Perfluoroalkyl Acids Including Isomers in Tree Barks from a Chinese Fluorochemical Manufacturing Park: Implication for Airborne Transportation

Abstract

Measurement of airborne perfluoroalkyl acids (PFAAs) is challenging, but important for understanding their atmospheric transport. Tree bark is good media for monitoring semivolatile compounds in the atmosphere. Whether it could work as an indicator of airborne PFAAs was first examined in this study. Bark and leaf samples collected around a Chinese fluorochemical manufacturing park (FMP) were analyzed for PFAAs and their branched isomers. Total PFAA concentrations (∑PFAAs) in the bark (mean, 279 ng/g dw) and leaf (250 ng/g dw) samples were comparable. ∑PFAAs in the barks collected within the boundaries of the FMP were significantly (p < 0.05) higher than those outside the FMP, and displayed a decreasing spatial trend as the distance from the FMP increased. However, such spatial difference and trend were not observed for the leaves. PFAA compositional profiles in most of the tree barks were consistent with each other, but different from those in tree leaves. These results indicated that tree barks mainly accumulated airborne PFAAs, while uptake from soil and translocation could make partial contribution to those in leaves. Perfluorooctanoate and perfluorooctanesulfonate in barks had strictly consistent isomeric compositions with their electrochemical fluorination products. Overall, these results indicated that the bark could be a good indicator of airborne PFAAs with respect to their occurrence, isomeric signature, and atmospheric transport.