微塑料对城市污水中胞内和胞外抗性基因的富集特征研究

作为近年来国内外关注的焦点问题，微塑料不仅本身具有生物毒性，还能携带多种污染物构成复合污染.然而目前对于微塑料携带抗性基因的污染特征尚鲜有研究.考察了聚丙烯、聚苯乙烯、聚乙烯及再生聚乙烯4种微塑料对城市污水中胞内与胞外抗性基因的富集特征与影响因素.结果表明:4种微塑料对胞外抗性基因的富集倍数在3.12×102~4.07×103之间，显著高于胞内（4.44×101~2.14×103），且对于同种污水类型，最高能达胞内的13.1倍.微塑料对二沉池出水中抗性基因的富集倍数（2.14×103~4.07×103）显著高于污水厂进水（3.12×102~7.61×102）和活性污泥（4.44×101~5.84×102）.微塑料类型对抗性基因的富集有显著影响，其中聚丙烯的富集能力最强，最高达3.03×1014 copies/g（胞内抗性基因）和6.27×1013 copies/g（胞外抗性基因）；聚苯乙烯对胞外基因的富集倍数高于聚乙烯，而对于胞内基因的富集倍数低于后者；再生聚乙烯与聚乙烯的富集能力无显著差异.微塑料对抗性基因的富集量与微塑料的粒径、浓度均成反比，富集过程遵循准二级动力学模型.研究显示，微塑料能大量富集污水中的抗性基因，特别是胞外抗性基因，从而显著提高抗性基因的迁移能力，增大后续公共健康风险. 

Enrichment of Intracellular and Extracellular Antibiotic Resistance Genes by Microplastics in Municipal Wastewater

As a worldwide hot-spot issue in recent years, microplastics (MPs) not only show biological toxicities, but also carry various contaminants and cause combined pollution. However, the current studies on the combined pollution of MPs carrying ARGs in municipal wastewater are still scarce. This study investigated the enrichment of intracellular ARGs and extracellular ARGs by four kinds of MPs, including polypropylene (PP), polystyrene (PS), polyethylene (PE) and recycled polyethylene (RCPE) in municipal wastewater, and then explored the influencing factors. The results showed that the enrichment of extracellular ARGs by MPs was 3.12×102-4.07×103, which was 13.1 times that of intracellular ARGs (4.44×101-2.14×103) for the same type of sewage. Higher enrichment of ARGs (2.14×103-4.07×103) by MPs was observed in the secondary effluent compared with the influent (3.12×102-7.61×102) and activated sludge (4.44×101-5.84×102). The enrichment of ARGs was also affected by the type of MPs. PP showed the highest enrichment capacities amongst all MPs, which were 3.03×1014 copies/g for intracellular ARGs and 6.27×1013 copies/g for extracellular ARGs. Compared with PE, the enrichment of PS was higher for extracellular ARGs, but it was lower for intracellular ARGs. No significant difference between RCPE and PE was found for the enrichment capacity. The enrichment of ARGs was negatively correlated with the size and concentration of MPs. In addition, the kinetics of ARGs enrichment by MPs was well described by the quasi-secondary kinetic model. This study indicates that MPs will dramatically enrich ARGs, especially extracellular ARGs in wastewater, which will lead to a significantly high mobility and consequently high risks to public health.