Transports fluviaux de matières dissoutes et particulaires sur un bassin versant en région tropicale : le bassin amont du Niger au cours de la période 1990-1993

Entre janvier 1990 et juillet 1993, 85 échantillons ont été prélevés sur les eaux du Niger à la station de Bamako (Mali). A partir des analyses effectuées et des données de débits disponibles sur cette période particulièrement sèche, ont pu être calculés les flux spécifiques pour les différentes espèces dissoutes (par ordre décroissant : HCO3 > SiO2 >> COD > Na > Ca > K > Mg >> Cl > SO4 >> Fe > Al) et le flux spécifique des matières en suspension. Le flux spécifique de TDS, caractéristique de l'intensité de l'altération chimique, est de 8 t/km2/an, alors que le flux de TSS, représentatif de la vitesse de l'érosion mécanique, est de 5 t/km2/an. Ces flux de matières dissoutes et particulaires sont ensuite comparés à ceux de 16 bassins fluviaux d'Afrique tropicale. On a pu enfin déterminer des relations TDS-drainage et TSS-drainage caractéristiques de cette zone tropicale. (Résumé d'auteur

Suspended sediment load and mechanical erosion in the Senegal basin : estimation of the surface runoff concentration and relative contributions of channel and slope erosion

Cette étude a pour but de mieux cerner les mécanismes d'acquisition de la charge solide et de l'évolution de l'érosion dans le bassin du fleuve Sénégal de 1979 à 1984. L'estimation annuelle du volume ruisselé permet de quantifier les différentes composantes de l'hydrogramme de crue et de préciser ses relations avec les concentrations de MES. Au cours de la période sèche étudiée, le début moyen annuel 330 m3/S ne représente que 46 % du module interannuel de 1903 à 1984. A l'exutoire du bassin versant le flux moyen particulaire s'élève à 1,9 millions de tonnes/an. L'érosion des versants est quatre fois supérieure à celle des berges de la vallée alluviale. (Résumé d'auteur

SciPy 1.0: fundamental algorithms for scientific computing in Python.

SciPy is an open-source scientific computing library for the Python programming language. Since its initial release in 2001, SciPy has become a de facto standard for leveraging scientific algorithms in Python, with over 600 unique code contributors, thousands of dependent packages, over 100,000 dependent repositories and millions of downloads per year. In this work, we provide an overview of the capabilities and development practices of SciPy 1.0 and highlight some recent technical developments

Multi-ancestry genome-wide association analyses improve resolution of genes and pathways influencing lung function and chronic obstructive pulmonary disease risk.

Lung-function impairment underlies chronic obstructive pulmonary disease (COPD) and predicts mortality. In the largest multi-ancestry genome-wide association meta-analysis of lung function to date, comprising 580,869 participants, we identified 1,020 independent association signals implicating 559 genes supported by ≥2 criteria from a systematic variant-to-gene mapping framework. These genes were enriched in 29 pathways. Individual variants showed heterogeneity across ancestries, age and smoking groups, and collectively as a genetic risk score showed strong association with COPD across ancestry groups. We undertook phenome-wide association studies for selected associated variants as well as trait and pathway-specific genetic risk scores to infer possible consequences of intervening in pathways underlying lung function. We highlight new putative causal variants, genes, proteins and pathways, including those targeted by existing drugs. These findings bring us closer to understanding the mechanisms underlying lung function and COPD, and should inform functional genomics experiments and potentially future COPD therapies

Distribution and origin of lead in stream sediments from small agricultural catchments draining Miocene molassic deposits (SW France)

International audienc

Physical and chemical weathering rates and CO2 consumption in a tropical lateritic environment : the upper Niger basin

The chemical composition of Niger river water measured bimonthly at Bamako (Mali) during the period 1990-1992 provides an estimate of present weathering rates in the upper Niger basin. The dominant weathering process is kaolinite formation ("monosiallitization"). However, seasonal variations promote gibbsite formation in the rainy season (September) and smectite development in the dry season (May). The results show that lateritic profiles continue to develop even during very dry episodes. The rate of profile development, calculated as the difference between the chemical weathering rate at the base of the soil profile and mechanical erosion rate at the soil surface, is about 1.3 to 3.7 m/Myr. A comparison between 43 river basins of the world shows that, for similar runoff, the CO2 flux consumed by silicate weathering is about two times lower in lateritic areas than in nonlateritic zones. (Résumé d'auteur