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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Inorganic cobalt compounds exhibit bioaccumulation potential with BCF values ranging from 100-4000 for marine fish, and <10-1000 for freshwater fish. In contrast, acetic acid exhibits no bioaccumulation potential.

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Additional information

Cobalt di(acetate) readily dissociates in aqueous solution into free cobalt ions and acetic acid. The pKa of 7.75 indicates that at pH values below, cobalt(di)acetate is almost completely dissociated, wherease the percentage decreases at higher pH values. Therefore an assessment on the bioaccumulative potential of cobalt di(acetate) has been performed by means of its dissociation products. The main conclusions are:

a) The inorganic component (cobalt) is bioaccumulative.

b) The organic component (acetic acid CAS: 64-19-7) is not bioaccumulative.

a) Summary according the bioaccumulation potential of cobalt and cobalt compounds, as given in CICAD 69 (WHO 2006)

60Co is taken up by unicellular algae with reported concentration factors (dry weight) of 40 000 for Scenedesmus obliquus and 18 000 for Selenastrum capricornutum (Nucho et al., 1988; Corisco & Carreiro, 1999). Freshwater molluscs have concentration factors of 100–14 000 (~1–300 in soft tissue). Much of the cobalt taken up by molluscs and crustaceans from water or sediment is adsorbed to the shell or exoskeleton; very little cobalt is generally accumulated in the edible parts (Amiard & Amiard-Triquet, 1979; Smith & Carson, 1981). Similarly, in laboratory studies with Daphnia magna, adsorption to the exoskeleton was the major contamination process (Adam et al., 2001). In studies with starfish (Asterias rubens), accumulation of 57Co was found to be predominately from seawater rather than from food (Warnau et al., 1999). Bioaccumulation factors for marine fish and freshwater fish are 100–4000 and <10–1000, respectively (Smith & Carson, 1981). However, accumulation is mostly in the viscera and skin of the fish, not the edible parts of the fish (Smith & Carson, 1981). In carp (Cyprinus carpio), accumulation from water accounted for 75% of 60Co accumulated from both water and food; accumulation from water and food was additive (Baudin & Fritsch, 1989). Depuration halflives were 53 and 87 days for fish contaminated from food and water, respectively (Bandin & Fritsch, 1989). Biomagnification of cobalt up the food-chain does not occur (Smith & Carson, 1981).

b) Acetic acid does not bioaccumulate because these acids and their salts dissociate and biodegrade rapidly ( American Chemistry Council´s Acetic Acid and Salts Panel (2003). This is underlined by the low log Pow of acetic acid (-0.31).

References:

WHO (2006). Concise International Chemical Assessment (CICAD) Document 69, Cobalt and inorganic cobalt compounds.

Nucho R, Rambaud A, Foulquier L, Baudin JP (1988) Bioaccumulation du 60Co par une algue planctonique, Scenedesmus obliquus. Influence du stade de développement de la culture sur la fixation du radionucléide. Acta Oecologica Oecologia Applicata, 9(2):111–125.

Corisco JAG, Carreiro MCV (1999) Co60 transfer from water to the freshwater planktonic algae Selenastrum capricornutum Prinz. In: Anagnostoopoulos P, Brebbia CA, eds. Water pollution V: Modeling, measuring, and prediction. Boston, MA, WIT Press, pp. 427–436 (Progress in Water Resources, Vol. 1).

Amiard JC, Amiard-Triquet C (1979) Distribution of cobalt 60 in a mollusc, a crustacean and freshwater teleost: Variations as a function of the source of pollution and during elimination. Environmental Pollution, 20(3):199–213.

Smith IC, Carson BL (1981) Trace metals in the environment. Ann Arbor, MI, Ann Arbor Science Publishers.

Baudin JP, Fritsch AF (1989) Relative contributions of food and water in the accumulation of 60Co by a freshwater fish. Water Research, 23(7):817–823.

American Chemistry Council´s Acetic Acid and Salts Panel (2003). Robust summaries for carboxylic food acids and salts category. In: U.S. High Production Volume (HPV) Chemical Challenge Program, 16 Apr 2003