Sorption and desorption of bisphenol A on agricultural soils and its implications for surface and groundwater contamination

This study investigates the sorption and desorption behavior of bisphenol A (BPA) in four distinct agricultural soils—clay, silt loam, loam, and sandy loam—collected from Khyber Pakhtunkhwa (KP) province, Pakistan. These soils vary in key physicochemical properties such as pH, organic carbon content (% OC: 0.05–1.3), and texture. Sorption isotherms were developed based on aqueous BPA concentrations and were well described by a linear sorption model, with correlation coefficients (R²) exceeding 0.95, indicating strong model fit. The soil organic carbon content was the primary factor influencing BPA sorption, with partition coefficients (Kd) ranging from 1.2 to 4.6 L/kg and organic carbon-normalized partition coefficients (log KOC = 3.05 ± 0.11) aligning closely with BPA's reported octanol-water partition coefficient (log KOW = 3.3–3.4). The sorption capacity followed the order: clay > silt loam > loam > sandy loam, corresponding to their respective OC and clay contents. Soil pH exhibited a weak correlation with BPA sorption, though alkaline soils (pH > 8) showed enhanced desorption behavior. Desorption was observed to be rapid and largely reversible, with 62.5–84.7 % of BPA mass desorbed, while up to 15 % remained strongly bound after two desorption steps—indicating potential long-term retention. The results suggest that soils with low OC and clay content pose a higher risk for BPA mobility, with implications for groundwater contamination and food safety in agricultural regions.