CAREER: Generation of Sediment Heterogeneity by Macrophytes and Macrofauna and Consequences for Redox Chemistry and Trace Metal Speciation

摘要智力价值：沿海和内陆湿地地区受到快速增长的人口的巨大影响。这通常会导致金属和养分负荷增加，同时湿地水文、动物和植物群也会发生重大变化。沿海和内陆湿地的可持续发展（和修复）战略取决于金属和营养物质物种形成、生物利用度和流动性及其对湿地动植物种群的依赖的准确预测模型的发展。在盐沼和沿海海洋之间或内陆湿地和淡水含水层之间的敏感界面，情况尤其如此。生活在富有机质盐沼和淡水湿地的大型植物和大型动物在其周围沉积物中产生显著的三维、时间变化的地球化学异质性。这对底栖生物的氧、金属和营养物质的通量、氧化还原敏感化学物质的内部循环以及有机物降解动力学有着巨大的影响。接下来的实验室和实地调查将用于评估这些影响，并推进沉积物氧化还原化学和痕量金属形态、生物利用度和流动性的复杂3D数学模型的发展。(1)混合模式矿物组合的金属吸附实验将用于推导表面络合的热力学稳定性常数，并评估其对自然沉积物的适用性。(2)相邻植被和非植被沉积物的大块沉积物特性（矿物学、孔隙水化学、痕量金属形态）将作为WMU创新的新实地课程的一部分进行测量。(3)利用微电极、SEM/TEM和激光烧蚀ICP-MS等技术，对根系和洞穴周围沉积物的矿物学和微量金属形态进行微尺度分析。(4)痕量金属掺杂铁氧化物的化学和微生物介导的还原溶解导致的痕量金属形态的变化将被量化。(5)利用人工根系控制的实验室中观实验，评估根系中氧和挥发性有机化合物泄漏导致的矿物学和痕量金属形态的微观三维变化。更广泛的影响：这项研究包括一个全面整合的研究和教育计划。在为期6周的暑期课程中，学生将有机会参加在佐治亚州萨佩洛岛（NSF-LTER站点）和密歇根州的实地研究。本课程将从WMU及周边机构招收学生，特别是那些没有研究生研究项目的机构，以及那些传统上代表性不足的群体大量入学的大学。此外，整整一周的课程将与中学教育教师讲习班同时进行。教师们将有机会亲身参与一个活跃的科学研究项目，并鼓励他们在密歇根科学教师年会上传播基于这一经验的课程。与研究的实验室部分相关的项目将纳入本科地球化学课程。除了传统的研究生指导外，来自卡拉马祖地区数学与科学学院的本科生和积极性很高的高中生将参与研究的各个方面，并在国家或国际科学会议上展示个人项目的成果。通过这项研究资助的设备将成为WMU研究生和本科生可用的研究基础设施的宝贵补充，WMU是一个快速发展的博士研究机构。

AbstractIntellectual Merit: Coastal and inland wetland areas are enormously impacted by rapidly growing human populations. This typically leads to increased metal and nutrient loading together with significant changes in wetland hydrology, fauna and flora. Sustainable coastal and inland wetland development (and remediation) strategies depend on the development of accurate, predictive models of metal and nutrient speciation, bioavailability and mobility and their dependence on wetland flora and fauna populations. This is particularly true at the sensitive interface between saltmarshes and the coastal ocean or between inland wetlands and freshwater aquifers. Macrophytes and macrofauna inhabiting organic-rich saltmarsh and freshwater wetlands produce significant three-dimensional, temporally varying, geochemical heterogeneity in the surrounding sediments. This has a tremendous influence on benthic fluxes of oxygen, metals and nutrients, internal cycling of redox sensitive chemical species, and organic matter degradation kinetics. The following laboratory and field investigations will be used to assess these influences and to advance the development of sophisticated 3D mathematical models of sediment redox chemistry and trace metal speciation, bioavailability and mobility. (1) Metal adsorption experiments on mixed model mineral assemblages will be used to derive thermodynamic surface complexation stability constants and to assess their applicability to natural sediments. (2) Bulk sediment properties (mineralogy, pore water chemistry, trace metal speciation) in adjacent vegetated and unvegetated sediments will be measured as part of an innovative new field course at WMU. (3) Microscale analyses of mineralogy and trace metal speciation in sediments surrounding roots and burrows will be completed using microelectrodes, SEM/TEM, and laser ablation ICP-MS. (4) Changes in trace metal speciation resulting from chemically versus microbially mediated reductive dissolution of trace-metal doped iron oxides will be quantified. (5) Controlled laboratory mesocosm experiments with artificial roots will be used to assess microscale 3D changes in mineralogy and trace metal speciation resulting from root leakage of oxygen and labile organic compounds. Broader Impacts: This study includes a fully integrated plan of research and education. An innovative 6-week summer course is proposed in which students will have the opportunity to participate in field research at Sapelo Island, Georgia (an NSF-LTER site) and at field sites in Michigan. Students will be recruited for this course from WMU and surrounding institutions, especially those without graduate research programs and from colleges with significant enrollments of traditionally underrepresented groups. In addition, a full week of the course will coincide with a secondary education teacher workshop. The teachers will have a hands-on opportunity to participate in an active scientific research program and will be encouraged to disseminate curricula resulting from this experience at the Michigan Science Teachers Annual Meeting. Projects related to the laboratory portions of the study will be incorporated into an undergraduate geochemistry course. In addition to traditional graduate student mentoring, undergraduate students and highly motivated high school students from the Kalamazoo Area Math and Science Academy will participate in all aspects of the research, presenting results of individual projects at national or international scientific conferences. Equipment funded though this study will be a valuable addition to the research infrastructure available to graduate and undergraduate students at WMU, a rapidly growing doctoral research institution.