Enhanced Ecological Risk of Plastic-Associated Chemicals by Microplastics in the Riverine Benthic Food Web

Microplastics (MPs) can be ingested by organisms and influence the bioavailability of plastic-associated chemicals (PACs), which may subsequently be transferred and biomagnified through food webs. Understanding their trophic transfer in benthic ecosystems is essential for ecological risk evaluation. This study examined the accumulation of MPs and PACs in benthic organisms of the lower Yangtze River, assessed their biomagnification and dietary intake, and evaluated PAC-related ecological risks across trophic levels. MPs and PACs widely co-occurred in benthic fauna, with concentrations of 63.04-1.55 × 10³ items/g and 304.91-1.84 × 10⁵ ng/g dry weight, respectively. MPs were predominantly <500 μm, dominated by fibers and fragments. 50 of 58 PACs were detected, with phthalate esters prevailing. Notably, cobiomagnification of MPs and 24 PACs occurred in Limnoperna lacustris, with BMFs of 13.52 and 1.76-179.32. Seven priority PACs (DnBP, DnOP, DEHP, EHMC, HMS, EHS, and OC) cobiomagnified with MPs, posing significant risks to predators (average risk characterization ratio: 3.15-3.77 × 10³). Risks of PACs to consumers were governed by their biomagnification and dietary intake. High consumption of the low-risk Limnoperna lacustris mitigated the elevated PAC risk in Eriocheir sinensis. This study provides critical insights into trophic transfer, biomagnification, and ecological risks of MPs and PACs in riverine benthic food webs.