Chemical Characteristics of PM10 at Background Stations of Central and Eastern China in 2016-2017

The characteristics of PM10 and its chemical composition from December 2015 to December 2017 are studied at three regional atmospheric background stations（Longfengshan,Lin'an,and Jinsha） in central and eastern China.The water-soluble ions(F-,Cl-,NO3-,SO42-,PO43-,Na+,K+,NH4+,Ca2+,Mg20),carbon-containing compounds（OC,EC） and main elements in PM10 samples are analyzed.The average PM10 concentration at Lin'an(62.2±36.6 μg·m-3) during the whole period is the highest,followed by Jinsha(57.6±31.8μg·m-3),and that at Longfengshan(57.5±55.3 μg·m-3) is the lowest.At those stations,the annual PM10 mass concentrations are lower than the national second-level air quality standard.The concentrations of PM10in 2016-2017 show a downward trend,with the reductions of concentrations about 29.3% at Lin'an and 26.2% at Jinsha compared with the results during the year of2013.The concentrations of SO42-,NO3-and NH4+during the whole period are 9.9,8.2 μg·m-3and 3.7 μg·m-3at Lin'an,and 10.2,6.7 μg·m-3 and 2.6 μg·m-3at Jinsha,respectively,which are all higher than those at Longfengshan,with the average concentrations of 5.9 μg·m-3 for SO42-,4.9 μg·m-3 for NO3-,and 2.1 μm-3 for NH4+.However,the ratio of NO3-/SO42- at Longfengshan and Lin'an are relatively higher.The concentrations of OC and EC during the whole period are 10.1μg·m-3 and 2.7μg·m-3 at Longfengshan,6.1 μg·m-3 and 3.1 μg·m-3 at Lin'an,and 4.7 μg·m-3 and 2.3 μg·m-3 at Jinsha.Compared to the year of 2013,the concentrations of SO42-,NH4+and OC during the whole period decrease by 38.1%,26.0%,and 55.6% at Lin'an,respectively,and decrease by 46.3%,51.9%,and 44.7% at Jinsha,while the concentrations of NO3-increase by 12.3% and 15.5% at Lin'an and Jinsha,respectively.The concentrations of EC decreases by 27.9 % at Lin'an,but increases by 4.5 % at Jinsha.The ratio of NO3-/SO42-increase obviously at all the stations,which indicates the increases of nitrate aerosols,due to the continuously control of coal combustion emissions and increase of car ownership.The seasonal concentrations of PM10,NO3-,EC and the ratio of NO3-/SO42-are lowest in summer at three stations.Meanwhile,the mass concentrations of SO42-,NO3-and NH4+are basically higher in winter than in other seasons.