Les marais sont de plus en plus menacés par les activités anthropogéniques mettant en péril leur capacité de filtrant des eaux des bassins versants. Cette étude a permis de déterminer l’efficacité de ...rétention des nutriments par les marais de Ciranga et de Kabamba et les effets de l’utilisation des terres et de la végétation sur la rétention des nutriments. Les échantillons d’eau ont été prélevés à l’entrée de la rivière dans le marais et à l’embouchure, et aussi sur sept stations identifiées dans le marais caractérisées par différents types de végétation et d’utilisation. Les prélèvements ont été effectués mensuellement entre août 2011 et juillet 2012. L’efficacité de rétention relative des polluants a été calculée par la différence entre la concentration au site de à l’entrée du marais et celle au site récepteur. Les résultats montrent que l’efficacité de rétention des nutriments des marais de Ciranga et de Kabamba diffèrent au vu de leur état d’utilisation des terres et de la couverture végétale. Le marais de Ciranga a une potentialité de rétention des nutriments plus élevée que le marais de Kabamba. L’efficacité de rétention du marais Ciranga est de 13% pour l’azote, mais celui de Kabamba est de 2% pour le phosphore. Le marais de Ciranga possède une concentration élevée en phosphore dans la rivière Lwiro (0,5 µmole/l). Par ailleurs, la rétention d’azote total est plus significative dans le marais de Kabamba que dans le marais de Ciranga. Comme le marais de Kabamba a été drainé et transformé en terre de culture, sa fonction naturelle de purification a été réduite. Des mesures de restauration des marais seraient d’une grande importance pour la stabilité du Lac Kivu et d’autres écosystèmes importants de la région.
Cette étude a été conduite afin d’évaluer les risques pour la santé liés à la production de déchets en milieu rural d’Irhambi Katana à l’est de la République Démocratique du Congo (RDC). La mesure ...des quantités des déchets produits par ménage dans six localités du groupement d’Irhambi Katana et l’analyse microscopique des échantillons des déchets ont été réalisées. La comparaison avec les données des centres de santé et la détermination de l’apport de ces déchets en éléments nutritifs du sol ont été réalisées. Les ménages du groupement d’Irhambi Katana produisent en moyenne 0,3 kg de déchets par jour. Ces déchets domestiques renferment plusieurs agents pathogènes tels que Balantidium coli, Shigella flexneri, Ascaris lombricoïdes et Escherichia coli qu’on peut associer à des maladies diarrhéiques couramment rencontrées dans les statistiques des centres de santé comme l’ascaridiose, la shigelose, l’amibiase et le choléra. Mais aussi ces déchets contiennent des matières organiques fertilisantes du sol comme l’azote et le phosphore en quantité importante (1272 mg P/kg; 8,89 % de N /kg). Une sensibilisation de la population dans la gestion des déchets domestiques pour éviter les maladies dues à la mauvaise gestion des déchets ainsi que l’usage de ces déchets dans la fertilisation des sols est recommandée.
The Albertine Rift is one of Africa's major biodiversity hotspots. However, the aquatic fauna of its western border in Democratic Republic of Congo (DRC) remains understudied and poorly ...characterised. Kahuzi-Biega National Park (KBNP) in DRC is a crucial link for biodiversity conservation of this hotspot; however, scientific studies of this rich biodiversity are scarce because of insecurity and harsh field conditions. In the current study, benthic macroinvertebrates communities and some environmental conditions were investigated in 10 rivers in the KBNP. Eighty-four morphospecies, belonging to 47 families and 12 orders, were sampled from 13 sites. The abundance and diversity of taxa within systematic groups varied across the study area. Spatial distribution of systematic groups was also analysed. The high morphospecies richness, characterised by the number of families and Shannon's and Simpson's Diversity Indices, recorded at some sites was probably owing to the diversity of substratum and undisturbed environmental conditions observed in these forested rivers. Conversely, some sites presented lower species richness, possibly because of unfavourable natural conditions.
This study has been carried out in order to evaluate new chemical drugs from plants for biocidal activity before use to avoid noxious effect on human beings and animals or plants and also to prevent ...the worsing of environment. In fact, many natural products endowed with biological active principles are obtained from plant material used in the holistic medicines. Presently, scientists pay attention to the study of plant extracts hoping to discover cheaper and efficient new drugs for health care and for pest control. On this point of view, the safety tests of extract from
Maesa lanceolata (Myrsinaceae) candidate for snails control in the Democratic Republic of Congo, were undertaken. Portion of powdered steam barks was extracted with EtOH to obtain saponins that were submitted to tests. Saponins were fractionated by using TLC techniques and biocidal activity tests were performed on fishes, molluscs and mousquitoes. Saponins exhibited powerful biocidal activity against aquatic adult insects (Aeschnidae, Coenagrionidae, Hydrobidae), moustiquitoes (
Anopheles gambiae, Anopheles funestus, Culex sp), snails (
Biomphalaria pfeiffeiri and
Lymnae natalensis), furcocercariae of Schistosoma mansoni and fish (
Haplochromis sp, Oreochromis nilotica and
Oreochromis macrochi)r. As results,
Maesa lanceolata (Myrsinaceae) contains a saponin-mixture endowed with molluscicidal activity at a dose of 1
mg/l. It may be a real candidate for snail control programs but it is harmful to aquatic biota. Attention must be paid to its utilization to avoid the ecological disturbance in the environment, especially when indigenous populations use it for fishing during the dry season.
In the Lake Kivu region, water erosion is the main driver for soil degradation, but observational data to quantify the extent and to assess the spatial-temporal dynamics of the controlling factors ...are hardly available. In particular, high spatial and temporal resolution rainfall data are essential as precipitation is the driving force of soil erosion. In this study, we evaluated to what extent high temporal resolution data from the TAHMO network (with poor spatial and long-term coverage) can be combined with low temporal resolution data (with a high spatial density covering long periods of time) to improve rainfall erosivity assessments. To this end, 5 minute rainfall data from TAHMO stations in the Lake Kivu region, representing ca. 37 observation-years, were analyzed. The analysis of the TAHMO data showed that rainfall erosivity was mainly controlled by rainfall amount and elevation and that this relation was different for the dry and wet season. By combining high and low temporal resolution databases and a set of spatial covariates, an environmental regression approach (GAM) was used to assess the spatiotemporal patterns of rainfall erosivity for the whole region. A validation procedure showed relatively good predictions for most months (R2 between 0.50 and 0.80), while the model was less performant for the wettest (April) and two driest months (July and August) (R2 between 0.24 and 0.38). The predicted annual erosivity was highly variable with a range between 2000 and 9000 MJ mm ha−1 h−1 yr−1 and showed a pronounced east–west gradient which is strongly influenced by local topography. This study showed that the combination of high and low temporal resolution rainfall data and spatial prediction models can be used to improve the assessments of monthly and annual rainfall erosivity patterns that are grounded in locally calibrated and validated data.
The water quality of the Lwiro River, Democratic Republic of Congo (DRC), Central Africa, was investigated on a monthly basis from December 1999-October 2000, at six stations along a hydraulic ...gradient from source to mouth, to evaluate the impact of land use on temperature, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD
5
), alkalinity and suspended solids. Upstream, where forests are conserved, minimal changes of physico-chemical parameters of water were observed. Downstream, DO was reduced, due to the increased organic matter content which increased the decomposition rate. BOD
5
and suspended solids increased downstream. Greater changes were found near agricultural areas and villages. Wetlands appear to mitigate BOD
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and DO impacts.
The evaluation of the biocidal activity of the fruit of
Solanum sisymbriifolium involving non target organisms such as aquatic insects, fish and snails lead to the isolation of the steroidal ...alkaloids, solamargine and β-solamarine, from the active fractions. The fractions A3 and C, with biological activity against fish, snail and aquatic insect and larvae, are able to affect the good functioning of ecosystem found on alimentary chain. The fraction B seems to be less toxic to fish and aquatic insect and larvae. The fraction B could thus be used as molluscicide in the future.
A bioassay-guided fractionation of the fruit of
Solanum sisymbriifolium involving non target organisms such as aquatic insects, fish and snails lead to the isolation of steroidal alkaloids, solamargine and β-solamarine, from the active fractions. The fraction B seems to be less toxic to fish and aquatic insect and larvae contrary to others extracts and fractions. Thus the fraction B can be used as a molluscicide in the future.
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