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This work aimed to detect changes in trace element chemical speciation in sewage sludge (SS) after the ozonation process. The modified Community Bureau of Reference (BCR) sequential extraction procedure was performed to determine the chemical speciation of trace elements in SS after the ozonation process. To assess potential soil contamination with trace elements from sewage sludge after the ozonation process, the risk assessment code (RAC) coefficient was used. The bioaccumulation factor (BAF) and translocation factor (TF) values were also calculated to characterize the efficiency of trace element accumulation in the studied plant species from soil fertilized with sludges after the ozonation process. Generally, the mean concentration of total trace elements in the SS after the ozonation process was higher, but the differences were statistically significant only in the case of Mn, Cu, Pb, and Cd. The dominant fraction of Fe, Cr, Pb, and Cd was the residual fraction F4, while the extractable/exchangeable fraction F1 was present in the smallest amount. Therefore, in the case of Mn, Zn, and Ni, the ozonation process had a significant impact on the increase in the content of these elements in the F1 fraction. The application of the SS stabilized by ozonation process for maize and wheat fertilization did not significantly affect the bioaccumulation of most of the analyzed metals in aboveground biomass. Higher values of BAF coefficients after the application of ozonated SS were found only in the case of Cu and Ni. In turn, the determined TF coefficients were lower than 1 in most cases. The obtained results showed that the slight change in the concentration of Zn, Mn, and Ni in fraction F1 causes a specific risk of their mobility in the soil environment. It should be noted that due to the variable composition of sewage sludge, an analysis of the content of individual trace elements in chemical fractions should be carried out to assess its actual impact on the environment. This can help to indicate further actions that should be undertaken to limit their negative impact on the environment. [ABSTRACT FROM AUTHOR]

This work aimed to detect changes in trace element chemical speciation in sewage sludge (SS) after the ozonation process. The modified Community Bureau of Reference (BCR) sequential extraction procedure was performed to determine the chemical speciation of trace elements in SS after the ozonation process. To assess potential soil contamination with trace elements from sewage sludge after the ozonation process, the risk assessment code (RAC) coefficient was used. The bioaccumulation factor (BAF) and translocation factor (TF) values were also calculated to characterize the efficiency of trace element accumulation in the studied plant species from soil fertilized with sludges after the ozonation process. Generally, the mean concentration of total trace elements in the SS after the ozonation process was higher, but the differences were statistically significant only in the case of Mn, Cu, Pb, and Cd. The dominant fraction of Fe, Cr, Pb, and Cd was the residual fraction F4, while the extractable/exchangeable fraction F1 was present in the smallest amount. Therefore, in the case of Mn, Zn, and Ni, the ozonation process had a significant impact on the increase in the content of these elements in the F1 fraction. The application of the SS stabilized by ozonation process for maize and wheat fertilization did not significantly affect the bioaccumulation of most of the analyzed metals in aboveground biomass. Higher values of BAF coefficients after the application of ozonated SS were found only in the case of Cu and Ni. In turn, the determined TF coefficients were lower than 1 in most cases. The obtained results showed that the slight change in the concentration of Zn, Mn, and Ni in fraction F1 causes a specific risk of their mobility in the soil environment. It should be noted that due to the variable composition of sewage sludge, an analysis of the content of individual trace elements in chemical fractions should be carried out to assess its actual impact on the environment. This can help to indicate further actions that should be undertaken to limit their negative impact on the environment.

Abstract Several sequential extraction procedures are widely applied for metals chemical fractionation in the literature. However, their limitations to be used in different soils and metals have not been discussed in detail. This study compares two of the most commonly used extraction methods for metals chemical fractionation: Tessier and BCR. The objectives were to i) assess the differences between concentrations of metals extracted in each fraction by both Tessier and BCR procedures; ii) elucidate if soil properties affected the extraction ability of each fraction from both procedures; and iii) evaluate how land use contributes to different chemical metal distribution. Results indicated that both methods provide similar results when were applied to the same soil, since non-significant differences were found in metal concentrations between both methods at each fraction. Conversely, when we compared among land uses, significant differences were found in the metal concentration between both methods, especially between agricultural/urban/industrial against forest soil. Redundancy analysis showed that in carbonate-rich soils, BCR extraction method could cover up the real concentration of exchangeable metals with those bound to the carbonate phase, being the Tessier method the most suitable one for this kind of soils. Therefore, although sequential extraction is a useful tool to understand the distribution of metals in soil, the method used must be selected according to the land use and specific soil characteristics, taking into account at least, soil carbonate content. Highlights • Sequential extraction is an useful tool to stablish differences in metal distribution among land uses. • Metal fractionation among land uses depends on the metal concentration. • BCR method can cover up the real behaviour of the exchangeable fraction in calcareous soils. [ABSTRACT FROM AUTHOR]

The European Community Bureau of Reference method (BCR) was used for evaluating the effects of pine bark amendment (0, 24 and 48 g kg −1 ) and ageing (1 and 30 days) on Cd, Cu, Ni, Pb and Zn fractionation, on samples from an acid mine soil. In addition, the stirred flow chamber technique was applied for analyzing heavy metals desorption from the unamended and pine bark amended mine soil. When the unamended soil were not subjected to ageing, the added heavy metals were mainly accumulated as soluble fraction (>90% for Cd, Ni and Zn; 71% for Cu; and 45% for Pb). Pine bark amendment and ageing had little effect on Cd, Ni and Zn fractionation, whereas important changes were detected for Cu and Pb in response to both pine bark amendment and ageing (decrease in the soluble fractions, and increase in less mobile fractions). Desorption experiments showed that both pine bark amendment and ageing decreased heavy metals release from the mine soil. The results of this study indicate that pine bark amendment could be used to increase heavy metals retention (especially in the case of Cu and Pb) in acid mine soils, thus reducing the risks of metal transfer to uncontaminated environmental zones. [ABSTRACT FROM AUTHOR]