The Tracers Of Combustion Emission In Snow Of Tibetan Plateau And Their Environmental Implications

The Tibetan Plateau and its surrounding mountains are referred to as "the Third Pole". Compared to the other Polar regions, the Tibetan Plateau is more close to anthropogenic zone, which make it an ideal area for the research on the relationship between human activities and global climate change. Recent studies have shown that the atmospheric pollutants from the south side of the Himalayas(i.e. Atmospheric Brown Clouds, ABCs) could enter the Tibetan Plateau, and may exert profound impacts on the regional climate and environment. Research about combustion emission tracers in snow is very rare in the world at present, mainly limited by the sample treatment method or instrument. Through the analysis of the black carbon(BC), ions, biomass-burning acids, etc. in snowpit and seasonal snow samples in Tibetan Plateau, the main purpose of this dissertation is to distinguish the relative contribution to BC and dissolved organic carbon(DOC) from different energy structure. Furthermore, this research aims to reveal the sources and the transport pathway of these compounds basing on backward air mass trajectories, and to evaluate the climatic/environmental significance of the combustion emission.In general, the main results achieved in this researchare are as follows:(1) An experimental protocol on BC analysis in snow or ice sample using Single Particle Soot Photometer(SP2) was first established in China. Based on the new developed method, the BC concentrations of snowpit and seasonal snow samples from Tibetan Plateau were successfully measured. The online recovery could be higher than 75%.(2) This is the first study to use SPE-GC-MS to measure three biomass-burning acids in snow samples. The detection limit of the three acids are 0.002 ng mL-1 for p-hydroxybenzoic acid, 0.001 ng mL-1 for vanillic acid, and 0.004 ng mL-1 for dehydroabieticacid, respectively, which is low enough to treat the snow samples with low concentration level in Tibetan Plateau. The concentrations of these three acids in the snowpit and seasonal snow samples in Tibetan Plateau are presented for the first time in the dissertation.(3) The contribution fractions to DOC and BC from different energy structure were quantified through the relationship and distribution pattern among the ions and biomass-burning acids concentration and also by the aid of the Positive Matrix Factorization(PMF) model. The results indicated that biomass burning was the main source of DOC in the snow and ice in Tibetan Plateau(49.9%) while fossil fuel burning and biomass burning contributed almost the same to BC(45.7% and 49.8%,separately). In particular, the south part of Tibetan Plateau was significantly influenced by the air pollutants from South Asia.(4)The optical properties of dissolved organic matter(DOM) in snow samples were explored. The Mass Absorption Efficiency at 365nm(MAE365) of DOM in the snow samples in Tibetan Plateau are comparable with those in aerosol samples otherwhere. However, in consideration of the high OC/EC ratio in snow, the influence of DOM to the snow albedo can not be ignored. Furthermore, it could be observed from the fluorescence Excitation-Emission Matrices(EEM) that the natural organic matters such as plant, spores mixed with soil dust were also important sources to the DOM in Tibetan Plateau.