Aid and Universal Primary Education

Universal Primary Education (UPE) is one of the main objectives of development aid. However, very little empirical evidence of its effectiveness actually exists. Until very recently, the quality of available data was not sufficient to obtain robust results regarding the relationship between international aid and educational achievements. In this article, the latest, more disaggregated and more reliable data is used to study the relationship between aid to education and educational achievements. The focus here not only on educational variables in term of coverage, but also in term of equity and process. The year of Fast Track Initiative (FTI) endorsement is used as an original instrument to tackle the endogeneity problem of aid. Our results are very robust and indicate that aid to primary education has a strong effect on primary school enrollment and gender parity. A negative impact on repetitions rate is also indicated while no effect on the pupil teacher ratio can be observed. Diminishing return in the effectiveness of aid to primary education may also be highlighted. Finally, the governance variables do not appear to have an impact on this relationship.aid effectiveness, education, Sector-specific aid

Sources and transfers of particulate organic matter in a tropical reservoir (Petit Saut, French Guiana): a multi-tracers analysis using d¹³C, C/N ratio and pigments

International audienceCarbon cycling and organic matter transfers in the tropical Sinnamary river system (French Guiana), including a mid-stream reservoir (Petit Saut) and its estuary on the Atlantic coast, were studied during the dry season by analyzing the organic carbon isotopic ratios (d13C-OC), C/N ratios and pigments contents of suspended matter, sediments, sediments traps and epiphytic and epilithic biofilms. In the River upstream as well as in surface sediments at the entrance of the reservoir and at the littoral zone of the reservoir, particulate organic matter (POM) was in majority of terrestrial origin, with a d13C-C/N signature close to the one of soil and litter collected in the surrounding forest and with high OC/total pigments ratios. High concentrations of Pheopigments a and b in these surface sediments showed that this terrestrial POM, either carried by the river and eolian transport or present in the soil before flooding, undergoes intense degradation. Deeper in the sediment, the d13C profile showed a decreasing trend with depth typical of what is found in soils, showing that the flooded soil still remains present at the reservoir bottom 10 years after flooding. At the center of the reservoir, POM in the water column, in sediment traps and in surface sediments was in majority of aquatic origin with low C/N and OC/total pigments ratios. In the oxic epilimnion at 3 m depth, Chl a, Chl b and Lutein showed the predominance of Chlorophyceae to the phytoplankton community. At this depth, a C/N ratio of 21 suggests a large contribution of transparent exopolymeric particles to the bulk POM, which, in addition, was 13C-depleted due to a significant contribution of methanotrophic bacteria. At 7 m depth, below the oxicline, high concentrations of BChl d and occasionally BChl c revealed the presence of anoxygenic phototrophic bacteria, namely Chlorobiaceae. In the sediment traps, Chl a, Chl b, Lutein and BChl c and BChl d confirmed the contribution of plankton to the sedimentary POM. This material was undergoing intense degradation as revealed by high concentration of pheopigments and by an increase in C/N ratio and an increase in d13C-OC with trap depth. Scytonemin was found in a biofilm developed on tree trunks at the reservoir surface and in all sediment traps. Other tracers showed however that the contribution of the biofilm to the sedimentary POM was minor compared to the planktonic source. In the Sinnamary downstream of the dam, POM became more 13C-depleted showing a larger contribution of methanotrophic bacteria. Chl b, Lutein and BChl c + BChl d originating from the reservoir progressively decreased downstream as the result of mineralization. At the estuarine mouth, fucoxanthin showed the presence of diatoms and the d13C-C/N signature matched the one of POM carried by the Amazonian coastal mobile mud belt

Caractérisation et dynamique des matières organiques stabilisées au sein des complexes organo-minéraux de sols tropicaux, Ile de La Réunion

Les interactions entre les phases minérales et les matières organiques du sol (MOS) conduisent à la formation de complexes organo-minéraux (cplxMO/Mi) qui protègent les MOS contre la biodégradation. Ces cplxMO/Mi sont peu étudiés alors qu ils jouent un rôle prépondérant dans le stockage du carbone (C) organique dans les sols. Notre travail porte sur (i) la caractérisation des MOS liées aux phases minérales et (ii) l évaluation de la dynamique du C stabilise au sein des cplxMO/Mi. Nous avons étudié trois types de sols tropicaux, issus de l île de La Réunion (Andosol perhydraté, Andosol et Cambisol). Les MOS sont analysées par méthode spectroscopique et pyrolytique. Nos résultats montrent que les polysaccharides, les lipides et les composes azotes sont fortement présents dans les cplxMO/Mi, contrairement à la lignine. Les MOS liées aux oxydes de fer présentent un temps de recyclage nettement plus élevé que les MOS liées aux aluminosilicates faiblement cristallisés et celles liées à la gibbsite.Interactions between mineral phases and soil organic matter (SOM) lead to the formation of organo-mineral complexes (OM/Micplx), which protect SOM against biodegradation. These OM/Micplx are poorly studied while they have a preponderant role in soil organic carbon (C) storage. Our work focused on (i) the characterization of SOM bound to mineral phases and (ii) the evaluation of C dynamics within OM/Micplx. We studied three different tropical soils which come from La Reunion island (hydric Andosol, Andosol and Cambisol). SOM were analyzed with pyrolitic and spectroscopic method. Our results shown that polysaccharids, lipids and N-compounds (proteins and/or amino acids) were strongly present in OM/Micplx, contrary to lignin. SOM associated with iron oxides have a turn-over higher than SOM associated with aluminosilicates poorly crystallized and SOM associated with gibbsite. Overall, origin and turnover of SOM changed according to the type of mineral phases with which they were bound to.SAINT DENIS/REUNION-Droit Lettre (974112101) / SudocSudocFranceReunionFRR

Analyses multi-élémentaires de sols par LIBS : vers un dosage in situ des métaux et du carbone total

International audienceL’anthropisation des sols a entrainé la présence importante d’éléments en traces métalliques (ETM) dont les teneurs varient de la dizaine à plusieurs milliers de mg.kg-1. Ces concentrations restent dépendantes du type de sols et de l’historique des sites industriels. Actuellement, les polluants métalliques sont analysés in situ par des outils XRF portatifs, mais pour des études plus larges que les ETM, les éléments légers restent mal ou non dosés et la présence d’eau reste problématique. Nous avons choisi ici d’utiliser un outil portableLIBS (Laser Induced Breakdown Spectroscopy) car cette technique a été validée depuis une dizaine d’années au sein de la communauté des Géosciences.Nous décrirons la technique analytique LIBS, son fondement physique, sa mise en pratique pour le cas présenté, ses atouts et ses points faibles au regard des analyses plus communément utilisées. Nous montrerons l’apport spécifique de l’outil portable LIBS (Z300 © SciAps) pour la détection des éléments lourds et des légers comme le carbone sur différents types de sols (sols agricoles, forestiers et anthropisés)et pour optimiser l’échantillonnage et diminuer le coût des analyses. En utilisant des données globales (ICP-AES) obtenues sur les mêmes sols, des courbes d’étalonnage ont été réalisées afin d’obtenir des estimations quantitatives rapides des éléments majeurs et traces. La détection et la quantification du carbone total dans des pastilles de sol sont un atout supplémentaire pour cet outil portable

Bioavailability and transfer of elevated Sm concentration to alfalfa in spiked soils

International audienceRare earth elements (REEs) have been widely used in recent decades and their exploitation has led to industrial REE emission and to contaminated soils especially in former mining areas. This raised people's concerns on the accumulation and toxicity of REEs in soils and plants, and consequences on plant health. Although many studies dealt with REE in soils and plants, there is still a need to precise their toxicity, bioavailability and transfer to plants in contaminated sites in order to restore such ecosystems. We studied the bioavailability and transfer of a REE to Medicago sativa grown on two contaminated soils differing in their chemical characteristics. A pot experiment was set up in a growth chamber where two natural soils were spiked or not with samarium (Sm) as a model REE. Two chemical extractants were tested to estimate the bioavailability of Sm in the soil, its decrease with time and its transfer to the plants. Results showed that DTPA extractable Sm was well correlated with Sm uptake in alfalfa shoots. The experiment pointed out a significant ageing effect since DTPA extractable Sm significantly decreased within two weeks in the soils and was significantly lower in the less acidic soil than in the other. The uptake of Sm from soil to alfalfa shoots depended on the soil pH and on the spiking concentration. The soil to plant transfer factor was low (<0.08) but a 30% reduction of alfalfa biomass was observed when the soils were spiked with 100 to 200 mg kg-1 of Sm

Dynamics of PAHs and derived organic compounds in a soil-plant mesocosm spiked with 13C-phenanthrene

International audiencePolycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous and persistent soil pollutants. Their fate and the influence of the plant rhizosphere on their dynamics has been extensively studied, but studies mainly focused on their dissipation rate. We conducted a plant-soil mesocosm experiment to study the fate and distribution of PAHs or derived compounds in the extractable fraction, the residual soil, the shoot biomass and the root biomass. The experiment was conducted for 21 days using ryegrass and a forest soil spiked with 13C-labeled phenanthrene (PHE), using combined IRMS and NanoSIMS for analyses. Almost 90% of the initial extractable PHE content was dissipated within 3 weeks, but no rhizospheric effect was highlighted on PHE dissipation. More than 40% of 13C-PHE was still in the soil at the end of the experiment, but not as PHE or PAH-derived compounds. Therefore it was under the form of new compounds (metabolites) and/or had been incorporated into the microbial biomass. About 0.36% of the initial 13C-PHE was recovered in the root and shoot tissues, representing similar 13C enrichment (E13C) as in the soil (E13C ≈ 0.04 at.%). Using NanoSIMS, 13C was also localized at the microscale in the roots and their close environment. Global 13C enrichment confirmed the results obtained by IRMS. Some hotspots of 13C enrichment were found, with a high 32S/12C14N ratio. Comparing the ratios, sizes and shapes of these hotspots suggested that they could be bacteria

No significant transfer of the rare earth element samarium from spiked soil to alfalfa by Funneliformis mosseae

International audienceRare earth elements including samarium have been widely used in modern technologies in recent decades. Following over-exploitation and soil contamination, they can accumulate in plants and be toxic at high concentrations. Arbuscular mycorrhizae benefit plants in metal-contaminated soils by improving their survival and growth and alleviating metal toxicity, but little information is available about soil contaminated by rare earth elements. We performed two experiments using samarium to study the role of arbuscular mycorrhizal fungi on plant growth and samarium transfer to alfalfa in a samarium-spiked soil. A pot experiment was conducted in a soil spiked with two concentrations of samarium and a non-spiked control, inoculated or not with a metal-tolerant Funneliformis mosseae. A compartmented pot experiment was then performed with a separated compartment containing samarium-spiked sand only accessible by F.mosseae fungal hyphae to further study the transport of samarium from the soil to alfalfa. The biomass of alfalfa grown on samarium-spiked soil was reduced, while it was significantly higher following arbuscular mycorrhiza inoculation in the pot experiment, both in the control and samarium-spiked soil. Although mycorrhizal plants had a higher phosphorus content than non-mycorrhizal ones, there was no significant difference in samarium concentrations between mycorrhizal and non-mycorrhizal plants. The compartment experiment confirmed that there was no significant samarium transfer to the plant by F.mosseae. Other fungi and plants should be tested, and field experiments performed, but our results suggest that arbuscular mycorrhizal plants might be considered in phytorestoration of rare-earth-contaminated soils