微塑料PVC与磺胺甲恶唑联合暴露大型溞引发的急慢性毒理效应

ACUTE AND CHRONIC TOXICOLOGICAL EFFECTS ON COMBINED EXPOSURE OF MICROPLASTIC PVC AND SULFAMETHOXAZOLE TO DAPHNIA MAGNA

  • 摘要: 为研究微塑料和抗生素的联合毒性效应与机制, 文章以大型溞(Daphnia magna)为受试生物, 以聚氯乙烯(Polyvinyl chloride, PVC)和磺胺甲恶唑(Sulfamethoxazole, SMZ)为代表性污染物, 开展污染物吸附互作和联合暴露实验(包括48h急性和21d慢性毒性实验), 关注污染物暴露对大型溞的生长生殖、氧化应激、肠道损伤和行为运动指标变化。结果显示, PVC对SMZ具有物理吸附作用; 在48h急性毒理实验中, PVC (1 mg/L)的存在减少了大型溞体内SMZ的含量, 从而降低了SMZ的致死率; 在21d慢性毒理实验中, SMZ单独或者与PVC(1 mg/L)联合暴露对大型溞致死率、蜕皮数和体长无明显影响, 但均会引发大型溞氧化应激和肠道损伤, 降低其运动能力, 并且PVC会加剧SMZ诱发的上述毒性效应。研究发现, 与短期暴露(48h)相比, 慢性毒性实验(21d)更能真实反馈PVC和SMZ的联合毒性; 两类污染物在水环境中长期共存时, 微塑料对抗生素的毒性增强作用需引起重视。研究可为微塑料-抗生素共存时的环境健康风险评估提供数据参考。

     

    Abstract: With the increasing production and application of plastics, there is growing concern regarding the ubiquitous distribution of microplastics and their coexistence with various contaminants. Meanwhile, antibiotics have been ubiquitously detected in aquatic environments due to their extensive production, poor absorption, and improper disposal of unused drugs. Sulfamethoxazole (SMZ), commonly used in veterinary medicine and aquaculture as an antibacterial compound, has been found in aquatic environments frequently. Interestingly, SMZ is also used as a feed additive to promote animal growth in farms and fish aquaculture. Polyvinyl chloride (PVC) microplastics, one of the most commonly used plastic materials, have been detected in various environmental compartments, including sediment, surface water, marine, and freshwater. Despite the toxicity of PVC and SMZ has been extensively studied, the combined toxic effects induced by the two pollutants on aquatic organisms remain largely unknown. In this study, adsorption experiments between PVC and SMZ were conducted. Then, Daphnia magna, a commonly used aquatic crustacean in ecotoxicological assessments, was chosen as the model organism to investigate the joint toxic effects of PVC and SMZ through 48h acute and 21d chronic toxicity experiments. We assessed a chain of parameters, including survival, growth, reproduction, intestinal structure, and locomotor behavior. The results showed that PVC could absorb SMZ through physical interaction. In the acute toxicity experiments, the presence of PVC (1 mg/L) reduced the SMZ content in D. magna individuals, thereby attenuating the lethal effects induced by SMZ exposure. In the chronic toxicity experiments, exposure by SMZ alone or in combination with PVC (1 mg/L) showed no significant effect on the mortality ratio, number of molts, or body length of the D. magna. However, the exposure to individuals of D. magna by SMZ alone or in combination with PVC aroused oxidative stress, intestinal damage, and locomotor inhibition. Moreover, the presence of PVC exacerbated the toxic effects. In conclusion, the findings revealed both antagonistic and synergistic toxic effects of PVC on SMZ, depending on the exposure dose and time. The chronic assays (21d) performed with the mixture of environmentally relevant concentrations of contaminants indicated that PVC enhanced the toxicity of SMZ to D. magna. This study provides new insights into the ecotoxicological effects caused by the co-existence of PVC and SMZ in aquatic environments. The study can also convince a reference for the underlying mechanisms of environmental behavior and toxicity aroused by the coexistence of microplastics and antibiotics on aquatic organisms.

     

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