International audience | From 1899 to 2002, sandy Luvisol in the Paris region has been intensively irrigated with raw wastewater, resulting in major soil pollution by metallic trace elements (MTE). To identify the soil phases implicated in retaining these metals, sequential extractions were performed on a solum irrigated with untreated wastewater and another reference solum. The endogenous and exogenous fractions of MTE in the contaminated soil were discriminated using correlations between MTE and major elements defined from unpolluted soils of the area. In the contaminated soil no exogenous lead and chromium are present below the surface horizon, whereas exogenous zinc and copper are found down to the base of the solum. The endogenous MTE are mainly found in the residual fraction. Exogenous MTE appear to be associated with organic matter in the surface horizon, and exogenous zinc seems to be readsorbed on iron and manganese oxyhydroxides in the underlying horizons. After 100 years of intensive irrigation with wastewater, no exogenous Pb and Cr are found in the subsoil, while exogenous Zn and Cu are found down to the base of the solum, mostly readsorbed.

Fifteen soil profiles were taken from Ar-Ramtha wastewater treatment plant, 65 km north of Amman. Twelve of them represent soil planted with barley and irrigated with wastewater for the past 2, 5, and 15 years. The remaining three profiles represented a control area that has been only rainfed. Soil samples were collected in four replicates from each depth in each soil profile. Field and laboratory experiments were conducted to study the effect of irrigation with treated wastewater on hydraulic properties of surface and subsurface vertisols. Soil infiltration rate (IR), hydraulic conductivity (HC), and water retention (at 33 kPa and 1.5 MPa) were measured. The application of wastewater for 2, 5, and 15 years reduced soil hydraulic conductivity, whereas the infiltration rate decreased for 2 and 5 years, compared with non-irrigated area. Sites irrigated for 15 years with treated wastewater are characterized by higher percentages of large cracks, therefore revealed the highest infiltration rate. Soil available water changed due to wastewater application in decreasing order of: control (rainfed), 15, 5, 2 years of wastewater application.

The present study aimed to look at the fate of protozoan parasite Cryptosporidium parvum oocysts applied through surface drip irrigation on reclaimed water irrigation-history and non-history sandy-loam (Hamra) soil columns. A new and simple isolation method for recovery of oocysts from soil samples was developed and used along this study. The new soil isolation method of oocysts is based on the “two phase separation method” formerly used to recover Clostridium perfringens spores from sediments and soil samples with minor modifications. The range recovery achieved by this method was 64-95% (mean 61.2 ± 17.4). The objectives of the second part of this study were to investigate several physical and chemical factors governing transport and survival of C. parvum oocysts in sandy-loam soil columns by breakthrough curves. Comparison of fresh water and reclaimed water irrigation revealed that reclaimed water irrigated-history soil was more hydrophobic allowing water flow through channels with poor oocysts retention and fast flow. Examination of the organic matter effect (originating from reclaimed water irrigation) on oocysts breakthrough revealed that their soil infiltration increased. Calculations of oocysts concentration at different columns depths showed that most of the oocysts were retained in the first 5 cm of soil column. In the present study, comparing the two soil types (history and non-history of effluents irrigation) beside the surface electrostatic charge, one of the main elements found to affect oocysts infiltration and transport in soil columns was soil hydrophobicity caused by soluble organic matter originating from reclaimed water irrigation. Therefore, prior to application in soil irrigation, reclaimed water should be treated to high quality (i.e. membrane technology as the best option) to prevent enhanced transport of various pathogens through those irrigated soils.