Evaluating long-term contamination in soils amended with sewage sludge

Abstract

Sewage sludge application on agricultural fields is a managing practice of increasing use because of its benefits to soil and crops. However, if not well controlled, sludge application may lead to soil contamination. In Europe, threshold values for sewage sludge amendment have only been derived for heavy metals; and there is not any legal limitation for persistent organic pollutants (POPs) concentration in sewage sludge. In order to evaluate the fate of these contaminants in the soil matrix, a multimedia model was developed and executed for a case-study. The model, which was applied to different POPs, was used to predict the transport between soil phases (air, water, organic matter and mineral matter) based on fugacity values. In general terms, the simulation results showed a tendency of reaching a constant value through the simulation time for all the contaminants. The removal rate was highly correlated with the high-life in soil, which was found to be the most sensitive parameter of the analysis. No significant differences were found in the results for the two types of soil evaluated, characterized by different textures, pH, organic matter and nutrient content. The model here developed is considered to provide reliable results to predict the environmental fate of POPs in sewage sludge-amended soils. In the future, the feasibility to apply the model to other chemical pollutants, such as volatile compounds, will have to be studied. © Springer-Verlag Berlin Heidelberg 2009.