Collaborative Research: Soil-Snow-Atmosphere Exchanges of Mercury in the Interior Arctic Tundra

这个项目的目标是表征土壤-雪-大气的汞动力学（Hg）在冰雪为主的北极苔原。积雪中的汞从非挥发性形式化学转化为气态元素汞（GEM），可导致汞从雪中大量脱气，从而减少大气沉积的影响。与在中纬度积雪中看到的GEM化学相反，在阿拉斯加布鲁克斯山脉北坡的图利克湖进行的初步观测提供了证据，表明在冻土带积雪中光化学GEM形成和脱气受到抑制，并且在冬季的大部分时间里，间隙GEM实际上转化为非挥发性汞。这些模式导致GEM中间隙积雪空气耗尽的时间延长。如果得到证实，这种化学反应可能意味着大气中的GEM向雪或下伏土壤的净转移，从而增加了向冻土带生态系统的汞沉积。拟议的项目目标是调查(1)确定北极积雪和苔原土壤中GEM损耗和形成的频率和潜在过程；(2) GEM动态引起土壤、积雪和大气之间垂直汞交换的程度；(3)这些过程如何提供额外的资源&amp；#8722；或者水槽&amp；#8722；汞通过大气-地表转移和融雪输入。土壤、雪和空气中的GEM浓度以及垂直交换将在Toolik野外站进行表征。测量将通过积雪采样歧管系统进行，该系统允许在未受干扰的积雪和大气中的多个深度对痕量气体进行全自动化和连续的整个冬季测量。这些实验将由通量室测量加以补充，以评估下面冻土带土壤的贡献。其他微量气体观测以及土壤、雪、融水和土壤水的化学特征将被纳入评估GEM动态和汞收支的环境和生物地球化学控制。这项拟议的研究将利用Toolik场站正在进行的LTER和NEON项目，提供雪中过程、冻土带土壤和淡水生物地球化学循环、北极污染进口和生态系统过程之间的联系。该项目将直接涉及高中生、本科生、研究生和一名博士后科学家。它将通过在课堂上进行研究报告、参观实验室和利用研究结果进行数据分析，扩大与当地高中化学班的现有合作关系。向科学界的传播将通过同行评议的出版物和会议报告，以及与美国和国际监管机构的沟通来完成。将通过新闻发布、机构出版物、开放日活动和网站向公众宣传。数据将在科罗拉多大学的国家冰雪数据中心存档，分发给国内和国际极地研究界。

The goal of this project is to characterize soil-snow-atmosphere dynamics of mercury (Hg) in the snow-dominated Arctic tundra. Chemical conversion of Hg in snowpack from non-volatile forms to gaseous elemental mercury (GEM) can lead to substantial degassing of Hg from snow, thereby reducing the impact of atmospheric deposition. Contrary to the GEM chemistry seen in the midlatitude snowpack, preliminary observations from Toolik Lake, on the north slope of the Brooks Range, Alaska, provide evidence that photochemical GEM formation and degassing are suppressed in tundra snow and that for much of the winter, interstitial GEM is actually converted into non-volatile Hg. These patterns result in extended periods when interstitial snowpack air is depleted in GEM. If confirmed, this chemistry would likely signify a net transfer of atmospheric GEM to snow or underlying soils, thereby increasing Hg deposition to tundra ecosystems. Proposed project objectives are to investigate (1) the frequency and underlying processes that determine GEM depletion and formation in arctic snowpack and tundra soils; (2) the degree to which GEM dynamics cause vertical Hg exchange between soils, snow, and the atmosphere; and (3) how these processes provide additional sources − or sinks − of Hg via atmosphere-surface transfer and snowmelt input. GEM concentrations in soils, snow, and air, as well as vertical exchanges, will be characterized at Toolik Field Station. Measurements will be made by means of a snow-sampling manifold system allowing for fully automated and continuous all-winter measurements of trace gases at multiple depths in the undisturbed snowpack and the atmosphere. These experiments will be supplemented by flux chamber measurements to assess the contribution of the underlying tundra soils. Other trace gas observations, and chemical characterization of soil, snow, melt water, and soil water will be incorporated to assess the environmental and biogeochemical controls on GEM dynamics and the Hg budget. This proposed research will leverage ongoing LTER and NEON projects at the Toolik Field station, providing linkages between in-snow processes, tundra soil and freshwater biogeochemical cycling, pollution import into the Arctic, and ecosystem processes. The project will directly involve high school, undergraduate, graduate students, and a postdoctoral scientist. It will expand an existing partnership with local high school chemistry classes through research presentations in classrooms, laboratory tours, and data analyses using study results. Dissemination to the scientific community will be accomplished through peer-reviewed publications and conference presentations, and by communication with U.S. and international regulatory agencies. The general public will be reached through news releases, institutional publications, open house events, and a web site. Data will be archived at the National Snow and Ice Data Center at the University of Colorado for distribution to the national and international polar research community.