Environmental occurrence and source apportionment of synthetic phenolic antioxidants in typical coastal bays: Drivers and source-specific risk assessment

Synthetic phenolic antioxidants (SPAs) are emerging contaminants whose occurrence, sources, and risks in marine ecosystems remain poorly understood. This study assessed the occurrence, associated factors, potential sources, and ecological and human health risks of 16 SPAs in seawater, sediments, and clams from coastal bays of the Shandong Peninsula based on a single sampling campaign conducted in August 2024. Given the limited data available for SPAs, the driver, source, and risk analyses were exploratory and aimed to identify potential environmental and health implications. Σ₁₆ SPA concentrations ranged from 24,200 to 46,900 ng/L in seawater, 22,400–133,000 ng/g d.w. in sediments, and 49,600–156,000 ng/g d.w. in clams, with relatively higher levels in Laizhou Bay. Multivariate analyses identified matrix-specific associations with NO₂⁻-N, DOP, and GDP in seawater; DIN, DON, and Area in sediments; and RP, DON, and TDN in clams. Source apportionment suggested that petroleum and lubricants, plastics, and food- and feed-related applications were potential major sources. In both seawater and sediments, more than 50% of the investigated congeners showed high screening-level ecological risks, while approximately 15% showed moderate risks. Dietary exposure through clam consumption also indicated potential human health concerns. Source-specific analysis identified plastics, petroleum and lubricants, and food- and feed-related applications as potential risk contributors. These findings provide preliminary evidence of SPA contamination, sources, and risks in coastal ecosystems and support further monitoring, refined risk assessment, and targeted pollution management.