生物质炭对坡耕地紫色土水分物理特性和抗生素迁移的影响机理与调控研究

In this study, biochars produced at different slow pyrolysis temperatures using various biomasses will be used to control the transport of three antibiotics (sulfadiazine, tylosin, norfloxacin) in purple soil which is widely distributed in Southwest China. Parameters including soil's aggregate stability, wettability, macropore contribution to flow, and available water capacity, fraction of mobile water, concentration and composition of dissolved organic matter, degradation, adsorption, and desorption coefficients and retardation factor of antibiotics will be determined. Using field stabilized biochar-amended soil, laboratory batch and undisturbed column experiments and in situ field trials on sloping farmland plots will be conducted to examine the physical and chemical mechanisms of soil-biochar-antibiotics interactions regarding water availability and migration of antibiotics through surface runoff and leaching. Bromide, deuterium, and oxygen-18, will be used as tracers for the mobile fraction of soil water, and three-dimensional excitation?emission matrices fluorescence spectroscopy and UV absorption spectroscopy of dissolved organic matter as fingerprints indicating its sources. The effectiveness of using optimized mixture of biochars and constructing ridge-ditch at foot slope to reduce antibiotics transport in dissolved, sediment and colloidal particle-associated forms will be tested at the field sloping plot scale, which will be also numerically simulated using dual-porosity model and calibrated parameters with field data.

以常用抗生素磺胺嘧啶、泰乐菌素和诺氟沙星为目标污染物，以西南地区分布广泛的紫色土坡耕地为对象，分析土壤-生物质炭-抗生素相互作用，重点考察土壤的团聚体稳定性、可润湿性、大孔隙水流贡献率、有效水含量和可动水比例、溶解性有机质浓度与组成、抗生素的降解率、吸附与解吸常数、迟滞系数等指标，通过批量平衡实验、原状土柱实验以及野外坡耕地标准径流观测场试验，利用溴离子、氢氧稳定同位素(氘和氧-18)和溶解性有机质的三维激发-发射荧光和紫外吸收光谱特征，揭示不同原料和热解温度制备的生物质炭对土壤导水特性与有效水持留能力、抗生素的水溶态、泥沙与胶体颗粒结合态迁移规律的影响，阐明其微观物理与化学机理，获取坡耕地抗生素迁移模型预测所需的双孔域水力学与反应性迁移参数，评估生物质炭的面施结合含生物质炭边沟-地埂的修建用于控制坡耕地抗生素迁移流失的效果和可行性。

本项目以常用抗生素磺胺嘧啶、泰乐菌素和诺氟沙星为目标污染物，以西南地区分布广泛的紫色土坡耕地为对象，通过吸附-解吸批量平衡实验、填装与原状土柱穿透实验以及野外坡耕地小区及土槽（6度）试验与降雨事件性观测等，利用溴离子、氢氧稳定同位素（氘和氧-18）示踪法和溶解性有机质的三维激发—发射荧光和紫外吸收光谱特征法源解析法，阐明了土壤—生物质炭—抗生素相互作用及生物质炭老化作用的影响机制；发现施用1%混合农作物秸秆生物质炭一年后，采用van Genuchten（1980）单孔域模型拟合所得的水分特征曲线的拐点斜率增大，说明土壤物理质量发生改善；采用双指数双孔域模型拟合则进一步发现，施用生物质炭能降低对植物无效的土壤滞留水和易流失的结构性孔隙水的含量，而基质性孔隙中的植物有效水含量和饱和导水率显著提高；发现泰乐菌素和诺氟沙星吸附性较强，主要集中在坡耕地土壤表层，迁移能力弱，而吸附性较弱的磺胺嘧啶的迁移性比其他两种抗生素强；面施1%生物质炭能有效降低土壤孔隙水中的抗生素浓度；在坡耕地地表径流产生的初期，坡底边沟-地埂式含5%生物质炭可渗透反应墙的构建能有效降低地表径流量，并能阻控磺胺嘧啶随径流的迁移；生物质炭老化作用对土壤中抗生素吸附及迁移的影响因抗生素理化性质而异，生物质炭理化性质的变化和溶解性有机质的流失是关键过程。这些研究结果为低山丘陵区抗生素的环境迁移行为及归趋分析、生物质炭土壤环境效应评估及流域非点源污染防治提供了重要的科学依据。