Effects of endogenous and exogenous dissolved organic matter on sorption behaviors of bisphenol A onto soils

Abstract

The transport of organic contaminants in groundwater might be greatly affected by coexistence of dissolved organic matter (DOM) from different sources. In this study, the effects of endogenous and exogenous DOMs (referred to as DOM_en and DOM_ex, respectively) on sorption behavior of bisphenol A (BPA) onto two reference soils were investigated by batch experiments and microscopic characterization. The results showed that BPA sorption onto soils was dominated by soil organic matter content and affected by DOM properties. The effect of DOM_en on BPA sorption was also related to the inorganic components of the two soils. The decrease of organic matter content reduced the sorption capacity of fluvo-aquic soil. However, because the content of available inorganic components in black soil was high, after removing DOM_en, more inorganic sites were exposed to increase the sorption capacity. In addition, DOM_en could form complexes with BPA in solution, thus the removal of DOM_en promoted BPA sorption onto black soil. Under the experimental conditions, contribution of DOM_ex to the total sorption of BPA onto both soils was not more than 30%. Results of dialysis experiments and soil sorption experiments indicated that effects of coexisting DOM_ex on BPA sorption was related to the affinity of DOM_ex to soils and complexation of BPA and DOM_ex. Since the affinity of DOM_ex to fluvo-aquic soil was relatively low, the complex of BPA and DOM_ex in solution was the main inhibition mechanism for BPA sorption. For black soil, higher complexation proportion of BPA with DOM_ex adsorbed onto soil which promoted BPA sorption onto soil. The findings are of significance for understanding the co-migration of DOM with BPA through soils.

Keywords: Bisphenol A; Dissolved organic matter (DOM); Endogenous DOM; Exogenous DOM; Soil; Sorption.