Fate of phthalates and BPA in agricultural and non-agricultural soils of the Paris area (France)

This study (i) investigated the concentration levels of nine phthalates and bisphenol A (BPA) in sludge samples originating from a French wastewater treatment plant (WWTP), (ii) studied the distribution of target compounds according to soil depth and calculated their half-lives, and (iii) compared the contamination level of the agricultural soil with those of soils with other land uses. The sludge contamination levels varied from a few hundred nanograms per gram dry weight (dw) for diethyl phthalate (DEP), di-iso-butyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and butyl-benzyl phthalate (BBP) to a few micrograms per gram dw for diethylhexyl phthalate (DEHP), di-iso-nonyl phthalate (DiNP), and di-iso-decyl phthalate (DiDP). After sludge application, an 8-fold increase for DEHP level and a 3-fold increase for BPA level occurred in the surface horizon of the soil. The mean distribution of phthalates according to the depth showed a positive gradient for the low molecular weight compounds and inversely, a negative gradient for the highest ones. The half-lives in the 0–20-cm soil horizon were 64 days for DEHP and 36 days for BPA. A predictive environmental concentration (PEC) of 0.3 μg g−1 dw was estimated for DEHP, while the experimental value was 0.16 μg g−1 dw, suggesting degradation processes in soil and/or formation of non-extractable residues. Comparisons of contamination levels for soils from different origins (urban, rural, agricultural, and forest) showed that the urban soil remained the most contaminated one, prior to the agricultural soil after treatment.