New insight into the mechanism underlying the effect of biochar on phenanthrene degradation in contaminated soil revealed through DNA-SIP.

Biochar has been widely used for the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil, but its mechanism of influencing PAH biodegradation remains unclear. Here, DNA-stable isotope probing coupled with high-throughput sequencing was employed to assess its influence on phenanthrene (PHE) degradation, the active PHE-degrading microbial community and PAH-degradation genes (PAH-RHDα). Our results show that both Low-BC and High-BC (soils amended with 1 % and 4 % w/w biochar, respectively) treatments significantly decreased PHE biodegradation and bioavailable concentrations with a dose-dependent effect compared to Non-BC treatment (soils without biochar). This result could be attributed to the immobilisation of PHE and alteration of the composition and abundance of the PHE-degrading microbial consortium by biochar. Active PHE degraders were identified, and those in the Non-BC, Low-BC and High-BC microcosms differed taxonomically. Sphaerobacter, unclassified Diplorickettsiaceae, Pseudonocardia, and Planctomyces were firstly linked with PHE biodegradation. Most importantly, the abundances of PHE degraders and PAH-RHDα genes in the 13C-enriched DNA fractions of biochar-amended soils were greatly attenuated, and were significantly positively correlated with PHE biodegradation. Our findings provide a novel perspective on PAH biodegradation mechanisms in biochar-treated soils, and expand the understanding of the biodiversity of microbes involved in PAH biodegradation in the natural environment.

Interactions between microplastics and organic compounds in aquatic environments: A mini review.

Microplastics (MPs) are widely distributed in aquatic environments. They may release toxic substances or act as carriers for other organic compounds and pathogens, with potential to cause harm to the ecological environment and human health. A key concern is how MPs interact with organic compounds. We reviewed related works conducted under both laboratory conditions and in field aquatic environments to investigate the mechanisms of interactions between MPs and organic compounds from three perspectives: MPs, organic compounds, and environmental factors. The crystallinity and specific surface area of the MPs, and the functional groups, ionic form and strength of both MPs and organic compounds are key factors affecting their interactions. Environmentally realistic concentration settings for both MPs and organic compounds are critical for interpretation of the results of sorption experiments. The effect of salinity on interactions is mainly due to changes in pH. These results contribute to a better understanding of the environmental behavior, and potential ecological and human health risks of microplastics.