One Century Air Deposition Of Hydrocarbon Recorded In Travertine In North Tibetan Plateau, China

Twenty-seven samples were collected from travertine in North Tibetan Plateau(NTP), and the concentrations of n-alkanes ranged from 1.02 to 2.12 ng/g. 27 samples are divided into 5 stages, which are consistent with time sequence, according to three parameters: the predominant constituents, abundance distribution of the odd/even terms(CPI), and the contribution ratios of biogenic(Wax-Cn) or anthropogenic(non-WaxCn). N-alkanes from both man-made and natural emit, so the changing of three parameters represents which is in dominant position of two main sources of n-alkanes. In different stage the main source of n-alkanes is disparity and general compliance with historical conditions. From 1951 to 1933(stage 1), the main sources of n-alkanes is natural emit. As time goes on, during the Second World War and the Liberation War(stage 2) n-alkanes originate from burning is in dominant position. In stage 3(1954-1963), as the war was ended natural source return to the main source. In stage 4(1967-1999) due to the development of the western region concentrations of n-alkanes grows slowly and proportion of man-made by burning increase year by year. The last stage(2003-2011) with the development of the tourism industry in NTP produce a lot of nalkanes by burning coal and yak/sheep dung, on the other hand there are more and more touring cars than before certainly to produce more automobile exhaust, which will exacerbate the amount of man-made n-alkanes.In the twenty-seven anarce samples, concentrations of PAHs ranged from 0.62 to 2.97 ng/g. According to the results of PCA, the samples were divided into five groups, which was consistent with sectionalization of n-alkanes. This proves that n-alkanes and PAHs have experienced same atmospheric deposition process, in every periods, both of them, in every periods, produced similar influence by same historical conditions. The major sources of PAHs were distinguished by the fractional proportions and molecular diagnostic ratios in each group. In group I, the PAHs originated mainly from the burning of yak/sheep dung. In group II, PAH sources were dominated by fossil fuel combustion which transported into the NTP by LRAT. The PAHs in samples of group III source of burning of yak/sheep dung of the location is primary. Due to the development of the western region, the main sources of PAHs is both of burning yak/sheep dung and coal. The last groupsources were dominated by traffic emission.