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冻土带中汞(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)可导致大量汞从雪中脱气，从而减少大气沉积的影响。与中纬度积雪中看到的宝石化学相反，阿拉斯加布鲁克斯山脉北坡的Toolik湖的初步观察提供了证据，表明光化学宝石的形成和脱气在冻土带雪中受到抑制，而且在冬季的大部分时间里，间隙宝石实际上被转化为不挥发的汞。这些模式导致宝石中间质积雪空气耗尽的时间延长。如果得到证实，这种化学很可能意味着大气中的宝石净转移到雪或下面的土壤中，从而增加了对苔原生态系统的汞沉积。拟议的项目目标是调查(1)决定北极积雪和冻土带土壤中宝石消耗和形成的频率和潜在过程；(2)宝石动力学导致土壤、雪和大气之间垂直汞交换的程度；以及(3)这些过程如何通过大气-地表转移和积雪输入提供额外的汞来源或汇。土壤、雪和空气中的宝石浓度以及垂直交换将在图利克野外站进行表征。测量将通过积雪采样管路系统进行，允许在整个冬季对未受干扰的积雪和大气中多个深度的痕量气体进行全自动和连续的测量。这些实验将得到通量室测量的补充，以评估下面的冻土带土壤的贡献。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对宝石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图利克野外站正在进行的LTER和霓虹灯项目，提供雪中过程、冻土和淡水生物地球化学循环、北极污染输入和生态系统过程之间的联系。该项目将直接涉及高中、本科生、研究生和一名博士后科学家。它将通过课堂上的研究报告、实验室参观和使用研究结果进行数据分析，扩大与当地高中化学课堂的现有合作伙伴关系。对科学界的传播将通过同行评议的出版物和会议报告，以及通过与美国和国际监管机构的沟通来实现。将通过新闻稿、机构出版物、开放参观活动和一个网站接触到普通公众。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.