成都市PM10中碳质气溶胶长期来源特点

Long-Term Source Characteristics of Carbonaceous Aerosol in PM_(10) of Chengdu City,China

大气颗粒物中包含多种组分的气溶胶,其中碳质气溶胶由于对人体健康、能见度有较大影响,已受到越来越多的关注.为研究碳质气溶胶的长期变化规律,采集了成都市2009—2013年的PM_(10)样品,对其中所含的无机元素、水溶性离子及碳组分分别进行测定,并使用"PMF(正定矩阵因子分解法)-比值"模型分别对PM_(10)和所含的碳质气溶胶的来源进行分析.结果表明,1月、2月、5月和12月的碳质气溶胶浓度较高,其中1月、2月和12月的OC/EC(有机碳与元素碳质量浓度之比)较高,并且PMF-比值模型计算结果也显示冬季SOC增多,表明冬季可能有更多的二次有机碳(SOC)生成;5月的char-EC/soot-EC(二者质量浓度之比,其中char-EC=EC1-OP,soot-EC=EC2+EC3,它们可更好地区分源类)较高,K含量也较高,表明可能有更多的生物质燃烧排放.PM_(10)解析共发现6类源,依次为地壳扬尘(26.5%)、二次硫酸盐(25.1%)、燃煤&生物质燃烧混合源(17.3%)、二次硝酸盐&二次有机碳混合源(12.3%)、机动车源(11.8%)和水泥尘源(7.0%);碳质气溶胶解析发现,OC主要来源依次为机动车源(38.2%)、燃煤&生物质燃烧混合源(33.1%)和二次有机碳(25.3%),char-EC的主要来源是燃煤&生物质燃烧混合源和机动车源,分别占50.5%和45.4%,soot-EC则主要受机动车影响(达73.2%).研究显示,成都市PM_(10)主要来自于地壳扬尘、二次生成和燃煤&生物质燃烧,而碳质气溶胶主要来自于机动车、燃煤&生物质燃烧.

Atmospheric particulate matter is comprised of a variety of components.Due to the large proportion and the influence on human health and visibility,the carbonaceous aerosol has attracted much attention.For the research on the long-term variation of carbonaceous aerosol,PM 10 samples were collected during 2009-2013 in Chengdu City.The inorganic elements,water-soluble ions and carbon composition were determined.Moreover,PMF-ratio model is applied to quantify the sources of PM 10 and carbonaceous aerosol.Results present that concentration of carbonaceous fractions shows it highest value in winter and May.OC EC ratio is higher in winter and the modeled results show that SOC increased in winter,which might indicate more secondary carbon(SOC)in winter.Furthermore,char-EC soot-EC and K concentration is higher in May,which may illustrate more biomass combustion in May.Six source categories are identified,including crust dust(26.5%),the secondary sulfate(25.1%),coal combustion&straw burning(17.3%),secondary nitrate&the secondary organic carbon(12.3%),vehicle exhaust(11.8%),cement dust(7.0%).Major contributors to OC in PM 10 are vehicular exhaust(38.2%),coal combustion&straw burning(33.1%)and SOC(25.3%).The coal combustion&biomass combustion and vehicle exhaust contributed 50.5%and 45.4%of char-EC.Vehicle exhaust dominates soot-EC(73.2%)in PM 10.PM 10 mainly comes from the crust dust,secondary sulfate,coal combustion&straw burning.The carbonaceous aerosol mainly comes from the vehicle exhaust and coal combustion&straw burning.