Zhao Yuanyuan, Jia Huiting, Deng Hui, Xing Wenzhe, Feng Dan, Li Jiatong, Ge Chengjun, Yu Huamei, Zhang Ying, Chen Haiying
College of Ecology and Environment, Hainan University, Renmin Road, Haikou 570228, China; Key Laboratory of Agro-Forestry Environmental Processes and Ecological Regulation of Hainan Province, Hainan University, Haikou 570228, China; Key Laboratory of Environmental Toxicology, Hainan University, Ministry of Education, Haikou 570228, China.
College of Ecology and Environment, Hainan University, Renmin Road, Haikou 570228, China; Key Laboratory of Agro-Forestry Environmental Processes and Ecological Regulation of Hainan Province, Hainan University, Haikou 570228, China; Key Laboratory of Environmental Toxicology, Hainan University, Ministry of Education, Haikou 570228, China; Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, Guangzhou 510006, China.
Sci Total Environ. 2023 Feb 1;858(Pt 3):160092. doi: 10.1016/j.scitotenv.2022.160092. Epub 2022 Nov 9.
As a reliable environment-friendly alternative, biodegradable plastic mulching films have been introduced into agricultural practice to reduce the adverse threats posed by conventional plastic products. Information regarding whether potential untoward effects of biodegradable plastics exist in soil and how strong are such effects on terrestrial organisms, however, still remains unknown. This study examined differences in the responses of earthworm, represented by Eisenia fetida, to exposure to biodegradable (PLA: polylactic acid) and conventional microplastics (PVC: polyvinylchloride, LDPE: low-density polyethylene) in soil with biogas slurry irrigation. Mortality, growth, histopathology and biochemical enzymes of the earthworms exposed to different concentrations of microplastics (5, 20 and 50 g/kg wet weight of soil, respectively) were investigated after 28 days of incubation in the experiment. The obtained results showed that the ecotoxicity of microplastics (MPs) to earthworms was time-dependent. Regardless of MPs type, continuous exposure to MPs at the concentration of 50 g/kg induced mucous vacuolization, longitude muscle disorder, and granular lipofuscin-like deposits generation in the epithelium. Moreover, tissue fibrosis and cavity formation were also observed in intestinal tissue. The presence of MPs stimulated the oxidative stress system of the earthworms, as indicated by the enhancement of malonaldehyde (MDA) content in vivo. The antioxidative defense system in earthworms was supposed to collapse at the MPs concentration of 50 g/kg after 28 days of exposure. Interestingly, PLA exhibited similar ecotoxicity effects with LDPE, which might violate the original intention of biodegradable plastics with less harmful or nontoxic influence on the terrestrial biotas. Thus, knowledge regarding the molecular and genetic mechanisms of the earthworms in soil containing biodegradable plastics should be further explored to better understand the risk posed by biodegradable plastics in the agroecosystem.
作为一种可靠的环保替代品，可生物降解塑料地膜已被引入农业实践，以减少传统塑料制品带来的不利威胁。然而，关于可生物降解塑料在土壤中是否存在潜在不良影响以及对陆地生物的影响强度如何，仍然未知。本研究考察了以赤子爱胜蚓为代表的蚯蚓在沼气液灌溉土壤中暴露于可生物降解塑料（聚乳酸：PLA）和传统微塑料（聚氯乙烯：PVC、低密度聚乙烯：LDPE）后的反应差异。在实验孵化28天后，研究了暴露于不同浓度微塑料（分别为土壤湿重的5、20和50 g/kg）的蚯蚓的死亡率、生长情况、组织病理学和生化酶。所得结果表明，微塑料对蚯蚓的生态毒性具有时间依赖性。无论微塑料类型如何，持续暴露于浓度为50 g/kg的微塑料会导致上皮细胞出现粘液空泡化、纵肌紊乱以及颗粒状脂褐素样沉积物生成。此外，在肠道组织中还观察到组织纤维化和腔隙形成。微塑料的存在刺激了蚯蚓的氧化应激系统，体内丙二醛（MDA）含量的增加表明了这一点。暴露28天后，在微塑料浓度为50 g/kg时，蚯蚓的抗氧化防御系统可能会崩溃。有趣的是，PLA表现出与LDPE相似的生态毒性效应，这可能违背了可生物降解塑料对陆地生物群落危害较小或无毒的初衷。因此，应进一步探索蚯蚓在含有可生物降解塑料的土壤中的分子和遗传机制，以更好地了解可生物降解塑料在农业生态系统中带来的风险。
