Effects of Contact Time on the Sequestration and Bioavailability of Different Classes of Hydrophobic Organic Chemicals to Benthic Oligochaetes (Tubificidae)

Abstract

Differences in bioavailability of hydrophobic organic compounds (HOC) to benthic deposit feeders have been related to differences in sediment-HOC contact time and sequestration (formation of slowly desorbing fractions) status. As a consequence, it was postulated that contact time and/or sequestration should be incorporated into risk assessment. In the present study, we investigated the effect of contact time on the bioavailability and sequestration of different classes of HOC. For this purpose, we simultaneously measured the steady-state accumulation into benthic oligochaetes (Tubificidae) and the distribution over rapidly and slowly desorbing fractions in laboratory-contaminated sediment at different contact times. The decrease in rapidly desorbing fractions (Frap) of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and 2,2-bis (4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE) after a contact time of 959 d did not exceed a factor of 1.2. Similarly, the reduction in bioavailability was a factor of 2.3 at maximum, indicating that long contact times do not necessarily result in pronounced bioavailability reduction. For chlorobenzenes, the bioavailability was reduced with a factor of 5 to 18. This decrease corresponded with a pronounced reduction in Frap, which was attributed to losses of rapidly desorbing compounds. Over 75% of the variation in biota-to-sediment accumulation factors (BSAFs) of the PAHs and chlorobenzenes at the three contact times could be explained by differences in Frap. The present study provides evidence of a relationship between sequestration status and bioavailability of HOC to benthic deposit feeders.

The role of desorption for describing the bioavailability of select polycyclic aromatic hydrocarbon and polychlorinated biphenyl congeners for seven laboratory‐spiked sediments

“…These regressions were not quite as good as that found for PAH only (r 2 ϭ 0.76 [1]) or for PAH and chlorobenzenes (r 2 ϭ 0.77, [2]). If we remove the PCBs from the regressions, then the linear regressions for BSAF versus F rapid for PAH only would have r 2 values for 54 and 64% for L. variegatus and Diporeia, respectively, where our regression is across seven sediments and that of Kraaij et al [1,2], which is for a single sediment. Thus, these appear to be comparable considering the potential additional variability that would result from accumulation across seven sediments.…”

The contrasting roles of sedimentary plant‐derived carbon and black carbon on sediment‐spiked hydrophobic organic contaminant bioavailability to Diporeia species and Lumbriculus variegatus

“…The sediments were spiked in equimolar concentrations at 360 nmol/kg with four radiolabeled HOCs in two treatment groups including one PAH and one polychlorinated biphenyl congener in each treatment. The four radiolabeled HOCs were 3 H-pyrene (PY, specific activity 25.2 Ci/mmole), 14 C-3,3Ј,4,4Јtetrachlorobiphenyl (TCBP, specific activity 12.5 mCi/mmole), 3 H-benzo[a]pyrene (BaP, specific activity 50.0 Ci/mmole), and 14 C-2,2Ј,4,4Ј,5,5Ј-hexachlorobiphenyl ([HCBP], specific activity 12.6 mCi/mmole). Nonlabeled PY (purity Ͼ99%) and BaP (purity Ͼ98%) obtained from Aldrich (Milwaukee, WI, USA) were added with the radiolabeled compounds to limit the amount of radioactivity required.…”

“…In an analogous manner, bioaccumulation investigations have also focused on the kinetics of HOC bioaccumulation, with the thought that HOC accumulation is a function of rate limitations ensuing from intra-aggregate HOC desorption [11][12][13]. Recent studies in this area suggest that HOCs are sorbed to ''rapid desorbing'' and ''slower desorbing'' pools of organic matter in sediment aggregates [13][14][15][16]. This approach has indicated that the most rapidly desorbing pool of an HOC from a particle aggregate may be the most relevant with respect to HOC bioaccumulation [12][13][14]17,18].…”

“…Recent studies in this area suggest that HOCs are sorbed to ''rapid desorbing'' and ''slower desorbing'' pools of organic matter in sediment aggregates [13][14][15][16]. This approach has indicated that the most rapidly desorbing pool of an HOC from a particle aggregate may be the most relevant with respect to HOC bioaccumulation [12][13][14]17,18]. In that context, Shor et al [19] have presented a systematic view of polycyclic aromatic hydrocarbon (PAH) desorption kinetics from sedimentary particles as a function of sediment grain size, composition, and PAH hydrophobicity in which they state that the magnitude of the readily desorbable fraction of a PAH can be predicted * To whom correspondence may be addressed (peter.landrum@noaa.gov).…”

Baseline toxicity of a chlorobenzene mixture and total body residues measured and estimated with solid‐phase microextraction

“…Aquatic ecotoxicology and risk assessment traditionally have relied on quantifying the contaminant concentrations in water and sediment that elicit toxic effects. However, there are many important factors, such as bioavailability, uptake kinetics, habitat, and feeding behavior, which determine to what extent the toxicants present in the system will reach the target sites in organisms (e.g., [1][2][3][4][5][6][7][8]). Measuring the internal concentration in organisms themselves automatically takes into account many of the factors that impact the correlation between external concentration and toxicity and, therefore, is a better indicator of the concentrations at target sites than external concentrations [6,[9][10][11][12].…”