Toxics

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants, yet most studies evaluate wastewater and surface waters as separate environmental compartments, limiting understanding of PFAS transport across connected aquatic systems. This study investigated PFAS occurrence, mixture composition, and cumulative contamination across municipal wastewater treatment plant (WWTP) effluent and hydrologically connected surface waters within a single watershed in southwestern Illinois, USA. The concentrations of 55 targeted PFAS in WWTP and surface water samples were determined by U.S. EPA Methods 533, 537, and 1633 coupled with solid-phase extraction and high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Mixture-based statistical approaches, including Bray–Curtis dissimilarity analysis, non-metric multidimensional scaling (NMDS), and permutational multivariate analysis of variance (PERMANOVA), were used to evaluate compositional similarity among sampling matrices. PFAS were detected in every sample, with 20 compounds identified overall. WWTP effluent exhibited the highest cumulative PFAS burden (median ΣPFAS = 49.6 ng/L) and greatest chemical diversity, with 18 compounds detected compared with 9–10 compounds in individual surface-water systems (median ΣPFAS = 9.75–18.2 ng/L). Perfluorobutanoic acid (PFBA), perfluorobutane sulfonic acid (PFBS), perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), and perfluoropentanoic acid (PFPeA) were consistently detected across sampling matrices, whereas perfluorodecanoic acid (PFDA), perfluoropropane sulfonic acid (PFPrS), perfluoro-4-ethylcyclohexane sulfonic acid (PFECHS), perfluorononanoic acid (PFNA), perfluoropentane sulfonic acid (PFPeS), 6:2 fluorotelomer sulfonate (6:2 FTS), 2h-perfluoro-2-decenoic acid (FOUEA), and N-methyl perfluorooctane sulfonamidoacetic acid (N-MeFOSAA) were detected exclusively in WWTP effluent. PFAS chemical diversity was strongly correlated with cumulative PFAS concentrations (Spearman ρ = 0.94, p < 0.001). This is the first study to document PFAS concentrations in WWTP effluent and Richland Creek in southern Illinois. PFAS mixture composition differed significantly among water sources, with water source explaining 53.8% of compositional variation (PERMANOVA, p < 0.001); more broadly, the distinction between WWTP effluent and surface water explained 34.1% of compositional variation (p < 0.001). These findings demonstrate distinct but compositionally related PFAS profiles across municipal WWTP effluent and hydrologically connected surface waters. The results also highlight the value of mixture-based approaches for characterizing PFAS occurrence, cumulative contamination, and compositional patterns across interconnected aquatic systems. Such approaches provide additional information beyond individual-compound assessments and may support wastewater management, environmental monitoring, and future PFAS risk assessment.

Mangroves are important sinks for marine microplastics, yet the effects of micro- and nanoplastics on mangrove seedlings remain insufficiently understood. Here, an outdoor pot experiment simulating mangrove field conditions was conducted to investigate the physiological and biochemical responses of Rhizophora stylosa (R. stylosa) seedlings to polystyrene microplastics (PS MPs; 5 μm) and nanoplastics (PS NPs; 100 nm) at concentrations of 50 and 500 mg/kg dry soil. Leaf net photosynthetic rate, total chlorophyll content, oxidative stress indicators in roots and leaves, and soil physicochemical properties were assessed. All four PS treatments significantly reduced leaf net photosynthetic rates compared with the control. At the end of the exposure period, total chlorophyll content decreased significantly by 52.6–64.8% under all treatments except the low-concentration PS NP treatment. PS NPs increased leaf catalase activity and reduced hydrogen peroxide (H₂O₂) content in both roots and leaves, whereas PS MPs had limited effects on the measured oxidative stress indicators. No significant changes were observed in soil physicochemical properties, including nitrogen content, C:N ratio, ammonium nitrogen, nitrate nitrogen, pH, and oxidation–reduction potential. Overall, PS exposure primarily affected photosynthetic performance and chlorophyll accumulation in R. stylosa seedlings, while its effects on the measured oxidative stress indicators and soil physicochemical properties were comparatively limited. These findings provide experimental evidence for assessing the potential physiological impacts of micro- and nanoplastic pollution on mangrove seedlings.

Surface sediments from 9 rivers in the hinterland of the Yellow River Delta in China were analyzed for five p-phenylenediamines (PPDs) and their quinones (PPDQs). PPDs and PPDQs were widely detected, with ΣPPDs and ΣPPDQs ranging from 0.02 to 31.7 ng/g dry weight (dw) and 0.03 to 72.8 ng/g dw, respectively. N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) was the dominant PPD, accounting for 42.96% of ΣPPDs, whereas N,N′-diphenyl-p-phenylenediamine quinone (DPPDQ) was the predominant PPDQ, contributing 59.3% of ΣPPDQs. ΣPPDs and ΣPPDQs concentrations differed significantly among rivers, with marked variation within the same basin. Significant differences in ΣPPDs and ΣPPDQs were observed among the economic level–road exposure groups. Most site-specific ΣRQ values (92.0%) were below the screening threshold of 1, with a median ΣRQ of 0.124. DPPDQ contributed the most to ΣRQ (39.32%), followed by 6PPD-quinone (6PPDQ) (24.14%) and N-cyclohexyl-N′-phenyl-p-phenylenediamine quinone (CPPDQ) (8.71%). The findings provided insights into the environmental behavior and monitoring of tire-derived contaminants in urban rivers.