Comparison of Perfluorooctanoic Acid Mobility in Soil with and without Alfalfa.

Perfluorooctanoic acid (PFOA) is a fully fluorinated organic compound (C₈HF₁₅O₂) that is widely used in consumer products as a surfactant because of its chemical resistance to stains, grease, and water. Perfluorooctanoic acid is a persistent organic pollutant because it is globally distributed, stable in the environment, resistant to metabolism and elimination, and toxic. It is present at high levels in municipal biosolids which are applied to agricultural fields as fertilizer. Bioaccumulation of PFOA occurs in humans, primarily in the liver, but little research has been conducted on the transfer of PFOA from the field to food to humans. In this study, a pulse input of radiolabeled [¹⁴C]-PFOA was applied to pots containing bare soil, or soil with alfalfa growing. The pots were periodically watered and the soil mobility of the ¹⁴C-PFOA was monitored, as well as uptake into plant roots, stems, and leaves, each week for 10-weeks. By the 10^th week, the peak PFOA concentration progressed to a depth of 22 cm in the bare pots, while the peak PFOA concentration only progressed to ~7 cm for the pots with plants, indicating plant presence reduced downward mobility. The PFOA was taken up by the plants within the first week and was detected in all tissues of the plants. Also, the PFOA concentrations increased through time in the leaf tissue, which contained the highest concentrations of PFOA, indicating the PFOA translocated from the roots, through the stems, and eventually aggregated in the leaves. The PFOA concentrations in the plant tissues were strongly correlated with the top soil layer (2.5 cm), and no other soil layer. The novel results of this study have important implications on food safety in light of the rapid and facile transfer of PFOA from surface soils and into an important livestock crop.