非稳态pe+pH水稻土中硫对镉形态与有效性的影响机理

稻田土壤中硫（S）的形态与有效性是影响水稻吸收Cd的一个重要因子，但目前关于稻田土壤中S影响水稻Cd吸收的研究结果存在矛盾之处，这可能与非稳态pe+pH条件下水稻根际土壤S的形态转化驱动机制及S形态介导下Cd有效性变化机理不清有关。本项目拟选择不同性质水稻土，根据稻田土壤不同pe+pH情景（幼苗期强还原、根系泌氧、淹水及干湿交替），利用根箱、土培及盆栽试验，结合土壤Eh、pH原位测定、SEM/TEM-EDS测定及PCR扩增技术等，研究稻田土壤非稳态pe+pH条件下：1）水稻根际/非根际土壤中S形态转化及其与pe+pH量化关系；2）土壤中铁氧化物及S还原菌（SRB）群落变化对S形态转化影响；3）土壤性质对S形态转化影响及其预测模型；4）根际S形态对水稻根表微观结构影响及其与水稻根系吸收、转运Cd关系。通过上述研究，为揭示非稳态pe+pH下稻田土壤中S对水稻Cd吸收、转化影响机理。

The forms and its effectiveness of sulfur (S) are important factors affecting the uptake and accumulation of Cd by rice cultivars in paddy soils, however, contradictions still exist about the effect of sulfur on the uptake and translocation of Cd by rice plants in paddy soils, which may be related to the unclear mechanisms about the transfer of S forms and thereafter its influence on uptake of Cd by rice plants in paddy soils with unstable pe+pH conditions. Several kinds of paddy soils with various soil properties will be selected for study for this project, typical scenarios of paddy soils with unstable pe+pH condition (strong reduction in seedling stage, oxygen secretion by root, flooding and dry and wet alternation) will be simulated, and root box culture experiment, soil incubation and pot experiment will be conducted combined with the in-situ determination technology of Eh and pH value in soils, SEM/TEM-EDS and PCR measure technology to study: 1) the relationship between morphological transformation of S and pe+pH in rhizosphere/non rhizosphere paddy soils; 2) the effects of the forms of iron oxides and community of S reducing bacteria (SRB) on the morphology of S in soils; 3) the effects of soil properties on the morphology of S transformation and its prediction model; 4) the influence of forms of S on the microstructure of root surface of rice plants and their relationship with Cd uptake and its translocation in plants in rhizosphere/non rhizosphere soil. Through the above study, this project intends to reveal theoretical basis for the study of effect of S on the uptake and transformation of Cd by rice cultivars under unstable pe+pH conditions in paddy soils.