Changes in the mineral composition of paddy soils upon redox cycles

研究目的是阐明与氧化还原条件相关的矿物转化过程和土壤溶液组成的变化。假设水稻种植的持续时间根据氧化还原状态（记忆效应）分离了相似母质的土壤，这反映在矿物组合、土壤溶液化学组成和碳储量上。计划的工作包括氧化还原条件的实地测量，土壤溶液的分析和风化实验，测试矿物沿着最近（筑坝后50至1000年）的水稻土与非水稻土的时间序列进行比较。将分析近期、埋藏的古代（距今3000年）和史前水稻土（距今6000年）及其非灌溉/栽培的对应土壤的矿物组合差异。批量实验将提供氧化还原条件对测试矿物和土壤溶液组成影响的额外信息。结果将使用程序代码PHREEQC进行评估，以确定溶质的形态和矿物相的可能溶解和沉淀，并将更好地了解受氧化还原条件影响的矿物转化。

The study objective is to elucidate the processes of mineral transformation and changes in the composition of the soil solution as related to redox conditions. It is assumed that the duration of rice cultivation separates soils of comparable parent materials according to the redox status (memory effect), which is reflected by the mineral assemblage, the chemical composition of soil solution, and the carbon storage. The planned work includes field measurements of redox conditions, analyses of soil solutions and weathering experiments with test minerals along a chronosequence of recent (50 to 1000 years after dyking) paddy soils in comparison with non-paddy soils. Recent, buried ancient (up to 3000 years) and prehistoric paddy soils (up to 6000 years old) and their non-irrigated/cultivated counterparts will be analysed for differences in the mineral assemblage. Batch experiments will provide additional information on effects of redox conditions on test minerals and composition of the soil solution. The results will be evaluated using the program code PHREEQC for speciation of solutes and possible dissolution and precipitation of mineral phases and will provide a better understanding of mineral transformation as affected by redox conditions.