Collaborative Research: Manganese(III)-driven carbon oxidation at oxic-anoxic interfaces

土壤是地球上碳的一个巨大而动态的陆地。微生物氧化碳的速度决定了有多少碳留在土壤中或以二氧化碳的形式排放。 即使土壤碳氧化率的小幅增加也会增加大气中的二氧化碳含量，影响全球气候。锰（Mn）是一种丰富而有效的氧化剂，但其对土壤碳氧化速率的影响尚不清楚。该项目将为锰化合物如何改变土壤中碳氧化的速度提供新的认识。这些新的科学知识将有助于改善我们对未来二氧化碳排放的预测，并将有助于社会制定新的战略来限制排放。该项目将与校园和当地社区的多样性计划合作，使妇女和少数民族学生能够从事STEM职业。锰基氧化剂的形成正在成为土壤中C氧化速率的关键调节剂，从而成为土壤中CO2排放的关键调节剂。虽然溶解的Mn（III）物种是环境系统中最有效的氧化剂之一，但对Mn（III）驱动的碳氧化的控制几乎是未知的。该项目的总体目标是确定控制土壤中Mn（III）介导的碳氧化速率的基本地球化学和微生物因素。我们的中心假设是，缺氧-缺氧界面是溶解Mn（III）的酶促形成的“热点”，随后解聚和溶解其他抗性有机物，从而提高微生物CO2的生产。拟议的研究集成了微传感器，光谱和多组学方法，以解决耦合锰和碳循环在土壤中的细尺度梯度。为了实现总体目标，具体目标是（i）定义Mn（III）形成的地球化学控制沿着好氧-，（ii）确定Mn（III）形成的微生物驱动因素，（iii）评估Mn（III）形成对土壤中缺氧-好氧界面C氧化的影响。传播所产生的数据集将支持努力将锰和碳氧化还原循环耦合到地球化学模型。首次将C氧化的高度显著的Mn依赖性整合到模型中，预计将大大提高预测环境和人类对土壤CO2排放影响的准确性。 该项目团队将努力将这一多学科的研究工作纳入战略，使妇女和少数民族研究生，本科生和高中生追求干的职业生涯。一个三点计划将这项研究与直接的跨学科教育和公共宣传相结合，其中包括：（i）为一名少数民族博士生提供地球化学研究生培训，（ii）为三名少数民族本科生提供与哈佛森林REU方案合作进行独立研究的机会，及（iii）与Girls Inc.合作，为来自当地一所高中的45名少数族裔女学生举办了为期多天的讲习班。马萨诸塞州的霍利奥克。为讲习班编写的教育材料将通过参加一年一度的马萨诸塞州环境马拉松活动加以传播。与哈佛森林和女孩公司合作制定了一项全面的评估计划。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Soils are a large and dynamic terrestrial of carbon on earth. How fast microbes oxidize carbon determines how much either stays in soils or is emitted as carbon dioxide. Even a small increase in soil carbon oxidation rate could increase the amount of carbon dioxide in the atmosphere, impacting global climate. Manganese (Mn) is an abundant and potent oxidizer, but its impact on the rate of soil carbon oxidation is not known. This project will provide new understanding of how manganese compounds change how fast carbon is oxidized in soils. This new scientific knowledge will help improve our predictions of future carbon dioxide emissions and will help society develop new strategies to limit emissions. This project will work with diversity programs on campus and in the local community to empower women and minority students to pursue STEM careers. The formation of Mn-based oxidants is emerging as a key regulator of C oxidation rates, and thus CO2 emissions, in soils. Although dissolved Mn(III) species are among the most potent oxidants in environmental systems, the controls on Mn(III)-driven carbon oxidation are virtually unknown. The overall objective of this project is to identify fundamental geochemical and microbial factors controlling the rate of Mn(III)-mediated carbon oxidation in soils. Our central hypothesis is that oxic-anoxic interfaces are "hotspots" for the enzymatic formation of dissolved Mn(III), which subsequently depolymerizes and solubilizes otherwise resistant organic matter, and so enhances microbial CO2 production. The proposed research integrates microsensor, spectroscopic, and multi-omics approaches to resolve coupled Mn and carbon cycles across fine-scale gradients in soils. To accomplish the overall objective, the specific aims are to (i) define the geochemical controls on Mn(III) formation along oxic-, (ii) identify the microbial drivers of Mn(III) formation, and (iii) assess the impact of Mn(III) formation on C oxidation at oxic-anoxic interfaces in soils. Disseminating the resulting dataset will support efforts to incorporate the coupling of Mn and C redox cycles into biogeochemical models. Integrating the highly significant Mn-dependence of C oxidation into models for the first time is expected to vastly improve accuracy in predicting environmental and human impacts on soil CO2 emissions. The project team will work to incorporate this multidisciplinary research effort into strategies to empower women and minority graduate, undergraduate and high school students to pursue STEM careers. A three-point plan integrates this research with direct interdisciplinary education and public outreach, which includes: (i) graduate training in biogeochemistry for one minority PhD student, (ii) opportunities for independent research for three minority undergraduate students in partnership with the Harvard Forest REU program, and (iii) multi-day workshops for a total of 45 female minority students from a local high school hosted in collaboration with Girls Inc. Holyoke, Massachusetts. Educational materials developed for the workshops will be disseminated through participation in the annual Massachusetts Envirothon. A thorough evaluation plan was developed in collaboration with Harvard Forest and Girls Inc. staff to measure the success of the proposed Broader Impacts activities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.