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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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In aquatic systems, cobalt accumulates from water to plants (BCF >100 to 5000), with higher trophic levels showing reduced accumulation; BCF <300 for invertebrates, with both freshwater and marine fish showing BCF/BAF < 10.

 

Of the 64 documents retrieved for cobalt aquatic bioaccumulation / bioconcentration, only 18 were of relevant quality. The majority of the studies calculated BCF and/or BAF from the efflux kinetics through exposure either through water or diet as opposed to the ratio of the tissue to water or food burdens. BCFs for green algae, phytoplankton and higher plants (e. g., duckweed and fucus) varied greatly and were generally high, varying between 180 and 4000. However, this wide range of values is expected with essential metals, especially in situations where organisms are exposed to a range of environmental concentrations and physiological mechanisms are successfully functioning to maintain homeostatic concentrations. In those situations where external concentrations are low, active sequestration of cobalt is necessary to achieve adequate tissue concentrations. In these cases BCF values will be high while the opposite is true when concentrations are elevated. These organisms must actively sequester large concentrations of these materials in order to achieve physiologically necessary concentrations. Higher food chain organisms exhibited significantly reduced BCFs, ranging from 30-161 for bivalves (mussel and scallop), 265 for a crustacean (D. magna) and <1 to 7 for freshwater (rainbow trout) and marine (sea bass) fish. A marine trophic transfer study (Mathews & Fisher, 2008) established cobalt tissue concentrations across a number of trophic pathways, incorporating phytoplankton, zooplankton, a sea break and sea bass. The reported trophic transfer value was <1. Though of limited quantity, these studies indicate that cobalt does not biomagnify through either freshwater or marine trophic foodwebs.