Polychlorinated biphenyl behavior in soils amended with biosolids

Abstract

Assessment of the mobility of polychlorinated biphenyls (PCBs) in soils, amended with biosolids at a rate of 30 Mg ha −1, was performed using an incubation process and leaching columns. The incubation process was carried out for 0, 30, and 60 d under field capacity conditions at 25 °C. The mobility of PCBs was assessed using solutions of 0.5 mol L −1 CaCl 2 and 25 mg L −1 linear alkylbenzenes sulfonate (LAS). Ultrasound-assisted pressurized solvent extraction (US-PSE) was utilized for compound separation from the solid matrix. Compounds were determined by gas chromatography coupled to mass spectrometry. The biosolids, containing a background PCB concentration about 300 μg kg −1, were spiked with the analytes at 300 mg kg −1 to obtain a clearer determination of their behavior when the biosolid was mixed with soil. In biosolid-amended soils, an increase was observed in the extractability of PCBs with increasing incubation time, which may be attributed to organic matter breakdown. The leaching column study showed that CaCl 2 was unable to mobilize the PCBs from the biosolid to the soil, whereas LAS mobilized these compounds within the time scale implicit in the experiment (30 d). The most mobilized congeners in the columns corresponded to those with the greatest molecular weight (hexa- and heptachlorinated), probably due to the higher hydrophobicity of these compounds. Results indicate that the presence of important concentrations of LAS in biosolids could mobilize PCBs from soil to the freatic level.