Per- and polyfluoroalkyl substances (PFAS) in commercial composts, garden soils, and potting mixes of Australia

In developing and developed countries, urban gardening has increasingly become an integral part of local food systems for good quality produce, for enhanced urban health and sustainability. There are few gardens with naturally perfect soils for growing plants. However, the soils with poor texture and fewer nutrients can be improved by different types of organic amendments such as composts, garden soils and organic potting mixes that are commercially available in the consumer markets worldwide to promote healthy plant growth. In this study, we assessed 19 different commercially available composts, garden soils, and potting mixes for the presence of 38 per- and polyfluoroalkyl substances (PFAS). The total (Ʃ38) PFAS in the samples ranged between 1.26 to 11.84 µg kg−1 (dry weight). The total concentration of perfluorinated carboxylic acids (ƩPFCAs) was higher than that of perfluoroalkyl sulfonic acids (PFSAs) in all products. The total oxidizable precursor assay (TOPA) was applied in the analysis of composts and potting mixes, which revealed an increase in short-chain ƩPFCAs concentrations ranging from 0.48 to 7.63 µg kg−1, which suggested the transformation of PFCAs precursors to short-chain PFCAs. The measured concentrations of short-chain PFCAs after TOPA in the soil substrates have the potential to contribute to plant uptake and food chain transfer of PFAS to humans due to their high mobility.