Impact of dissolved organic matter chemical properties on perfluorooctane sulfonate solution binding affinities and adsorption on soils

The fate and bioavailability of perfluorooctane sulfonate (PFOS) in soils is significantly influenced by its interactions with dissolved organic matter (DOM), which is elevated in soil solutions due to the land application of organic amendments. Evaluating the effects of DOM chemical properties on PFOS affinity and adsorption-desorption processes in soil is essential to better predict PFOS behavior in soils. We studied the interactions between PFOS and DOM from locally sourced and commercial organic amendments, including biosolids, animal manure, composts, and humic acid. Additionally, we measured PFOS adsorption on a kaolinitic Ultisol (Gwinnett) and adsorption-desorption on a smectitic Vertisol (Vaiden). PFOS affinity for DOM was strongly correlated with the humification index (HIX, r² = 0.94), protein-like fluorophores (C3, r² = 0.76), and aromaticity (specific UV absorption at 254 nm [SUVA₂₅₄], r² = 0.71). The presence of 100 mg C L⁻¹ DOM from biosolids and animal waste enhanced PFOS adsorption by up to 90%, whereas DOM from plant and terrestrial sources reduced adsorption by as much as 40%. Strong correlations were observed between PFOS adsorption enhancement on Gwinnett and C3 (r² = 0.72), SUVA₂₅₄ (r² = 0.68), and HIX (r² = 0.62). In contrast, PFOS adsorption on Vaiden was substantially lower and less influenced by DOM, though DOM type still affected PFOS adsorption-desorption hysteresis on Vaiden. This study offers a framework for using easily measurable DOM chemical properties to predict DOM's impact on PFOS fate and behavior in soils.