T9 AM Bioaccumulation and Biomagnification
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 339-340

(KEN-1117-839465) Determination of steady-state tissue concentrations for invertebrates in contaminated sediment.

Kennedy, Alan¹, Lotufo, Guilherme², Bridges, Todd², Reiss, Mark³, Steevens, Jeffery², ¹ Analytical Services, Inc., Vicksburg, Mississippi, USA² US Army Engineer Research and Development Center, Vicksburg, Mississippi, USA³ US Environmental Protection Agency, New York, New York, USA

ABSTRACT- Risk assessment of contaminated marine sediments often involves quantification of compounds in tissues via laboratory bioaccumulation exposures of benthic invertebrates (e.g., the polychaete, Nereis virens, and bivalve, Macoma nasuta). The stipulated 28 day exposure, however, is too short to allow some compounds to reach steady-state, defined as a stable concentration in exposed organisms (i.e., organisms removed from exposure prior to attaining steady-state may underestimate body-residues in situ). Steady-state bioaccumulation of a compound in tissue can be estimated using uptake and elimination rate constants derived from temporal residue trends or by establishing statistical congruence between residues measured at three successive time points. Experiments were conducted using two New York Harbor sediments to assess bioaccumulation of PAHs, PCBs, chlorinated pesticides, dioxins and Hg (total and methylated). Temporal trends were determined by sampling tissue during seven successive time points over an exposure of 56 days for N. virens and 119 days for M. nasuta. Steady state biota-to-sediment accumulation factors (BSAF), time-to-steady-state (TSS) and multiplication factors (MF) to estimate steady-state from 28 day residues were determined for each organism and compound. Nereis virens attained apparent steady-state within roughly 28 days for PAHs, Hg and most PCBs but longer TSS were determined for some dioxins and pesticides. The TSS for M. nasuta was generally longer than 28 days for most compounds, exceeding 100 days for some pesticides and dioxins. Thus, exposure time required to attain steady-state was organism- and compound-specific and 28 day tissue-residues may underestimate in situ bioaccumulation, and subsequently risk to benthos and higher trophic level organisms. Results acquired in this study allowed development of site-specific MFs for estimating steady-state residues from 28 day measures. These estimated residues can then be used in sediment evaluations to more accurately calculate contaminant bioaccumulation within food webs as part of ecological and human-health risk assessments.

Key words: State-state, bioaccumulation, sediment, invertebrate