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Combined effects of dissolved organic material and water hardness on toxicity of cadmium to Daphnia magna
Author(s) -
Penttinen Sari,
Kostamo Auli,
Kukkonen Jussi V. K.
Publication year - 1998
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620171217
Subject(s) - daphnia magna , dissolved organic carbon , soft water , hard water , environmental chemistry , chemistry , toxicity , cadmium , humic acid , acute toxicity , ecotoxicity , fertilizer , organic chemistry
The interaction between dissolved organic material (DOM) and water hardness and their effects on the acute toxicity of cadmium (Cd) to Daphnia magna was studied. At an original hardness (0.1 mmol Ca + Mg per liter) of humic lake water (DOC 19.6 mg/L), Cd was significantly less toxic in the humic than in the reference (DOC < 0.2 mg/L) water. Furthermore, after dilution down to 10% (dissolved organic carbon [DOC] 2.0 mg/L), the humic water still decreased the lethality significantly. The results suggest that the reduced toxicity of Cd in the lake water is due to complexation with DOC. An increase in water hardness (from 0.1 to 0.5 or 2.5 mmol Ca + Mg per liter) decreased the measured binding coefficient of Cd to DOM. In addition, the acute toxicity of Cd decreased, and the difference between the reference and humic water disappeared. As a conclusion, DOM in the soft lake water had a protective effect against Cd toxicity. In hard water, obviously, the added hardness cations, especially Ca 2+ , effectively competed with Cd 2+ for available binding sites in DOM. Simultaneously, Ca 2+ ions interfered also with the uptake of Cd 2+ either by competing in transport through cell membranes or by reducing membrane permeability.