Predicting Bioavailability of Sediment Polycyclic Aromatic Hydrocarbons to Hyalella azteca using Equilibrium Partitioning, Supercritical Fluid Extraction, and Pore Water Concentrations

Abstract

Polycyclic aromatic hydrocarbon (PAH) bioavailability to Hyalella azteca was determined in 97 sediments from six former manufactured-gas plants and two aluminum smelter sites. Measurements of Soxhlet extractable, rapidly released based on mild supercritical fluid extraction, and pore water dissolved concentrations of 18 parent and 16 groups of alkyl PAHs (PAH34) were used to predict 28 daysurvival based on equilibrium partitioning and hydrocarbon narcosis models. Total PAH concentrations had little relationship to toxicity. Amphipods survived in sediments with PAH34 concentrations as high as 2990 microg/g, while sediments as low as 2.4 microg/g of PAH34 resulted in significant mortality. Equilibrium partitioning using either total extractable or rapidly released concentrations significantly improved predictions. However, pore water PAH34 concentrations were best for predicting amphipod survival and correctly classified toxic and nontoxic sediment samples with an overall model efficiency of 90%. Alkyl PAHs accounted for 80% of the toxicity, demonstrating that careful measurement of the 16 alkyl clusters in pore water is required. Regression analysis of the pore water PAH34 data from 97 field sediments against amphipod survival resulted in a mean 50% lethal residue value of 33 micromol/g of lipid, consistent with 32 micromol/g of lipid for fluoranthene determined by others in controlled laboratory conditions, thus demonstrating the applicability of EPA's hydrocarbon narcosis model when using pore water PAH34 concentrations.

Identifying the causes of sediment‐associated contamination in the Illinois River (USA) using a whole‐sediment toxicity identification evaluation

“…Second, knowing concentrations of alkyl PAHs can provide additional information for sediment TIEs. Hawthorne et al [33] reported that up to 81% of the predicted toxicity noted in one of their study sites was caused by alkyl PAHs. These two factors show that using generalized TUs may over-or underestimate toxicity.…”

“…First, PAH TU values were based on LC50s obtained from the equilibrium sediment benchmarks. Hawthorne et al [33] showed that TU values for individual sites might be overestimated due to differential bioavailability among PAHs in sediment, and that the organic carbon normalized partitioning coefficients (K OC values) used by equilibrium sediment benchmarks might not account for the heterogeneous distribution of organic contaminants in sediment. The exhaustive sediment extraction technique used in the present study may overestimate bioavailability.…”

“…The exhaustive sediment extraction technique used in the present study may overestimate bioavailability. One approach that can reduce this source of variation for PAH toxicity would be to use freely dissolved pore-water concentrations measured by solid phase microextraction methods [33][34][35][36][37]. Second, knowing concentrations of alkyl PAHs can provide additional information for sediment TIEs.…”

Influence of historical industrial epochs on pore water and partitioning profiles of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Oslo Harbor, Norway, sediment cores

“…Typically, risk assessments are based on C sed [38]. Although C sed of pollutants serve as very useful markers for delineating industrial epochs and deposition rates, C sed has a weak correlation with bioavailability [9][10][11][12]. Thus, measurements of C pw are recommended for more accurate risk assessments.…”

“…However, for organic contaminants, it has been shown that freely dissolved sediment porewater concentrations, C pw (mol/L pw ), are more appropriate for such assessments than C sed , because C pw is more closely linked with toxic endpoints and bioaccumulation [9][10][11][12]. To date, however, sediment core studies measuring C pw are only just emerging [13], most likely because methods needed for determining C pw in thin sediment layers have only recently been developed [14,15].…”