Assessing metal bioavailability in soils using luminescence-based microbial biosensors

Laboratory and field-scale experiments were carried out to investigate the bioavailable fraction of heavy metal pollutants using luminescence-based microbial biosensors. Laboratory experiments demonstrated that 90 % of the variation in the biosensor response was explained by the free metal ion concentration in a range of Zn and Cu aqueous standards at different pH values, the only exception being Cu2+ at pH 7.0. The free metal ion concentration was predicted using GEOCHEM-PC. Similarly, field-scale experiments where Zn was the main pollutant present showed that overall it was the concentration of soil solution Zn2+ which explained most of the variation in the response of the biosensors. The concentration of Zn2+ in soil solution was measured using a calcium saturated cation exchange resin. Luminescence-based microbial biosensors were shown to provide rapid, inexpensive techniques to predict the bioavailable fraction of heavy metals in environmental samples. Such biosensors may therefore serve as powerful tools in the assessment of toxicity and bioremediation potential of contaminated sites resulting in a more effective management of waste.