Microbial succession and functional responses in riverine sediments following transient 6PPD exposure and rapid contaminant dissipation

N -(1,3-Dimethylbutyl)- N ′-phenyl- p -phenylenediamine (6PPD), a widely used tire antioxidant, can be transformed into the highly toxic oxidation product 6PPD-quinone (6PPD-Q). Although both compounds are increasingly detected in aquatic environments, their potential impacts on sediment microbial communities remain poorly understood. Here, sediment–water microcosms combined with amplicon sequencing, ecological network analysis, community assembly analysis, and metagenomics were used to investigate the attenuation of 6PPD and associated microbial responses at environmentally relevant concentrations. Both 6PPD and 6PPD-Q dissipated rapidly, with most of the added compounds attenuated within the first few days of incubation. Despite this rapid dissipation, transient 6PPD exposure was associated with shifts in microbial community succession, network characteristics, community assembly processes, and nutrient-related physicochemical properties, including increased NH 4 + and SO 4 2− concentrations. Metagenomic analyses indicated that carbon-cycling functional potential remained comparatively stable, whereas nitrogen- and sulfur-cycling functional potential exhibited greater variation across treatments and incubation periods. These microbial and functional responses remained detectable after substantial dissipation of both 6PPD and 6PPD-Q. Together, these findings suggest that transient exposure to tire-derived contaminants can influence sediment microbial community structure and functional potential after the dissipation of the parent compounds. This study highlights the importance of considering microbial ecological responses when evaluating the environmental implications of tire-derived contaminants in aquatic sediments. Download: Download high-res image (336KB) Download: Download full-size image