Predicting toxicity to Hyalella azteca in pyrogenic‐impacted sediments – Do we need to analyze for all 34 PAHs?
PAHs are major drivers of risk at many urban/industrialized sediment sites. The USEPA currently recommends using measurements of 18 parent + 16 groups of alkylated PAHs (PAH‐34) to assess the potential for sediment‐bound PAHs to impact benthic organisms at these sites. ASTM Method D7363‐13 was developed to directly measure low‐level sediment pore water PAH concentrations. These concentrations are then compared to ambient water criteria (final chronic values – FCVs) to assess the potential for impact to benthic organisms. The inter‐laboratory validation study that was used to finalize ASTM D7363‐13 was developed using 24 of the 2‐, 3‐, and 4‐ring PAHs (PAH‐24) that are included in the USEPA PAH‐34 analyte list. However, it is the responsibility of the user of ASTM Method D7363 to establish a test method to quantify the remaining 10 higher molecular weight PAHs which make up PAH‐34. These higher molecular weight PAHs exhibit extremely low saturation solubilities that make their detection difficult in pore water, which has proven difficult to implement in a contract laboratory setting. As a result, commercial laboratories are hesitant to conduct the method on the entire PAH‐34 analyte list. This paper presents a statistical comparison of the ability of the PAH‐24 and PAH‐34 pore water results to predict survival of the freshwater amphipod Hyalella azteca, using the original 269 sediment samples used to gain ASTM D7363 Method approval. The statistical analysis shows that the PAH‐24 are statistically indistinguishable from the PAH‐34 for predicting toxicity. These results indicate that the analysis of freely‐dissolved pore water PAH‐24 is sufficient for making risk‐based decisions based on benthic invertebrate toxicity (survival and growth). This reduced target analyte list should result in a cost saving for stakeholders and broader implementation of the method at PAH‐impacted sediment sites. This article is protected by copyright. All rights reserved