Transformation and Leaching Simulation of 6:2 and 8:2 diPAP and Related Metabolites in Unsaturated Soil Column Studies with MACRO

Abstract PFAS (perfluoroalkyl substances) are widespread in the environment and are found in almost every medium. Besides persistent PFAS, their transforming precursors gained attention since they may be a reservoir for persistent PFAS in soil. Only little information is available about the behavior of these precursors and the simultaneous leaching of their transformation products. However, this information is urgently needed to improve estimates of contamination levels. For this purpose, two precursors and their non-degradable metabolites were simulated using the MACRO model, with parameter values optimized using the evolutionary algorithm caRamel. A constant first-order transformation rate did not adequately represent the leaching of transformation products, but a variable transformation rate that decreased at the date of an equilibrium soil moisture provided a good representation of the precursor transformation and leaching of transformation products. The results are new evidence that variable environmental parameters such as soil moisture may affect the transformation rate of precursors. The simulation study is a step towards describing the behavior of PFAS precursors through physically-based models.