Appraisal of biological remediation options for the recovery of a mixed contaminated soil from a gravel pit

Abstract

Abstract The biological remediation of mixed contaminated soils is exceedingly challenging as it often requires actions to minimize metal-induced risks while degrading organic contaminants. In this study, we assessed the effectiveness of three biological remediation options (rhizoremediation, biostimulation, mycoremediation), applied together or separately, for the recovery of a mixed contaminated soil from a gravel pit. We evaluated the effectiveness of these remediation strategies in terms of both reduction in soil contamination levels and recovery of soil health. The combination of biostimulation (by the application of composted sewage sludge) and rhizoremediation with Medicago sativa plants resulted in the highest recovery of soil health. The application of the composted sewage sludge led to the highest reduction in anthracene and polychlorinated biphenyls concentrations. Still, the studied biological remediation options did not manage to decrease soil contamination levels below some of the limits set by the regional legislation. By contrasts, they enhanced soil health, as reflected by the values of soil microbial indicators, pointing out to the fact that they can stimulate soil functioning in a relatively short period of time, long before the concentration of soil contaminants is significantly reduced.