Influence of oxic/anoxic condition on sorption behavior of PFOS in sediment

Sediment components and redox properties change with oxic/anoxic condition, which affect the environmental transport of perfluorooctane sulfonate (PFOS). Herein, the influence of oxic/anoxic condition on the variation of redox and residual components of sediments, where organic matter, iron and manganese oxides are separated from the original sediment collected from Lake Taihu, China, are investigated. Meanwhile, the distinguishing sorption behaviors of PFOS on various residual sediments under oxic and anoxic condition are studied. Sediment after extracting iron and manganese (S-FeMn), which possessed the highest organic carbon (0.99%), had the highest affinity for PFOS under oxic condition. However, anoxic environment resulted in an increase of the pH, dissolving of organic carbon and de-protonation of S-FeMn, which caused the lower sorption capacity of PFOS on S-FeMn. Sediment after extracting manganese (S-Mn) had the higher sorption ability in anoxic environment because the Fe2+ from S-Mn provided more effective electrostatic sites for anionic PFOS. When the environment changed to oxic condition, the iron existed as trivalent form in S-Mn, which resulted in a block of effective sorption site and reduced the sorption amounts of PFOS. The higher percentage of manganese oxides restrained the sorption of PFOS. Hence, whether or not oxic/anoxic condition promoted the PFOS sorption depended on both the percentage and form of various components in the sediment. The study generated further insight into the environmental transport of PFOS in the sediments with different properties and the wetland system, where oxic/anoxic subsurface flow was constructed.