Use of marble cutting sludges to immobilize heavy metals and decrease toxicity of contaminated soils.

Abstract

Heavy metal contamination of soils is particularly dangerous to living organisms. Several studies have demonstrated that marble cutting sludges show a high capacity to remove heavy metal from contaminated soils. In this study, the immobilization effect of these sludges used as an amendment was studied in two sediments from a site affected by mining activities and two soil samples from a highly industrialised area. The samples were mixed with marble cutting sludges to provide four stabilised samples from which forty lixiviums were studied. The results suggest that the addition of these sludges, consisting mainly of carbonates, to heavy metal-polluted soils and sediments, decreases available metal forms. As a complement to chemical analysis and the determination of total contaminants, bioassays can provide information on the stabilisation effects. The leached solutions showed a non-toxic effect when they were submitted to the Microtox® bioassay. The carbonate content seems to play a role in the chemical stabilisation of metals and in lowering the toxicity of these types of sample.