Effects of biodegradable and non-degradable microplastics on microbial availability and degradation of phenanthrene in soil

Biodegradable plastics have been increasingly used, however, may decompose into microplastics (MPs) more quickly than traditional plastics. In this study, biodegradable polybutylene adipate-co-terephthalate (PBAT) MPs were selected, and non-degradable polyethylene (PE) was used as the reference MPs. The impact of PBAT and PE MPs on microbial availability and degradation of phenanthrene in soil was investigated. The results showed that both the type and addition amount (0.2% and 2%, w/w) of MPs significantly affected phenanthrene degradation. Degradation ratio was reduced by the addition of MPs (by 10.6-80.2%), which was in the order of soil with PBAT > soil with aged PE > soil with PE no matter whether earthworms were present or not. Moreover, compared to PE, addition of PBAT more significantly decreased the concentration of phenanthrene in porewater and the polycyclic aromatic hydrocarbon (PAH)-degrader abundance, which is due to higher sorption affinity of phenanthrene to PBAT and more significant increase in the content of dissolved organic carbon in soil with PBAT, respectively. Additionally, compared to soil without MPs, phenanthrene degradation in soil with MPs was more significantly raised by the presence of earthworms, which is due to a more significant increase in the PAH-degrader abundance. • Biodegradable PBAT MPs were compared with non-degradable PE MPs. • Reduction of PHE degradation ratio by PBAT added was higher than that by PE added. • Higher sorption affinity of PHE to PBAT led to lower PHE bioavailability in soil. • Larger increase in DOC content inhibited PAH-degrader growth in soil with PBAT. • Earthworms more obviously increased PHE degradation in soil with MPs.