The equilibrium partitioning theory may be used to describe the partitioning of nonionic organic chemicals between water, sediment, and aquatic biota. This paradigm was employed to compare the relative magnitudes of organic carbon-normalized sediment-quality criteria that are intended to protect either benthic organisms from the direct toxic effects of sediment-associated chemicals or humans from the indirect health effects posed by the ingestion of contaminated aquatic animals. Comparison of calculated sediment-quality criteria for a variety of hydrophobic chemicals suggests that human health-based end points often result in more restrictive criteria than aquatic effects-based values. Review of published field data indicates that the equilibrium partitioning paradigm may, depending on contaminant class, either over-or underestimate the extent to which sedimentassociated contaminations are bioaccumulated. Despite the limitations of adopting this simple theory for criteria development, calculations reveal that regulatory decisions involving sediments contaminated with such chemicals may be dictated by human health concerns if current risk assessment methodologies are applied. Keywords -Sediment-quality criteriaEquilibrium partitioning Bioaccumulation Human health risk assessment Nonionic organic chemicals T.F. PARKERTON ET AL. METHODS Aquatic effects-based criteriaSediment organic carbon serves as the dominant sorptive phase for nonionic hydrophobic organic chemicals [16]. If the chemical is assumed to be in equilibrium between sediment interstitial water and particulate organic carbon phases, then the relationship between particulate and dissolved chemical phase is: oc C S f a , C,,, = -= C,K where C,,, = organic carbon-normalized sediment C, = bulk sediment concentration [mg kg f,, = fraction sediment organic carbon [kg oc C,,, = pore water concentration [mg L-'1 KO, = sediment organic carbodwater partition concentration [mg kg oc-'I dry-'] kg dry-'] coefficient [L kg oc-'1.Equation 1 serves as the basis for proposed organic carbon-normalized sediment-quality criteria for nonionic hydrophobic chemicals, criteria that are intended to protect aquatic life [13]. This is accomplished by replacing the pore water concentration by the final chronic value (FCV) of the chemical and deriving the KO, from the chemical's octanol/water partition coefficient (KO,,,). Thus, the expression for computing an aquatic effectsbased sediment-quality criterion (SQC) is

The equilibrium partitioning theory may be used to describe the partitioning of nonionic organic chemicals between water, sediment, and aquatic biota. This paradigm was employed to compare the relative magnitudes of organic carbon‐normalized sediment‐quality criteria that are intended to protect either benthic organisms from the direct toxic effects of sediment‐associated chemicals or humans from the indirect health effects posed by the ingestion of contaminated aquatic animals. Comparison of calculated sediment‐quality criteria for a variety of hydrophobic chemicals suggests that human health‐based end points often result in more restrictive criteria than aquatic effects‐based values. Review of published field data indicates that the equilibrium partitioning paradigm may, depending on contaminant class, either over‐ or underestimate the extent to which sediment associated contaminations are bioaccumulated. Despite the limitations of adopting this simple theory for criteria development, calculations reveal that regulatory decisions involving sediments contaminated with such chemicals may be dictated by human health concerns if current risk assessment methodologies are applied.

No abstract

No abstract

No abstract