生物质炭老化对热带稻菜轮作土壤中抗生素归趋的影响及数值模拟

Biochar(BC) possesses good characteristics such as porous, alkali, strong adsorption capacity, and can be potentially applied in the reclamation of antibiotics pollution in tropical soils. However, the physical and chemical characteristics and environmental effects of soil would change under long term environmental effects. Rice-vegetable rotation cultivation is a quite common way of agricultural land use in tropical region. Consider the facts such as special hydrothermal features, low pH value and unstable characteristics of the system with long-term use of livestock manure based fertilizers, and the antibiotics in livestock manure-based fertilizers are easy to transport and have serious environmental risk, and therefore it is important to investigate their environmental fate under the process of BC aging, in the rice-vegetable rotation cultivation soil. In this proposal, the rice-vegetable rotation cultivation soil in Hainan will be used, and aging treatment will be placed on various BC with different characteristics. To quantifiably describe the environmental behavior of antibiotics in soil-water system under the unstable pH condition, the effects of BC aging on the physical-chemical characteristics and the adsorption, transport, and degradation behaviors of antibiotics will be studied, an acid-buffering model will be also modeled. Moreover, it also aims to elucidate the effects of aged BC on the antibiotics-absorption of rice and vegetables. The contents of antibiotics absorbed by crops will be taken as sources in an antibiotics’-fate model, and further combine with a water/ H+-transport model, to explain the effects of BC aging on the physical-chemical absorption by crops and their environmental effects in the crop-soil system.The above work will provide a theoretical basis for scientific fertilizer usage and the forecast of antibiotics environmental behavior.

生物质炭具多孔、碱性、吸附性强等特点，在土壤污染治理中具良好的潜力。但长期环境作用可导致其物理及化学性能、环境效应发生变化。稻菜轮作是热区常见的农业土地利用方式。针对该系统长期施用有机肥、水热规律特殊、pH值低且不稳定的实际，结合粪肥中抗生素易迁移和环境风险大的特点，探讨生物质炭老化过程中抗生素在热区稻菜轮作地中的环境归趋显得十分重要。本研究将以海南省稻菜轮作土壤为研究介质，对不同性质的生物质炭进行多种老化处理；研究生物质炭老化对土壤理化性质和抗生素吸附、迁移、降解行为的影响，并建立酸缓冲模型，实现pH不稳定下土水系统中抗生素环境行为的定量表达；研究老化生物质炭对稻菜抗生素吸收的影响，将作物吸收作为源汇相加入抗生素归趋模型；进一步联合水分和H+运移模型，定量揭示生物质炭老化对兽药抗生素在热带稻菜轮作系统中的物理化学作物吸收及其环境效应的影响。为合理施用生物质炭和预测抗生素归宿提供理论依据。

生物质炭具多孔、碱性、吸附性强等特点，在土壤污染治理中具良好的潜力。长期环境作用可导致其物理及化学性能、环境效应发生变化，但相关的研究还少有报道。本文以热区典型的农业废弃物为原材料制备生物质炭，调查了不同老化条件（恒温恒湿CM、变温恒湿VT、干湿交替AWD）对生物质炭理化性质的影响，在此基础上，研究了老化生物质炭对土壤中抗生素的吸附、迁移和降解等环境行为的影响。随着老化过程的进行，生物质炭的理化性质发生了明显的变化，且不同的老化方式和老化时间对生物质炭理化性质的影响强度也有所不同。老化增加了生物质炭的灰分、芳香性、疏水性及氧含量，进而影响了生物质炭对土霉素的吸附能力。不同条件下老化的生物质炭-土壤在不同老化阶段对土霉素的吸附过程均符合最初快速吸附、期间慢速吸附、最后吸附平衡的规律，伪二级动力学能对数据进行很好地拟合。与新鲜生物质炭-土壤相比，当老化进行到第100天时，其对土霉素的吸附能力增强，当老化进行到第300天时，其吸附能力降低。在老化的各个阶段，恒温恒湿和变温恒湿老化对生物质炭-土壤吸附能力的抑制作用均大于干湿交替老化，其吸附能力表现为AWD＞CM＞VT。老化生物质炭-土壤对土霉素的吸附反应均为自发、吸热且熵增大的反应，吸附过程主要为物理吸附。当生物质炭输入到土壤中后，土壤的基本理化性质和矿物质养分发生了明显的改变，且生物质炭的添加会抑制土壤中空心菜的种子发芽，但在生长后期促进了空心菜的生长。生物质炭处理降低了土霉素在空心菜茎叶中的迁移，且随着生物质炭添加量的增多，抑制作用增大。此外，生物质炭的施入可促进土霉素在土壤中的降解效率，且生物质炭的老化方式可影响土霉素在生物质炭土壤中的降解性能。通过上述实验获得的参数，利用Hydrus-1D软件建立淋溶动态模型，有效地阐述和预测了抗生素在老化生物质炭土壤中的迁移行为。本研究所得结果可为在热区农业土壤中合理施用生物质炭和预测抗生素归宿提供理论依据。