The study of Holcombe and Andrew (1978) also indicated that an increase in alkalinity and pH further ameliorated zinc toxicity to the two trout species.Īn exponential, inverse relationship has been shown to exist between water hardness and the uptake and toxicity of zinc. The difference between the alkalinity (43 mg/L as CaCO 3) and pH (7.35) of the two test waters was negligible. In hard water (hardness, 170 mg/L as CaCO 3), the corresponding toxicity values were 1.9 mg/L for the rainbow trout and 5.0 mg/L for the brook trout. Holcombe and Andrew (1978) determined a zinc toxicity (LC50) in soft water (hardness, 44 mg/L as CaCO 3) of 0.76 and 2.4 mg/L to rainbow trout ( Oncorhynchus mykiss) and brook trout ( Salvelinus fontinalis), respectively. Mount 1966, Holcombe & Andrew 1978, Bradley & Sprague 1985, Everall et al. Typically, inorganic and organic complexes ameliorate the uptake and toxicity of zinc by reducing the concentration of Zn 2+.Ī number of studies have established the uptake and toxicity of zinc in aquatic organisms decreases with increasing water hardness (e.g. It is generally considered that Zn2+ is the form of zinc primarily responsible for eliciting a toxic response in aquatic organisms. The current analytical practical quantitation limit (PQL) for zinc is 0.2 µg/L in fresh water (NSW EPA 2000). These can be coupled with measured and/or predicted speciation calculations to determine the bioavailability of various zinc species. 1996, Stumm & Morgan 1996).īioassays are typically used to ascertain metal-organism interactions.
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