EAR-PF Short- and long-term effects of wildfire and permafrost thaw on mercury cycling and bioavailability across a major northern river delta landscape

Scott Zolkos博士获得了美国国家科学基金会EAR博士后奖学金，将在哈佛大学和伍兹霍尔研究中心开展研究和教育计划。拟议的研究将调查野火和永久冻土解冻对北部高纬度生态系统中汞及其向神经毒物甲基汞转化的影响。北方土壤是地球上最大的天然汞储存库。随着北方变暖加速永久冻土融化，加剧野火和水文循环，并加强陆地-淡水联系，储存的汞很容易释放和转化。在湖泊和池塘等淡水中，甲基汞进入食物网可能对生态系统和人类健康产生重大影响。阿拉斯加育空-库斯科维姆三角洲（YK）的土壤和淡水将被分析，以更好地了解野火和永久冻土融化梯度中的汞释放和甲基化。通过测试YK三角洲生态系统干扰对汞循环的影响，本工作旨在从过程水平到跨空间和时间尺度推进对快速变化的北方污染物循环的理解。教育和外联活动包括本科生指导、与当地北方居民共同生产和转让知识，以及通过国际早期职业极地科学家网络向公众传播研究成果。北部野火和永久冻土解冻的最重要影响之一是土壤中的汞（Hg）释放到大气和淡水中，并产生甲基汞（MeHg）。湖泊和池塘整合了整个流域的生物地球化学过程，为测试生态系统干扰对汞循环的影响提供了理想的环境。在最近和历史烧伤的流域工作，拟议的研究将使用空间替代时间的方法来确定野火和永久冻土融化对汞循环在短（次十年）和长（十年）时间尺度上的影响。土壤汞的天气测量将与野火严重程度的遥感估计和全球大气汞模型相结合，以确定土壤燃烧释放到大气中的汞的大小和命运。汞浓度（总汞和甲基汞）和稳定同位素、有机物和营养物的耦合水化学测量将用于限制野火对解冻季节淡水中汞的水文运输和甲基化的影响。将通过测试汞、溶解有机物的光谱特性和水面反射率遥感测量之间的关系，开发跨区域淡水衡量这些影响的模型。除了开发下一代北方汞循环模型外，更广泛的影响还包括通过北极星项目指导和培训本科生，并与阿拉斯加北部社区开展外展活动。该项目获得了地球科学部水文科学项目的共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Scott Zolkos has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Harvard University and the Woods Hole Research Center. The proposed research will investigate the effects of wildfire and permafrost thaw on mercury and its transformation into the neurotoxicant, methylmercury, in northern high-latitude ecosystems. Northern soils represent Earth’s largest natural reservoir of mercury. The stored mercury is vulnerable to release and transformation as northern warming accelerates permafrost thaw, intensifies wildfire regimes and hydrological cycles, and strengthens land-freshwater linkages. In freshwaters like lakes and ponds, the uptake of methylmercury into food webs has potentially significant implications for ecosystem and human health. Soils and freshwaters in the Yukon-Kuskokwim (YK) Delta, Alaska, will be analyzed to better understand mercury release and methylation across gradients of wildfire and permafrost thaw. By testing the effects of ecosystem disturbance on mercury cycling in the YK Delta, this work seeks to advance understanding of rapidly changing northern contaminant cycles, from a process level to across spatial and temporal scales. Education and outreach activities include undergraduate mentoring, knowledge co-production and transfer with local northern residents, and public dissemination of findings through international early-career polar scientist networks.Among the most significant implications of northern wildfires and permafrost thaw is the release of mercury (Hg) from soils into the atmosphere and freshwaters, and the production of methylmercury (MeHg). Lakes and ponds integrate biogeochemical processes across their watersheds, providing an ideal setting to test the effects of ecosystem disturbance on Hg cycling. Working in watersheds within recent and historical burns, the proposed research will use a space-for-time substitution approach to determine wildfire and permafrost thaw effects on Hg cycling over short (sub-decadal) and long (decadal) timescales. Synoptic measurements of soil Hg will be paired with remote sensing estimates of wildfire severity and a global atmospheric Hg model to determine the magnitude and fate of Hg released from soil combustion into the atmosphere. Coupled hydrochemical measurements of Hg concentration (total and MeHg) and stable isotopes, organic matter, and nutrients will be used to constrain wildfire effects on the hydrologic transport and methylation of Hg within freshwaters during the thaw season. Models for scaling these effects across regional freshwaters will be developed by testing the relationships between Hg, spectral properties of dissolved organic matter, and remote sensing measurements of water surface reflectance. In addition to the development of the next generation of northern Hg cycle models, broader impacts include mentoring and training of undergraduate students through the Polaris Project and outreach activities with northern communities in Alaska. This project received co-funding from the Hydrological Science program in the Earth Science division.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.