三极雪冰中铅浓度变化及其污染来源同位素示踪研究进展

Research progress on changes of lead concentration and their isotope tracing of pollution sources in tripolar snow and ice

铅是一种对人类危害极大的有毒重金属元素,示踪铅的来源是控制铅污染的前提。由于铅同位素在自然过程中难以发生明显的分馏而保留了污染源区的特点,成为追踪铅污染源强有力的“指纹”工具。雪冰作为冰冻圈重要的环境介质,因具有保存大气铅的特征,对雪冰的研究可以重建区域和全球的大气污染变化,探讨过去铅排放的活动历史。本文系统地总结了三极地区(南极、北极、青藏高原及周边地区)雪冰中铅浓度与铅同位素记录、空间分布以及使用铅同位素对雪冰铅源进行识别与解析的相关研究。结果表明:三极地区雪冰铅浓度呈现第三极>北极>南极的空间分布特征,其中第三极北部地区雪冰中铅浓度整体较南部偏高且拥有更低的^(206)Pb/^(207)Pb比值。冰芯环境记录表明,铅污染显著发生在古罗马和中世纪时期、工业革命时期(采矿、冶炼、燃煤)和20世纪下半叶(含铅汽油使用前后),三极地区雪冰中铅浓度峰值主要出现在20世纪70年代左右。铅同位素示踪显示矿物粉尘是三极地区雪冰中铅的主要自然来源,其中南极不同地点雪冰还受到火山活动不同程度的影响。南极雪冰中的铅污染主要来源于澳大利亚和南美洲国家,北极雪冰中的铅污染主要来源于北美和欧亚大陆,第三极不同冰川雪冰中的铅来源存在差异。

Lead is a toxic heavy metal element that is extremely harmful to humans.Tracing the source of lead is a prerequisite for controlling lead pollution.Since the lead isotope is difficult to undergo obvious fractionation in the natural process and retains the characteristics of the pollution source area,it has become a powerful“fingerprint”tool for tracking lead pollution sources.As an important environmental medium of the cryosphere,snow and ice have the characteristics of preserving atmospheric lead.The study of snow and ice can reconstruct regional and global atmospheric pollution changes and explore the activity history of past lead emissions.This paper systematically summarizes the lead concentration and lead isotope records,spatial distribution in snow and ice in the three polar regions(Antarctic,Arctic,Qinghai-Tibet Plateau and surrounding areas),and related studies on the identification and analysis of lead sources in snow and ice using lead isotopes.The results show that the lead concentration in snow and ice in the three poles presents the spatial distribution characteristics of the Third Pole>Arctic>Antarctic,and the lead concentration in snow and ice in the northern part of the Third Pole is higher than that in the south and has a lower ^(206)Pb/^(207)Pb ratio.Ice core environmental records show that lead pollution occurred significantly during the Ancient Roman period and the Middle Ages,the Industrial Revolution period(mining,smelting,coal burning),and in the second half of the 20th century(before and after the use of leaded gasoline),with the peak concentration of lead in snow and ice in the tripolar region mainly appeared around the 1970s.Lead isotope tracers show that mineral dust is the main natural source of lead in snow and ice in the tripolar region,and the snow and ice in different locations in Antarctic are also affected by volcanic activities to varying degrees.The lead pollution in Antarctic snow and ice mainly comes from Australia and South American countries,the lead pollution in Arctic snow and ice mainly comes from North America and Eurasia,and the sources of lead in different glaciers and snow ice of the Third Pole are different.