硫对秸秆还田下土壤镉有效性和稻米镉累积的影响机理

Crop straw incorporation is popular in oilseed rape (wheat)-rice rotation area. It was reported that straw incorporation increased soil fertility, also reduced the accumulation of cadmium (Cd) in rice, but results of a few experiments indicated straw incorporation increased soil Cd activity and promoted the accumulation of Cd in rice. The conflict was contributed to differences of soil pH, DOC due to straw incorporation, however, few knowledge is available about influence of sulfur on soil Cd available, and sulfur involved in migration and accumulation of Cd in rice under straw incorporation. A series of experiments (soil incubation experiments, pot experiments, field trials) were used to investigate the influence of straw incorporation of oilseed rape/wheat with different Cd accumulation ability to soils with different sulfur levels on the formation of S2-, SO42-. FeS, Cys. GSH in soil and soil pore water, and the formation of Cys、GSH、PC in rice, and sulfur-containing compounds involved in formation and activity of Cd (Cd2+, CdS) in soil, and root surface, plants (root, stem, shell, brown rice, aleurone layer, flag leaf), and subcellular (cell wall, cytoplasm, vacuole) of rice with different ability of Cd accumulation based on advance technologies, such as isotope tracer, FSEM+EDAX, GC/HPLC-MS, XAS etc., under two soil water managements (flooding during whole rice growth period; flooding before grain filling stage, subsenquent pre-harvest drainage). The results could help to understand sulfur involved straw incorporation on availability of Cd in soil, and accumulation of Cd in brown rice; and help to develop measures to reduce risk of Cd to food chain.

秸秆还田在油菜(小麦)-水稻轮作区普遍。秸秆还田可培肥土壤，减少稻镉累积；但镉污染区秸秆还田可提高稻镉累积，其与秸秆还田导致土壤pH、DOC变化有关；但硫对秸秆还田土壤镉活性及植株体镉运移影响的研究少。采用土壤培养、盆栽试验、田间试验，借助同位素示踪、扫描电镜、GC/HPLC-MS、XAS等技术，在二种水分管理(全生育期淹水、前期淹水+灌浆期排水)，前茬种植镉硫富集差异的油菜、小麦，将秸秆还田于不同硫水平的土壤上种植不同镉富集能力的水稻，探明土壤和孔隙水中S2-、SO42-、FeS、半胱氨酸、谷胱甘肽和稻植株体中半胱氨酸、谷胱甘肽、植物螯合肽形成规律，及其与土壤、根表、稻植株体（根、茎、壳、米、糊粉层、剑叶）和亚细胞（细胞壁、细胞质及液泡）中镉（Cd2+、CdS）含量的关联性；探明硫对秸秆还田土壤镉有效性和稻米镉累积的调控机制及影响机理，结果为减少污染稻田镉风险提供依据。