INTERACTION OF SELECTED ENDOCRINE DISRUPTING CHEMICALS TO BIOSOLIDS-DERIVED DISSOLVED ORGANIC MATTER (BDOM) BY SOLID PHASE EXTRACTION METHOD

Environmental pollution by endocrine disrupting chemicals (EDCs) such as bisphenol-A (BPA), 17α-ethinylestradiol (EE2), and 4-nonylphenol (4-NP) is widespread either in land or in water systems. Predicting the fate and transport of these compounds is difficult because the degree to which the compound is held in the soil or released into the soil water depends on the interaction among the system components, e.g., EDCs, soil matrix, and dissolved organic matter contributed by the land application of biosolids. In this study, we explored the interactions of BPA, EE2, and 4-NP to the previously characterized biosolids-derived dissolved organic matter (BDOM) samples using the solid phase extraction method. The goal is to quantitatively determine the extent of binding between the BDOM and the EDC because the formed BDOM-EDC complex is most likely to behave differently than the free BDOM or EDC compounds during the transport processes.

The bulk BDOM characterized by ¹³C-NMR and FTIR was dominated by N-acetylated carbohydrates and aromatic compounds. The presence of nitrogen and oxygen functional groups contributed to the hydrophilicity, while the aromatic and aliphatic components greatly contributed to the hydrophobic properties of the material. The generated isotherms showed that the EDC-BDOM adsorption showed non-linearity. When the EDCs were equilibrated with the BDOM, the index of heterogeneity n from the Freundlich isotherms of BPA, EE2, and 4-NP are 0.89, 0.21, and 0.69, respectively. Although we cannot directly compare the adsorption capacity, K_F because of the varying n values of BPA, EE2, and 4-NP, the adsorption capacity, K_F values are 25047, 3673, and 3639 mg^1-nLⁿ kg^-1, respectively. Among the EDCs, the relatively high K_F value for BPA than EE2 and 4-NP may suggest that the abundance of N-acetylated functional groups of the BDOM provided more adsorption sites for the relatively more hydrophilic BPA compound.