondary conversion, source analysis and other research work. The results showed that the average seasonal mass concentration of PM2.5 in Hengyang during the sampling period was 94.25 mu g/m(3) in winter, 64.76 mu g/m(3) in spring, 38.30 mu g/m(3) in autumn and 26.30 mu g/m(3) in summer, and the total water-soluble ions accounted for 56.17%. 39.16%, 44.42% and 47.14% of the total mass concentration of PM2.5, respectively. The ratio of anion and cation equivalents shows that PM2.5 is acidic in autumn and winter in Hengyang. and alkaline in spring and summer. The annual average values of SOR were 0.467 and NOR were 0.202, what's more, the secondary conversion of gaseous precursors was obvious in winter, spring and autumn, because their AE/CE was much larger than 0.1. In addition to NH4NO3 and (NH4)(2)SO4, there is also a small amount of NH4Cl in spring and summer. However, on the basis of NH4NO3 and (NILO:Satin autumn and winter, there are still very small amounts of nitrates, such as NaNO3 and KNOT, Source analysis found that water-soluble ions in atmospheric PM2.5 mainly originated from the secondary conversion of industrial emissions, coal burning, biomass combustion, and secondary transformation of gaseous precursors emitted from coal combustion and motor vehicles.