北京市大气颗粒物分级样品的铅同位素丰度比测量与来源研究

Lead Isotopic Measurements and Source Study for Size-Selective Aerosol Samples in Beijing

报道了北京市2004年夏、冬季分级采样样品的化学组成和铅同位素丰度比数据,并对铅来源进行了分析。采用电感耦合等离子体原子发射光谱（ICP-AES）和电感耦合等离子体质谱（ICP-MS）技术分析了24个无机元素浓度,同时用多接收器电感耦合等离子体质谱（MC-ICP-MS）技术测定铅同位素丰度比。结果表明：细颗粒（PM2.5）中的铅含量明显高于粗颗粒（PM10~2.5）,可吸入颗粒物（PM10）中80%以上的铅存在细颗粒。细颗粒的206Pb/207Pb比值处于1.140~1.156的范围;粗颗粒的206Pb/207Pb比值处于1.127~1.148的范围,总体上低于细颗粒。北京市大气铅来源复杂、多样,有2个或3个以上,主要来源除了燃煤排放还有涉铅有色冶金排放。基于前期工作积累的较多样品测量数据,燃煤排放的206Pb/207Pb代表性比值为1.163 3;涉铅有色冶金排放源的数据较少,初步判断处于1.11~1.15之间,中值为1.13。夏季、冬季细颗粒中燃煤源贡献率分别为0.51和0.59;涉铅有色冶金源的贡献率分别为0.49和0.41。北京市大气铅污染同时具有当地排放和区域性排放的贡献和特征。

Size-selective aerosol samples,both fine fractions（PM2.5） and coarse fractions（PM10-2.5） were collected in 2004 in Beijing.There were 11 pairs in summer and 12 pairs in winter,respectively.For those samples 24 elements were determined using either ICP-AES or ICP-MS,and lead isotope abundances were measured using MC-ICP-MS.It was revealed that lead contents in fine fractions were substantially higher than those of coarse fractions.More than 80% of lead in PM10 samples was in the fine fractions.The 206Pb/207Pb ratios of fine fractions fell in the range of 1.140-1.156,while those of coarse fractions were lower,in the range of 1.127-1.148.There were three or more sources for aerosol lead in Beijing.The major sources include coal combustion and non-ferrous industrial emissions.Based on rich data accumulated so far,the representative 206Pb/207Pb ratio of coal combustion in Beijing is taken as 1.163 3.The data of non-ferrous industrial emissions have been limited and estimated in the range of 1.11-1.15,with 1.13 in the middle.Coal combustion emissions accounted for aerosol lead in Beijing a fraction of 0.51 and 0.59 in summer and winter,respectively;while lead related non-ferrous industrial emissions a fraction of 0.49 and 0.41,respectively.The aerosol lead in Beijing has contributions from both local emission sources and regional ones as well.