Doctoral Dissertation Research: The Impact of Thawing Permafrost on Coastal Groundwater and Mercury Cycling in the Arctic

博士论文研究：永久冻土融化对北极沿海地下水和汞循环的影响

• 批准号: 2134865
• 负责人: Matthew Charette
• 金额: $ 6.6万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2134865&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Impact; Thawing

Mercury (Hg) is an environmental contaminant that can cause neurotoxicity in humans and wildlife. Due to atmospheric circulation patterns and plant uptake, a large amount of Hg emitted in the Northern Hemisphere is deposited in Arctic soils. However, the fate of this deposited Hg remains an active area of debate, particularly in the face of climate change. While growing evidence shows that rivers and coastal erosion are important sources of Hg to the Arctic Ocean, it is not presently understood how groundwater impacts Hg cycling through soils into Arctic rivers and coastal regions. The chemical environment of coastal aquifers will determine whether Hg is trapped in coastal sediments or discharged into the Arctic Ocean, where it has the potential to harm fish, wildlife, and the communities that depend on these animals to survive. This study will quantify Hg fluxes and identify important chemical transformations of Hg through the coastal aquifer in a representative Beaufort Sea lagoon system, which characterizes over 50% of the Alaskan Beaufort Sea coastline. These results will be shared with Indigenous communities along the Beaufort Sea coast, and project researchers will provide space for open dialogue with interested community members. The study work will also support ongoing efforts by the US Fish and Wildlife Service to improve understanding of land-ocean processes that impact fish and wildlife populations within the Arctic National Wildlife Refuge and how coastal resources may be impacted by climate change and development. The study will address the following scientific questions: (1) How do the dissolved and soil organic carbon content and the chemical composition of the subterranean estuary impact the retention in sediments or discharge of Hg into coastal waters? (2) How do seasonal differences in groundwater flow due to freeze-up and thaw periods impact the fluxes of Hg into the Beaufort Sea coast? (3) How will climate change and permafrost thaw impact the amount of Hg available for groundwater mobilization? These questions will be addressed with isotopic (radium), biogeochemical (organic carbon), hydrologic (salinity, pressure, temperature, seepage meters), select metals (iron and manganese), and Hg measurements across the land-lagoon groundwater interface. Measurements will be conducted from spring thaw, through late summer, and up to winter freeze-up. Laboratory experiments will also be conducted to discern the impact of groundwater and soil chemistry on the chemical species involved with Hg transport. Future impacts will be probed by measuring Hg in permafrost cores and unexposed tundra soils and performing saltwater intrusion experiments. This study will lay the groundwork for the first box model of Hg in the Arctic that includes measured groundwater contributions, known in temperate and tropical regions to be a significant contributor of Hg to coastal waters.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

汞 (Hg) 是一种环境污染物，可能对人类和野生动物造成神经毒性。由于大气环流模式和植物吸收，北半球排放的大量汞沉积在北极土壤中。然而，这种沉积的汞的命运仍然是一个争论活跃的领域，特别是在面临气候变化的情况下。虽然越来越多的证据表明河流和海岸侵蚀是北冰洋汞的重要来源，但目前尚不清楚地下水如何影响汞通过土壤循环进入北冰洋河流和沿海地区。沿海含水层的化学环境将决定汞是否被困在沿海沉积物中或排放到北冰洋，汞有可能危害鱼类、野生动物以及依赖这些动物生存的社区。这项研究将量化汞通量，并确定汞通过代表性波弗特海泻湖系统沿海含水层的重要化学转化，该系统代表了阿拉斯加波弗特海海岸线 50% 以上的特征。这些结果将与波弗特海沿岸的土著社区分享，项目研究人员将为与感兴趣的社区成员进行公开对话提供空间。这项研究工作还将支持美国鱼类和野生动物管理局正在进行的努力，以提高对影响北极国家野生动物保护区内鱼类和野生动物种群的陆地-海洋过程以及气候变化和发展如何影响沿海资源的了解。该研究将解决以下科学问题：（1）溶解和土壤有机碳含量以及地下河口的化学成分如何影响沉积物中的保留或汞向沿海水域的排放？ (2) 冻融期引起的地下水流量季节差异如何影响流入波弗特海沿岸的汞通量？ (3) 气候变化和永久冻土融化将如何影响可用于地下水动员的汞量？这些问题将通过陆地-泻湖地下水界面的同位素（镭）、生物地球化学（有机碳）、水文（盐度、压力、温度、渗流计）、精选金属（铁和锰）和汞测量来解决。测量将从春季解冻开始，一直到夏末，一直到冬季结冰。还将进行实验室实验，以了解地下水和土壤化学对汞迁移涉及的化学物质的影响。将通过测量永久冻土核心和未暴露的苔原土壤中的汞并进行盐水入侵实验来探讨未来的影响。这项研究将为北极第一个汞箱模型奠定基础，其中包括测量的地下水贡献，众所周知，在温带和热带地区，地下水是汞对沿海水域的重要贡献者。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来获得支持。