Nowadays, while plastics offer convenience, they also pose significant environmental threats. Discarded plastic products can remain in the environment for hundreds of years. Although some plastics are biodegradable, the microplastics (MPs) resulting from their partial degradation remain harmful. Biodegradation may offer a way to break down various types of plastics without harming the environment. Soil plays a significant role in the degradation of organic matter in nature. Soil organisms are supposed to be the key to biodegradation of plastics in soil. The study aimed to explore the effect earthworms have on the biodegradation of MPs in soil. Eisenia fetida was used in the study and plastics involved in the experiment are polystyrene (PS), the non-biodegradable plastic, and polylactic acid (PLA), the biodegradable plastic. In the experiment, soil containing earthworms was supplemented with PS MPs and PLA MPs, with control groups established. After experimenting, 16S-rRNA sequencing was performed on the microbes from the soil and earthworm guts. The experimented MPs were extracted. SEM and FTIR analyses were conducted to assess the morphological and chemical changes in the MPs. The study found that the involvement of earthworms promoted the degradation of PLA MPs, but had no significant effect on PS MPs in the short term. In addition, the presence of earthworms can make some microbes able to participate in degradation and be more adaptable to MPs in soil.
Zhou et al. (Thu,) studied this question.