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

土壤是地球上巨大的、动态的碳陆地。微生物氧化碳的速度决定了有多少留在土壤中，或者以二氧化碳的形式排放出去。即使土壤碳氧化速率略有增加，也可能会增加大气中的二氧化碳含量，从而影响全球气候。锰是一种丰富而有效的氧化剂，但它对土壤碳氧化速率的影响尚不清楚。该项目将提供对锰化合物如何改变土壤中碳的氧化速度的新理解。这一新的科学知识将有助于改进我们对未来二氧化碳排放的预测，并将帮助社会制定限制排放的新战略。该项目将与校园和当地社区的多样性项目合作，以增强妇女和少数族裔学生追求STEM职业的能力。锰基氧化剂的形成正在成为土壤中碳氧化速率的关键调节因素，从而影响二氧化碳的排放。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锰(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，氧-缺氧界面是酶促形成溶解的Mn(III)的“热点”，随后解聚和溶解原本具有抗性的有机物，从而提高微生物的二氧化碳产量。这项研究集成了微传感器、光谱和多组学方法，以解决土壤中精细梯度上耦合的锰和碳循环问题。为实现这一总体目标，具体目标是：(1)明确土壤中氧化-缺氧界面上锰(III)形成的地球化学控制；(2)确定锰(III)形成的微生物驱动因素；(3)评价土壤中锰(III)形成对氧化-缺氧界面上碳氧化的影响。传播所产生的数据集将支持将锰和碳氧化还原循环的耦合纳入生物地球化学模型的努力。首次将碳氧化对锰的高度依赖性纳入模型，有望极大地提高预测环境和人类对土壤二氧化碳排放的影响的准确性。该项目团队将努力将这一多学科的研究工作纳入战略，以增强妇女和少数族裔研究生、本科生和高中生从事STEM职业的能力。一项三点计划将这项研究与直接的跨学科教育和公共宣传结合在一起，其中包括：(I)为一名少数族裔博士生提供生物地球化学研究生培训；(Ii)与哈佛森林REU计划合作，为三名少数族裔本科生提供独立研究的机会；以及(Iii)与马萨诸塞州Girls Inc.Holyoke合作，为当地一所高中的45名少数族裔女学生举办为期数天的研讨会。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进行传播。与哈佛森林和女孩公司的工作人员合作制定了一项全面的评估计划，以衡量拟议的更广泛影响活动的成功。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.