北京典型污染过程PM_(2.5)的特性和来源

Characteristics and sources of PM_(2.5) in typical atmospheric pollution episodes in Beijing

通过采集北京2010年12月—2011年3月冬春季节大气细颗粒物PM.25样品,分析了冬春季典型污染时段灰霾和沙尘期间大气细颗粒物PM.25的质量浓度和其中元素、水溶性离子、有机组分OC和EC特性,及其季节变化和来源。结果表明,北京灰霾和沙尘期间PM2.5日均质量浓度分别高达301.8μg/m3和284.8μg/m3,是美国EPAPM2.5日均质量浓度限值(35μg/m3)的8.62倍和8.14倍。灰霾时段,人为污染元素(S、Cu、Zn、As、Se、Cd、Sb、Pb)、二次无机离子(NH4+、NO3-、SO24-)和二次有机碳(SOC)的质量浓度均高于沙尘天气和非污染天气。沙尘天气时地壳元素(Na、Mg、Al、Ca、Fe等)的质量浓度高于灰霾天气和非污染天气。北京冬春季节PM2.5主要来源于燃煤和工业过程、二次转化、地面扬尘、机动车尾气和生物质燃烧。灰霾污染时段二次转化贡献率较高,沙尘污染时段地面扬尘贡献率较高。

To study the characteristics and sources of PM2.5 in typical atmospheric pollution episodes during winter and spring in Beijing, the samples of PM2.5 were collected at the air quality monitoring site during winter and spring from 12/2010 to 03/2011. The periods are typical seasons for two types of heavy air pollution, i.e. haze and dust to happen often. Concentration of PM2.5, elements, water soluble ions and organic and elemental carbons of PM2.5 were analyzed for typical haze, dust, unpolluted weather during winter and spring. The results indicated that daily concentrations of PM2.5 during haze and dust days were up to 301.8 ＆mu;g/m3 and 284.8 ＆mu;g/m3, that were 8.62 and 8.14 times of the daily standard of EPA. Enrichment factor method was used to analyze the natural sources or anthropogenic sources of different elements during non heavy air pollution periods. Polluting elements S, Cu, Zn, As, Se, Cd, Sb, Pb were mainly released from coal combustion, motor vehicle exhaust and waste burnt; while Na, Mg, Al, Ca, Fe were main crustal elements. NH4＋, NO3-, SO42- were found to be the dominant ionic species of PM2.5. The value of OC/EC （4.085） exceeded 2 suggesting that the OC of Beijing during haze belongs to secondary pollution source. Concentrations of anthropogenic source elements S, Cu, Zn, As, Se, Cd, Sb, Pb in PM2.5during haze were higher than that of unpolluted weather and dust. The concentrations of secondary inorganic particles NH4＋, NO3-, SO42- and secondary organic carbons of PM2.5 during haze were higher than that of another two types of weather. Concentrations of crustal elements Na, Mg, Al, Ca, Fe during dust days were higher than that of unpolluted weather and haze. PM2.5 were mainly released from coal combustion and industry, secondary reaction, soil, motor vehicle and waste burnt during winter and spring. Contribution of secondary reaction was higher than other sources during haze, while contribution of soil was higher than others during dust.