Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 3, 6708PB Wageningen, the Netherlands.
Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 3, 6708PB Wageningen, the Netherlands; Agroecología, El Colegio de la Frontera Sur, Unidad Campeche, Av Polígono s/n, Cd. Industrial, Lerma, Campeche, Mexico.
J Hazard Mater. 2023 Apr 5;447:130765. doi: 10.1016/j.jhazmat.2023.130765. Epub 2023 Jan 9.
The accumulation of microplastics poses potential risks to soil health. Here, we did a preliminary exploration on the potential of Lumbricus terrestris (Oligochaeta) to reduce low-density polyethylene (LDPE), polylactic acid (PLA), and polybutylene adipate terephthalate (PBAT) microplastic (20-648 µm) contamination in soils. The ingestion of microplastics-contaminated soil (1% of microplastics, dw/dw) in a mesocosm system and the ingestion of pure microplastics in the Petri Dish by earthworms were studied. Results show that earthworms survived in the microplastics-contaminated soil (0% mortality in 35 days) but barely when exposed solely to microplastics (30-80% mortality in 4 days). Size-dependent ingestion of microplastics was not observed. The fragmentation of LDPE microplastics in the gizzard facilitated by soil was confirmed by the significantly increased ratio of small-sized (20-113 µm) microplastics from the bulk soil to the gut (from 8.4% to 18.8%). PLA and PBAT microplastics were fragmented by gizzard without the facilitation of soil, the ratios of small-sized (20-113 µm) PLA and PBAT microplastics in the gut were 55.5% and 108.2% higher than in respective pristine distributions. Substantial depolymerization of PLA (weight-average molar mass reduced by 17.7% with shift in molecular weight distribution) and suspected depolymerization of PBAT were observed in the worm gut, while no change in the molar mass was observed for PLA and PBAT microplastics buried in the soil for 49 days. Our results suggest that ingested microplastics could undergo fragmentation and depolymerization (for certain polymers) in the earthworm gut. Further research is needed to reveal the mechanisms of polymer depolymerization in the earthworm gut and to evaluate the feasibility of microplastic bioremediation with earthworms.
微塑料的积累对土壤健康构成潜在风险。在这里，我们初步探索了赤子爱胜蚓（Oligochaeta）减少土壤中低密度聚乙烯（LDPE）、聚乳酸（PLA）和聚对苯二甲酸丁二醇酯（PBAT）微塑料（20-648μm）污染的潜力。在中观系统中，用受微塑料污染的土壤（微塑料占干重的 1%）喂食赤子爱胜蚓，并在培养皿中用纯微塑料喂食蚯蚓。结果表明，蚯蚓可以在受微塑料污染的土壤中存活（35 天内无死亡率），但当仅暴露于微塑料时，蚯蚓几乎无法存活（4 天内死亡率为 30-80%）。没有观察到对微塑料的尺寸依赖性摄取。通过土壤对胃中 LDPE 微塑料的破碎作用得到了证实，从大块土壤到肠道中小尺寸（20-113μm）微塑料的比例从 8.4%显著增加到 18.8%。PLA 和 PBAT 微塑料在胃中没有土壤的帮助下被破碎，肠道中小尺寸（20-113μm）PLA 和 PBAT 微塑料的比例分别比原始分布高出 55.5%和 108.2%。在蚯蚓肠道中观察到 PLA 发生了大量解聚（重均分子量降低了 17.7%，分子量分布发生了转移），并怀疑 PBAT 发生了解聚，而 PLA 和 PBAT 微塑料在土壤中掩埋 49 天后，其分子量没有变化。我们的结果表明，摄入的微塑料可能在蚯蚓肠道中发生破碎和解聚（对于某些聚合物）。需要进一步研究以揭示蚯蚓肠道中聚合物解聚的机制，并评估利用蚯蚓进行微塑料生物修复的可行性。
