Sorption Constant of Bisphenol A and Octylphenol Onto Size-Fractioned Dissolved Organic Matter Using a Fluorescence Method

Dissolved organic matter (DOM) is a complex and heterogeneous mixture ubiquitously present in aquatic systems. DOM affects octylphenol (OP) and bisphenol A (BPA) distribution, transport, bioavailability, and toxicity. This study investigated OP and BPA sorption constants, log K(COC), with three size-fractioned DOM. The molecular weights of the sized fractions were low molecular weight DOM (LDOM, <1 kDa), middle molecular weight DOM (MDOM, 1–10 kDa), and high molecular weight DOM (HDOM, 10 kDa–0.45 μm). The log K(COC) ranged from 5.34 to 6.14 L/kg-C for OP and from 5.59 to 6.04 L/kg-C for BPA. The OP and BPA log K(COC) values were insignificantly different (p = 0.37) and had a strong positive correlation (r = 0.85, p < 0.001). The OP and BPA LDOM log K(COC) was significantly higher than the HDOM and MDOM log K(COC) (p = 0.012 for BPA, p = 0.023 for OP). The average specific ultraviolet absorption (SUVA(254)) values were 32.0 ± 5.4, 13.8 ± 1.0, and 17.9 ± 2.8 L/mg-C/m for LDOM, MDOM, and HDOM, respectively. The log K(COC) values for both OP and BPA had a moderately positive correlation with the SUVA(254) values (r = 0.79–0.84, p < 0.002), which suggested the aromatic group content in the DOM had a positive impact on sorption behavior.