Sewage sludge and fly ash mixture as an alternative for decontaminating lead and zinc ore regions

Many years of heavy industrial processes in the Upper Silesian Industrial Region in Poland (ore flotation, metal smelting and battery scrap processing) have resulted in lead, zinc and cadmium pollution of the air and soil. The most significant issues stem not only from elevated levels of these metals in environmental compartments, but also from the uneven pattern of their distribution. Point sources of local metal concentration are to be found dispersed over areas of contaminated soil. Such distribution is a challenge for remediation technology, as it precludes the introduction of standard procedures. Metals present in the soil pose a constant risk for living organisms. One of the most effective ways of limiting their ecological impact is by decreasing their mobility. In this study, the effect of introducing sewage sludge and fly ash mixtures (sluash material) into contaminated soil was evaluated. We tested the mixture in terms of the probability of its ecotoxicological impact on plant growth and development. The data obtained have shown that even low doses (3%) of sluash are effective in reducing the bioavailability of lead, cadmium and zinc, resulting in a decrease of their concentration in plants. The application of sluash also led to stabilize soil pH. It also had a positive impact on the total number of soil bacteria and soil fungi.