Assessment of Polluted Soil Remediation Using Bacterial Community Tolerance to Heavy Metals as an Indicator

The assessment of remediation on metal-polluted soils is usually focused on total and/or bioavailable metal content. However, these chemical variables do not provide direct information about reductions in heavy metals pressure on soil microorganisms. We propose the use of bacterial communities to evaluate the efficiency of three remediation techniques: crushed mussel shell (CMS) and pine bark (PB) as soil amendments and EDTA-washing. A soil sample was polluted with different doses of Cu, Ni, and Zn (separately). After 30 days of incubation, the remediation techniques were applied, and bacterial community tolerance to heavy metals determined. If bacterial communities develop tolerance, it is an indicator that the metal is exerting toxicity on them. Soil bacterial communities developed tolerance to Cu, Ni, and Zn in response to metal additions. After remediation, bacterial communities showed decreases in bacterial community tolerance to Cu, Ni, and Zn for all remediation techniques. For Cu and Ni, soil EDTA-washing showed the greatest reduction of bacterial community tolerance to Cu and Ni, respectively, while for Zn the soil amendment with PB was the most effective remediation technique. Thus, bacterial community tolerance to heavy metals successfully detect differences in the effectiveness of the three remediation techniques.

Automated summary

The assessment of metal-polluted soils' remediation usually focuses on the total and/or bioavailable metal content, but these chemical variables cannot directly provide information about the reduction of heavy metals' pressure on soil microorganisms. We propose the use of bacterial communities as indicators to evaluate the effectiveness of three remediation techniques, and found that the tolerance of bacterial communities can indicate the toxicity of metals. Soil bacterial communities developed tolerance to Cu, Ni, and Zn after metal additions, and all remediation techniques resulted in a decrease in bacterial community tolerance to Cu, Ni, and Zn. Soil EDTA-washing showed the greatest reduction of bacterial community tolerance to Cu and Ni, while soil amendment with PB was the most effective remediation technique for Zn.