Evaluation of a Rapid Biosensor Tool for Measuring PAH Availability in Sediment
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Decades of research has shown that measuring freely dissolved PAH (Cfree) in sediment is superior to measurement of “total” concentrations of PAHs in sediment and sediment porewater, as Cfree is a much better predictor of bioavailability and toxicity to aquatic organisms.

Passive sampling techniques and equilibrium partitioning (EqP) models (such as 1-carbon and 2-carbon models) have been used for measuring and predicting Cfree, respectively, but these techniques require weeks for analytical chemical measurements and subsequent data evaluation. This study evaluated the performance of a portable, field-deployable antibody-based PAH biosensor technique that can provide measurements of PAH Cfree within a matter of minutes using a small volume of sediment porewater. Four sediments with a wide range of PAHs (ΣPAH 2.4 to 307 mg/kg) derived from petroleum, creosote, and urban PAH sources were analyzed via bulk chemistry methods, exposed ex situ to polyethylene passive samplers, and compressed to yield a porewater sample that was analyzed via the biosensor. Mean ΣPAH Cfree, determined by the biosensor for the four sediments (3.1 to 55 µg/L) were within a factor of 1.1 (on average) compared to mean ΣPAH Cfree determined by the passive samplers (2.0 to 52 µg/L). All mean ΣPAH Cfree values differed by factor of 3 or less. In contrast, 1-carbon and 2-carbon EqP ΣPAH Cfree predictions overpredicted passive sampler-derived Cfree measurements by an average factor of 6.4 and 6.0, respectively. The biosensor was also useful in identifying sediments that are likely to be non-toxic to benthic invertebrates. In two of the four sediments, biosensor results of 20 and 55 µg/L exceeded a potential biosensor screening level of 10 µg/L (derived from prior research), indicating toxicity could not be ruled out. Toxic Units (TU) measured in these two sediments using the passive sampler Cfree results were also greater than the TU threshold of 1 (6.7 and 5.8, respectively), confirming the conclusions reached with the biosensor. In contrast, the other two sediments were identified as non-toxic by both the biosensor (biosensor results of 3.1 and 4.3 µg/L) and the passive sampler (TU of 0.039 and 0.34). These results indicate that the biosensor is a promising tool for rapid screening of sediments potentially-impacted with PAHs, and further evaluation of the biosensor with additional sediments is recommended.

Publication Summary

  • Geosyntec Authors: Jason Conder
  • All Authors: Jason Conder
  • Title: The Society of Environmental Toxicology and Chemistry (SETAC) North America 41st Annual Meeting
  • Event or Publication: Event
  • Practice Areas: Per- and Polyfluoroalkyl Substances (PFAS)
  • Citation: Jason Conder, Ph.D., (California), Jennifer Arblaster (Vermont), and Alice Wang, Ph.D., (Massachusetts) will present at the Society of Environmental Toxicology and Chemistry (SETAC) North America 41st Annual Meeting at 8:00-12:00 PM CST on November 15, 2020.
  • Date: November 15, 2020
  • Location: Virtual
  • Publication Type: Platform Presentation