Yun Deng,Jiankun Huang,Xingwen Lu,Da Chen,Fei Wang
Due to the limited documentation on thermal treatment of per - and polyfluoroalkyl substances (PFAS), this study investigated the thermal degradation behavior, mechanisms, mineralization, and gaseous product toxicity of five environmentally ubiquitous PFAS, including perfluorooctanesulfonic acid (PFOS), perfluorooctane sulfonamide (PFOSA), 6:2 chlorinated polyfluoroalkyl ether sulfonate (F 53B), perfluorooctanoic acid (PFOA), and 1H,1H,2H,2H-perfluoro-1-decanol (8:2 FTOH). Results showed that thermal stability of PFAS is dictated by their functional groups, presenting a stability hierarchy of sulfonic acid (PFOS, F 53B) > sulfonamide (PFOSA) > carboxylic acid (PFOA) > hydroxyl (8:2 FTOH). Thermal decomposition of these PFAS was initiated with cleavage of bonds connecting the functional group to the perfluorinated chain followed by stepwise chain-shortening reactions, yielding various perfluoroalkanes, perfluoroalkenes, and hydrofluoroalkanes. Calcium hydroxide remarkably enhanced fluorine mineralization into calcium fluoride and suppressed the formation of organofluorinated compounds during PFAS thermal treatment. Toxicity predictions indicated reduced acute toxicity for thermal degradation products compared to parent PFAS, but they still pose potential risks to human health. This implies that optimizing thermal treatment conditions is essential, focusing not only on mineralization efficiency but also on suppressing the formation of harmful by-products. These findings provide a systematic understanding of PFAS thermal decomposition and identify potentially hazardous gaseous by-products.
Shuyan Zhao,Tao Zhou,Lingyan Zhu,Bohui Wang,Ze Li,Liping Yang,Lifen Liu
N-ethyl perfluorooctane sulfonamide (N-EtFOSA) is an important perfluorooctanesulfonate (PFOS) precursor (PreFOS) which is used in sulfluramid. The present work studied the uptake, translocation and metabolism of N-EtFOSA in wheat ( Triticum aestivum L.), soybean ( Glycine max L. Merrill) and pumpkin ( Cucurbita maxima L.) by hydroponic exposure. Except for parent N-EtFOSA, its metabolites of perfluorooctane sulfonamide acetate (FOSAA), perfluorooctane sulfonamide (PFOSA), PFOS, perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS) were detected in the roots and shoots of all the three plant species examined. This suggested that plant roots could take up N-EtFOSA from solutions efficiently, and translocate to shoots. A positive correlation was found between root concentration factors (RCFs) of N-EtFOSA and root lipid content. Much higher proportion of N-EtFOSA transformation products in plant tissues than in the solutions suggested that N-EtFOSA could be in vivo metabolized in plant roots and shoots to FOSAA, PFOSA and PFOS, and other additional shorter-chain perfluoroalkane sulfonates (PFSAs), including PFHxS and PFBS. The results suggested that plants had biotransformation pathways to N-EtFOSA that were different than those from microorganisms and animals. This study provides important information about the uptake and metabolism of PreFOSs in plants.
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