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

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.