Variation in baobab (Adansonia digitata L.) root tuber development and leaf number among different growth conditions for five provenances in Malawi

The baobab tree is an underutilised indigenous fruit tree in sub-Saharan Africa which, at the same time is vulnerable to overexploitation in areas close to centres of demand, as currently baobab use is limited to wild, baobab trees. Baobab seedlings are known to form root tubers, but little is known about their growth characteristics and its yield potential. This study aims to investigate the root tuber and leaf development of baobab seedlings grown from seeds of five provenances, sown at three different planting distances in two nursery trials at climatically distinct locations in Malawi, namely Mzuzu and Mangochi. The observed yield data was fed into preliminary farm-gate profitability analyses for three different scenarios that differed by planting distance. Results indicate increased growth rates for root dry mass and number of developed leaves with increasing planting distance. However, we did not find a significant effect of seedling provenance on any of the measured plant growth parameters. Seedlings invested mainly into root development during the growth period, with root tubers reaching an average fresh weight of 41 ± 39 g and an average length of 24 ± 11.9 cm at 138 days after sowing. Profitability analyses showed a potential total net benefit of 12.78 USD per harvest cycle of 16 weeks and per 100 m² of land cultivated with baobab root tubers, which was better than an alternative scenario of maize cropping on the same area that showed a negative total net benefit when cost of family labour was included. However, the heterogeneity of root tuber development as affected by abiotic and biotic factors like soil fertility and water availability, as well as genetic origin warrant further investigation

Étude de polluants émergents dans l’environnement. les perturbateurs endocriniens : aspects analytiques et comportement dans les stations d’épuration

Les effets perturbateurs endocriniens d’un certain nombre de composés ont été mis en évidence depuis quelques années. Ces composés sont connus pour provoquer des altérations au niveau du système endocrinien des animaux et peuvent avoir des effets indésirables sur les systèmes reproducteurs. Ces composés sont susceptibles de se trouver dans l’environnement au travers des rejets des stations d’épuration. Il est important et nécessaire de disposer de méthodes d’analyse permettant la quantification de ces composés afin de pouvoir suivre leur comportement au niveau des stations d’épuration, notamment pour les composés les plus actifs comme les œstrogènes. Cette étude présente dans un premier temps l’aspect analytique de la problématique ainsi que les performances des méthodes développées. Dans une deuxième partie, elle présente les performances d’un traitement biologique sur l’élimination des composés œstrogéniques

Modélisation d'un BRM et impact de la décantation primaire

International audienceWithin the AMEDEUS European project, a work package is dedicated to biological modelling of Membrane Bioreactors (MBR) processes as well as the impact of a pre-treatment by primary sedimentation on sludge production, sludge characteristics and permeate quality. The supposed interest of this pre-treatment is to decrease sludge production and to improve oxygen transfer by decreasing sludge concentration. Two MBR pilots were operated side by side under the same operating conditions, one fed by screened (1 mm screen) raw municipal wastewater and the other by primary settled raw municipal wastewater. This side by side operation allows a true comparison of the performances and model calibration. In average, screened water was observed to contain 30% more solids than settled water. In this study, the sludge age was fixed at 40 days and then modified to 15 days to calibrate the model on a broad range of operating conditions in order to validate and identify the biological activated sludge model (ASM) limits. With a sludge retention time (SRT) of 15 days, sludge production is less important in the pilot fed by settled water because of better bio-accessibility behaviour of settled water. In comparison with ASM1 default parameter values, calibrated parameters are quite different concerning nitrification and denitrification because of an improvement of oxygen transfer induced by lower floc size distribution (KOA=0.25–0.3g O2/m3, KOH=0.1g O2/m3). With a SRT of 40 days, model calibration is not validated and the pilot fed with screened water has a sludge production reduction that is less important than the one of the pilot fed by settled water where accumulation of inert organic matter is observed