Collaborative Proposal: Response of mercury cycling to disturbance and restoration of low-gradient forested watersheds

合作提案：汞循环对低梯度森林流域干扰和恢复的响应

• 批准号: 1851618
• 负责人: Joel Blum
• 金额: $ 20.49万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1851618&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Response; mercury; cycling

Environmental pollution of mercury is a global concern. Due to foliar uptake of atmospheric mercury, forested ecosystem represents an important receptor of mercury pollution, while low-gradient forest watersheds in the southeastern United States represent hotspots for production of highly toxic methylmercury that poses a risk to humans and wildlife through consumption of fish and other high trophic level food sources. Throughout the southeastern region, there is an initiative to restore the native longleaf pine over the existing loblolly pine. The proposed research will examine how forest restoration affects various mercury cycling processes in southeastern coastal plain forests. This work will lead to an enhanced understanding of how forest restoration can affect the retention of mercury within watersheds and the production of toxic methylmercury. The proposed work will provide unique training opportunities for undergraduate and graduate students of diverse academic backgrounds from the University of North Carolina at Greensboro (UNCG), a minority serving institution, the University of Michigan (U-M), and the Clemson University. Also, home-schooled students in the coastal region of South Carolina will be involved in the sample collection and processing in order to provide a more formal STEM training to these groups of children lacking resources. The principal investigators will integrate this research into teaching materials of existing classes, including field visits and case studies, and also carry out outreach to professional foresters to inform them about how forestry practices may alter mercury cycling. The work will be widely disseminated through seminars, conference presentations, and peer-reviewed publications. The project proposes to use stable mercury isotopes as an integrative tool to better understand the effects of short-term forest disturbance (prescribed fires, thinning, and clear cut) and longer-term forest restoration (switching back to native tree species with lower water demand) on mercury cycling in a low-gradient coastal forested watershed in South Carolina, where mercury methylation is extensive in poorly drained soils. The project will take place in a paired watershed at Santee Experimental Forest, a typical coastal plain forest headwater watershed. Specifically, the project will use stable mercury isotope ratios to monitor depositional pathways of mercury into the experimental forested watershed and also to distinguish the depositional pathways of mercury exported by the streams. Further, methylmercury isotopes measured in terrestrial and aquatic food web components will provide insights into methylmercury formation and degradation pathways during and after forest manipulation in the experimental watershed. Thus, the proposed work will provide a unique chance to test the utility of stable mercury isotopes for tracking atmospheric mercury deposition and mercury methylation and for following uptake of mercury from different sources into the food webs of both experimental and reference watersheds. Further, microcosm studies will be conducted in order to disentangle different environmental factors and their effects on mercury methylation in these forest soils. Through answering these interrelated questions, the proposed work will be able to reveal the effects of forest management on mercury deposition and methylmercury production in a forested ecosystem in the southeastern region of North America.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.

汞的环境污染是全球关注的问题。由于叶子吸收大气中的汞，森林生态系统是汞污染的重要受体，而美国东南部的低梯度森林流域是剧毒甲基汞的生产热点，甲基汞通过食用鱼类和鱼类而对人类和野生动物构成风险。其他高营养级食物来源。在整个东南部地区，有一项举措是在现有的火炬松上恢复原生长叶松。拟议的研究将研究森林恢复如何影响东南沿海平原森林的各种汞循环过程。这项工作将加深人们对森林恢复如何影响流域内汞的保留和有毒甲基汞的产生的了解。拟议的工作将为北卡罗来纳大学格林斯伯勒分校（UNCG）、密歇根大学（U-M）和克莱姆森大学的不同学术背景的本科生和研究生提供独特的培训机会。此外，南卡罗来纳州沿海地区在家接受教育的学生也将参与样本收集和处理，以便为这些缺乏资源的儿童群体提供更正式的 STEM 培训。主要研究人员将把这项研究纳入现有课程的教材中，包括实地考察和案例研究，并向专业林业人员进行推广，让他们了解林业实践如何改变汞循环。这项工作将通过研讨会、会议演讲和同行评审出版物广泛传播。该项目建议使用稳定汞同位素作为综合工具，以更好地了解短期森林干扰（规定的火灾、间伐和砍伐）和长期森林恢复（改用需水量较低的本地树种）的影响）关于南卡罗来纳州低梯度沿海森林流域的汞循环，那里的汞甲基化在排水不良的土壤中广泛存在。该项目将在桑蒂实验森林的一个配对流域内进行，这是一个典型的沿海平原森林源头流域。具体来说，该项目将使用稳定的汞同位素比率来监测汞进入实验森林流域的沉积途径，并区分溪流输出的汞的沉积途径。此外，在陆地和水生食物网成分中测量的甲基汞同位素将深入了解实验流域森林操纵期间和之后甲基汞的形成和降解途径。因此，拟议的工作将提供一个独特的机会来测试稳定汞同位素在跟踪大气汞沉积和汞甲基化方面的效用，以及跟踪实验和参考流域的食物网从不同来源吸收汞的情况。此外，还将进行微观研究，以理清不同的环境因素及其对这些森林土壤中汞甲基化的影响。通过回答这些相互关联的问题，拟议的工作将能够揭示森林管理对北美东南部地区森林生态系统汞沉积和甲基汞生产的影响。该奖项反映了 NSF 的法定使命，并被认为值得支持通过使用基金会的智力优点和更广泛的影响审查标准进行评估。