Stochastic Framework for Addressing Chemical Partitioning and Bioavailability in Contaminated Sediment Assessment and Management

Amanda A. Brennan, David R. Mount, Nathan W. Johnson

Research output: Contribution to journalArticlepeer-review


Passive sampling to quantify net partitioning of hydrophobic organic contaminants between the porewater and solid phase has advanced risk management for contaminated sediments. Direct porewater (Cfree) measures represent the best way to predict adverse effects to biota. However, when the need arises to convert between solid-phase concentration (Ctotal) and Cfree, a wide variation in observed sediment-porewater partition coefficients (KTOC) is observed due to intractable complexities in binding phases. We propose a stochastic framework in which a given Ctotal is mapped to an estimated range of Cfree through variability in passive sampling-derived KTOC relationships. This mapping can be used to pair estimated Cfree with biological effects data or inversely to translate a measured or assumed Cfree to an estimated Ctotal. We apply the framework to both an effects threshold for polycyclic aromatic hydrocarbon (PAH) toxicity and an aggregate adverse impact on an assemblage of species. The stochastic framework is based on a "bioavailability ratio"(BR), which reflects the extent to which potency-weighted, aggregate PAH partitioning to the solid-phase is greater than that predicted by default, KOW-based KTOC values. Along a continuum of Ctotal, we use the BR to derive an estimate for the probability that Cfree will exceed a threshold. By explicitly describing the variability of KTOC and BR, estimates of risk posed by sediment-associated contaminants can be more transparent and nuanced.

Original languageEnglish (US)
Pages (from-to)11040-11048
Number of pages9
JournalEnvironmental Science and Technology
Issue number16
Early online dateJul 26 2021
StatePublished - Aug 17 2021
Externally publishedYes

Bibliographical note

Funding Information:
Funding for this research was provided by the University of Michigan Water Center with funds from the Erb Family Foundation (#3002700653), the US Army Corps of Engineers Detroit District (Department of Defense, #W911XK-12-C-0021), and the Minnesota Pollution Control Agency (Con ID_62815).

Publisher Copyright:
© 2021 American Chemical Society.


  • bioavailability
  • passive sampling
  • probability
  • species sensitivity distribution
  • toxicity


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