Abstract
A total of 30 samples of total suspended particles were collected at an urban site in Lhasa, Tibet from August 2006 to July 2007 for investigating carbonaceous aerosol features. The fractions of contemporary carbon ( f c) in total carbon (TC) of ambient aerosols are presented using radiocarbon ( 14C) measurements. The value of f c represents the biogenic contribution to TC, as the biosphere releases organic compounds with the present 14C/ 12C level ( f c = 1), whereas 14C has become extinct in anthropogenic emissions of fossil carbon ( f c = 0). The f c values in Lhasa ranging from 0.357 to 0.702, are higher than Beijing and Tokyo, but clearly lower than the rural region of Launceston, which indicates a major biogenic influence in Lhasa. Seasonal variations of f c values corresponded well with variations of pollutants concentrations (e.g. NO 2). Higher f c values appeared in winter indicating carbonaceous aerosol is more dominated by wood burning and incineration of agricultural wastes within this season. The lower f c values in summer and autumn may be caused by increased diesel and petroleum emissions related to tourism in Lhasa. δ 13C values ranged from − 26.40‰ to − 25.10‰, with relative higher values in spring and summer, reflecting the increment of fossil carbon emissions.
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