Impact of biosolid application rates on competitive sorption and distribution coefficients of Cd, Cu, Ni, Pb, and Zn in an Alfisol and an Entisol

We investigated the effect of biosolid application rates (0 (control), 20 (BS1), 50 (BS2), and 100 Mg ha−1 (BS3)) on competitive sorption and distribution coefficients (Kd) of Cd, Cu, Ni, Pb, and Zn in an acidic Alfisol and in an alkaline Entisol originating from Greece. Sorption of all metals was stronger in the Entisol than that in the Alfisol. Lead showed the highest Kd followed by Cu, Cd, Zn, and Ni in both soils. Sorption of Cd, Cu, Ni, Pb, and Zn increased significantly with increasing biosolid application rate in the Alfisol. Although sorption of Cd, Ni, Pb and Zn in the Entisol incremented significantly, sorption of Cu decreased significantly with increasing the biosolid application rate compared to control. Sorption of Cd, Cu, Ni, Pb, and Zn enhanced with raising the added metal concentrations under the three rates (BS1, BS2, and BS3) in both soils. The impact of biosolid rates on metal sorption was more pronounced in the Alfisol than in the Entisol. Lead and Cu were more affected by biosolid than Cd, Zn, and Ni in both soils. This study shows that biosolid application enhanced sorption of the studied metals in the Alfisol at the three rates, while it enhanced Cd, Ni, Pb, and Zn sorption in the Entisol at high rates, thereby decreasing their mobilization. However, application of biosolid to the Entisol at the three rates decreased Cu sorption and thus might increase its mobilization.