Carryover of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) from Soil to Plants

Abstract

Within the scope of a joint project to study soil-to-plant carryover of polyfluorinated compounds (PFCs), five cultivated plants (spring wheat, oats, potatoes, maize, and perennial ryegrass) were sown or planted in Mitscherlich pots. Six variants per species were used, each with a different concentration level of PFOA and PFOS (from 0.25 to 50 mg/kg as aqueous solution) to detect possible concentration dependence in the transfer of these two PFCs from soil to plant. PFOA and PFOS were detected by liquid chromatography-tandem mass spectrometry after appropriate sample preparation (partial drying, mincing, homogenizing, extraction). Since PFOA and PFOS presently represent the most widely studied PFCs, they are classified as "leading compounds." The results show that concentrations of PFOA/PFOS in the plants vary greatly, depending on the concentrations applied to the soil. PFOA values were higher than PFOS values in all plants except potatoes, in which these differences could be quite substantial. From the results presented here it can be seen that uptake and storage are much more intensive in the vegetative portion of the plant than relocation in the storage organs. This is particularly evident from the the comparison of concentrations found in the grain and ear and those in the straw or rest of the plant in spring wheat, oats, and maize. Transfer from "soil to crops" provides a possible explanation for the presence of PFCs in foodstuffs and in human body fluids such as blood, plasma, serum, or breast milk. The aim of the present study was to determine whether a statistically significant, concentration-dependent carryover of PFOA and PFOS in crop plants can take place, which would provide a potential entrance point for these substances into the food chain.

Mechanistic studies of perfluorooctane sulfonate, perfluorooctanoic acid uptake by maize (Zea mays L. cv. TY2)

“…Results obtained by Lechner and Knapp (2011) showed that PFOA concentrations in carrots and potatoes were higher than those of PFOS. However, PFOS concentrations in maize ears were higher than PFOA (Stahl et al 2009). Our finding showed that the steady concentrations of PFOS in maize roots and shoots were higher than those of PFOA ( Fig.…”

“…Liu (2009) reported that PFOS was more toxic than PFOA for cucumber, higher concentrations. Stahl et al (2009) suggested that toxic effect of PFOS and PFOA to plants was dependent on plant species.…”

“…Accumulation of PFCs by grass decreased with PFC increasing chain length (Yoo et al 2011). The accumulation inhibited the growth and development of plants (Stahl et al 2009). Although the above works focused on the carryover of PFCs from soil to plants, the uptake mechanisms of PFCs by plants are still not known.…”

“…The migration of PFCs from soil to plants and their subsequent consumption by animals or human is a likely pathway for PFCs to enter the food chain (Stahl et al 2009;Lechner and Knapp 2011;Yoo et al 2011). Thus it is important to understand how PFCs are transported into the plant root system.…”

“…Thus it is important to understand how PFCs are transported into the plant root system. Carryover of PFCs from soils to agricultural crops was reported to be dose dependent (Stahl et al 2009) and varied with the plant species and with the substance (Lechner and Knapp 2011). Accumulation of PFCs by grass decreased with PFC increasing chain length (Yoo et al 2011).…”