Contamination of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in sediment of the Cau River, Vietnam

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are recognized as emerging environmental pollutants because of their high persistence in various environmental matrices and toxic effects on humans and animals. In Vietnam, PFOA and PFOS have been detected in surface water and sediment in recent studies. The objectives of this study were to evaluate the spatial and vertical distribution, determine the factors affecting the sorption onto sediment, and assess the environmental risk of PFOS and PFOA in the sediment of the Cau River. The average concentrations of PFOS and PFOA in the surface sediment were 2.66 ng/g and 0.84 ng/g, respectively. The highest concentrations were recorded in the areas receiving wastewater from domestic and industrial activities. According to the depth, the contents of target chemicals in the surface sediments (0-5 cm) were lower than those in the second layer (5-10 cm). The remaining layers have decreasing concentration as the depth of the sediment increases. The water-sediment distribution coefficient was relatively different for PFOS and PFOA with log Kd values ranging from 1.31 to 1.86 and from 0.08 to 1.31, respectively. This study also demonstrated that the level of PFOS and PFOA in sediment is significantly correlated with total organic carbon content of sediment. No apparent relation was found between PFOS, PFOA concentration in sediment, and particle size distribution. Risk quotients of the two compounds were below 0.01, indicating that the environmental risk in the sediment is negligible at present. The results of this study provide an overview of PFOS and PFOA contamination in sediment in the Cau River, Vietnam.