胶体作用下抗生素在不同质地土壤中的运移行为及数值模拟

The problem of antibiotic pollution in the soil environment has been widely concerned. The colloidal particles which are widely present in soil can serve as carriers to enhance or weaken the migration of antibiotics in underground environment, playing an important role in the fate of antibiotics. In this research, sulfadiazine (SDZ) resulting mostly from the use of contaminated excrements as fertilizer on agriculture land is investigated. Based on lots of laboratory experiments, combined with spectral analysis and other technical means, the transport rule of clay mineral colloids (kaolinite and montmorillonite) and soil water dispersive colloids are studied in different texture soils, as well as the influence of solution pH, ionic strength and flow rate. On this basis, the driving effect of colloid transport on the migration of sulfadiazine and its influencing factors are investigated under the two conditions of the coexistence of sulfadiazine with the colloid and the sulfadiazine already in the soil. Based on the experimental data, a sulfadiazine transport model under colloid action is constructed and the effect of colloid on sulfadiazine transport in soil is revealed. In addition, uncertainty analysis methods (DREAM) is used to identify the model parameters and perform sensitivity analysis in order to identify the major factors affecting the migration of sulfadiazine. Then the fate of SDZ in soils is simulated under some designed schemes which are close to natural situation. Through this research it can provide theoretical and scientific basis for soil environmental protection and pollution restoration.

土壤环境的抗生素污染问题已受到人们的普遍关注，土壤中广泛存在的胶体物质可作为载体增强或减弱地下环境中抗生素的迁移能力，对抗生素的归趋起着重要作用。本项目将以畜禽粪便土地利用所引入的磺胺嘧啶作为研究对象，主要采用室内土柱实验，借助光谱分析等技术手段，在研究黏土矿物胶体（高岭石和蒙脱石）和水分散土壤胶体在不同质地土壤中运移规律及其溶液pH、离子强度和流速影响的基础上，研究磺胺嘧啶与胶体共存时和存在于土壤时，胶体运移对磺胺嘧啶运移的驱动作用及其影响因素。以实验数据为基础，构建胶体作用下磺胺嘧啶运移模型，揭示胶体对土壤中磺胺嘧啶运移的影响规律。采用不确定性分析方法（DREAM）对模型参数进行识别和敏感性分析，识别出影响磺胺嘧啶迁移的主要因子，模拟预测与实际相符的预设方案下，磺胺嘧啶在土壤中的迁移行为，为土壤环境保护和污染修复提供理论基础和科学依据。

土壤抗生素污染已受到人们的普遍关注，土壤中广泛存在的有机、无机胶体可作为载体或干扰污染物的界面反应，对污染物的归趋起重要作用，并受土壤理化性质的影响。因此，开展了不同pH、阳离子类型、离子强度条件下，胶体（高岭石、蒙脱石、铁氧化物）对多孔介质中磺胺嘧啶（SDZ）和环丙沙星（CIP）运移的影响研究，探讨了不同形态（溶解态、胶体态）抗生素迁移特征，构建了胶体协同抗生素运移的数学模型；结合光谱分析明确了腐殖酸（HA）对SDZ在土壤中吸附迁移的影响及其作用机理。另外，针对日益突出的土壤重金属污染问题，开展了不同化学条件下，蒙脱石和腐殖酸胶体协同Cu运移的影响研究；实验并模拟分析了重金属在层状土壤中的共运移特征及模拟预测的不确定性。结果表明，高岭石胶体的携带作用促进了SDZ的迁移，随pH的升高，SDZ的移动性增强；Ca2+对胶体的聚沉和桥键作用抑制了SDZ的迁移。pH和阳离子对CIP运移的影响大于SDZ，不同pH条件下，胶体的携带和限制吸附作用共同主导了CIP的迁移；不同阳离子条件下，高岭石胶体促进了CIP 的迁移且移动性随离子强度和价态的增加而增加，而蒙脱石胶体则抑制了CIP的迁移，运移的影响主要受胶体的移动性及其对CIP吸附能力的控制。实现了对不同形态抗生素运移的模拟，提高了胶体作用下抗生素运移模拟预测的可靠性和准确性。铁氧化物胶体抑制了SDZ的运移，且改变了Cd对SDZ运移的影响，低Cd浓度下通过竞争吸附作用促进SDZ的运移，高Cd浓度下通过形成三元表面络合物抑制SDZ运移。HA通过疏水分配、氢键、络合和 π-π作用抑制了SDZ的迁移，被滞留的SDZ会缓慢释放，构成土壤和地下水污染的潜在风险。升高pH或降低离子强度，大量Cu随蒙脱石胶体的释放而发生迁移，使污染加剧。提出了重金属复合污染土壤中的“滚雪球效应”，确定性模型与蒙特卡方法相结合可提高层状土壤中污染物运移模拟预测的可靠性。