Composition and sources of polycyclic aromatic hydrocarbons in cryoconites of the Tibetan Plateau glaciers.

Dark-colored cryoconite can absorb substantial solar radiation, reduce the surface albedo of glaciers, and thus greatly accelerate glacier melting. Organic matters in cryoconites such as polycyclic aromatic hydrocarbons (PAHs) are kind of the light absorbing compositions. In this study, 15 PAHs containing 3-7 rings were identified in 61 cryoconites samples collected from seven glaciers over the Tibetan Plateau (TP). The average concentration of total PAHs in cryoconites samples was in the range of 6.67-3906.66ngg-1 dry weight. The highest average total PAH concentration was found in the southeastern TP, followed by the northern TP. The central TP contained the lowest amount of PAHs. Moreover, correlation analysis showed that total organic carbon (TOC) and grain size were only a minor factor for the accumulation of PAHs in cryoconites of the TP. Factor analysis and diagnostic ratios indicated that the PAHs were produced mainly from the incomplete combustion of coal, fossil fuels and biomasses. The exhaust gas of locomotives also contributed to the accumulation of PAHs in the glaciers. The PAHs in these seven glaciers showed low toxic equivalent quantity (TEQ), and thus had low biological risk. Nevertheless, the pollution of PAHs in the southeastern TP needs to be addressed.