In developing countries, the burden of diarrhoea is still enormous. One way to reduce transmission of pathogens is by water quality interventions. Solar water disinfection (SODIS) is a low-cost and simple method to improve drinking water quality on household level.
Abstract:The purpose of the study was to investigate changes of soil chemical and biological properties changes resulting from a single application of the fungicide Ridomil Gold plus copper (Ridomil Gold plus)(mefenoxam 6% + copper oxide 60%) at the following rates 0.25, 0.5, 1, 2, and 10 g m -2 . Selected chemical properties generally differed between fungicide rates over longer incubation periods. Microbial activity indices (available N, ammonification rates and specific enzymatic systems) were more sensitive indicators of change. Values of these indicators generally increased with incubation period and decreased or increased at high rates. Significant changes in P availability occurred after 90 days of incubation at rates ≥ 1 g m -2 . Incorporation of the fungicide significantly increased NH 4 + levels in soil after 75 days of incubation. These changes stimulated soil microbial activity as evidenced by increased ammonification rates especially at long-term exposure. Of the enzyme activities studied, dehydrogenase and ß-glucosidase activities were the most sensitive to ridomil gold plus. This sensitivity was more pronounced with the dehydrogenase activity.
Tous droits réservés © Revue des sciences de l 'eau, 2004 Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne.https://apropos.erudit.org/fr/usagers/politique-dutilisation/ Cet article est diffusé et préservé par Érudit.Érudit est un consortium interuniversitaire sans but lucratif composé de l'Université de Montréal, l'Université Laval et l'Université du Québec à Montréal. Il a pour mission la promotion et la valorisation de la recherche. Résumé de l'article L'évolution spatio-temporelle, qualitative et quantitative du peuplement phytoplanctonique a été suivie au lac municipal de Yaoundé. Pour cela des prélèvements hebdomadaires ont été effectués de novembre 1996 à décembre 1997, au niveau d'une station de la zone centrale du lac.Trois descripteurs (indice de diversité spécifique, régularité et diagrammes rangs-fréquences) ont été utilisés pour l'analyse de la dynamique de la structure du peuplement. L'indice de diversité spécifique obtenu à partir des biomasses spécifiques, par la formule dérivée de celle de SHANNON et WEAVER (1949), est compris entre 0,68 et 4,64 bits/µg. La régularité (PIELOU, 1966) varie de 0,14 à 0,84; les faibles valeurs correspondant dans l'ensemble à la présence des espèces fortement dominantes. Les profils des diagrammes rangs-fréquences, établis en coordonnées log-log, associés aux faibles valeurs de la diversité, sont essentiellement caractéristiques des stades pionniers (1 et 1') de l'évolution d'un lac tel que décrits par MARGALEF (1967) et FRONTIER (1976. Le stade 2 est rare alors que le stade 3 est absent.Une analyse simultanée basée sur les variations spatio-temporelles de la densité cellulaire et de l'indice de diversité spécifique, sur les valeurs de la régularité, et sur les profils des diagrammes rangs-fréquences révèle le caractère immature permanent des populations phytoplanctoniques inféodées à ce biotope, et caractérise ainsi un milieu eutrophe à hypereutrophe où aucun stade d'équilibre n'est atteint. La richesse du milieu en éléments biogènes et sa faible profondeur (Zmax=4,3 m) sont à l'origine de sa vulnérabilité. L'événement susceptible d'interrompre la succession des populations s'est avéré être le brassage des eaux, provoqué aussi bien par les pluies que les vents dont l'énergie cinétique est fréquemment suffisante pour entraîner un brassage complet d'une colonne d'eau de hauteur aussi faible. SUMMARYThe Yaounde municipal lake (3°52'N, 11°32'E) is a shallow hypertrophie water body (Z max = 4.3 m), situated downtown Yaounde. It is an artificiel lake resulting from a dam constructed in 1951 across a small river named Mingoa. Like many other water bodies in urbanised areas, this ecosystem switched rapidly from being mesotrophic to hypertrophie during the 1980's, due to the expansion of human activity and an inefficient treatment of wastewater in its catchment area. This study was carried out with the objective to anal...
Significance and suitability of Aeromonas hydrophila vs. fecal califorms in assessing microbiological water quality Djuikom, E.; Njiné, T.; Nola, M.; Kemka, N.; Zébazé Togouet, S. H.; Jugnia, Louis-B. ORIGINAL PAPERSignificance and suitability of Aeromonas hydrophila vs. fecal coliforms in assessing microbiological water quality E. Djuikom AE T. Njiné AE M. Nola AE N. Kemka AE S. H. Zébazé Togouet AE Louis-B. Jugnia Abstract We examined the significance and suitability of Aeromonas hydrophila versus fecal coliforms in assessing microbiological water quality. For this, we used the membrane filtration method to simultaneously estimate the abundance level of A. hydrophila and fecal coliforms in waters from the Mfoundi river watershed at Yaoundé, and compared how fluctuations in A. hydrophila abundance matched those observed with fecal coliforms index as an indicator of water quality in the system under study. Our results revealed that waters were not safe according to the standards for water quality established by the Word Health Organization (WHO). They also indicated the prevalence of A. hydrophila as compared to fecal coliforms, and suggested that water from the Mfoundi River and its tributaries could be classified as hypereutrophic based on the density of Aeromonas. Moreover, the spatial distribution of fecal coliforms and A. hydrophila exhibited similar trends within the different water bodies investigated, suggesting that A. hydrophila can be used as indicator of water quality in highly polluted waters. We concluded that waters from the Mfoundi River watershed at Yaoundé represent a great potential risk of infection for users, and foresee that the next challenge will be to determine, among other factors, the physico-chemical factors influencing the observed spatial distribution.
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