Transport and retention of polybrominated diphenyl ether in landfill and e-waste contaminated soils: a laboratory-scale soil flushing approach

Abstract

The movement of contaminants through subsurface is usually a complex phenomenon. As such, contaminant–soil interaction is important to assess the fate and transport of contaminants through the soil as well as groundwater flow systems. Thus, laboratory-scale columns are pertinent tools for studying the release potential of hydrophobic organic contaminants from soil or waste materials. Herein, a laboratory study was conducted to investigate the flushing potential of polybrominated diphenyl ether (PBDE) contaminated soils in two laboratory-scale soil packed columns; L\u2009=\u200947 cm and D\u2009=\u20096.51 cm. The project aimed to mimic the transport behaviour of persistent organic pollutants in the soil environment as well as proffer an optional method for soil remediation. Transport of the L-PBDE (labelled) surrogate compounds through the soil columns was dependent on sorption and the physicochemical characteristics of both the soil and L-PBDEs. Labelled brominated diphenyl ether 209 (L-BDE-209) in the surrogate compound mixture was the predominant congener eluted from both columns, followed by labelled brominated diphenyl ether 139 (L-BDE-139) and labelled brominated diphenyl ether 77 (L-BDE-77). The estimated equilibrium partition coefficients (Kd) for the applied compound mixture in both columns were 1.79 L kg−1 and 1.35 L kg−1 for landfill site (LSA-SA) and electronic waste (eW-GH) soil columns, respectively. Mass balance and ideal mass recovery of the L-PBDE compounds showed that a significant fraction of the initial contaminant mass (over 95%) was retained in the soils, which articulates the retention capability of some soil types.