青藏高原东南部冰川雪冰重金属元素特征

Characteristics of heavy metal elements deposited on glaciers in the southeastern Tibetan Plateau

雪冰可以很好地记录大气重金属元素的含量水平。基于2015年6月在青藏高原东南部(藏东南)地区采集的4条冰川的雪坑和表层雪冰样品,分析并讨论了雪冰重金属元素特征。结果显示,Pb、Cd等重金属元素含量与高原其他地区雪冰中一致,含量总体较低,显著低于天山和阿尔卑斯山雪冰中Pb和Cd含量,与格陵兰地区雪冰Pb和Cd含量大致相当,但显著高于南极地区雪冰中Pb和Cd含量,这表明藏东南雪冰中元素含量仍代表全球背景地区大气环境状况。元素富集因子结果显示,Pb、Cr、Cd、Cu、Zn、Mo、Sn等发生强烈富集(EFs>10),而以地壳源为主的元素如Fe、Ti、Mn、Th等则富集较弱。主成分分析表明,不同重金属元素的污染来源存在差异;结合后向气团轨迹分析,推断藏东南地区雪冰元素含量不可避免地受到南亚地区人类活动排放污染物的显著影响。目前,藏东南地区冰川呈显著退缩状态,强烈的冰川消融可释放大量的重金属元素进入河流,可能对下游地区的人类生产生活以及生态系统产生重要影响。

Atmospheric heavy metal elements can be preserved in snow and ice. Based on the snowpit and surface snow/ice samples collected from glaciers in the southeastern Tibetan Plateau during June 2015,elements concentrations were analyzed and discussed. The results indicate that the concentrations of heavy metal elements,such as Pb and Cd,are a little lower than that recorded in snow/ice in other regions of the Tibetan Plateau,and much lower than that in Tianshan Mountains and European Alps; they are comparable to that in Greenland and Canadian Arctic,while much higher than that in Antarctica. These results suggest that element concentrations in snow/ice in the southeastern Tibetan Plateau can represent atmospheric conditions in the background of the remote area. The enrichment factors show that elements such as Pb,Cr,Cd,Cu,Zn,Mo and Sn had strongly enriched with EFs10,while crustal elements such as Fe,Ti,Mn and Th had enriched weakly. Principal component analysis suggests that there were different sources of pollution among different heavy metal elements.Using backward trajectories analysis,it is revealed that the anthropogenic emissions from South Asia had paid a significant role on the heavy metal element enrichment recorded on the glacier snow/ice. Nowadays,glaciers on the plateau are retreating rapidly,causing abundant heavy metal elements releasing from glacier meltwater flowing into the rivers,which may profoundly affect the human life,industrial activities and ecosystem in the downstream regions.