青藏高原冰芯重建大气汞沉降历史的时空差异及其影响机理研究

Mercury (Hg) is a toxic heavy metal and a global pollutant with special physical and chemical properties. Snow/ice are globally regarded as excellent archives for documenting the modern and past changes in atmospheric Hg deposition. Known as the "Third Pole", the Tibetan Plateau is remote, isolated, and presumed to be a pristine region characterized by extremely high altitude and harsh climatic conditions. Therefore, ice cores retrieved from the high altitude glaciers of the Tibetan Plateau are ideal for historical reconstruction of Hg pollution. In this proposed research, several deep ice cores were drilled from different climatic regions to reconstruct the variation of atmospheric Hg deposition during the past several hundred years over the Tibetan Plateau. Combined with ice core records for other chemical/physical parameters, we plan to comprehensively interpret the temporal and spatial differences in long-term variation of atmospheric Hg deposition by a contrastive and integrated analysis of several ice core records, and explore the influence mechanisms behind these differences. Furthermore, isotope signatures of Hg from ice core records were introduced to further interpret the temporal and spatial differences in historical records of atmospheric Hg deposition, and quantify the relative contribution from anthropogenic Hg emissions since the onset of the industrial period to different climatic regions of the Tibetan Plateau. This proposed research will not only enhance our understanding of Hg biogeochemical cycling in the "Third pole" region, but also provide beneficial reference in forecasting the trends in Hg release through glacier melting and assessing the potential environmental risks to downstream ecosystems. Most importantly, the proposed research will offer scientific basis for Chinese government to better fulfill the international Hg convention.

汞是一种具有特殊物理化学性质的有毒重金属元素和全球性污染物。雪冰是记录大气汞沉降的独特环境介质；青藏高原具有独一无二的“高寒高冷”气候特征和广泛发育冰川区，是全世界范围开展冰芯记录大气汞变化历史研究的理想场所。本研究拟通过在青藏高原典型气候区钻取的数支深孔冰芯高分辨率重建过去数百年来大气汞沉降的变化历史；结合相关冰芯记录的环境参数和指标，通过综合集成对比分析揭示造成青藏高原大气汞沉降历史时空差异的原因及其影响机理；利用汞同位素对冰芯记录大气汞沉降历史时空差异性进一步深入探讨，并量化人类活动释汞(工业革命以来)对青藏高原不同气候区的贡献率。本研究将提升“第三极”地区雪冰汞地球化学循环规律的认知水平，为预测未来冰川释汞变化趋势和评估汞污染物“二次释放”的环境风险提供重要参考，以及为我国更好履行国际汞公约提供科学依据。

汞是一种具有特殊物理化学性质的有毒重金属元素和全球性污染物。雪冰是记录大气汞沉降的独特环境介质；青藏高原具有独一无二的“高寒高冷”气候特征和广泛发育冰川区，是全世界范围开展冰芯记录大气汞变化历史研究的理想场所。本研究拟通过在青藏高原典型气候区钻取的数支深孔冰芯高分辨率重建过去数百年来大气汞沉降的变化历史；结合相关冰芯记录的环境参数和指标，通过综合集成对比分析揭示造成青藏高原大气汞沉降历史时空差异的原因及其影响机理；利用汞同位素对冰芯记录大气汞沉降历史时空差异性进一步深入探讨，并量化人类活动释汞（工业革命以来）对青藏高原不同气候区的贡献率。本项目总体上根据研究计划执行，并拓展了部分研究内容。主要研究成果包括：1）结合冰芯和湖芯记录集成重建了500年来大气汞沉降历史记录，揭示了高原冰芯湖芯汞记录主要指示了南亚和区域大气汞二次大战以来显著持续升高的历史；2）利用湖芯重建了喜马拉雅山南坡湖芯汞同位素记录，揭示了二战以来南亚大气汞排放持续升高，湿沉降是偏远地区湖泊汞沉降的主导途径；3）冻土样品汞同位素特征揭示青藏高原的生态系统受跨境大气汞传输和沉降的显著影响；4）通过喜马拉雅山南北坡2个典型城市站点大气颗粒态汞的研究，揭示了第三极地区大气汞的传输、沉降和迁移转化与颗粒态汞密切相关；5）分析了青藏高原7条冰川冰尘样品，揭示了冰尘对大气汞的强烈富集。在本项目的支持下，已在国内外一流刊物上发表论文10篇（SCI论文10篇）。培养中国科学院青年创新促进会成员1名，博士生1名。本项目的成果对理解青藏高原汞的地球化学循环提供了数据和理论支撑，为我国更好的履行国际汞公约提供科学依据。