Use of groundwater and reclaimed water for agricultural irrigation: Farmers' practices and attitudes and related environmental and health risks.

Agricultural reuse of treated wastewater (TWW) for irrigation is widely practiced. Its conjunctive use with freshwater is becoming more common to guarantee food security, while the rationale behind and its sustainability are quite arguable. The objective of this study is to better understand the drivers of the conjunctive use of TWW and groundwater (GW) in Nabeul region, Tunisia, and the potential environmental and health impacts taking into account farmers' practices and attitudes toward reuse. TWW used for irrigation exhibited relatively high salinity and high microbiological load. GW has a very high salinity. TWW and GW showed low concentrations of heavy metals (Al, Cd, Co, Cu, Cr, Mn, Ni, Pb, and Zn). Concentrations of pharmaceutical compounds were between Limits of Quantification and 13 µg/L. In GW, values were relatively high, especially for caffeine, carbamazepine, ofloxacin, and ketoprofen. Farmers have a low perception of the polluting load of TWW and GW and of their potential long-term impacts on agricultural environment, human health, and agricultural productivity. GW availability has facilitated its conjunctive use with TWW, either to augment water quantity and/or to improve its quality. Despite its low quality, GW timeliness for irrigation was the main driver to guarantee a better yield and quality of produces. Soil microbial community, bacterial biomass, denitrifying potential and carbon oxidation profiles were similar under TWW, GW and their conjunctive use. Though an effect of the sampling period was observed with a high abundance of denitrifying bacteria in the wet season and a low carbon oxidation activity at the end of the dry season. The conjunctive use of TWW and GW is very likely unsustainable from health and environmental perspectives. Balancing farmers' economic profit against the preservation of agricultural activity, linked to cultural and natural heritage, remains one of the challenges for decision-makers and regional stakeholders.

EDTA-enhanced phytoremediation of lead-contaminated soil by the halophyte Sesuvium portulacastrum.

The low bioavailability of Pb and low number of Pb-tolerant plant species represent an important limitation for Pb phytoextraction. It was recently suggested that halophyte plant species may be a promising material for this purpose, especially in polluted salt areas while Pb mobility may be improved by synthetic chelating agents. This study aims to evaluate Pb extraction by the halophyte Sesuvium portulacastrum in relation to the impact of EDTA application. Seedling were cultivated during 60 days on Pb artificially contaminated soil (200, 400, and 800 ppm Pb) in the presence or in the absence of EDTA (3 g kg(-1) soil). Results showed that upon to 400 ppm, Pb had no impact on plant growth. However, exogenous Pb induce a decrease in shoot K(+) while it increased shoot Mg(2+) and had no impact on shoot Ca(2+) concentrations. Lead concentration in the shoots increased with increasing external Pb doses reaching 1,390 ppm in the presence of 800 ppm lead in soil. EDTA addition had no effect on plant growth but strongly increased Pb accumulation in the shoot which increased from 1,390 ppm in the absence of EDTA to 3,772 ppm in EDTA-amended plants exposed to 800 ppm exogenous Pb. Both Pb absorption and translocation from roots to shoots were significantly enhanced by EDTA application, leading to an increase in the total amounts of extracted Pb per plant. These data suggest that S. portulacastrum is very promising species for decontamination of Pb(2+)-contaminated soil and that its phytoextraction potential was significantly enhanced by addition of EDTA to the polluted soil.