Sorption behaviours and transport potentials for selected pharmaceuticals and triclosan in two sterilised soils

Abstract

Pharmaceuticals and personal care products (PPCPs) are emerging environmental pollutants, which, in addition to direct deposition processes, can find their way into surface soils through the agricultural application of sewage sludge and irrigation practices using contaminated wastewater. Therefore, it is important to assess the extent to which soils are able to retain PPCPs and to prevent their downward migration towards groundwaters. To further our understanding in this area, batch sorption experiments and artificial rainwater leaching experiments have been performed using five compounds (bezafibrate, carbamazepine, chloramphenicol, diclofenac and triclosan) possessing a range of physicochemical properties in two soils with differing acidities and organic carbon contents. The determined K oc values for triclosan and diclofenac consistently demonstrated their lower potential mobilities in both soils. The predicted high mobility of chloramphenicol is supported by its efficient leaching potential (89–100 %) in both soils whereas bezafibrate, diclofenac and carbamazepine demonstrate slightly lower affinities for the leachate (61–96 %) for soil A and are strongly retained (>99 %) by soil B. The amount of PPCP in the leachate, the rate of leaching and the depth of soil penetration are explained in terms of the soil characteristics and the properties of the individual PPCPs (such as solubility and pKa) with soil organic content being shown to be a critical factor controlling the ability of a soil to retain a PPCP in the surface layers. The findings contribute to the scientific knowledge required by practitioners and regulators as they consider future subsoil contamination by PPCPs and subsequent possible threats to groundwater resources and surface water habitats.