Sorption and dialysis experiments to assess the binding of phenolic xenobiotics to dissolved organic matter in soil.

ABSTRACT

The binding of two phenolic compounds, nonylphenol (NP) and bisphenol A (BPA), and the herbicide metabolite hydroxydesethyl terbuthylazine (HDT) to dissolved organic matter (DOM) as well as its impact on the environmental fate of the compounds in soil have been investigated. In sorption studies with an acidic silty loam soil and a neutral loam soil, no impact of added DOM on adsorption and desorption coefficients was observed. Adsorption coefficients normalized to soil organic carbon (Koc) of the compounds on the loamy silt soil spanned three orders of magnitude 90, 890, and 9,140 L/kg for HDT, BPA, and NP, respectively. Significantly lower Koc values for HDT on the neutral loam soil as compared to the acidic loamy silt soil indicated additional polar interactions between the latter and the basic herbicide metabolite. In dialysis experiments with fulvic acid from silty loam soil (FA) and peat humic acid (HA), a formation of analyte-DOM associates was observed only for HA. The degree of association was characterized by distribution coefficients normalized to the dissolved organic carbon concentration (KDOC). Values for NP (8,970 L/kg) and BPA (860 L/kg) corresponded with the respective soil sorption coefficients, suggesting similar binding mechanisms in both cases.