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

知识价值：森林火灾调动的汞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时向大气中排放的汞，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。火灾还导致湖泊和水库中缺氧、硫酸盐还原条件的发展，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集中在食物链中。在本提案中，研究概述了火对土壤有机质强结合汞和防止甲基化和生物积累能力的影响。这项研究是由三个假设驱动的，这些假设解决了由火引起的土壤有机质中硫氧化态的变化以及这些变化对汞结合的影响。假设是：(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的强汞结合能力，因为硫的氧化态增加了；(3)沉积物掩埋恢复或增加了土壤有机质的强汞结合能力，因为硫化氢在湖泊和水库沉积物中的结合。土壤和湖泊/水库沉积物采样将在受野火和规定燃烧影响的流域进行。汞对土壤、沉积物和提取的有机物的吸附和解吸，将使用炉子加热来检查，以可重复地评估热量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。更广泛的影响：本建议的更广泛影响包括三个独特的特点：(1)圣胡安合作实验室的发展，该实验室由科罗拉多大学、刘易斯堡学院、山地研究所以及圣胡安山区的联邦、地区和州土地管理机构共同发起；(2)通过科罗拉多大学和伊利诺伊大学的成熟和成功的项目招收代表性不足的研究生；(3)在科罗拉多大学建立科罗拉多水质推广中心（CWQOC）。圣胡安合作实验室最近成立，旨在加强和建立科罗拉多西南部地区的研究和教育项目。在科罗拉多大学外联委员会的支持下，正在建立科罗拉多水质外联中心，为处理水质问题的流域利益相关者团体和市政当局提供一个全州范围的途径，以寻求有水质问题的教师和学生的帮助。

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.