John Wiley & Sons, Ltd.

THE INFLUENCE OF Ca AND pH ON THE UPTAKE AND EFFECTS OF Cd IN FOLSOMIA CANDIDA EXPOSED TO SIMPLIFIED SOIL SOLUTIONS

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The present study aimed to quantify the components of a biotic ligand model (BLM) for the effects of Cd on Folsomia candida (Collembola). Assuming that soil pore water is the main route of exposure and to exclude the effects of soil particles on metal availability, animals were exposed for seven days to different Cd concentrations between 0.1 and 100 mM in simplified soil solutions at different Ca concentrations (0.2, 0.8, 3.2, and 12.8 mM) or at different pH (5.0, 6.0, and 7.0). Higher Ca concentrations decreased the toxicity of Cd (adult survival) in test solutions, while toxicity was slightly lower at pH 7 and 6 than at pH 5, suggesting a mitigating effect of Ca and to a lesser extent pH on Cd toxicity to F. candida. Internal Cd concentrations in the animals increased with increasing exposure level but were significantly reduced by increasing Ca concentrations and not significantly affected by pH. Using Langmuir isotherms, binding constants for Cd, Ca, and protons and the fraction of binding sites occupied by Cd were calculated and used to predict effects of Cd on survival. Predicted toxicity showed a good agreement with measured responses when Ca and pH were used as separate factors or combined together. The present study shows indications of protective effects of Ca but less of protons on the toxicity and uptake of Cd in F. candida upon exposure to simplified soil solutions, which can be described using the principles of a biotic ligand model. Environ. Toxicol. Chem. © 2013 SETAC

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