Sampling of freely dissolved per- and polyfluoroalkyl substances (PFAS) in surface water and groundwater using a newly developed passive sampler

Passive sampling methods offer several advantages over traditional grab water sampling techniques, including time-integrative results which better represent long-term concentrations at the site and separation of the freely dissolved fraction of the contaminant which offers insight into the associated risk. This paper describes the performance of a newly developed equilibrium regimen passive sampler designed specifically for per- and polyfluoroalkyl substances (PFAS), called PFAS INSIGHT®. The sampler is effective in sampling ionic (sulfonates and carboxylates) and non-ionic (PFAS precursors) PFAS from aqueous solutions with detection limits similar or lower (depending on the analyte) to those achievable with conventional water sample analysis. Results include laboratory characterization of sorbent adsorption kinetics and adsorption isotherms for 15 PFAS analytes with carbon chain lengths of 4-12, the effects of the sample matrix on PFAS partitioning, and sorbent extraction efficiency. Results from PFAS INSIGHT® field deployments demonstrate good agreement between the concentrations calculated from the passive sampler data and the concentrations measured directly in conventional water samples. Approximately 35% of the passive sampling results were within 2-fold of the conventional water sample concentrations, 71% within 5-fold, and 88% within 10-fold.

Reduced bioavailability and ecological risks of polycyclic aromatic hydrocarbons in Yangshan port of East China Sea: Remediation effectiveness in the transition from construction to operation

To assess the remediation effectiveness of ecological restoration in the transition period from construction to operation of Yangshan Port, the largest deepwater port of East China Sea, we employed equilibrium passive sampling and partitioning theory to assess the changing bioavailability and flux of polycyclic aromatic hydrocarbons (PAHs) in relation to bioaccumulation and ecological risks in marine organisms. Due to the ecological restoration efforts, both the bulk and bioavailable concentrations of PAHs in sediment and surface seawater samples decreased dramatically after the port entered the operation phase, as compared with those reported during the last construction phase. PAH concentrations in the marine organisms also showed a dramatic decline, and corresponded to the change in the freely dissolved fractions of PAHs in sediment/surface water according to their thermodynamic potential for bioaccumulation. While trophic magnification of ΣPAHs was observed in the pelagic communities, concentrations of PAHs in benthic species were relatively consistent across multiple trophic levels, and were generally higher than those in pelagic species. The differing bioaccumulation between benthic and pelagic species may be related to the habitat-specific bioavailability of PAHs and the prey-predator relations among different species. The incremental lifetime cancer risks (ILCR) of PAHs in marine organisms also dropped by nearly three orders of magnitude, and were lower than the guideline (1 × 10^-6) proposed by the U.S. EPA, except for several species at higher trophic levels. Overall, our study highlights an integrated use of passive sampling and equilibrium partitioning theory as a robust tool that can be applied to assess the effectiveness of ecological remediation in the port environment with quantitative, mechanistic insights from bioavailability to bioaccumulation.

Equilibrium sampling reveals increasing thermodynamic potential of polycyclic aromatic hydrocarbons during sewage sludge digestion

The reuse of digested sludge from wastewater treatment plants (WWTPs) as soil fertilizer poses a risk for contamination of soil and water environments. The present study provides a new approach for investigating the exposure of hydrophobic organic chemicals in sewage sludge. The methodology of equilibrium sampling with multiple thicknesses of silicone was successfully validated and applied to complex sludge matrices. Polycyclic aromatic hydrocarbon (PAH) concentrations in silicone (C_silicone) were determined and compared across four WWTPs. Activity ratios (ARs), defined as C_silicone at equilibrium with digested sludge (final product) over C_silicone at equilibrium with secondary sludge (intermediate product), were in the range 0.85-20 with all except one AR>1. These ARs thus revealed increased thermodynamic potential of both parent and alkylated PAHs in digested sludge compared with secondary sludge, and thereby higher exposure of PAHs in sludge after digestion than before digestion. This observation can be explained by the concept of "solvent depletion" as organic matter decreased by a factor of 1.3 during digestion, resulting in reduced sorptive capacity and increased freely dissolved concentrations (C_free). The PAHs with logK_ow > 6 had ARs close to 1.3, whereas PAHs with logK_ow < 6 showed higher ARs than the organic matter decrease factor of 1.3. C_free in digested sludge were higher than reported in rural soil and generally consistent with levels reported for Baltic Sea sediment.

Equilibrium sampling of polychlorinated biphenyls in River Elbe sediments--Linking bioaccumulation in fish to sediment contamination

Equilibrium sampling can be applied to measure freely dissolved concentrations (cfree) of hydrophobic organic chemicals (HOCs) that are considered effective concentrations for diffusive uptake and partitioning. It can also yield concentrations in lipids at thermodynamic equilibrium with the sediment (clip⇌sed) by multiplying concentrations in the equilibrium sampling polymer with lipid to polymer partition coefficients. We have applied silicone coated glass jars for equilibrium sampling of seven 'indicator' polychlorinated biphenyls (PCBs) in sediment samples from ten locations along the River Elbe to measure cfree of PCBs and their clip⇌sed. For three sites, we then related clip⇌sed to lipid-normalized PCB concentrations (cbio,lip) that were determined independently by the German Environmental Specimen Bank in common bream, a fish species living in close contact with the sediment: (1) In all cases, cbio,lip were below clip⇌sed, (2) there was proportionality between the two parameters with high R(2) values (0.92-1.00) and (3) the slopes of the linear regressions were very similar between the three stations (0.297; 0.327; 0.390). These results confirm the close link between PCB bioaccumulation and the thermodynamic potential of sediment-associated HOCs for partitioning into lipids. This novel approach gives clearer and more consistent results compared to conventional approaches that are based on total concentrations in sediment and biota-sediment accumulation factors. We propose to apply equilibrium sampling for determining bioavailability and bioaccumulation potential of HOCs, since this technique can provide a thermodynamic basis for the risk assessment and management of contaminated sediments.