太原市大气PM_(2.5)中铅同位素特征研究

使用ICP-MS测定太原市2009年夏季至2010年春季典型月份中存在于PM2.5上的铅(Pb)及同位素特征,分析了铅的浓度水平、季节变化特征,探讨了铅同位素丰度比特征,并由富集因子法初步解析了铅的来源。结果显示,太原市环境大气中存在于PM2.5上的Pb含量为270.83ng/m3,低于我国环境空气质量标准(GB3095-2012)中对颗粒物中铅的年均限值,在国内属中等水平。冬季存在于PM2.5中的Pb浓度水平最高,与取暖燃煤排放有关;扬尘中的Pb富集则对春季的Pb污染有较大贡献。Pb与PM2.5的相关性显示夏季和冬季二者来源一致,皆为燃煤排放;206 Pb/207 Pb与208 Pb/206 Pb的同位素丰度比特征也表明PM2.5中Pb的主要源于燃煤排放,由于冬季煤炭消费量较高,其燃烧排放对PM2.5中Pb的贡献高于其他季节。采样期间PM2.5中Pb的富集因子(20.45)显示,Pb主要源于人为活动的排放;春季的富集因子(10.76)接近10,表明春季时自然源的Pb对PM2.5的贡献较大。

Isotope Characteristics of Lead in PM2.5of Taiyuan City, China

PM_2.5 samples were collected in Taiyuan City, China from summer 2009 to spring 2010, and lead (Pb) and its isotopic abundance were detected using ICP-MS. Levels and seasonal variation characteristics of lead were reported, and the characteristics of lead isotope abundance and its sources were discussed by enrichment factor method. Results show that the average concentration of Pb in PM_2.5 in Taiyuan was 270.83 ng/m³ during the sampling time, lower than that in the ambient air quality standards of China (GB3095-2012), but still at the medium pollution level in most cities in China. The concentration of Pb in PM_2.5 in winter was the highest the whole year due to the excessive coal combustion for heating. In spring, Pb from dust might be the main source for the Pb enrichmentin PM_2.5. Pb and PM_2.5 had the same main source of coal emission both in summer and winter by the correlation relationship. The isotopic abundance ratios of ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb show that the main source of Pb in PM_2.5 was coal emissions, especially in winter. Enrichment factor of Pb was 20.45 for the whole samples, and was mainly related to human activities. In spring, the enrichment factor was 10.76 and means the more contribution of natural enrichment.