An investigation into the long-term binding and uptake of PFOS, PFOA and PFHxS in soil – plant systems

This study investigated the potential aging and plant bioaccumulation of three perfluoroalkyl acids (PFAAs), perfluorosulphonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanesulphonic acid (PFHxS) in 20 soils over a six-month period. Sorption coefficients (Log Kd) ranged from 0.13–1.28 for PFHxS, 0.17–1.06 for PFOA and 0.98–2.03 for PFOS, respectively, and bioaccumulation factors (Log BAFs) ranged from 0.29–1.24, 0.22–1.46 and 0.05–0.65 for PFHxS, PFOA and PFOS, respectively. Over the six-month period, Kd values significantly increased for PFHxS and PFOA but the magnitude of the increase was very small and did not translate into differences in plant PFAA-concentrations between aged and freshly spiked treatments. The Kd and BAF values were modelled by multiple linear regression (MLR) to soil physico-chemical properties and by partial least squares regression to soil spectra acquired by mid-infrared spectroscopy (DRIFT−PLSR). Modelling of each PFAA was influenced by different soil properties, including organic carbon, pH, CEC, exchangeable cations (Ca2+, Mg2+, Na+ and K+) and oxalate extractable Al. BAF values were not strongly correlated to any soil property but were inversely correlated to Kd values. Our results indicate that limited aging occurred in these soils over the six-month period. [Display omitted] •PFOS, PFOA and PFHxS appear to retain bioavailability in soil over time.•PFHxS was the most, and PFOS the least, bioaccumulative PFAA across a range of soils.•PFAA bioaccumulation in plant shoots was mainly dependent on organic carbon content.•Across soils, bioaccumulation was inversely related to PFAA partitioning.