Multimedia and Full-Life-Cycle Monitoring Discloses the Dynamic Accumulation Rules of PFAS and Underestimated Foliar Uptake in Wheat near a Fluorochemical Industrial Park

The escalating concern of perfluoroalkyl and polyfluoroalkyl substances (PFAS), particularly at contaminated sites, has prompted extensive investigations. In this study, samples of multimedia including air, rhizosphere soil, and tissues of wheat at various growing stages were collected near a mega fluorochemical industrial park in China. Perfluorooctanoic acid (PFOA) was predominant in both air and soil with a strong correlation, highlighting air deposition as an important source in the terrestrial system. PFAS concentrations in wheat decreased in the stem and ear but increased in the leaves as wheat matured. Specifically, perfluorobutanoic acid (PFBA) dominated in the aboveground tissues in the full-life-cycle, except that PFOA surpassed and became predominant in leaves during the filling and maturing stages, hinting at an airborne source. For all PFAS, both bioaccumulation factors and translocation factors (TFs) were inversely correlated with the carbon chain length during the full-life-cycle. The obtained TF values were considerably higher than those obtained from ambient sites reported previously, further suggesting an unneglectable foliar uptake from air, which was estimated to be 25% for PFOA. Moreover, spray irrigation remarkably enhanced the absorption of PFAS in wheat via foliar uptake relative to flood irrigation. The estimated daily intake of PFBA via wheat consumption and air inhalation was 0.50 μg/kg/day for local residents, at least one magnitude higher than the corresponding threshold, suggesting an alarmingly high exposure risk.