Bioavailability and Bioaccumulation of 6:2 Fluorotelomer Sulfonate, 6:2 Chlorinated Polyfluoroalkyl Ether Sulfonates, and Perfluorophosphinates in a Soil–Plant System

Abstract

As emerging alternatives of legacy perfluoroalkyl substances, 6:2 fluorotelomer sulfonate (6:2 FTS), 6:2 chlorinated polyfluoroalkyl ether sulfonates (6:2 Cl-PFESA), and perfluorophosphinates (C6/C6 and C8/C8 PFPiAs) are supposed to be partitioned to soil and highly persistent in the environment. The uptake of novel per-and polyfluoroalkyl substances (PFASs) by plants represents a potential pathway for their transfer in the food chain. In this study, the bioavailability of these four novel PFASs in soil and the bioaccumulation characteristics in greenhouse-grown wheat (Triticum aestivum L.), maize (Zea mays L.), soybean ( Glycine max L. Merrill), and pumpkin (Cucurbita maxima L.) were investigated. The results indicated that these novel PFASs with higher hydrophobicity were more easily sequestrated in soil, and the fractions extracted by methanol could well describe their bioavailability, which could be stimulated by low-molecular-weight organic acids at rhizospheric concentrations. A negative relationship was found between root soil concentration factors (RSCFs) and hydrophobicity (log K ow ) of the target PFASs. This correlation was also found in the translocation factors (TF) from roots to shoots. Furthermore, the uptake and transfer of the target PFASs were regulated by the protein contents in plant roots and shoots.

Greenhouse-Scale Comparison of 10 Native Pacific Northwest Plants for the Removal of Per- and Polyfluoroalkyl Substances from Stormwater

“…However, given the relatively high accumulation of PFNA and PFDS in the plant roots (Figure S5), it can be assumed that sorption to plant roots is a critical function of PFNA and PFDS accumulation. This is in agreement with numerous studies that have observed an increased accumulation of PFAS with increased chain length. − ,,, This is presumably due to their increased attraction to the root lipids and inability to cross the Casparian strip. ,,,, However, further research is needed to understand the accumulation mechanisms of PFNA and PFDS in plants.…”

New Insights into the Accumulation, Transport, and Distribution Mechanisms of Hexafluoropropylene Oxide Homologues, Important Alternatives to Perfluorooctanoic Acid, in Lettuce (Lactuca sativa L.)

“…As a type of surfactant, the target PFASs may change the permeability of the cell membrane, which would promote plant uptake of nutrient elements such as magnesium and nitrogencrucial components of the chlorophyll molecule. Eventually, the shoot biomass would be enhanced, possibly due to the rise of the chlorophyll content. ,,,, The HFPO homologues and PFOA were not found in the roots and shoots of the control group (Table S2), suggesting that their uptake from endogenous sources and foliar uptake were negligible. Generally, the root concentrations were as follows: PFOA ≥ HFPO-DA > HFPO-TA > HFPO-TeA for both LT and HT (Figure ).…”

“…Eventually, the shoot biomass would be enhanced, possibly due to the rise of the chlorophyll content. 25,26,31,32,40 The HFPO homologues and PFOA were not found in the roots and shoots of the control group (Table S2), suggesting that their uptake from endogenous sources and foliar uptake were negligible. Generally, the root concentrations were as follows: PFOA ≥ HFPO-DA > HFPO-TA > HFPO-TeA for both LT and HT (Figure 1).…”

“…Long-chain PFASs with higher hydrophobicity (log K ow ), such as HFPO-TA and HFPO-TeA, are preferentially sequestered in soils compared with short-chain PFASs. This may be because long-chain PFASs preferentially occupy the inner hydrophobic micropores of soil and thus are physically entrapped. , Another potential interpretation is that long-chain PFASs preferentially bind to the more hydrophobic DOC components such as humic acid, while short-chain PFASs tend to associate with more soluble constituents like fulvic acid . However, further studies are required to accurately identify the composition of DOC derived from lettuce root exudate and their influence on HFPO homologues’ bioavailability.…”

“…Extensive utilization of HFPO homologues has resulted in their inevitable release into the environment. ,− Subsequently, the measurable levels of HFPO-DA, HFPO-TA, and HFPO-TeA have been frequently reported in various environmental matrices worldwide. ,,, Notably, HFPO homologues have gradually become dominant in PFAS emissions . Though these alternatives were developed to obtain environmentally friendly products, their potential for persistence and toxicity as being similar to that of PFOA is increasingly coming to light. − Moreover, HFPO-DA and HFPO-TA were revealed to be more persistent, bioaccumulative, and toxic than PFOA. ,,− Soil is an important sink for PFASs and the major exposure medium for crops. ,, Crops, especially vegetables, have been recognized to be the primary source of human exposure to PFOA, whether directly or indirectly through food chain transfer. ,− The bioaccumulation factors (BAFs) of various PFASs in crops range from 0.36 to 48.0, with the highest BAFs observed in leafy vegetables. , Hence, concerns about the potential risks of HFPO homologues in soil–crop systems should be taken seriously into account, given that HFPO homologues not only have similar molecular structures to PFOA but also share the same characteristics …”