Impact of manganese-driven redox processes on groundwater quality and soil carbon cycling

保护地下水资源和排放温室气体是加拿大和全世界的重大环境问题。土壤在这些挑战中扮演着核心角色。我的氧化还原生物地球化学研究项目的主要目标是了解地下水污染威胁，并从机理上理解矿物对土壤固碳的控制--土壤是生物圈中最大的动态陆地碳库。通过使用多学科方法，拟议的研究计划解决了两个基本问题：(I)矿物(例如，锰氧化物)、微生物和有机物之间的相互作用如何控制威胁地下水质量的氧化还原活性地源污染物？以及(Ii)锰氧化物在土壤碳循环中的作用是什么？锰氧化物是环境系统中最活跃的矿物相之一，几乎影响到每一个元素循环。锰不仅被认为是水生和土壤系统中污染物和碳动态的重要控制因素，而且越来越多地被认为是饮用水中一种新出现的令人担忧的污染物。这项研究的目的是为了更好地了解土壤中锰的动态循环，以便提供安全的饮用水和优化土壤中的固碳。这项研究涉及以下三个方面：(1)确定地下水中锰释放的物理和生物地球化学控制；(2)评价锰和碳在控制地源砷活化的地球化学过程中的竞争作用；(3)量化锰氧化物对复杂有机碳化合物的非生物转化。研究结果将为改进对面临地源污染风险的地下水资源的管理提供有价值的信息。调查重要的地下水资源以寻找本地污染物，对于减少公众接触和确定脆弱地区进行监测和管理至关重要，以防止昂贵的污染物调动。除了帮助更有效地分配管理资源外，拟议的研究还将为控制地下过程提供宝贵的见解，以便将未来来自自然来源的地下水污染降至最低。这些结果将为水资源管理者提供宝贵的信息，说明含水层地质作用或成壤作用和生物地球化学过程是否能更好地预测地下水污染。最后，调查氧化锰促进碳矿化的程度将提高预测环境变化和土地管理转变如何影响二氧化碳排放的准确性。这种对土壤和自行车上矿物控制的更好理解，对于确保加拿大实现巴黎协议中承诺的2030年减排目标至关重要，特别是考虑到魁北克最近的立法要求到2020年完全禁止垃圾填埋场使用有机物。

The preservation of groundwater resources and the release of greenhouse gases represent critical environmental issues in Canada and worldwide. Soils play a central role in these challenges. The main goals of my research program in redox biogeochemistry are to understand groundwater contamination threats and to generate mechanistic understanding of mineral control on carbon sequestration in soils - the largest dynamic terrestrial carbon reservoir in the biosphere. By using a multidisciplinary approach, the proposed research program addresses two essential questions: (i) How do interactions among minerals (e.g., manganese oxides), microorganisms, and organic matter control redox-active geogenic contaminants which threaten groundwater quality? and (ii) What is the role of manganese oxides in soil carbon cycling? Manganese oxides are among the most reactive mineral phases in environmental systems and influence nearly every elemental cycle. Not only is Mn gaining recognition as an important control on both contaminant and carbon dynamics in aquatic and soil systems, but it is increasingly recognized as a contaminant of emerging concern in drinking water. The objective of this research program is to develop a better understanding of the dynamic cycling of Mn in soils, in order to provide safe drinking water and optimize carbon sequestration in soils. The proposed research addresses the following three axes: (1) Identifying physical and biogeochemical controls on Mn release in groundwater; (2) Evaluating competitive effect of Mn and C on geochemical processes controlling mobilization of geogenic As; and (3) Quantifying the abiotic transformation of complex organic C compounds by Mn oxides. The results will provide valuable information for the improved management of groundwater resources that are at risk of geogenic contamination. Surveying vital groundwater resources for native contaminants is critical to reduce public exposure and identify vulnerable areas for monitoring and management in order to prevent costly contaminant mobilization. In addition to helping allocate management resources more efficiently, the proposed research will provide valuable insight into controlling subsurface processes in order to minimize future groundwater contamination from natural sources. These results will provide water managers valuable information on whether aquifer geology or pedogenic and biogeochemical processes serve as better predictors of groundwater contamination. Finally, investigating the extent to which Mn oxides promote C mineralization will improve the accuracy of predicting how environmental changes and shifts in land-management may impact CO2 release. This improved understanding of mineral control on soil  cycling will be critical to ensure Canada reaches its 2030 emission reduction targets as committed to in the Paris agreement, especially in light of recent Québec legislation that calls for a complete ban of organic matter from landfills by 2020.