土壤矿物质在生物炭调控除草剂迁移中的影响与作用机制

The herbicides' movement in soil can be properly regulated by adjusting the sorption capacity of biochars as the soil amendment, by which the herbicides' pollution can be minimized without impacting their efficacies. But the performance of biochars in soils will be affected by the soil compositions and properties. Particularly in the soils with low content of organic matters and high leaching risk, the influence and action mechanisms of minerals in soils are worthy of further investigations. In this project, the typical combinations of clay minerals are selected due to their relative high sorption capacity and by simulating the mineral compositions in real soils. The various sorption interactions, as well their complementary or competing relationships in the complex system of clay minerals and biochars will be investigated, and the bonding principles among the various components will be further probed. The release experiments through simulative soil layers and leaching experiments in simulative soil columns will be carried out to investigate the roles of clay minerals on regulating the release and leaching behaviors with biochars. The mass transfer mechanisms at the interface between solid and aqueous phases, and leaching mechanisms in the one-dimensional soil columns will be discussed. The sorption, release and leaching behaviors will be mathematically analyzed and associated between each other, so as to understand the action mechanisms for regulating the release and movement of herbicides by using biochars in soils with high leaching risk. Finally, the performance will be tested and verified by using real soils. The research work is beneficial for improving the knowledge on movement of pollutants in soils amended with biochars, and guiding the practices on controlling the non-point agricultural pollution and on soil improvement using biochars.

利用生物炭吸附性能的可调性，作为土壤改良剂可调控除草剂在土壤中的迁移，在保持其药效的前提下最大限度地控制其污染。但是，生物炭输入土壤后的调控效果将受到土壤组成和性质的影响，尤其在有机质含量低、除草剂淋溶风险高的土壤中，土壤矿物质的影响及作用机制尚待深入探讨。本项目拟模拟真实土壤矿物质中吸附作用较强的粘土矿物组合，考察它们与生物炭复合后影响除草剂迁移的各种吸附作用、及互补或竞争关系，深入探讨各组分之间的结合原理。通过模拟土层释放实验、模拟土柱淋溶实验考察粘土矿物在生物炭调控除草剂释放和淋溶行为的作用，探讨除草剂由固相向水相的界面传质机理和一维土柱内的迁移机理。对吸附、释放和淋溶行为进行数学分析和关联，探明高淋溶风险土壤中利用生物炭调控除草剂释放和迁移的作用机制，并采用真实土壤加以验证。研究工作可加深对生物炭改良土壤中污染物迁移规律的认识，为控制农业面源污染、推广生物炭改良土壤提供理论指导。

由于生物炭在固碳减排、土壤改良、环境修复等方面的良好应用前景，近年来受到科学界乃至公众的广泛关注。作为吸附性能良好的土壤改良材料，生物炭输入后将改变土壤中除草剂原有的动态吸附-脱附平衡，进而影响除草剂的药效和土壤中的迁移行为。本项目以调控除草剂在土壤中的迁移行为为目标，考察典型土壤矿物质与生物炭复合体系中影响除草剂迁移的各种吸附作用、以及相互之间的互补或竞争关系，探讨典型矿物质对生物炭调节除草剂释放和淋溶行为的影响，探索除草剂在生物炭改良土壤中的迁移调控机制。完成的主要研究工作和取得的重要结果包括：.1）探讨了生物炭/矿物质复合体系中对除草剂的吸附竞争和互补关系。在复合体系中，虽然生物炭对吸附除草剂的相对贡献超过矿物质，但是仍有大量除草剂分布在矿物质表面，生物炭吸附的除草剂主要位于炭内部孔结构中。吸附位置的差异导致除草剂向水相释放速率的不同，为利用生物炭调控除草剂释放和迁移提供了依据。.2）发现氧化铝和蒙脱石可转移生物炭中的未碳化含氧有机质，提高生物炭的比表面积和孔容，发生所谓的“扩孔效应”。这种扩孔效应导致生物炭/矿物质复合体系对除草剂的吸附增强、释放延缓，有助于抑制除草剂的垂向淋溶。.3）对表征除草剂吸附、释放和淋溶行为的特征参数进行关联分析，初步提出基于矿物质和生物炭相互作用下的除草剂迁移调控机制。同时，选用红壤等真实土壤填充土柱，验证了生物炭改良土壤对除草剂释放和迁移的调控作用。.4）部分研究结果已整理发表SCI学术论文7篇、中文核心期刊论文2篇，其中SCI一区论文5篇。研制了基于粘土矿物和生物炭的除草剂缓释制剂，获得授权发明专利6项。进行了乙草胺水基悬浮剂的田间应用试验，取得了良好的缓释和污染减控效果。.本项目研究工作深化了对生物炭改良土壤中除草剂释放和迁移规律的认识，可为利用生物炭控制农药污染、提高农药利用率提供理论指导。