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

智力成果：森林火灾引发的汞正在落基山脉地区湖泊和水库的水生生物体内积累。最近的研究主要集中在森林火灾期间汞排放到大气中，但火灾也会将汞排放到溪流、湖泊和水库中。土壤有机质有效地隔离了森林流域中沉积的大部分汞，火灾导致大部分土壤有机质的破坏或侵蚀。火灾还导致湖泊和水库出现缺氧、硫酸盐还原的状况，这些湖泊和水库接收来自受火灾影响的流域的径流，在这些状况下，汞在生物学上转化为甲基汞，这种形式的汞很容易在水生生物体内积累，并集中在食物链中。在该提案中，研究概述了火灾对土壤有机质强烈结合汞并防止甲基化和生物累积能力的影响。该研究由三个假设驱动，解决了火灾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：（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，（3）沉积物埋藏恢复或增加，湖库沉积物中硫化氢的掺入使土壤有机质具有较强的汞结合能力。将在受野火和规定焚烧影响的流域进行土壤和湖泊/水库沉积物取样。将使用熔炉加热来检查土壤、沉积物和提取的有机物对汞的吸附和解吸，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）光谱学。更广泛的影响：该提案的更广泛的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、刘易斯堡学院、山区研究所以及圣胡安山区的联邦、地区和州土地管理机构的一项倡议，（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募代表性不足的研究生，以及（3）在科罗拉多大学建立科罗拉多水质外展中心（CWQOC）。该圣胡安合作实验室最近成立，以加强和建立西南部科罗拉多地区的研究和教育计划。在科罗拉多大学外展委员会的支持下，正在建立科罗拉多水质外展中心，为流域利益相关者团体和处理水质问题的市政当局提供全州范围的途径，以寻求教师和学生的水质问题的帮助。

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.