Uptake of perfluorinated alkyl acids by crops: results from a field study† Sebastian Felizeter,‡ a Heinrich J ¨ urling, b Matthias Kotthoff,§ b Pim De Voogt ac and Michael S. McLachlan * d Four crops with different edible plant parts (radish, lettuce, pea and maize) were grown in outdoor lysimeters on soil spiked with 13 perfluorinated alkyl acids (PFAAs) at 4 different levels. PFAA concentrations were measured in soil, soil pore water, and different plant parts at harvest. Edible part/soil concentration factors ranged over seven orders of magnitude and decreased strongly with increasing PFAA chain length, by a factor of 10 for each additional fluorinated carbon (n CF ) for pea. Three processes were responsible for most of the variability. The first was sorption to soil; calculating whole plant concentration factors on the basis of concentration in pore water instead of soil reduced the variability from five orders of magnitude to two. Second, the journey of the PFAAs with the transpiration stream to the leaves was hindered by retention in the roots driven by sorption; root retention factors increased by a factor 1.7 for each n CF . Third, transfer of PFAAs from the leaves to the fruit via the phloem flow was also hindered – presumably by sorption; fruit/leaf concentration factors decreased by a factor 2.5 for each n CF .A simple mathematical model based on the above principles described the measured concentrations in roots, leaves, fruits and radish bulbs within a factor 4 in most cases. This indicates that the great diversity in PFAA transfer from soil to crops can be largely described with simple concepts for four markedly different species. Environmental signicance Due to their persistence and hydrophilicity, many PFAAs have a strong potential to be taken up from soil into plants and to accumulate in foliage. There they can harm the plant and enter the food web, contributing to exposure of higher organisms including humans. Here we show that sorption to soil is the major process modulating plant uptake of PFAAs. Furthermore, we show that accumulation in the plant occurs primarily where the water is lost (in the leaves), while transport from there to fruits is inversely correlated with the tendency of the PFAA to sorb (chain length). Finally, we present a model that provides a simple framework for understanding and assessing PFAA accumulation in plants. Introduction In addition to having been detected ubiquitously in several environmental compartments including water, 1,2 biota 3 and the atmosphere, 4 peruorinated alkyl acids (PFAAs) have also been found in human blood serum and breast milk. 5–8 Because of their known and suspected toxic effects, 9–11 it is important to understand the pathways of human exposure to minimize the risk for exposure and possible adverse health effects. The European Food Safety Authority therefore established tolerable daily intakes (TDIs) for peruorooctanoic acid (PFOA), and peruoroctane sulfonic acid (PFOS) in response to concerns about these chemicals. 12 They recently revised these TDIs and established a new and much lower tolerable weekly intake rate of 4.4 ng per kg bw per week for the extended group of PFOA, PFNA, PFHxS and PFOS. 13 Food has been identied as the main source of human exposure, 14–19 and crops are one possible vector for PFAAs into the food supply. PFAAs are taken up by crops when grown in soil that has been contaminated, for instance via water reuse irrigation or biosolids application, 20,21 and there are two known cases where agricultural sites have been widely contaminated with PFAAs in Germany. 22,23 The aim of the presented work is to further our understanding of how PFAAs are transferred from soils to crops. Current knowledge of plant uptake of PFAAs has been summarized in several recent reviews. 24–26 In early research on a Universiteit van Amsterdam, Institute for Biodiversity and Ecosystem Dynamics, Science Park 904, 1098XH Amsterdam, The Netherlands b Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Schmallenberg, Germany c KWR Water Research Institute, 3430BB Nieuwegein, The Netherlands d Department of Environmental Science (ACES), Stockholm University, 106 91 Stockholm, Sweden. E-mail: michael.mclachlan@aces.su.se † Electronic supplementary information (ESI) available: Additional graphics and tables as mentioned. See DOI: 10.1039/d1em00166c ‡ Current address: Eurons Dr. Specht International GmbH, Hamburg, Germany. § Current address: Hamm-Lippstadt University of Applied Sciences, Department 2, Hamm, Germany. Cite this: Environ. Sci.: Processes Impacts, 2021, 23, 1158 Received 25th April 2021 Accepted 5th July 2021 DOI: 10.1039/d1em00166c rsc.li/espi 1158 | Environ. Sci.: Processes Impacts, 2021, 23, 1158–1170 This journal is © The Royal Society of Chemistry 2021 Environmental Science Processes & Impacts PAPER Open Access Article. Published on 14 July 2021. Downloaded on 12/10/2021 8:19:40 PM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. View Article Online View Journal | View Issue