Trace elements and lead isotopic composition of PM₁₀in Lhasa, Tibet

This paper presents the first detailed investigation on airborne trace metals and their potential major sources at Lhasa, the largest city in Tibetan Plateau (TP). The whole year PM10samples were collected during September 2007 and August 2008. The annual average concentration of PM10in Lhasa was 51.8±42.5μgm-3, lower than those of major Asian cities. Distinct seasonal patterns were observed in PM10concentration, with higher concentrations in winter, and lower in summer. The mean elemental concentrations were generally comparable with other urban areas, but significantly higher than those from a remote site in TP (i.e., Nam Co). Crustal elements, including Na, Mg, Al, K, Ca, Sc, Ti, V, Mn, Fe, As and Ba, had similar seasonal patterns in PM10, while other elements, such as Cr, Co, Ni, Cu, Zn, and Cd, had less distinct seasonal variations, suggesting more anthropogenic inputs of the latter group. The result of principle component analysis (PCA) on trace elements demonstrated that fugitive dusts, traffic emissions and waste incineration activities were probably the major sources of anthropogenic metals in the atmosphere at Lhasa. The Pb isotopic compositions revealed that the metal was mainly originated from nature background with a minor contribution from the cement factory. The data obtained in this study can be useful for making pollution control strategies in the city, and also valuable for trace element studies in other environmental medium, such as snow, ice core, and lake sediments in the TP region.