Bioavailability of Cr(III) and Cr(VI) to marine mussels from solute and particulate pathways

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Original languageEnglish
Pages (from-to)603-611
Journal / PublicationEnvironmental Science and Technology
Issue number2
Online published1 Feb 1997
Publication statusPublished - 1 Feb 1997
Externally publishedYes


Mussels have been extensively used as biological monitors of coastal contamination. This study measured the assimilation efficiencies (AEs) of Cr(III) and Cr(VI) in the mussel Mytilus edulis from ingested food, uptake from the dissolved phase, and the physiological efflux rates following uptake. A bioenergetic-based kinetic model was then employed to determine the relative contributions of different Cr species and their accumulation pathways to the overall concentration of Cr in mussels. The concentration factors of Cr(III) in four diverse marine phytoplankters ranged between 104 and 105, whereas for Cr(VI) they were 2 to 5 x 102. Rapid reduction of Cr(VI) to Cr(III) was observed in coastal sediments. AEs of Cr(III) in mussels from ingested sediments were consistently <1%, whereas the AEs of Cr(VI) from ingested phytoplankton were 1-10%. The uptake rate of Cr(VI) from the dissolved phase was 3 times higher than Cr(III). The efflux rate constant was 0.011 d-1 for mussels following 7 d dissolved uptake of Cr(VI) and 0.010 d-1 following 8 d ingestion of Cr(III)-labeled diatoms. The model predicted concentrations of Cr in mussels in South San Francisco Bay that are directly comparable to measured Cr concentrations. The model predicts that 13-38% of Cr in mussels is from dissolved Cr(VI), whereas the remaining Cr is from ingested Cr(III); dissolved Cr(III) and ingested Cr(VI) contribute little to Cr accumulation in mussels. The AE of Cr and its concentration in seston critically influence Cr concentrations in mussels.