Climatic and environmental implications from organic matter in Dasuopu glacier in Xixiabangma in Qinghai-Tibetan Plateau

Abstract

A series of organic compounds in snow and ice were identified from Dasuopu glacier in Xixiabangma in Qinghai-Tibetan Plateau. Organic compounds derived from natural organisms include n-alkanes ranging from C15 to C33, normal monocarboxylic acids of C 6 -C 18 , n-alkan-2-ones of C 24 -C 31 and esters. The unstable compounds widely present in lower troposphere disppear in the middle-upper troposphere. I^ots of other organic compounds from petroleum residues were also unexpectedly identified from the glacier, covering pristane, phytane, extended tricyclic terpanes of C 19 -C 29 , C 24 tetracyclic terpane, αβ hopane compounds of C 27 -C 35 , and cholestanes of C 27 -C 29 . The remote Xixiabangma region is unambiguously polluted from anthropology activities. The petroleum residues were proposed to be mainly from the Mideast and India, not from China. The organic pollutants from oil fires ignited during the well-known Gulf War which broke out in 1991 were also recorded in the glacier. Such organic indexes as n C 29 / n C1 7 , nC29/nC27 , n C29/ nC 24 , C 30 -ketone/C 30 -ester, C 24 -tetracyclic-/C 24 -tricyclic-terpane and CPIn ( n standing for n -alkanes) exhibit the same strong seasonal variation as δ 18 0, providing information on the atmospheric circulation of the plateau. These ratios decrease in summer half year when the monsoon dominated, and increase in winter half year when the westerly stream jet dominated.