Interactions between manganese oxides and dissolved organic matter in soil

锰氧化物是普遍存在的土壤矿物。它们是重金属的有效吸附剂，对有机和无机化合物具有高氧化电位。了解影响锰氧化物反应性的因素对于预测土壤中养分、污染物和有机质的循环至关重要。一个重要但很少研究的因素是溶解性有机物（DOM）。目前关于（1）陆地DOM在锰氧化物上的吸附、（2）DOM与锰氧化物之间的氧化还原反应以及（3）DOM对锰氧化物转化反应的影响的系统信息很少。出于这个原因，我们计划批量实验，探索不同类型的DOM（水提取物从土壤有机层，细菌外聚合物）的吸附土壤相关的锰氧化物（δ-MnO 2，锰钾矿，锂磷矿，钙锰矿）作为化学变量的函数，如pH值，离子强度和溶液组成。使用现代的，主要是光谱，光谱和色谱方法，我们将调查锰的形态变化，以及在分子水平上的有机物。此外，我们将评估DOM对锰（II）催化的氧化锰转化的程度和动力学的影响还原土壤条件下。总的来说，该项目将大大提高对锰氧化物的环境反应性以及土壤中锰和碳循环之间的耦合的理解。

Manganese oxides are ubiquitous soil minerals. They are effective sorbents for heavy metals and have a high oxidation potential for organic and inorganic compounds. The knowledge of factors that influence the reactivity of manganese oxides is crucial for predicting the cycling of nutrients and pollutants as well as organic matter in soils. An important but rarely studied factor is dissolved organic matter (DOM). There is currently little systematic information on (1) the adsorption of terrestrial DOM on manganese oxides, (2) redox reactions between DOM and manganese oxides, and (3) the influence of DOM on manganese oxide transformation reactions. For this reason, we plan batch experiments to explore the adsorption of different types of DOM (aqueous extracts from soil organic layers, bacterial exopolymers) to soil-relevant manganese oxides (delta-MnO2, cryptomelane, lithiophorite, todorokite) as a function of chemical variables such as pH, ionic strength and solution composition. Using modern, predominantly spectroscopic, spectrometric and chromatographic methods, we will investigate speciation changes of manganese as well as organic matter at the molecular level. In addition, we will evaluate the influence of DOM on the extent and kinetics of manganese(II)-catalyzed manganese-oxide transformation under reducing soil conditions. Overall, the project will significantly improve the understanding of the environmental reactivity of manganese oxides and the coupling between manganese and carbon cycles in soils.