Acute toxicity of antimony pentavalent to neonatal Daphnia magna and the influence of water quality parameters were investigated, and enzymatic activities of organisms at environmentally relevant levels of antimony were determined. EC50 values of antimony to neonatal D. magna were 90.3 and 63.8 mg/L at 24 and 48 h of exposure, respectively. Dissolved organic matter (FA and HA) and cation (Ca2+, Mg2+ or Na+) had significant protective effects on D. magna against antimony toxicity. With increasing pH in the range from 7.4 to 8.5, increase of EC50 were observed due to the competition of OH- on biotic ligands. Based on the biotic ligand model (BLM) concept, stability constants for the binding of Sb(OH)6- and OH- to the biotic ligand were estimated, and the Log [Formula: see text] - and LogKXOH- were 3.137 and 2.859, respectively. Moreover, antimony exposure in low concentrations significantly increased MDA levels and maybe exert oxidative stress to the organisms. Antimony can also induce toxicity in D. magna by affecting oxidative stress and neurotransmitter systems. The relatively comprehensive toxicological data can contribute to the toxicity prediction and ecological risk assessments of antimony.
Keywords: Antimony; Antioxidant stress; Ecotoxicity; Electrostatic effect; Natural organic matter.
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