Mobility of 4-nonylphenol and di(2-ethylhexyl) phthalate in three agricultural soils irrigated with untreated wastewater

Agricultural irrigation using raw wastewater is a popular practice in developing countries. However, as endocrine disrupting chemicals have been found in this water, the potential pollution of soil and water sources has become a source of concern. Such pollutants may be removed during the passage of wastewater through the soil by degradation and/or sorption. In this study the sorption and mobility of bis-2-ethyl(hexyl)phthalate (DEHP) and 4-nonylphenol (4-NP) in three different soils (Leptosol, Phaeozem and Vertisol) was compared. The distribution coefficients showed that DEHP is rapidly sorbed onto the three tested soils (K(d) between 1.8 × 10(4) and 4.2 × 0(4) L/kg), while sorption of 4-NP (K(d) between 15 and 80 L/kg) was weaker. In batch experiments the soil sorption capacity observed was as follows: Vertisol > Phaeozem > Leptosol for both compounds. However, in column experiments the retardation factor (R(F)) for 4-NP was higher than for the DEHP in the three soils. This suggests the possible migration of DEHP through the soil via colloids. The column results were found consistent with those observed in the field. It was concluded that the risk of groundwater contamination is higher for Leptosol soil than for Phaeozem and Vertisol soils and that DEHP can reach the aquifer prior to 4-NP.