Microbial Processes and Populations as Related to Zinc, Cadmium and Sulfur Speciation in Natural Metalliferous Soil Environments

土壤环境是经过生物和化学过程不断改造的生物地球化学系统。这项研究项目涉及对自然生物地球化学过程导致重金属水平升高的田间土壤的研究。总体假设是参与硫循环的微生物种群(硫氧化细菌，SOB；硫还原菌，SRB)决定了锌和镉在有机质丰富的土壤环境中的固相形态和分布。要研究的土壤是泥炭沉积，覆盖着从纽约州东部延伸到加拿大圭尔夫的洛克波特白云石矿层。这些泥炭沉积物可以通过生物地球化学过程浓缩Cd和Zn，当这些沉积物被排出时，这些金属的溶解度、迁移性和生物有效性都会增加，从而引发有机质和硫化物在好氧条件下的氧化。我们认为，这些土壤中微生物种群的结构、功能和活性决定了锌和镉的形态、溶解性、移动性和生物有效性。需要研究的关系包括土壤颗粒中微生物和矿物质或元素的空间分布(成像)、身份识别和共存。为此，将在雨季和旱季对土壤进行采样。将对这些土壤的垂直剖面进行研究，以评估微生物过程对金属迁移的影响。在实验室中，将进行氧化条件下的实验，以研究微生物群落结构和功能的变化对锌、镉的溶解和结合环境以及对S氧化态的潜在影响。将在微观尺度上使用一套涉及湿化学、光谱学、经典微生物学、分子生物学和荧光显微镜的技术来检验关于微生物在宏观尺度上的化学形态形成和流动性中的作用的假说。我们计划从激光共聚焦扫描显微镜(CLSM)和m-XRF和m-X射线衍射仪获得空间耦合数据，从而将土壤颗粒中微生物与锌和镉的分布联系起来。此外，我们将整合基于聚合酶链式反应和非聚合酶链式反应的分子分析，以获得有关感兴趣的微生物种群的定向、定量信息。所提出的活动的智力价值在于在受控条件下直接耦合微生物和地球化学分析，这将有助于我们更好地了解控制复杂土壤环境中痕量金属保留和溶解的生物地球化学过程。这一研究项目将提高我们在污染防治、修复和环境管理方面将微观和宏观过程联系起来的能力。这项提议还将支持为接受分子和地球化学技术培训的学生提供独特的跨学科教育。总体而言，这项研究将同时促进生物地球化学过程的基本知识，并促进环境科学家跨学科培训的重大创新。

Soil environments are biogeochemical systems under continual modification by biological and chemical processes. This research project involves the study of field soils with elevated levels of heavy metals that resulted from natural biogeochemical processes. The overall hypothesis is that microbial populations involved in sulfur cycling (sulfur oxidizing bacteria, SOB; sulfur reducing bacteria, SRB) determine the solid-phase speciation and distribution of Zn and Cd in organic-matter rich soil environments. The soils to be studied are peat deposits that overlie a mineral bed of Lockport Dolomite extending from Eastern New York State to Guelph (Canada). These peat deposits can concentrate Cd and Zn by biogeochemical processes, and the solubility, mobility and bioavailability of these metals can increase when such deposits are drained, initiating oxidation of organic matter and sulfides under aerobic conditions. We propose that the structure, function, and activity of microbial populations in these soils determine the speciation, solubility, mobility, and bioavailability of Zn and Cd. Among the relationships to be investigated are the spatial distribution (imaging), identity, and co-location of microbes and minerals or elements in soil particles. To do this, soils will be sampled during wet and dry seasons. Vertical profiles of these soils will be studied to assess the involvement of microbial processes in metal mobility. In the laboratory, experiments conducted under oxidizing conditions will be undertaken to investigate the potential effects that changes in microbial community structure and function might have on Zn and Cd dissolution and binding environment and to S oxidation states. A suite of techniques involving wet chemistry, spectroscopy, classic microbiology, molecular biology and fluorescence microscopy at the micro-scale will be employed to test hypotheses about the role of microorganisms in chemical speciation and mobility at macro-scales. We plan to obtain spatially coupled data from confocal laser scanning microscopy (CLSM) and m-XRF and m-XRD, thereby linking the distribution of microbes with Zn and Cd in soil particles. In addition, we will integrate PCR- and non-PCR-based molecular analyses to obtain directed, quantitative information about microbial populations of interest. The intellectual merit of the proposed activity lies in the direct coupling of microbiological and geochemical analyses under controlled conditions, which will help us better understand biogeochemical processes controlling trace metal retention and solubility in complex soil environments. This research project will advance our capabilities for linking micro- and macro-scale processes in pollution prevention, remediation, and environmental management. This proposal will also support a unique blend of interdisciplinary education for students who will be trained in molecular and geochemical techniques. Overall, this research will simultaneously advance basic knowledge of biogeochemical processes and promote significant innovations in interdisciplinary training of environmental scientists.