The present survey examines the trophodynamics of a suite of 19 perfluoroalkyl substances (PFASs) in a temperate macrotidal estuary (Gironde, SW France). Across the 147 biota samples (18 taxa) collected, perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (FOSA), and C-C perfluoroalkyl carboxylates (PFCAs) were the most-recurrent analytes. ΣPFASs ranged between 0.66-45 ng per g of wet weight of the whole body. Benthic organisms had relatively high ΣPFASs compared to demersal organisms and displayed specific composition profiles with higher relative abundances of C and C PFCAs. Trophic magnification factors (TMFs) were determined through the use of linear mixed effect models including censored data, thereby considering data below detection limits as well as the interspecific variability of δN and PFAS levels (random effects). TMFs were almost consistently >1 in the benthic food web as well as when considering all data pooled together, providing evidence for the biomagnification of several PFASs in estuarine environments. In addition, in contrast with previous observations, TMFs determined in the estuarine benthic web were found to significantly decrease with increasing chain length for C-C PFCAs and C-C perfluoroalkyl sulfonates. This suggests that PFAS chemical structure might not be necessarily predictive of TMFs, which are also influenced by the trophic web characteristics.

In the Orge River, the contribution of PFAA precursors decreases between the base and the top of the trophic web.

Pools of aquatic plants and benthic invertebrates were collected along with 47 individuals from three cyprinid fish species (Barbus barbus, Gobio gobio, Rutilus rutilus) at a site in the Rhône River (France). Carbon and nitrogen isotopic ratios (δC and δN) and a wide range of per- and poly-fluorinated chemicals (PFASs) were analysed in all samples. The sum of PFAS concentrations (ΣPFAS) increased from aquatic plants to fish dorsal muscles; molecular profiles were dominated by C9-C13 perfluorocarboxylic acids (PFCAs), while perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (FOSA) were detected in all samples at lower concentrations. ΣPFAS and especially ΣPFCAs were higher in barbels (B. barbus) than in other species, while roaches (R. rutilus) were less contaminated by PFOS than barbels and gudgeons (G. gobio). Gudgeons accumulated significantly higher FOSA concentrations. Young (small) barbels displayed significantly higher PFOS, perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) concentrations than did large specimens; conversely, perfluorotetradecanoic acid (PFTeDA) concentrations were significantly higher in large barbels. Multiple linear regressions were performed on the whole set of fish samples with size, mass and isotopic ratios as explicative variables, and several single compounds as explained variables. Regardless of the compound, the regressions did not explain much of the contamination variability. However, adding species as a qualitative variable, i.e. performing analyses of covariance (ANCOVAs) improved the fit greatly, while adding sex did not. Diet (i.e. δC and δN) was the main factor explaining interspecific differences. Biotransformation was assessed by comparing concentration ratios of PFOS or FOSA to their precursors in the food-web compartments. These ratios increased from invertebrates to fish, and differed among fish species, suggesting that biotransformation occurred but was species-specific. Biomagnification factor calculations showed that C11-C13 PFCAs, PFOS and FOSA were apparently biomagnified in barbels and gudgeons.

A wide range of persistent organic chemicals, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), some insecticides, as well as polybrominated diphenyl ethers (PBDEs) and some perfluoroalkyl substances (PFASs) were analyzed in 17 bed sediments collected along the Saigon River and at adjacent canal mouths from upstream to downstream in Ho Chi Minh City (Vietnam). Concentrations were rather low for PAHs, as well as for legacy PCBs and dichloro-diphenyl-trichlorethane and metabolites (DDTs), or below detection limits for several PFASs and all PBDEs measured. Several insecticides (chlorpyrifos-ethyl, and the pyrethroids cypermethrin and λ-cyhalothrin) displayed rather high concentrations at a few sites within the city. There was no distinct upstreamdownstream trend for PAHs, (DDTs) or PCBs. Although adjacent canal sediments tended to be more contaminated than Saigon River sediments, the differences were not significant. Emissions are almost certainly substantial for PAHs, and probably also for other contaminants such as PBDEs and some PFASs. During the dry season, contaminants are presumably stored in the city, either in canals or on urban surfaces. Heavy rainfall during the monsoon period carries away contaminated particle flows into the canals and then the Saigon River. The strong tidal influence in the river channel hinders the accumulation of contaminated particles. Contaminated deposits should accordingly be investigated further downstream in depositional environments, such as the mangrove.

Trophic magnification factors (TMFs, i.e. the average change in the log-concentration of a pollutant per trophic level) have been extensively assessed for the so-called persistent organic pollutants, especially organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), which are biomagnified along the food web. In contrast, trophic dilution was documented for pollutants with a high metabolic transformation rate, such as phthalate plasticizers and PAHs (Polycyclic Aromatic Hydrocarbons). However, the fate of their metabolites across the food web has been rarely investigated. In this comparative study, the trophodynamics of 104 micropollutants and 25 of their metabolites were investigated in a freshwater food web from the urban Orge River, France. Trophic levels were determined using stable isotopes. Pyrethroid pesticides and their metabolites were not detected. As predicted, PCBs and OCPs biomagnified (TMF > 1), while all chlorinated paraffins (CPs), PAHs and phthalates underwent a trophic dilution (TMF < 1). TMFs significantly decreased with metabolic transformation rate and increased with hydrophobicity. The levels of PAH or phthalate metabolites were not significantly correlated to trophic levels or underwent a trophic dilution. This study highlighted that the relative contribution of metabolite levels in TMF values calculated for both parent compound and its metabolite(s) is weak compared to TMF values of the parent compound only in a riverine food web.

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