Biogeochemical reactivity of Fe-organic matter coprecipitates

土壤中的铁(III)(氢氧化物)-有机缔合在铁、碳和磷酸盐等营养物质的生物地球化学循环中发挥着重要作用。在暂时潮湿或淹水的土壤中，这种缔合可以通过溶解的有机物(OM)与Fe(III)(Hydr)氧化物(FHO)的共沉淀形成。目前尚不清楚是什么因素控制了Fe(III)-OM共沉淀物的形成和组成，以及其结构性质如何转化为所涉及的FHO和OM组分的循环。因此，该项目的目标是阐明(I)不同环境条件下Fe(III)-OM共沉淀物的结构特性，(Ii)Fe(III)-OM共沉淀物在氧气和缺氧条件下随后的抗溶解稳定性，(Iii)Fe(III)-OM共沉淀物在氧化还原振荡时组成的变化，以及(Iii)它们对氧离子吸附的累积影响。为了实现这些目标，将进行各种批量试验。通过使用多种分析工具，本项目将从根本上了解非生物和生物对酸性和中性临时潮湿土壤和氧化还原振荡土壤中Fe(III)-OM共沉淀物的形成、结构和生物地球化学反应的控制。

Iron(III) (hydr)oxide-organic associations in soils have been recognized to play an important role in the biogeochemical cycling of iron, carbon, and of nutrients like phosphate. In temporarily moist or water-logged soils such associations can form via the coprecipitation of dissolved organic matter (OM) with Fe(III) (hydr)oxides (FHOs). At present, it is generally unknown which factors control the formation and composition of Fe(III)-OM coprecipitates and how the structural properties translate into the cycling of the FHO and OM component involved. The objectives of the project are thus to elucidate (i) the structural properties of Fe(III)- OM coprecipitates under different environmental conditions, (ii) the subsequent stability of Fe(III)-OM coprecipitates against dissolution under both oxic as well as anoxic conditions, (iii) the changes in Fe(III)-OM coprecipitate composition upon redox oscillations, and (iii) their cumulative effects on oxyanion sorption. To achieve these goals, various batch experiments will be conducted. By using multiple analytical tools, this project will gain a fundamental understanding of the abiotic and biotic controls on the formation, structure, and biogeochemical reactivity of Fe(III)-OM coprecipitates in acidic and neutral temporarily moist soils and soils subject to redox oscillations.