微塑料 (Microplastics, MPs) 是一种新兴污染物，并且已被证实在环境中无处不在。微塑料对水生生物的生态毒性已经被广泛研究，然而很少有研究关注土壤动物。本研究选择不同粒径聚苯乙烯 (0.04 μm和4.5 μm) 和聚乙烯 ( < 500 μm) 塑料微球为研究对象，以跳虫Folsomia candida为实验动物，研究了跳虫对微塑料的摄入以及排泄情况，微塑料对跳虫回避、繁殖行为和肠道微生物的影响以及微塑料复合污染对跳虫繁殖行为的影响，系统地揭示了微塑料对跳虫的生态毒性效应，这对土壤中微塑料的生态风险评估具有重要意义。主要研究内容及成果包括：
（1）跳虫能够摄入0.04 μm和4.5 μm的聚苯乙烯微塑料，主要分布在肠道中。粒径较小的微塑料在跳虫肠道内停留时间更长。环境浓度下4 μm聚苯乙烯微塑料不会使跳虫产生回避行为，但能够显著抑制跳虫的繁殖率，当土壤中微塑料浓度达到0.005%时，其繁殖率即明显降低；浓度为1%时跳虫繁殖率下降58%，无明显的剂量-效应关系。基于繁殖的半数效应浓度 (Half-maximal effective concentration, EC50) 值为0.23%。
（2）环境浓度的聚乙烯微塑料对跳虫的回避、繁殖行为有明显影响。跳虫对聚乙烯微塑料会产生显著的回避行为，且随着浓度升高，这种回避行为增强。28天的繁殖实验结果表明，随着聚乙烯微塑料浓度的上升跳虫的繁殖率呈现下降趋势。当微塑料浓度达到0.1%时，跳虫繁殖被明显抑制，在1%的最高微塑料浓度下，跳虫的繁殖率下降70.2%，基于繁殖的EC50值为0.29%。微塑料显著改变了跳虫肠道微生物群落，显著降低了跳虫肠道微生物的物种多样性。微塑料处理组中跳虫肠道内细菌沃尔巴克氏体 (Wolbachia) 相对丰度显著降低，这可能是造成跳虫繁殖率降低的原因之一；而慢生根瘤菌科 (Bradyrhizobiaceae)、剑菌属 (Ensifer) 和寡氧单孢菌 (Stenotrophomonas) 相对丰度显著升高，这可能影响土壤中的养分循环和污染物转化。
（3）微塑料复合污染对跳虫的繁殖毒性要显著低于单一微塑料污染的毒性。金霉素在土壤中浓度达到50 mg/kg时会显著抑制跳虫的繁殖，基于繁殖的EC50值为177.7 mg/kg。环境浓度下金霉素对跳虫的繁殖影响可能有限。当微塑料与有机污染物金霉素、BDE47和五氯酚复合污染土壤后，跳虫繁殖的抑制率相对于单一微塑料污染要显著缓解。
Microplastics (MPs) are an emerging pollutant and have proven to be ubiquitous in the environment. The ecotoxicity of MPs to aquatic organisms has been extensively studied, but few studies have focused on soil invertebrates. In this study, plastic microspheres with different particle sizes of polystyrene (0.04 μm and 4.5 μm) and polyethylene (< 500 μm) were selected as target pollutants. The soil springtail Folsomia candida was used as the experimental animal to study the ingestion, egestion, ecotoxicological effects of MPs and their combined pollution. This study systematically revealed the ecotoxicity effects of MPs on springtails which is of great significance for the ecological risk assessment of MPs in soil. The main research contents and results include:
(1) Springtails can ingest 0.04 μm and 4.5 μm of MPs, which are mainly distributed in the gut. 0.04 μm microplastics have a longer residence time in the gut relative to 4.5 μm. Environmental concentration of 4 μm polystyrene MPs did not cause avoidance behavior of springtails, but the reproduction behavior of the springtails was significantly inhibited. When the concentration of MPs in the soil reached 0.005%, the reproduction rate decreased significantly. When the concentration was 1%, the reproduction rate decreased by 58%, no obvious dose-effect relationship was observed. The EC50 value of reproduction was 0.23%.
(2) Polyethylene MPs with environmental concentration have a significant effect on the avoidance and reproduction behavior of springtails. Springtails exhibited significant avoidance behavior on polyethylene MPs. The number of springtails in the soil without MPs in the 0.5% and 1% treatment groups was significantly higher than that in the soil with MPs, accounting for 83% and 88%, respectively. The avoidance rates of the two treatments were 59% and 69%, respectively, and this avoidance behavior was stronger as the concentration increased. The results of 28-day reproduction experiment showed that the reproductive rate of springtails decreased with the increase of the concentration of polyethylene MPs in soil. When the concentration of MPs reached 0.1%, the reproduction rate of the springtails was significantly decreased compared with the control. At the highest MPs concentration of the experiment, the reproduction rate of springtails decreased by 70.2%, and the EC50 value based on reproduction was 0.29%. MPs significantly changed the gut microbial community of springtails, relative abundance of Wolbachia was significantly reduced, while the relative abundances of the Bradyrhizobiaceae, Ensifer and Stenotrophomonas were significantly increased. In addition, MPs significantly reduced the alpha diversity of the gut microbes in the gut of springtails.
(3) When the concentration of chlortetracycline reached 50 mg/kg in soil, the reproduction of springtails was significantly inhibited. The reproduction rate decreased by 61.1% at the concentration of 500 mg/kg, and the EC50 value based on reproduction was 177.7 mg/kg. The effect of environmental concentration of chlortetracycline on the reproduction of springtails may be limited. When the soil was contaminated by MPs combined with the organic pollutants chlortetracycline, BDE47 and pentachlorophenol, the inhibition of the reproduction rate of the springtails was significantly relieved compared to the soil with MPs pollution only.