Elemental compositions of PM_(2.5) and TSP in Lijiang,southeastern edge of Tibetan Plateau during pre-monsoon period

PM2.5 and total suspended particulate （TSP） samples were collected at Lijiang, southeastern Tibetan Plateau, China. Sixteen elements （Al, Si, S, K, Ca, Cr, Mn, Ti, Fe, Ni, Zn, As, Br, Sb, Pb and Cu） were analyzed to investigate their elemental compositions during the pre-monsoon period. The results showed that Ca was the most abundant element in both PM2.5 and TSP samples. The enrichment factors （EFs） ofSi, Ti, Ca, Fe, K and Mn were all below 10 for both PM2.5 and TSP, and these elements also had lower PM2.5/TSP ratios （0.32-0.34）, suggesting that they were mainly derived from crustal sources. Elements Cu, Zn, S, Br and Sb showed strong enrichment in PM2.5 and TSP samples, with their PM2.5/TSP ratios ranging from 0.66 to 0.97, indicating that they were enriched in the fine fractions and influenced by anthropogenic sources. Analysis of the wind field at 500 hPa and calculations of back trajectories indicated that Al, Si, Ca, Ti, Cr, Mn and Fe can be influenced by transport from northwestern China during the dust-storm season, and that S, K, Ni, Br and Pb reached high concentrations during westerly transport from south Asia. Combined with the principle component analysis and correlation analysis, elements of PM2.5 samples were mainly from crustal sources, biomass burning emissions and regional traffic-related sources.

Molecular distribution and seasonal variation of hydrocarbons in PM_(2.5) from Beijing during 2006

Normal （n）-alkanes and polycyclic aromatic hydrocarbons （PAHs） in PM2.5 were collected from Beijing in 2006 and analyzed using a thermal desorption-GC/MS technique. Annual average concentrations of n-alkanes and PAHs were 282 ±96 and 125 ± 150ng/m^3, respectively： both were highest in winter and lowest in summer. C19-C25 compounds dominated the n-alkanes while benzo[b]fluoranthene, benzo[e]pyrene, and phenanthrene were the most abundant PAHs. The n-alkanes exhibited moderate correlations with organic carbon （OC） and elemental carbon （EC） throughout the year, but the relation- ships between the PAHs, OC and EC differed between the heating and non-heating seasons. The health risks associated with PAHs in winter were more than 40 times those in spring and summer even though the PM2.5 loadings were comparable. Carbon preference index values （〈1.5） indicated that the n-alkanes were mostly from fossil fuel combustion. The ratios of indeno[123-cd]pyrene to benzo[ghi]pyrelene in summer and spring were 0.58 ± 0.12 and 0.63 ± 0.09, respectively, suggesting that the PAHs mainly originated from motor vehicles, but higher ratios in winter reflected an increased infuence from coal, which is extensively burned for domestic heating. A comprehensive comparison showed that PAH pollution in Beijing has decreased in the past 10 years.