| Influence of dissolved organic carbon on the speciation and toxicity of uranium to Australian tropical freshwater species (2008) | |||||||||||||
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| Uranium is one of the metals of ecotoxicological concern for the uranium mining industry in tropical Australia. In order to more fully assess the risk that U in waters discharged from mining activities poses to tropical freshwater ecosystems, the role of dissolved organic carbon (DOC) must be quantified. DOC is one of the key determinants of the bioavailability and aquatic toxicity of metals such as U that bind strongly to fulvic and humic material. Uranium toxicity to three tropical freshwater species, the Northern Trout Gudgeon (Mogurnda mogurnda), green hydra (Hydra viridissima) and unicellular green alga (Chlorella sp.) was assessed using the following DOC concentrations - 0, 1, 5, 10 and 20 mg/L. Tests were conducted in synthetic soft water (SSW) lacking organic carbon and in SSW supplemented with DOC (Suwannee River fulvic acid standard, IHSS). Results demonstrated that the toxicity of U to each species was highly influenced by DOC. The relationship between U toxicity and DOC concentration was modelled for each species using both simple linear and multivariate logistic regression analyses. Uranium toxicity to both M. mogurnda and Chlorella sp. was approximately four times lower in SSW containing 20 mg/L DOC than SSW devoid of organic carbon (M. mogurnda, 3 tests; IC50 increased from 1600 to 7200 :g/L; IC50=287[DOC]+1548, R2=98%, P | |||||||||||||
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