Toxicity of heavy metals (Ni, Zn) to desulfovibrio desulfuricans

This study is the first to address systematically five important factors necessary to quantify the toxicity of heavy metals to sulfate‐reducing bacteria: metal precipitation due to reaction with components in the media; metal adsorption onto solid phases; precipitation of metal sulfides due to reaction with sulfide initially present in an active microcosm; quantification of initial metal concentrations; and aqueous metal complexing, which reduces metal bioavailability. The toxicity of Ni and Zn to pure cultures of Desulfovibrio desulfuricans was quantified using a chemically defined medium at pH 7.2. Free heavy metal ion activity was calculated using MINTEQA2 and an amended database. A total activity of NP*(aq) + Zn²*(aq) greater than approximately 2.5 X 10‐⁵ molal is toxic to D. desulfuricans. The results indicate that attempts to remediate Ni and/or Zn contamination by bacterial sulfate reduction are likely to be successful only if total Ni + Zn activity is below this level in order to prevent heavy metal toxicity.

Keywords:

• heavy metals
• metal sulfides
• precipitation
• sulfate reduction
• sulfidogenesis
• toxicity