生物炭对土壤中典型抗生素污染物迁移行为的影响研究

Antibiotics, as an important group of pharmaceuticals and personal care products (PPCPs) that has been defined as emerging contaminants, are of growing public concerns over its threats to the safety of both environment and human health. Soil has become an easy target for contamination due to the continuous input of these compounds by the agricultural practice of using manure as fertilizer and discharge of untreated wastes from livestock and poultry industry that contain a large variety of antibiotics. In this study, three frequently-detected antibiotics are chosen as target contaminants that are from different drug categories and of distinctive physicochemical properties. Biochars are to be produced from the pyrolysis of different biomass feedstock in the absence of oxygen, and will be used as amending material for the study on their impacts on the transport behavior of selected antibiotics in soil by conducting a series of experiments such as batch, miscible displacement column, unsaturated transient flow column and undisturbed soil column experiments.The major objectives of this study include: (1) to observe the changes in the adsorption-desorption isotherms and kinetic parameters of the selected antibiotics in the soil with and without biochar amendment, to determine the effects of soil organic matters and pH on the adsorption of antibiotics in the biochar-amended soil, and to select the optimal biochar product and the addition ratio to soil that are suitable for the treatment of all the studied contaminants; (2) to understand the mechanism of biochar amendment on the control of transport of target antibiotics in soil, especially from the perspective of biochar's surface morphology and internal pore structure characteristics; (3)to evaluate the amendment efficacy of biochar addition to the antibiotic-polluted soil under real rainfall conditions by conducting field plot experiment. Overall, this study aims to demonstrate that biochar amendment has significant enhancement in the retention of veterinary contaminants in soil. Therefore, application of biochar as an amending material should be further developed as a novel technology for soil pollution recovery and control, in the light of decreasing the risk of non-point source pollution by these emerging contaminants.

生物炭作为一类新型环境功能材料而被广泛研究，但它对土壤中抗生素类污染物迁移行为的调控机理及影响因素尚不明确。本项目拟以不同生物质原料制备生物炭，以三种理化性质差异较大的典型抗生素为目标污染物，研究土壤中施用生物炭对抗生素迁移行为的影响：（1）通过室内批量平衡和土柱实验，查明添加生物炭后，土壤中抗生素吸附-解吸特征参数及迁移性的变化，阐明土壤有机质含量、pH等性质的影响，并确定对目标抗生素有效的最优生物炭种类及施用量；（2）通过对生物炭表面形态及孔隙结构特征的表征与分析，揭示生物炭促进土壤对抗生素吸附的微观机理；（3）通过野外小区试验，定量评估自然降雨条件下生物炭施用对抗生素流失迁移的控制效果。该研究可为生物炭的土壤污染原位修复与控制技术的研发提供理论依据和可靠数据。

本项目依照计划书开展相关研究工作，以氟喹诺酮类、磺胺二甲基嘧啶、土霉素类等抗生素为目标污染物，采用室内批量平衡、原状土柱及野外小区等多尺度实验或试验研究，阐明了污染物在典型紫色土耕地土壤中的吸附-解吸和淋失迁移特征及生物炭施用的影响机制。本研究通过表面化学性质与内部孔隙结构的表征和对比分析，优选了用于抗生素污染减控的生物炭产品，该生物炭同时具有一定的保水能力。目标污染物在紫色土中的吸附强弱表现为：土霉素>氟喹诺酮类>磺胺二甲基嘧啶，生物炭施用对抗生素（尤其是磺胺二甲基嘧啶）的吸附-解吸过程有显著性影响，但不简单表现为促进吸附作用，田间老化是一个不可忽略的因素，生物炭自身性质在老化中发生变化，可导致对抗生素吸附促进作用的减弱。在自然降雨过程中，抗生素发生不同程度的解吸和迁移，其中氟喹诺酮类抗生素由于吸附性较强，主要分布在表层土壤中，而磺胺二甲基嘧啶则随径流发生淋失迁移。施用生物炭可降低抗生素的淋溶速率，从而减少污染物的淋失通量。但另一方面，由施炭引起的优先流现象和溶解性有机物的增加，也可促进污染物发生垂直迁移和胶体辅助运移，从而降低生物炭的减控效果。本项目弥补了现有研究缺乏野外试验的不足，为该领域的生物炭调控技术发展提供了重要的科学依据，因此，对降低抗生素非点源污染风险、保护长江上游水土环境质量具有重要意义。项目执行期间共发表研究成果论文8篇，其中SCI论文3篇（含TOP期刊论文1篇），EI论文2篇，均标注本项目资助（第一标注6篇，第二标注2篇）。