Concentrations of perfluorooctanoate and perfluorooctane sulfonate in sediment of Western Cape Rivers, South Africa

Abstract

In this study, we report for the first time, concentrations of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in sediments from a South African environment, particularly for the largest catchment areas of the Western Cape, South Africa, an area associated with the largest agricultural sector with some of the produce and end-products intended for the international markets. Sample preparation and analysis were based on the ISO 25101: 2009(E) method, using solid phase extraction (SPE) followed by liquid chromatography combined with electrospray tandem mass spectrometry (LC-MS/MS). Sediment grain size analysis, core water characteristics and percent total organic carbon were also quantified. From the results, PFOS and PFOA were observed in all the river sediment samples and were found in concentrations up to 19 ng/g and 187 ng/g for Salt River, 121 ng/g and 772 ng/g for Diep River, and 75 ng/g and 193 ng/g for Eerste River, for both PFOS and PFOA, respectively. Some of these concentrations are higher than those previously reported in similar studies in various countries; this suggests there is cause for concern. Although sediment has a poor sorption capacity for both PFOS and PFOA in comparison with plants, the prevalence of PFOS and PFOA in sediment samples from rivers from which irrigation water is sourced for agricultural purposes, indicates a risk of agricultural produce contamination.