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Environmental fate & pathways

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Aluminium chloride is highly soluble in water dissociating to aluminium hydroxide and hydrochloric acid and thereby may change the pH of an aquatic system towards acidic. The latter is strongly dependent on the buffer capacity. Under circum neutral conditions, as typically met in most surface waters, aluminium hydroxide is forming complexes, precipitating to gibbsite. Under these conditions, bioaccumulation of aluminium is unlikely. However, under low pH conditions (< 6) aluminium may stay dissolved and may accumulate in fish. It is well established, that aluminium may accumulate in and on the gill (e.g. Poleo et al. 1995). It has been suggested that the rate of transfer of aluminium into the body of fish is either slow or negligible under natural environmental conditions (Spry and Wiener 1991). The initial uptake of aluminium by fish essentially takes place not on the gill surface but mainly on the gill mucous layer (Wilkinson and Campbell 1993). Fish may rapidly eliminate mucous and the bound aluminium following the exposure episode. In general, the potential for accumulation in fish will depend on the aluminium species present, and is therefore dependent on pH temperature, dissolved organic carbon (DOC) and numerous other ligands (Environment Canada 2000). According to EHC 194, bioconcentration factors for aluminium are inversely related to pH. For example: 215 at pH 5.3, 123 at pH 6.1 and 36 at pH 7.2. Based on results published by Roy R. (1999), Environment Canada (2000) calculated BCFs for fish in the range of 400 to 1365.

 

References:

- Cleveland L & Brumbaugh WG (1991). Residue dynamics and effects of aluminum on growth and mortality in brook trout. Environ Toxicol Chem 10: 243-248. Cited in EHC 194.

- Environment Canada (2000). State of science report for Aluminium chloride, Aluminium nitrate and Aluminium sulphate, Dec 2000

- Poleo ABS et al. (1995). Survival of crucian Carp, Carassius carassius, exposed to a high low-molecular weight inorganic Aluminium challenge source. Aquat Sci 57(4): 350-359

- Roy R (1999). The chemistry, bioaccumulation and toxicity of aluminum in the aquatic environment for the PSL2 assessment of aluminum salts. Report prepared by Fisheries and Oceans Canada for Environment Canada. 110 pp. (unpublished). Cited in: Evironment Canada (2000)

- Spry DJ, Wiener JG (1991). Metal bioavailability and toxicity to fish in low-alkalinity lakes - a critical review. Environ Pollut 71: 243-304. Cited in: Environment Canada 2000.

- WHO (1997). Environmental health criteria (EHC) 194, Aluminium

- Wilkinson KJ, PGC (1993). Aluminum bioconcentration at the gill surface of juvenile Atlantic salmon in acidic media.Environ Toxicol Chem 12: 2083-2095. Cited in: Environment (2000)

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