Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing, School of Science, Beijing 100049, China.
Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing, School of Science, Beijing 100049, China.
Environ Int. 2019 Mar;124:294-301. doi: 10.1016/j.envint.2018.12.057. Epub 2019 Jan 17.
Snow is an efficient scavenger for the deposition of contaminants. Atmospheric transport and snow deposition jointly control the distribution of pollutants in remote mountain/polar regions. But can the contaminants contained within snow be used to reflect the interactions of air circulation patterns? The physicochemical properties of perfluoroalkyl substances (PFASs) are unique because of their high water solubilities. Taking advantage of this, 15 surface-snow and 3 snow-pit samples were collected across a vast area of western China (spanning 20° of latitude and 25° of longitude), to investigate the concentrations, composition profiles (fingerprints), and deposition fluxes of PFASs. Both a high concentration (3974 pg/L) and deposition flux (4.0 μg/m/yr) for a total of 16 PFASs were found in the snow at Yulong, the most southern sample site, possibly because of its close proximity to source regions of pollutants in South Asia and high rate of snow deposition. Perfluorobutanoic acid was the most commonly found chemical in snow, but in general the PFAS composition in the snow of western China showed large spatial differences, with long-chain (C > 10) PFASs being relatively dominant in the north and west of the region and short-chain (C < 6) PFASs in the south and east. On the basis of the different compositions of PFASs in the snow of western China and the previously reported features of pollutant sources in Europe and India, we found that PFASs in snow can be used as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon. The belt along 33°N is a key location where both the Indian Monsoon and westerly winds can arrive/interact; however, the contribution of the monsoon was found to be above 70%, while that of the westerly winds can be lower than 30%. The western part of the 33°N belt was found to be more vulnerable to the Indian Monsoon, and could be grouped into the monsoon domain, while the influence of the westerly winds increased from west to east along the belt. This finding is opposite to previous results, which reported that the western part of the 33°N belt was mainly under the influence of the westerly winds, and for the first time quantifies the relative contribution of westerly winds and the Indian Monsoon to the atmospheric transport of chemicals.
雪是污染物沉积的有效清除剂。大气传输和雪沉积共同控制着污染物在偏远山区/极地地区的分布。但是，雪中所含的污染物能否用于反映空气环流模式的相互作用？全氟烷基物质（PFAS）的物理化学性质因其高水溶性而具有独特性。利用这一点，在中国西部广阔的地区（跨越 20 度的纬度和 25 度的经度）收集了 15 个表面雪和 3 个雪坑样本，以调查 PFAS 的浓度、组成分布（指纹）和沉积通量。在最南端的玉龙，雪样中发现了总共 16 种 PFAS 的高浓度（3974 pg/L）和沉积通量（4.0 μg/m/yr），这可能是因为其靠近南亚污染物的源区和高降雪率。在雪样中最常见的化学物质是全氟丁酸，但总的来说，中国西部雪样中的 PFAS 组成表现出很大的空间差异，长链（C>10）PFAS 在该地区的北部和西部相对占主导地位，而短链（C<6）PFAS 在南部和东部占主导地位。根据中国西部雪样中 PFAS 的不同组成以及欧洲和印度先前报道的污染源特征，我们发现雪中的 PFAS 可用作跟踪西风和印度季风相互作用的大气示踪剂。33°N 带是西风和印度季风都能到达/相互作用的关键位置；然而，季风的贡献被发现超过 70%，而西风的贡献可能低于 30%。33°N 带的西部更容易受到印度季风的影响，可以被归为季风区，而西风的影响则沿着带从西向东增加。这一发现与之前的结果相反，之前的结果报告称，33°N 带的西部主要受西风的影响，这是首次量化西风和印度季风对化学物质大气传输的相对贡献。
