Occurrence of Organic Contaminants and Microbial Community Structure in River Sediments and Mollusks from an E-Waste Recycling Area in Southeast China

This study investigated the characteristics and interrelationships of polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), and microbial communities in coastal river sediments and benthic mollusks collected from an e-waste recycling area in Taizhou, Zhejiang Province. In sediments, 16 PAHs and six PAEs were detected, with concentrations ranging from 2.66 to 379.99 μg/kg and 76.5 to 3426.57 μg/kg, respectively. Four-ring PAHs (particularly fluoranthene and pyrene) and Bis(2-ethylhexyl) phthalate (DEHP) were dominant, with DEHP posing a potential risk, especially at site 10, warranting further attention. In contrast, only eight PAHs and four PAEs were detected in mollusks, with concentrations of 60.14–523.10 μg/kg and 144.55–3005.71 μg/kg, respectively. Two-ring PAHs (particularly naphthalene) and Dibutyl phthalate (DBP) were dominant, likely derived directly from the overlying water. The PAHs in sediments primarily originated from fossil fuel combustion, biomass burning, and coal combustion, while PAEs were likely derived from the release of plastic waste from solid waste recycling. Lower concentrations and fewer PAH and PAE species were observed in the sediments near the ocean and at greater distances from the e-waste recycling sites. Significant differences were observed in microbial communities between sediment and mollusk samples. Dominant phyla shared by both sample types include proteobacteria, bacteroidetes, firmicutes, and acidobacteria. The concentration of low-ring PAHs was correlated with the microbial communities, particularly in mollusk samples. Relationships were also identified between microbial communities and DEHP concentrations in sediments or DBP concentrations in mollusks.