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

该项目的目标是描述以雪为主的北极苔原中汞（Hg）的土壤-雪-大气动力学特征。积雪中的汞从非挥发性形式化学转化为气态元素汞（GEM），可使雪中的汞大量脱气，从而减少大气沉降的影响。相反的GEM化学在中纬度积雪，初步观察图利克湖，在北坡的布鲁克斯范围内，阿拉斯加，提供的证据表明，光化学GEM的形成和脱气被抑制在苔原雪，并在冬季的大部分时间，间隙GEM实际上转化为非挥发性的汞。这些模式的结果，在延长的时期时，间隙积雪空气耗尽在创业板。如果得到证实，这种化学性质可能意味着大气中的汞净转移到雪或底层土壤中，从而增加了冻土带生态系统中的汞沉积。拟议的项目目标是调查：（1）决定北极积雪和冻原土壤中汞的消耗和形成的频率和基本过程;（2）汞的动力学在多大程度上导致土壤、雪和大气之间的汞垂直交换;以及（3）这些过程如何通过大气-地表转移和融雪输入提供额外的汞源或汇。将在图利克野外站对土壤、雪和空气中的GEM浓度以及垂直交换进行表征。测量将通过雪取样歧管系统进行，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和连续的整个冬季测量。这些实验将辅之以通量室测量，以评估底层冻原土壤的贡献。其他痕量气体观测以及土壤、雪、融水和土壤水的化学特性将被纳入评估GEM动态和汞收支的环境和地球化学控制。这项拟议的研究将利用图里克野外站正在进行的LTER和氖项目，提供雪中过程、冻原土壤和淡水地球化学循环、污染输入北极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、研究生和博士后科学家。它将通过在课堂上的研究报告、实验室图尔斯参观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伙伴关系。将通过同行评审的出版物和会议报告以及与美国和国际监管机构的沟通向科学界传播。将通过新闻稿、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，以便分发给国家和国际极地研究界。

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.