Biosensor assessment of arsenic and antimony bioavailability in mining soils and sediments
Mining and smelting activities are a major source of arsenic and antimony contamination in the environment. These contaminants have been neglected when such sites are investigated, hence there is a need for their environmental impacts to be assessed. An understanding of bioavailability underpins any such assessment. This measure can only be inferred from traditional chemical techniques and the use of novel bioavailability surrogate measures. This study used a suite of three lux-marked bacterial biosensors as complimentary tools to assess metalloid bioavailability and toxicity in soils contaminated by mining and smelting. This included two constitutively marked metabolic sensors which exhibit inhibition responses to toxicity, and an ars inducible biosensor which reports on metalloid bioavailability. The biosensor responses were first characterised using standard solutions, confirming that they exhibit dose dependent responses which indicate the speciation of bioavailable forms and account for contaminant interactions. The techniques were then applied to assessing a range of environmental samples from sites around the UK, and in Chile, contaminated by either historic or contemporary mining and smelting activities. The results indicated that the metabolic biosensors are powerful tools for assessing the toxicity of bioavailable contaminants while the ars inducible biosensor reports on arsenite bioavailability. The speciation of antimony in the environmental samples resulted in low bioavailable levels, and therefore it played no significant role in determining the biosensor responses. Metal co-contaminants tended to mask the effect of arsenic on the biosensor responses and cation exchange treatment proved a successful technique to mitigate this problem. This work also highlighted the impact of extraction methodology on the chemical composition of soil water and therefore the results obtained.