Tillage system affects soil organic carbon storage and quality in Central Morocco

Stabilizing or improving soil organic carbon content is essential for sustainable crop production under changing climate conditions. Therefore, soil organic carbon research is gaining momentum in the Mediterranean basin. Our objective is to quantify effects of no tillage (NT) and conventional tillage (CT) on soil organic carbon stock (SOCs) in three soil types (Vertisol, Cambisol, and Luvisol) within Central Morocco. Chemical analyses were used to determine how tillage affected various humic substances. Our results showed that, after 5 years, surface horizon (0–30 cm) SOC stocks varied between tillage systems and with soil type. The SOCs was significantly higher in NT compared to CT (10% more in Vertisol and 8% more in Cambisol), but no significant difference was observed in the Luvisol. Average SOCs within the 0–30 cm depth was 29.35 and 27.36 Mg ha−1 under NT and CT, respectively. The highest SOCs (31.89 Mg ha−1) was found in Vertisols under NT. A comparison of humic substances showed that humic acids and humin were significantly higher under NT compared to CT, but fulvic acid concentrations were significantly lower. These studies confirm that NT does have beneficial effects on SOCs and quality in these soils

Salinité et pollution par les nitrates des eaux souterraines de la plaine des Triffa

Les eaux souterraines de la plaine des Triffa (Basse Moulouya) deviennent de plus en plus polluées. Les résultats analytiques montrent que la plupart des puits sont chargés en sels et en nitrates, donc impropres à la consommation humaine et peuvent avoir un effet négatif sur les cultures maraîchères de la région. Dans la zone étudiée, des teneurs de 2,32 à 174,70 mg/l de NO3-, de 134 à 3614 mg/l de Cl- et de 103 à 1518 mg/l de Na+ ne sont pas exceptionnelles. Elles dépassent largement les normes fixées par l’OMS et la CEE (50 mg/l pour les NO3 -, de 250 mg/l pour Cl- et de 175 mg/l pour Na+). L’intensification de l’agriculture dans la plaine, notamment dans les périmètres irrigués, l’épandage excessif des engrais, les applications répétées, et à quantités fortes, de fumiers, l’irrigation, les précipitations et la remontée de la nappe dans certaines régions ont engendré une pollution croissante des ressources en eau

Experimental and modelling study of artificial radionuclides (

The interest on transfer coefficients studies have increased recently, since they are important parameters required understanding and reliably modelling the dispersion of conservative and non-conservative radionuclides in aquatic environments. The approaches, based in the implementation of the uptake kinetics of dissolved radionuclides by solid particles, are more appropriate than those based in the use of the distribution coefficients, kd. In this work, we present a series of tracing experiments to study the uptake of Pu, Am and Tc in natural aqueous suspensions from three aquatic systems (Gergal reservoir, Guadalquivir river, and the estuary of Tinto river) located in the South of Spain. The kinetic transfer coefficient for direct sorption depends on the total available surface of particles and on the concentration of active sites in the surface layer (what depends on the mineral composition, free edges, pores, coatings, etc.). In order to compare results from different environments and to fix the conditions of applicability of the derived coefficients, it is necessary to handle the particle size spectra and the mineral composition of natural occurring suspended loads. The time dependent uptake curves, covering up to a large period, are fitted to the numerical solutions calculated with different models of the uptake kinetics

Application of a liquid scintillation counter to the measurement of tracing radioactivity in experiments on suspended matter uptake in aquatic environments

The experiments on the study of the kinetic transfer coefficients of conservative and non-conservative radionuclides, in aquatic environments, need to determine radionuclide activity in large number of samples. Different radioactivity measurement techniques can be selected for analyses, but the liquid scintillation technique is preferred due to its easy sample treatment and its low time consumption. Samples are initially traced with a known activity of a selected radionuclide (239Pu, 241Am or 99Tc). The transference of radionuclides, from the water to the suspended matter, is studied through the determination of the residual activity in aliquots of water sample, which are successively collected with time. In this work, we present the experimental procedures used for the 239Pu, 241Am and 99Tc activity measurement by liquid scintillation counting, using a Wallac Quantulus 1220 spectrometer. Results of the application of this technique to traced water samples are also shown in this study