Iron plaque formation and its influences on the properties of polyethylene plastic surfaces in coastal wetlands: Abiotic factors and bacterial community.

Iron (Fe) plaques in coastal wetlands are widely recognized because of their strong adsorption affinity for natural particles, but their interaction behaviors and mechanisms with plastics remain unknown. Through laboratory incubation experiments, paired with multiple characterization methods and microbial analysis, this work focused on the characteristics of Fe plaques on low-density polyethylene plastic surfaces and their relationship with environmental factors in coastal wetlands (Mangrove and Spartina alterniflora soil). The results showed that iron plaques increased the adhesive force of the plastic surface from 65.25 to 300 nN and promoted the oxidation of the plastic surface. Fe plaque formation was stimulated by salinity, anaerobic conditions, natural organic matter, and a weak alkaline scenario (pH 8.0–8.3). The Fe content showed a stable positive correlation with heavy metals loading (i.e., As, Mn, Co, Cr, Pb, and Zn). Furthermore, we revealed that Fe plaque was positively regulated by Nitrospirae through 16S rRNA high-throughput sequencing analysis. Meanwhile, Verrucomicrobia and Kiritimatiellaeota. may act as depressants by consuming salt. This work illustrated that iron plaques could enhance the role of plastics in contaminant migration by altering their adsorption performance, providing new insights into plastic interface behavior and potential ecological effects in coastal wetlands. [Display omitted] • Linkage between plastics/microplastics and iron plaques has been revealed. • Salinity, pH, and oxygen affect the formation of Fe plaque on plastic surfaces. • The dominant Nitrospirae is associated with forming iron plaque on plastics. • Fe plaques on the LDPE surface enhance heavy metal adsorption. • Fe plaques promote the oxidation of plastic surfaces. [ABSTRACT FROM AUTHOR]