中国西部雪冰中铅污染的时空分异格局与形成机制

The atmospheric environment in mountainous area of western China is highly sensitive to climate change and human activities. The snow and ice record has been recognized as an effective indicator in the global change research, and mountain glaciers have been used as natural archives for studying historical trends of anthropogenic pollutants such as heavy metals. To accurately evaluate the impact of human activities on the regional atmospheric environment in the western China, it is necessary to carry out researches of snow/ice on a widespread region and longer time scales. Based on the heavy metal concentration and stable lead (Pb) isotopic composition of snow samples in a series of snow-pits of 14 typical glaciers from western China, the project will be focused on the temporal and spatial variation characteristics, source identification/apportionment of Pb in the western China. The transport pathways of Pb will be investigated by the CALIPSO and HYSPLIT models. A comprehensive record of Pb concentration and isotopes will also be determined from a recent 173m deep ice core from Laohugou glacier No.12. Qilian Mountain, spanning the last 400 years from 1600 to 2011 AD. Furthermore, historical emission patterns of anthropogenic Pb has reconstructed in the ice core, especially from the Industrial Revolution. This research will have significance for understanding the deposition mechanism of Pb in snow and ice, and will be helpful for further investigating the influence of human activities on the regional atmospheric environment.

我国西部高山地区具有对气候环境变化和人类活动影响的高度敏感性，人类活动释放的铅等污染物在该地区留下了不少证据，如雪冰记录的研究结果。深入了解人类活动对区域大气环境的影响，有必要对西部地区雪冰中铅开展更大范围和更长时间尺度的研究。本项目拟通过分析西部地区14条冰川雪坑中重金属含量及铅稳定同位素组成，探讨西部地区现代雪冰中铅沉积的时空分异格局，结合铅同位素示踪技术，分析雪冰中铅污染的主要来源，采用铅同位素二元混合模型定量地评估各污染源的贡献；并以2011年新钻取的祁连山老虎沟12号冰川173m深冰芯为研究对象，重建过去4百年（~1600-2011AD)，特别是工业革命以来铅的环境记录。集成研究该地区冰芯、湖泊沉积等代用指标的相关研究成果，探索不同时期人类污染对雪冰中铅的影响程度及成因。研究结果对于认识西部地区雪冰中铅沉积的机制有重要意义，对我国和相关国家和地区铅污染防治也将产生积极的推动作用。

中国西部高山地区能够敏感地响应气候和环境的变化，人类活动释放的铅等污染物在该地区留下了不少证据，比如雪冰记录的研究结果。评估人类活动对区域大气环境的影响，有必要对西部地区雪冰中铅进行更广范围和更长时间尺度的研究。采用TEM-EDX法分析了青藏高原典型冰川微粒单颗粒特征及其差异性，微粒主要由矿物粉尘（53.2％）、烟尘（16.5％）、有机颗粒（16.5％）、钙硫酸盐（7.6％）和飞灰颗粒（6.2％）组成，人为污染物质在位于青藏高原边缘地区冰川研究站点，气团后向轨迹聚类分析显示青藏高原边缘地区人类污染物含量较高与夏季周边地区（如南亚地区）人为污染物跨区域输入关系十分密切。（2）老虎沟地区微粒物源端元分析显示微粒来源主要包括2个部分，即远距离传输部分（中值粒径2.82~3.86μm）与局地区域粉尘贡献（中值粒径7.4~9.25μm），远距离传输部分具有较小的中值粒径和物源贡献率（24~52.2%）。对气流后向轨迹分析显示，其大气环境受来自于中亚粉尘源区的陆源矿物与河西走廊的人类活动污染共同作用。（3）西部地区4条冰川微粒Pb206Pb/207Pb变化范围：1.1514−1.2022；208Pb/207Pb：2.4243−2.5182。Pb同位素总体表现北部偏贫化，南部富集的特点。同位素端元分析结果显示，微粒Pb呈现自然与人为来源混合的特点，同位素二元混合模型估算结果显示人为Pb贡献率在28.6~47.2%，天山、老虎沟和玉龙等靠近人类聚集区的冰川具有更高的人为Pb贡献率。