Assisted phytostabilisation of As, Pb and Sb-contaminated Technosols with mineral and organic amendments using Douglas fir (Pseudotsuga menziesii (Mirb.) Franco).

Phytoremediation of metal(loid)s by conifers is not widely studied, although conifers may be interesting, particularly in temperate-cold areas and/or on acidic soils. In this study, seeds of Douglas fir were sown in greenhouse and cultivated for 3 months on two Technosols highly contaminated with different concentrations of Pb, As and Sb and collected in two French old former mines located in massif Central or close to it: a mine of gold at La Petite Faye and a mine of lead and silver at Pontgibaud. Two amendments, a nutrient solution (NS) and composted sewage sludge (CSS), were tested in order to stimulate Douglas fir growth and to reduce the metal(loid)s mobility and phytoavailability. The speciation determined by sequential extractions as well as mineralogy highlight different geochemical behaviours of Pb, As and Sb as a function of the Technosol. In all cases, CSS amendments significantly reduced Pb phytoavailability as well as the uptake and translocation of Pb and As. Moreover, CSS stimulated the growth of Douglas firs highlighting that this amendment could be a good strategy for a better phytostabilisation of these metal(loid)s.

Impact of treated urban wastewater for reuse in agriculture on crop response and soil ecotoxicity.

The scarcity of freshwater resources is a serious problem in arid regions, such as Tunisia, and marginal quality water is gradually being used in agriculture. This study aims to study the impact of treated urban wastewater for reuse in agriculture on the health of soil and food crops. The key findings are that the effluents of Sfax wastewater treatment plant (WWTP) did not meet the relevant guidelines, therefore emitting a range of organic (e.g., up to 90 mg L(-1) COD and 30 mg L(-1) BOD5) and inorganic pollutants (e.g., up to 0.5 mg L(-1) Cu and 0.1 mg L(-1) Cd) in the receiving aquatic environments. Greenhouse experiments examining the effects of wastewater reuse on food plants such as tomato, lettuce, and radish showed that the treated effluent adversely affected plant growth, photosynthesis, and antioxidant enzyme contents. However, the pollution burden and biological effects on plants were substantially reduced by using a 50 % dilution of treated sewage effluent, suggesting the potential of reusing treated effluent in agriculture so long as appropriate monitoring and control is in place.

Adsorption of a textile dye "Indanthrene Blue RS (C.I. Vat Blue 4)" from aqueous solutions onto smectite-rich clayey rock.

The adsorption of a textile dye, namely, Indanthrene Blue RS (C.I. Vat Blue 4) onto smectite-rich clayey rock (AYD) and its sulphuric acid-activated products (AYDS) in aqueous solution was studied in a batch system with respect to contact time, pH, and temperature. The adsorbents employed were characterized by X-ray diffraction, infrared spectroscopy and specific surface area, cation exchange capacity and point of zero charge were also estimated. The effect of contact time on dye adsorption showed that the equilibrium was reached after a contact time of 40 min for the both adsorbents. The optimum pH for dye retention was found 6.0 for AYDS and 7.3 for AYD. The equilibrium adsorption data were analysed using the Langmuir and Freundlich isotherms. The adsorption capacities (Q(m)) for AYD and AYDS were found 13.92 mg/g and 17.85 mg/g, respectively. The effect of temperature on the adsorption was also investigated; adsorption of Indanthrene Blue RS is an endothermic process. This study demonstrates that all the considered adsorbents can be used as an alternative emerging technology for water treatment.