重庆典型城区PM_(2.5)生物标志物组分特征及源指示

Composition characteristics and source implications of biomarkers in PM_(2.5) at a typical urban area of Chongqing

于2015年10月~2016年8月在重庆大学A区采集秋冬春夏4个季节PM_(2.5)样品(n=77),分析生物标志物(n-alkanes、UCM、藿烷和甾烷)组分特征,探讨季节变化和对来源的指示.结果表明,重庆沙坪坝区PM_(2.5)中Σn-alkanes(C11~C38)和UCM年均浓度分别为328.69ng/m^(3)和_(2.5)2μg/m^(3),均为冬季最高,夏季最低.28n-alkanes PMF源解析识别出4个因子:化石燃料燃烧(23.45%)、化石燃料残留(29.1%)、生物质燃烧(21.35%)和高等植物蜡排放(26.1%).UCM与可分离烷烃组分比例(U:R)为1.29~3.33.夏季U:R最低,可能是受温度和光照的驱使,微生物和植物的生命活动旺盛所致.藿烷Ts/Tm、C30αβ/C31αβ(22R)和C31αβ(22S)/(22S+22R)的年均值分别为1.15,5.26和0.59,指示以机动车尾气排放为主的高成熟度石油烃输入.甾烷C29αββ/(ααα+αββ)和C29ααα(20S)/(20S+20R)的年均值分别为0.40和0.53,主要指示高成熟度化石燃料残余物输入.PSCF分析表明,Σn-alkanes的潜在源区主要集中在四川东南部和重庆西部及其相接壤附近区域,UCM的潜在源区主要分布在四川东南部.

Seventy-seven PM_(2.5) samples covering four seasons from October 2015 to August 2016 were collected at an urban site of Chongqing University Campus A.These samples were analyzed for biomarkers including n-alkanes,UCM,hopanes and steranes to reveal the composition characteristics,seasonal variation and assess their source implications.The results showed that the annual average concentrations ofΣn-alkanes(C11~C38)and UCM were 328.69ng/m^(3) and _(2.5)2μg/m^(3),respectively.Both of them are the highest in winter,lowest in summer.The PMF analysis of 28n-alkanes identified 4source categories,including fossil fuel combustion(23.45%),fossil fuel residue(29.1%),biomass burning(21.35%)and plants wax emission(26.1%).The ratio of UCM to alkanes(U:R)ranged from 1.29 to 3.33.Possibly owning to the high temperature and intense light,the activities of microorganisms and plants were vigorous and resulted in the lowest U:R value in summer.The annual average of Ts/Tm,C30αβ/C31αβ(22R)and C31αβ(22S)/(22S+22R)for hopanes were 1.15,5.26 and 0.59,respectively,indicating sources from high-maturity petroleum hydrocarbons,such as the exhaustion from motor vehicles.The annual average of C29αββ/(ααα+αββ)and C29ααα(20S)/(20S+20R)for steranes were 0.40 and 0.53,respectively,indicating sources from fossil fuel residues with high thermal maturity.PSCF analysis showed that the potential source areas ofΣn-alkanes were mainly in southeastern Sichuan,western Chongqing and their adjacent areas;while the potential source areas of UCM were mainly in southeastern Sichuan.