Collaborative Research: Effects of Fire and Subsequent Sediment Burial on Sulfur and Mercury Binding in Organic Matter of Forest Soils

智力优势：森林大火动员的汞正在落基山脉地区湖泊和水库的水生生物中积累。最近的研究主要集中在森林火灾期间排放到大气中的汞，但火灾也会向溪流、湖泊和水库释放汞。土壤有机质有效地隔离了沉积在森林流域中的大部分汞，而火灾导致了大部分土壤有机质的破坏或侵蚀。火灾还导致接受火灾干扰流域径流的湖泊和水库形成缺氧的硫酸盐还原条件，在这些条件下，汞被生物转化为甲基汞，这种形式很容易在水生生物中积累并沿食物链向上浓缩。在这项建议中，研究概述了火对土壤有机质强烈结合汞的能力的影响，以及防止甲基化和生物积累的能力。这项研究是由三个假设驱动的，即火在土壤有机质中硫的氧化态中引起的变化以及这些变化对汞结合的影响。假设(1)森林火灾增加了土壤有机质中硫的氧化态，(2)森林火灾降低了土壤有机质对汞的强结合能力，这是由于硫的氧化态增加，(3)沉积物埋藏恢复或增加了土壤有机质对汞的强结合能力，因为湖泊和水库沉积物中加入了硫化氢。将在受野火和规定焚烧影响的流域进行土壤和湖泊/水库沉积物采样。将使用炉子加热来检测土壤、沉积物和提取的有机物对汞的吸附和解吸，以重复地评估加热对硫氧化和汞结合的影响。此外，这些材料中的硫和汞将用x射线吸收近边结构(XANES)和扩展x射线吸收精细结构(EXAFS)光谱进行表征。广泛影响：这项提议的更广泛影响涉及三个独特的特征：(1)圣胡安合作实验室的发展，这是科罗拉多大学、路易斯堡学院、山地研究所以及圣胡安山脉地区的联邦、地区和州土地管理机构的倡议，(2)通过科罗拉多大学和伊利诺伊大学成熟和成功的项目招收代表不足的研究生，以及(3)在科罗拉多大学建立科罗拉多州水质推广中心。圣胡安科罗拉多实验室最近成立，以加强和建立科罗拉多州西南部地区的研究和教育计划。科罗拉多州水质推广中心是在科罗拉多大学推广委员会的支持下建立的，旨在为处理水质问题的分水岭利益相关者团体和市政当局提供全州范围的途径，以寻求有水质问题的教职员工和学生的帮助。

Intellectual merit: Mercury mobilized by forest fire is accumulating in aquatic organisms in lakes and reservoirs in the Rocky Mountain region. Recent research has focused on mercury emitted to the atmosphere during forest fires, but fire also releases mercury to streams, lakes, and reservoirs. Soil organic matter effectively sequesters most of the mercury deposited in forested watersheds, and fire results in the destruction or erosion of most of the soil organic matter. Fire also results in the development of anoxic, sulfate-reducing conditions in the lakes and reservoirs receiving runoff from fire-disturbed watersheds, and under these conditions, mercury is biologically converted to methylmercury, the form that readily accumulates in aquatic organisms and concentrates up the food chain. In this proposal, research is outlined to examine the effect of fire on the ability of soil organic matter to strongly bind mercury and prevent methylation and bioaccumulation. The research is driven by three hypotheses addressing the transformations caused by fire in the oxidation state of sulfur in soil organic matter and the effect of these changes on mercury binding. The hypotheses are (1) that forest fire increases the oxidation state of sulfur in soil organic matter, (2) that forest fire decreases the strong mercury binding capacity of soil organic matter because of the increase in the oxidation state of the sulfur, and (3) that sediment burial restores, or increases, the strong mercury binding capacity of soil organic matter because of incorporation of hydrogen sulfide in the lake and reservoir sediments. Soil and lake/reservoir sediment sampling will be carried out in watersheds affected by wildfire and prescribed burn. Mercury adsorption to and desorption from the soils, sediments, and extracted organic matter, will be examined using furnace heating to reproducibly assess the effect of heat on sulfur oxidation and mercury binding. In addition, the sulfur and mercury in these materials will be characterized with x?]ray absorption near edge structure (XANES) and extended x?]ray absorption fine structure (EXAFS) spectroscopy.Broader Impact: The broader impacts of this proposal involve three unique features: (1) growth of the San Juan Collaboratory, an initiative of the University of Colorado, Fort Lewis College, the Mountain Studies Institute, and federal, regional, and state land management agencies in the San Juan Mountains region, (2) recruitment of under-represented graduate students through well-established and successful programs at the University of Colorado and University of Illinois, and (3) establishment of the Colorado Water Quality Outreach Center (CWQOC) at the University of Colorado. The San Juan Collaboratory was recently formed to enhance and establish research and educational programs for the southwestern Colorado area. The Colorado Water Quality Outreach Center is being established with the support of the University of Colorado Outreach Committee to provide a state-wide avenue for watershed stakeholder groups and municipalities dealing with water quality problems to seek assistance from faculty and students with water quality problems.