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Secondary effluents (SE) contain xenobiotic organics (XO) that may cause disturbance in living organisms. When SE are reused in agriculture, contamination of soils by XO is of concern. In this study, SE used for irrigation/aquifer recharge in Oued Souhil area (Nabeul, Tunisia), as well as effluents irrigated soils, were tested for their XO load. Estrogen receptor (ER), aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) in vitro based bioassays were used to assess potential activities of XO. Results were expressed as estrogen equivalent (E2 Eq), dioxin equivalent (TCDD Eq) and rifampicine equivalent (Rf Eq). Reclaimed water showed activities with 77.58 pM E2 Eq/L, 319.5 pM TCDD Eq/L and 197 nM Rf Eq/L. Instrumental analysis (GC/MS) revealed the presence of nonylphenol isomers mixture (NPm) (6600 ng/L) and pyrene (32 ng/L). In infiltration basin soil, activities and chemical compounds were the same as those detected in reclaimed water. In the irrigated plot, no estrogenic activity was observed, though AhR and PXR activities were detected. These results emphasize the transfer of active XO from reclaimed water to soils and their relative persistence. Further studies on mobility and persistence of mid-polar and polar active XO in soils should be examined in order to explain the observed activities.

Reclaimed water reused for irrigation and aquifer recharge contains ER, AhR and PXR active compounds not removed during treatment. In both practices (irrigation and aquifer recharge), spreading effluents on soils contribute to the transfer of active organic pollutants. While some of them may degrade, the more persistent ones are likely to accumulate and the more polar ones may infiltrate with water. Hence, impact of irrigation with reclaimed water on soil should be considered with respect to periodicity of this practice (dry/wet cycle) and cultivated crop (herbaceous ie fodder or woody ie citrus). Concerning groundwater, contamination by endocrine-disrupting organic contaminants may be of concern as furrow irrigation and uncontrolled aquifer recharge are practiced for more than 20 years. A follow-up integrating bioassays and instrumental analysis on more polar molecules is recommended.