Effect of the Addition of Chelators on the Acute Toxicity of Some Heavy Metals to Freshwater Organisms

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Effect of the addition of chelator on the acute toxicity of heavy metal ions to freshwater organisms was examined. The Cu(II) complexation ability estimated in this study was in the order: EDTA > NTA > IDA > citric acid, aspartic acid > humic acid, natural organic matters from lignite. Then, the acute toxicity of several heavy metal ions (Cu(II), Zn(II), Pb(II), Cd(II), and As(V)) were evaluated using Daphnia magna in the absence or presence of chelators. The acute toxicity for cationic metal ions greatly decreased when artificial chelators, such as ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), were added in the test solution. However, the correlation between toxicity reduction abilities for Cu(II) and the metal complexation ability of these chelators was poor. In addition, the Cu(II) uptake was decreased when EDTA and NTA were added in the test solution. A single logarithmic linearity between the Cu(II) toxicity (EC50) for D. magna and Cu(II) uptake was observed. It is concluded that the addition of chelators affects the complexation ability for heavy metals and metal uptake into the organism, and also the heavy metal toxicity reduction is directly dependent on the uptake of the metal.
Japan Society on Water Environmentの論文