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

土壤环境是一个不断受到生物和化学作用改造的生态地球化学系统。 该研究项目涉及对自然生态地球化学过程导致重金属水平升高的农田土壤的研究。 总的假设是，参与硫循环的微生物种群（硫氧化细菌，硫还原细菌，SRB）确定的固相形态和分布的锌和镉在有机质丰富的土壤环境。 待研究的土壤为泥炭沉积物，覆盖在从东纽约州延伸至圭尔夫（加拿大）的洛克波特白云岩矿床上。 这些泥炭沉积物可以集中镉和锌的土壤地球化学过程中，这些金属的溶解度，流动性和生物利用度可以增加，当这样的存款排水，启动氧化的有机质和硫化物在有氧条件下。 我们建议，在这些土壤中的微生物种群的结构，功能和活性决定的形态，溶解度，流动性和生物有效性的锌和镉。 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）、身份和共存。 为此，将在雨季和旱季对土壤进行取样。 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流动性的影响。 在实验室中，氧化条件下进行的实验将进行调查的潜在影响，微生物群落结构和功能的变化可能对锌和镉的溶解和结合环境和S的氧化态。 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在微观尺度的技术将被用来测试关于微生物在化学形态和流动性在宏观尺度的作用的假设。 我们计划从共聚焦激光扫描显微镜（CLSM）和m-XRF和m-XRD获得空间耦合数据，从而将土壤颗粒中微生物的分布与Zn和Cd联系起来。 此外，我们将整合基于PCR和非PCR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。 拟议活动的知识价值在于在受控条件下直接结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微量金属保留和溶解度的地球化学过程。 该研究项目将提高我们在污染预防，修复和环境管理中连接微观和宏观尺度过程的能力。 该提案还将支持为将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。总的来说，这项研究将同时推进地球化学过程的基础知识，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.