One consequence of the shift in land use from traditional food production to cotton production in West Africa is the application of different pesticides. The influence of this practice on the formation of pesticide residues in soils and sediments of seasonal dry pools was investigated in 2008 and 2009 in the region of the Pendjari biosphere reserve in Benin. The protected park area, the buffer zone with some sporadic agricultural practice and the agricultural zone of the Pendjari region were compared. GC-electron capture detector method was used to analyze selected pesticides covering the officially supplied pesticides and some organochlorine compounds. Residues of a-and b-endosulfan, endosulfan sulfate, chlorpyrifos, p,p 0 -dichlorodiphenyldichloroethane, p,p 0 -dichlorodiphenyldichloroethylene (DDE) were detected in soils of cotton fields and in sediments from adjacent pools within the agricultural and buffer zone. Concentrations were in the range of below detection limit (DL) to 150 mg/kg dry mass (dm) for endosulfan and endosulfan sulfate together and of below DL to 12 mg/kg dm for chlorpyrifos. In pool sediments, concentrations of total endosulfan were in a range of below DL to 47 mg/kg dm. The occurrence of the pesticides was directly linked to the cotton growing season. No residues were detected at the beginning of cotton growing season. Concentration levels of p,p 0 -DDE were in the range of below DL to 12 mg/kg dm.No pesticide residues were found in the protected park zone.

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Tous droits réservés © Revue des sciences de l 'eau, 2016 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 Les rejets d'eaux usées domestiques et industrielles de la ville de Kara affectent la qualité de l'eau de la rivière Kara. Notre travail porte sur l'évaluation de la capacité du charbon actif mésoporeux préparé par activation chimique à partir de la balle de riz à éliminer la demande chimique en oxygène (DCO) et contribuer ainsi à la réduction de la pollution de la rivière de Kara. Cinq échantillons d'eaux usées prélevés sur cinq sites de la ville de Kara ont été caractérisées par le pH, la température, la conductivité, les matières en suspension (MES), la DCO, la DBO 5 et les matières oxydables (MO). Les tests de réduction de la DCO ont été réalisés par la méthode batch avec la poudre de balle de riz et deux types de charbons activés. Les effets du pH du milieu, du temps de contact, de la masse de l'adsorbant, de la valeur initiale de la DCO et la nature de l'eau usée sur la réduction de la DCO ont été évalués. Les charbons activés présentent une capacité d'atténuation de la DCO plus élevée en comparaison avec la poudre de balle de riz pour la réduction de la DCO des eaux usées. Le taux d'abattement maximal de la DCO est obtenu à 100 % pour une eau usée dont la DCO était de 1 060 mg O 2•L-1 traitée à pH 8 avec le charbon CAG-Base à la concentration en adsorbant de 10 g•L -1 pendant 60 min de contact. REMOVAL OF COD IN WASTEWATERS BY ACTIVATED CHARCOAL FROM RICE HUSK ABSTRACTThe discharge of industrial wastewater and domestic sewage from Kara city affects the quality of Kara river water. To mitigate this water pollution, the capacity of mesoporous charcoal prepared from rice husk (RH) to remove the chemical oxygen demand (COD) in wastewater samples from five sites of Kara City was investigated. The temperature, pH, conductivity, total suspended solids (TSS), biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD) and oxidizable matters (OM) of samples were analyzed. Batch experiments were applied to study the COD reduction by using powdered RH and two types of activated charcoals (AC). The experimental parameters used to identify optimal conditions for COD abatement are solution pH, contact time, mass of adsorbent and initial value of COD including the nature of wastewater. Activated charcoals showed a higher attenuation capacity of the COD in comparison with the rice husk powder. Maximal abatement rate (100%) of COD removal was obtained for the wastewater sample with a COD of 1 060 mg O 2 •L -1 trea...

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This paper presents an evaluation using carbon fiber microelectrode (CFME) for the determination of glyphosate in soils from Burkina Faso treated with Glyphonet SL 360 by square wave voltammetry (SWV). The maximum intensity of the electrochemical response signal of glyphosate has been optimized and conditions using a 0.2 M of phosphate buffer solution at pH 5.2 as supporting electrolyte and the SWV parameters frequency of 60 Hz, a scan increment of 10 mV and a pulse height of 60 mV. The limit of detection for glyphosate in the Glyphonet SL 360 formulation was 25 µg L -1 while the quantification limit was 83 µgL -1 with a linear dynamic range up to 50 µg L -1 . In these conditions, a sequence of experiments led to recoveries in the range 88.5 to 102.3% for soil samples spiked with 50, 100 and 200 µgL -1 of glyphosate with a standard deviation of 11.5, 4.2 and 2.3% respectively indicating the precision of the method. The optimized method was successfully applied to determine the residues of glyphosate in soils collected in the fields in two different dates from the application period.

This work was focused on laterite soil as adsorbent for the removal of arsenic and phosphate from groundwater using column experiments. Results revealed a decrease of arsenic removal efficiency from 100 to 79% with flow rate increasing. Maximum removal of 100% for arsenic and 85% for phosphates was obtained for pH values between 3.5 and 6. The increase of initial arsenic concentration and phosphate amount caused an increase of arsenic adsorption up to 24 µg/g while 58.5 µg/g for phosphate. NaOH solution could desorb 86.8% of arsenic and the reuse of regenerated laterite indicated its efficiency in same experimental conditions.

Arsenic pollution is one of the global issues which affect the drinking water supply in Burkina Faso, mainly in rural areas. To mitigate this water pollution, ferromagnetic activated carbon (FAC) has been prepared by chemical activation using rice husk and iron chloride solution to be used as an adsorbent of arsenic. Characterization with some analytical techniques revealed this carbon is microporous with a specific surface area of 150 m2∙g-1 and ferromagnetic properties. This work aims to evaluate the equilibrium conditions of As(V) removal and the adsorption capacity of FAC. Batch experiments were undertaken to evaluate the performance of FAC for arsenic removal under various operating conditions and the mechanism of the removal process. Results showed an increase of the removal percentage with the increase of the contact time, indicating a saturation during 60 min. The removal of As(V) is influenced by the increase of the initial arsenic concentration causing an increase of the adsorption capacity of FAC. The increase of pH showed a variation of the removal percentage indicating a maximum removal at pH 7 which corresponds to an adsorption capacity of 153 µg∙g-1. Both monolayer adsorption and ion exchange constitute the mechanism of removal of As(V) using FAC. The kinetics of the process is described by a pseudo-second order model.