Collaborative Research on Snow and Ice Processes in the Deposition and Fate of Mercury in the Arctic

大气汞通过一系列复杂的大气化学反应进入北极生态系统，这些化学反应需要海冰，并导致提供活性溴、较低的环境温度和足够的阳光来进行光解。因此，几乎所有进入北极生态系统的大气汞最初都沉积在陆地和海洋的积雪中。在积雪融化之前，多达三分之一的初始沉淀物被重新排放到大气中，但其余的最终以积雪融化径流的形式结束。这种水中汞的命运是不确定的，无疑在陆地和海冰上是不同的。两个关键的悬而未决的问题是：最初储存的元素汞中有多少转化为有毒的甲基汞，以及这些甲基汞最终会在哪里停留？由于与冰雪有关的冰冻圈过程在很大程度上决定了这些问题的答案，因此这项工作开始研究这些过程。所研究的过程跨越北极海岸，具有泛北极的意义，并对人类和生态系统健康有直接影响。该项目包括实验和合成两个部分。沿着从楚科奇海内陆到巴罗和阿特卡苏克的横断面，将测量积雪中活性溴和汞的负载量。将在汞耗尽事件和融雪期间进行详细观察，比较和对比汞在陆地和海上的命运。来自冻土带、湖泊、冰以及陆地和海洋沉积物的融雪后样本将被分析并用于确定沉积的汞在哪里以及有多少被转化为甲基汞。操纵实验将被用来更好地了解汞是如何携带在积雪中的，以及在积雪融化期间它是如何释放的。研究团队和其他精选人员将举行一系列为期一周的务虚会，以合成北极水星系统。通过对北极汞系统的理解和建模，该小组将评估汞污染对人类和生物系统的影响可能会如何受到当今北极正在发生的前所未有的海冰和雪条件变化的影响。拟议活动的智力价值：这项研究填补了我们目前对北极水星系统的理解空白，即大气汞沉积后会发生什么。它还作为一座桥梁，将汞沉积的大气化学详细研究与大量与北极汞环境负荷和健康风险有关的研究联系起来。这项工作采取了一种系统的方法来解决汞问题，这既是必要的，也是新颖的。更广泛的影响：汞有毒，是北极居民和官员非常关心的问题。这项研究的结果将有助于评估北极汞污染是如何从全球汞水平得出的，以及污染物负荷可能如何对海洋冰雪条件的变化做出反应。将在一系列外联活动中向决策者和公众通报结果，这些活动包括传统的研究生培训、会议介绍、网站出版、课堂访问，以及通过由获奖作家制作和出版一本儿童书籍。

Atmospheric mercury enters the arctic ecosystem through a set of complex atmospheric chemical reactions that require sea ice and leads to provide reactive bromine, low ambient temperatures, and enough sunlight for photolysis. As a consequence, virtually all atmospheric mercury entering the arctic ecosystem is initially deposited in the snow pack, both on land and at sea. Up to one third of this initial deposit is re-emitted to the atmosphere before the snow melts, but the remainder ends up in snow melt run-off. The fate of this water-borne mercury is uncertain and undoubtedly different on land vs. sea ice. Two key unanswered questions are: How much of the elemental mercury initially deposited is converted to toxic methyl-mercury, and where does this methylmercury ultimately come to rest? Since cryospheric processes related to snow and ice in large measure determine the answers to these questions, this work sets out to study these processes. The processes studied straddle the Arctic Coast, have pan-Arctic significance, and have a direct impact on human and ecosystem health. The project has experimental and synthesis components. Along a transect from the Chukchi Sea inland to Barrow and Atqasuk, measurements will be taken of reactive bromine and mercury loading in the snow pack. Detailed observations will be made during mercury depletion events and during the snowmelt, comparing and contrasting the fate of mercury on land with that at sea. Post snowmelt samples from tundra, lakes, ice, and terrestrial and marine sediments will be analyzed and used to determine where and how much of the deposited mercury is converted to methyl mercury. Manipulation experiments will be used to better understand how mercury is entrained in the snow pack, and how it is released during the snowmelt. A series of weeklong retreats by the research team and selected others will be held to produce a synthesis of the Arctic Mercury System. By understanding and modeling the arctic mercury system, the group will assess how the impact of mercury pollution on human and biological systems is likely to be affected by the unprecedented changes in sea ice and snow conditions that are taking place in the Arctic today. Intellectual Merit of Proposed Activity: The research fills a gap in our current understanding of the Arctic Mercury System, namely what happens to atmospheric mercury after it is deposited. It also serves as a bridge, connecting detailed studies of atmospheric chemistry of mercury deposition with the large body of studies related to arctic mercury environmental loading and health risk. This work takes a systems approach to the mercury problem that is both essential and novel. Broader Impacts: Mercury is toxic and of great concern to arctic residents and officials. Results from this research will be useful in assessing how arctic mercury pollution is derived from global levels of mercury, and how that pollutant loading might respond to changes in sea ice and snow conditions. Results will be communicated to decision-makers and the public in a series of outreach activities that include traditional graduate student training, conference presentations, website publication, classroom visits, and through the production and publication of a children's book by an award-winning author.