Caractérisation des risques de contamination des agrosystèmes périurbains de Dakar par les éléments traces métalliques

L’application de produits résiduaires organiques (PRO) améliore la fertilité des sols, mais induit des effets négatifs sur les agrosystèmes, en raison de la présence de contaminants tels que les éléments traces métalliques (ETM). Cette étude vise à évaluer l’influence de deux doses (20 et 60 T.ha-1) d’apport de boue de station d’épuration STEP et de fiente de volaille sur la disponibilité de quatre ETM (Ni, Cd, Cr et Pb) dans un arenosol et un fluvisol. Une incubation de 88 jours en conditions contrôlées a été conduite sur les deux sols mélangés aux différentes doses de boue et de fiente. La disponibilité des ETM dans les sols incubés a été évaluée par la technique DGT (Diffusive Gradient in Thin films). Les boues ont abaissé le pH des deux sols tandis que les fientes ont alcalinisé l’arenosol durant les 14 premiers jours d’incubation. Ces PRO ont augmenté les concentrations de Ni, Cd, Pb et Cr disponibles dans les sols. Les  disponibilités du Ni, Cd et Pb sont plus élevées dans l’arenosol que dans le fluvisol. La boue à 60 T.ha-1 a induit les plus fortes disponibilités en Cd et Pb tandis que la fiente à 60 T.ha-1 a induit les plus fortes disponibilités en Ni et Cr dans les deux sols.Mots clés : Eléments traces métalliques, arenosol, fluvisol, boue d’épuration, fiente.  CHARACTERIZATION OF CONTAMINATION RISKS OF THE  SUBURBANAGROECOSYSTEMS OF DAKAR BY TRACE ELEMENTSOrganic wastes (OW) spreading improve soil fertility, but can induce negative effects on agroecosystems, due to the presence of contaminants such as trace elements (TE). This study aims to evaluate the impacts of two doses (20 and 60 T.ha-1) of sewage sludge and poultry manure on the availability of four trace elements (Ni, Cd, Cr and Pb) in arenosol and  fluvisol. Soils mixed with different doses of sewage sludge and poultry manure were incubated for 88 days under controlled conditions. The  availability of trace elements in incubated soils was evaluated by the DGT (Diffusive Gradient in Thin films) technique. Sewage sludge has decreased the pH of both soils while poultry manure induced an alkalinization of arenosol during the first 14 days of incubation. OW increased Ni, Cd, Pb and Cr availability in the soils. Availability of Ni, Cd and Pb were higher in arenosol than in the fluvisol. Sewage sludge at 60 T.ha-1 induced the highest availability of Cd and Pb while the poultry manure at 60 T.ha-1 induced the highest availability of Ni and Cr in both soils.Keywords : Trace elements, arenosol, fluvisol, sewage sludge, poultry manure

The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse

Dominant optic atrophy is a rare inherited optic nerve degeneration caused by mutations in the mitochondrial fusion gene OPA1. Recently, the clinical spectrum of dominant optic atrophy has been extended to frequent syndromic forms, exhibiting various degrees of neurological and muscle impairments frequently found in mitochondrial diseases. Although characterized by a specific loss of retinal ganglion cells, the pathophysiology of dominant optic atrophy is still poorly understood. We generated an Opa1 mouse model carrying the recurrent Opa1(delTTAG) mutation, which is found in 30% of all patients with dominant optic atrophy. We show that this mouse displays a multi-systemic poly-degenerative phenotype, with a presentation associating signs of visual failure, deafness, encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy. Moreover, we found premature age-related axonal and myelin degenerations, increased autophagy and mitophagy and mitochondrial supercomplex instability preceding degeneration and cell death. Thus, these results support the concept that Opa1 protects against neuronal degeneration and opens new perspectives for the exploration and the treatment of mitochondrial diseases

Modelling of the dynamics of AI and protons in the rhizosphere of maize cultivated in acid substrate

International audienc

Oxalate extraction and determination by ionic chromatography in calcareous soils and in mycorrhized roots environment

International audienc

Vinasse organic matter quality and mineralization potential, as influenced by raw material, fermentation and concentration processes

Both dilute and concentrated vinasse can be spread on agricultural fields or used as organic fertilizer. The effects of different characteristics of the original raw material on the biochemical composition of vinasse and their C and N mineralization in soil were investigated. Vinasse samples were obtained from similar industrial fermentation processes based on the growth of microorganisms on molasses from different raw material (sugar beet or sugar cane) and vinasse concentration (dilute or concentrated). The nature of the raw material used for fermentation had the greatest effect on the nature and size of the resistant organic pool. This fraction included aromatic compounds originating from the raw material or from complex molecules and seemed to be quantitatively related to acid-insoluble N. Samples derived from sugar beet were richer in N compounds and induced greater net N mineralization. The effect of evaporation varied with the nature of the raw material. Concentration led to a slight increase in the abundance of phenolic compounds, acid-insoluble fraction, and a slight decrease in the labile fraction of vinasses partly or totally derived from sugar beet. The effect of the dilute vinasse from sugar cane was greater. The concentrated vinasse had a smaller labile fraction, induced N immobilization at the beginning of incubation, and exhibited greater N concentration in the acid-insoluble fraction than the dilute vinasse

Variations in the cation exchange capacity of a ferralsol supplied with vinasse, under changing aeration conditions. Comparison between CEC measuring methods

International audienceThe spreading of vinasse may favour soil anoxia and affect cation exchange capacity (CEC). Our aims were to assess the reliability of CEC measurements in reducing conditions, quantify CEC variations in a ferralsol under changing aeration conditions, and understand the mechanisms involved. In a first experiment, soil slurry was incubated for a succession of 7 oxic, 28 anoxic and 28 oxic days, vinasse being supplied when anoxia began. CEC was measured at intervals by exchanging Mg2+, Cu-trien or Co(NH3)63+, the solutions being characterized before and after exchange. In a second experiment, soil CEC was measured after the elution of NH4+ solutions of pH 5 to 7. In a third experiment, we assessed the reduction of Co(NH3)63+ by Fe2+ and checked for induced changes by geochemical simulations. During the first oxic period, CEC varied according to method, in the order: Cu-trien < Mg2+<Co(NH3)63+<NH4+. It increased by 2 cmolc kg− 1 when pH increased from 5 to 7. After 28 days of anoxia, CEC estimates were 2.75, 1.43 and 5.1 times their initial values for the 0.05 M Mg2+, Cu-trien and Co(NH3)63+ methods respectively; pH after exchange was about the same as initial slurry pH (6.9), except after Co(NH3)63+ exchange when it was 9.4. This complex was partly reduced by Fe2+ leading to NH3 release, pH increase, Fe(OH)3 and Co(OH)2 precipitations, Co(II) adsorption and overestimation of CEC. After the return to oxic conditions, the CEC did not return to its initial value. At all dates, CEC measured by 0.05 M Mg2+ method agreed with the exchangeable cation measurement