硫酸亚铁和硝酸铁施用对根际土壤-水稻系统中镉运移的影响

我国稻田镉（Cd）污染治理刻不容缓.氮（N）、硫（S）和铁（Fe）的生物地球化学循环，以及Fe-N和Fe-S循环耦合体系，都与土壤-水稻系统中Cd运移密切相关.以N、S和Fe对水稻生长的营养供给为切入点，研发抑制稻米Cd累积的营养型阻控技术及产品，势必能为稻田Cd污染治理提供新的解决途径.本文在前期研究成果的基础上开展根际袋-盆栽试验，分析硫酸亚铁（FeSO₄）和硝酸铁［Fe（NO₃）₃］处理条件下根际土壤中Cd活性变化与水稻体内Cd转运规律，探索糙米Cd累积的影响因素及制约机制.结果表明，FeSO₄和Fe（NO₃）₃处理都显著减小了根际土壤中有效态Cd（NH₄Ac-Cd）含量，且前者减小的幅度（55.6%）小于后者（76.0%）；FeSO₄和Fe（NO₃）₃处理都明显改变了水稻体内Cd分布特征，但前者增大了糙米Cd含量（0.6mg ·kg^-1），而后者却减小了糙米Cd含量（0.1mg ·kg^-1）.根表铁膜对Cd的吸附或与Cd共沉淀、水稻根、茎和叶对Cd的累积量增大以及根、茎和结节对Cd的转运能力增强，是导致FeSO₄处理中糙米Cd含量增大的重要原因；Fe（NO₃）₃处理中糙米Cd含量减小，则可归结为无定形铁矿物对Cd的吸附或与Cd共沉淀、铁硫化物与Cd共沉淀、茎和结节对Cd的累积量减小以及根、叶和结节对Cd的转运能力减弱.本研究成果将为后期营养型阻控产品及施用技术研发提供科学依据，并为我国稻田Cd污染治理提供重要参考.

Effects of Ferrous Sulfate and Ferric Nitrate on Cadmium Transportation in the Rhizosphere Soil-Rice System

Cadmium (Cd) contamination in the agricultural soils of China is a serious and growing environmental problem that urgently needs to be controlled and completely remediated. The biogeochemical cycles of nitrogen (N), sulfur (S), and iron (Fe), and the coupled cycles of Fe-N and Fe-S have been reported to control Cd transportation in the soil-rice system. Exploring practical remediation strategies for Cd from the perspective of the application of nutrients such as N, S, and Fe for rice growth is expected to obtain farm-specific and state-of-the-art technologies and products to reduce the accumulation of Cd in rice grains. Using our earlier study as a basis, the rhizosphere bag-pot experiment with ferrous sulfate (FeSO₄) and ferric nitrateFe(NO₃)₃] treatments was conducted to investigate Cd bioavailability in rhizosphere soil and Cd translocation in rice plants, and to highlight some possible factors and mechanisms controlling Cd accumulation in rice grains. The results showed that both FeSO₄ and Fe(NO₃)₃ treatments reduced the bioavailable Cd (NH₄Ac-Cd) content in rhizosphere soil, with the decreasing extent being significantly lower in the former (55.6%) than in the latter (76.0%). Both FeSO₄ and Fe(NO₃)₃ treatments changed the distribution characteristics of Cd in rice tissues, and the FeSO₄ treatment increased the Cd content in brown rice (0.6 mg·kg^-1), but the Fe(NO₃)₃ treatment decreased the Cd content in brown rice (0.1 mg·kg^-1). Adsorption or co-precipitation of Cd by iron plaque, increased accumulations of Cd in root, stem, and leaf, and enhanced translocations of Cd from root, stem, and nodule to brown rice occurred with the increased Cd content in brown rice of the FeSO₄ treatment. However, the decreased Cd content in brown rice with the Fe(NO₃)₃ treatment was ascribed to adsorption or co-precipitation of Cd by poorly crystalline Fe oxides and solid Fe sulfides, decreased accumulations of Cd in stem and nodule, and weakened translocations of Cd from root, leaf, and nodule to brown rice. These findings provide a scientific basis for the exploration and application of nutritive soil amendment, and will have significance in regards to the remediation of Cd-contaminated agricultural soils in China.