广州PM_(2.5)化学组分特征及其与气象因子的关系

Chemical composition of PM_(2.5) and its relations with meteorological factors in Guangzhou

于2012年12月—2013年12月在广州城区(市站)和东部郊区(九龙)开展为期一年的PM2.5样品采集,并同步收集气象因子和气态污染物质量浓度等数据.结果表明,PM2.5中主要化学组分为有机质(OM)和硫酸盐(SO2-4),分别占市站和九龙PM2.5质量浓度的49.4%和15.2%及57.0%和17.3%.碳质气溶胶(OM和EC)贡献接近50%,二次无机气溶胶(SO2-4、NO-3和NH+4总和,SIA)贡献超过30%.由于以机动车尾气为代表的移动污染源在城市区域贡献较大,市站[NO-3]/[SO2-4]比值显著高于九龙.两个站点[NH+4]/[SO2-4]摩尔质量比均高于1.5,表明观测期间广州市干季大气处于富铵状态.市站和九龙站硫氧化率(SOR)和氮氧化率(NOR)的时空变化趋势与O3类似,表明大气光化学过程是影响广州市SOR和NOR的重要因素.相对湿度低于65%时,SOR和NOR均较高;温度对SOR和NOR的影响有显著的城郊差异.降雨对PM2.5及各化学组分浓度有显著去除作用.

In order to characterize major composition of PM2.5 and study its relations with meteorological factors in Guangzhou,we conducted one-year sampling from December 2012 to December 2013 at one urban site and one rural site,respectively.We analyzed water soluble ions,OC and EC in PM2.5.Gaseous pollutants(SO2,NO2,O3)and meteorological factors(temperature,relative humidity,rainfall precipitation)were also recorded simultaneously.Our results showed that organic matter(OM)and sulfate(SO4^2-)were the major components in PM2.5 at the two sites.Carbonaceous aerosols(OM and EC)contributed about 50%of PM2.5 and secondary inorganic aerosols(SO4^2-,NO3^-and NH4^+)accounted for more than 30%.Higher[NO3^-]/[SO4^2-]ratios were observed at the urban site,probably due to more influence of vehicle exhausts in urban area.The ratios of[NH4^+]to[SO4^2-]were higher than 1.5 at the two sites,suggesting ammonium-rich atmosphere in Guangzhou during our dry-season campaign.The spatial and seasonal trends of sulfur oxidation ratio(SOR)and nitrogen oxidation ratio(NOR)were consistent with those of O3,which indicated that photochemistry could significantly affect sulfate and nitrate formation in the air of Guangzhou.We also found that SOR and NOR were both high under relative humidity below 65%,while the impact of temperature on SOR and NOR was apparently different between urban and rural sites.Rainfall could efficiently remove PM2.5 and its major components.