Bioavailability of Cd in 110 polluted topsoils to recombinant bioluminescent sensor bacteria: effect of soil particulate matter
Date
2011
Authors
Ivask, A.
Dubourguier, H.C.
Pollumaa, L.
Kahru, A.
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Journal of Soils and Sediments, 2011; 11(2):231-237
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Abstract
Purpose: In this study, bioavailability and water extractability of Cd in a panel of 110 natural aged heavy metal-polluted soils from northern France containing up to 20.1 mg of Cd per kilogramme was evaluated.
Materials and methods: Particulate matter was removed by differential centrifugation of soil-water suspensions (liquid to solid ratio 10) resulting in soil-water extracts containing different size of particles. Chemical analysis of Cd and analysis of bioavailable Cd with recombinant bioluminescent Cd-sensing bacteria were applied in parallel to these fractionated soil solutions.
Results and Discussion: Extractability of Cd from soil to the aqueous phase was low—only 0.13% of the soil total Cd as a mean; however, Cd-sensing recombinant luminescent bacteria Bacillus subtilis incubated in soil–water suspensions for 2 h showed that in the conditions of contact exposure, the bioavailable fraction of Cd increased about 30-fold being 3.74% of the soil total Cd as a mean value. The total Cd content of soils was not a good predictor of either bioavailable or water-extracted fraction of Cd, but these fractions were rather determined by the combination of soil total Cd and physico-chemical properties—texture and organic matter content. Analysis of two selected “model” soils with Cd sensor bacteria showed that about 90% of the bioavailable Cd was associated with larger soil particles that were removed from the soil suspensions by centrifugation at 4,500×g, and even settling of the soil suspensions for 2 h removed already 65% of bioavailable Cd.
Conclusions: Thus, our results indicate a potential for remarkably higher environmental hazard for soil-associated heavy metals than just aqueous exposure.
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Copyright 2010 Springer-Verlag