施用有机肥对土壤-水稻系统砷形态转化的影响及作用机理

Arsenic is one of the typical pollutants in paddy soil of southern China. The environmental behavior of arsenic could be affected by the application of organic manure in soil. However, the effect and microbial mechanisms of organic manure on arsenic transformation in soil-rice system as organic matter are still unclear. Therefore, the research of microbial mechanisms of arsenic transformations affected by organic manure in soil-rice system will be full of theoretical importance and practical value, since it will help to reduce arsenic pollution in paddy soil based on rational application of organic manure. Therefore, field investigation, rice-pot trials, and anaerobic microcosms will be conducted to explore how the application of organic manure affects the formation of soil aggregate and root plaque. And the influence of organic manure application on the oxidation, reduction and methylation of arsenic in the soil will be discussed and answered. Furthermore, the coupling relationship between electron transfer of organic manure and its different component with the transformation of arsenic will be investigated. On this basis, real time PCR analysis, high-throughput sequencing, metagenome sequencing will be used to investigate the activity, diversity and abundance of the functional microorganisms of arsenic, explore the bacteria groups and mechanism that couple extracellular electron transfer with the transformation of arsenic; reveal the microbial mechanisms of arsenic behavior effected by organic manure. Finally, the response and mechanisms of arsenic transformations affected by organic manure in the soil-rice system will be clearly and systematically presented.

砷是我国南方地区水稻土中典型的污染物之一，有机肥的施用会影响砷在农田土壤中的环境行为，然而其作为有机质输入对土壤砷行为的影响规律与微生物机制还不清楚。开展有机肥对土壤-水稻系统中砷迁移转化的影响及微生物机制研究，可以为合理施用有机肥，减少水稻砷污染提供理论依据。本项目结合野外采样调查、水稻盆栽试验以及厌氧微宇宙培养试验，研究有机肥施用对土壤团聚体、水稻根表胶膜形成及土壤中砷氧化、还原和甲基化过程的影响，探讨有机肥及其不同组分介导的电子传递与土壤中砷迁移转化的耦合作用。在此基础上，采用实时荧光定量qPCR、宏基因测序技术，分析有机肥施用土壤中砷功能微生物菌群的活性、多样性与基因丰度，研究耦合电子传递和砷代谢主要功能微生物的类群及作用机理，探明有机肥作为有机质驱动砷迁移转化的微生物机制，最终系统阐述施用有机肥对土壤-水稻系统中砷形态转化的影响及作用机理。

砷（As）是我国南方地区水稻土中典型的污染物之一，如何降低砷的生物有效性，减少水稻土砷污染是当前研究的热点。有机质是影响土壤中砷迁移转化的重要因素，有机肥施用于农田一方面可以实现废物的资源化利用，增加土壤肥力，另一方面，作为有机质会影响砷在稻田土壤中的环境行为。然而有机肥对土壤-水稻系统中砷形态转化的影响规律与微生物机制还不清楚。本项目结合野外采样调查、土壤培养试验，研究有机肥施用对土壤中砷形态转化和水稻对砷吸收的影响及微生物机制；通过添加碳源培养试验探讨不同类型碳源对土壤砷形态转化的影响规律；将有机肥分成不同组分探索有机肥施用影响土壤砷迁移转化的主要组分，以及有机肥施用影响土壤溶解性有机质分子组成耦合砷迁移转化的规律，并对如何减少有机肥施用引起的土壤砷还原释放进行了探索性研究。研究结果表明：（1）有机肥的施用显著促进了较高砷含量土壤（> 30 mg/kg）中砷的还原释放和甲基化；虽然长期施用有机肥对水稻籽粒中总砷含量没有显著影响，但是稻米中As(III)显著增加，增加了稻米砷的毒性；长期施用有机肥促进了水稻根表胶膜中的砷还原，抑制了铁和硫还原，长期施用有机肥可能通过影响水稻根表胶膜砷，铁和硫相关微生物的氧化还原过程影响砷的生物有效性；（2）添加碳源促进了土壤砷的释放，增加土壤溶液中总砷的含量，葡萄糖处理的效果最显著；葡萄糖处理主要通过增加土壤溶液中溶解性有机碳的含量促进砷的释放；（3）有机肥中的富里酸是促进土壤砷还原释放和产甲烷的主要组分，添加锰氧化物可以促进土壤砷的氧化和吸附，通过抑制铁氧化物的还原溶解间接控制砷的释放，还可以减少有机肥施用引用的甲烷排放；有机肥施用后分解产生的单宁酸类物质与砷的还原释放相关，而不饱和烃类物质与砷的甲基化相关。该项目可以为合理施用有机肥，减少稻田土壤砷污染以及水稻砷吸收提供理论依据。