青藏高原五条冰川表雪中痕量元素的空间分布及污染评估

Spatial distribution and pollution assessment of trace elements in the surface snow of five glaciers on the Tibetan Plateau

为了认识青藏高原雪冰中痕量元素的空间分布特征与污染程度,对2013年4-5月采自求勉雷克、煤矿、玉珠峰、小冬克玛底和古仁河口冰川的表面样和雪坑样进行消解处理,并利用高分辨扇形磁场等离子体质谱仪(ICP-SFMS)测试了样品中19种痕量元素(Al、As、Ba、Co、Cr、Cs、Cu、Fe、Li、Mn、Mo、Pb、Rb、Sb、Sr、Ti、Tl、U、V)的总浓度.通过对5条冰川表面样进行空间对比,发现痕量元素在唐古拉山以北的求勉雷克、煤矿和玉珠峰冰川中浓度较高,在3条冰川中元素浓度的平均值在0.05 ng·g^(-1)(Tl)—6579.62 ng·g^(-1)(Al)之间,痕量元素在唐古拉山小冬克玛底冰川及唐古拉山以南的古仁河口冰川中浓度较低,在小冬克玛底冰川中元素的浓度介于0.004 ng·g^(-1)(Tl)—103.44 ng·g^(-1)(Al)之间,在古仁河口冰川中元素的浓度介于0.006 ng·g^(-1)(Tl)—361.83 ng·g^(-1)(Al)之间.计算痕量元素总浓度的富集系数(EF)表明,在5条冰川雪冰中的V、Mn、U、Ba、Rb主要来自于地壳粉尘,Sb、Mo、Pb、Cu、As在一些冰川雪冰中具有明显或较为严重的污染(EF≥5),这5种元素可能来自于有色金属冶炼、交通排放、化石燃料燃烧等人类活动.利用后向轨迹的聚类分析表明,5条冰川在非季风时期主要受到盛行西风的影响,其中求勉雷克、煤矿和玉珠峰冰川中的痕量元素主要来自中亚及新疆等地,小冬克玛底和古仁河口冰川中的痕量元素则主要来自于南亚及青藏高原西部地区.

In order to investigate the spatial distribution and degree of pollution of trace elements in snow and ice from the Tibetan Plateau （TP）,surface snow and snow pit samples were collected from Qiumianleike （QMLK）,Meikuang （MK）,Yuzhufeng （YZF）,Xiaodongkemadi （XDKMD） and Gurenhekou （GRHK） glaciers during April to May of 2013. The total concentrations of 19 trace elements （Al,As,Ba,Co,Cr,Cs,Cu,Fe,Li,Mn,Mo,Pb,Rb,Sb,Sr,Ti,Tl,U,V） in digested snow samples were determined by inductively coupled plasma sector field mass spectrometry （ICP-SFMS）. Comparing the surface snow samples of the 5 glaciers,the results indicate that the concentrations of the trace elements in the QMLK,MK,YZF glaciers （the region north of Tanggula Mountains （TGL Mts.）） were higher than those in the XDKMD glacier （TGL Mts.） and GRHK glacier （the region south of TGL Mts.）. The average concentrations of the trace elements in the QMLK,MK and YZF glaciers were between 0.05 ng·g-1 （Tl） and 6579.62 ng·g-1 （Al）. The concentrations of the trace elements in the XDKMD glacier were between 0.004 ng·g-1 （Tl） and 103.44 ng·g-1 （Al）, and those in the GRHK glacier were between 0.006 ng·g-1 （Tl） and 361.83ng·g-1 （Al）. EF calculations show that V,Mn,U,Ba and Rb might originate from the dust in 5 glaciers. Pollution of Sb,Mo,Pb,Cu and As were more serious （EF≥5）,which might derive from human activities such as nonferrous metals melting,traffic emission and fossil combustion. The cluster analyses of backward air trajectories indicate that westerly air masses prevailed in the 5 glaciers during the non-monsoon seasons. The trace elements from Central Asia and Xinjiang province could be transported to the QMLK,MK and YZF glaciers,while the trace elements from South Asia and the western TP could be transported to the XDKMD and GRHK glaciers.