Plants diversity and phytoaccumulators identification on the Akouedo landfill (Abidjan, Côte d’Ivoire)

Phytoremediation is an emerging technology to remediate contaminated soils. Their implementation in developing countries may be limited by the plant species used. To overcome this situation, plants from the Akouedo landfill have been inventoried in order to identify indigenous plants adapted to soil and environmental conditions. Two sampling zones have been defined, based on the waste dumping activities or not. Four plots (50 × 50 m2) have been defined. The plant species collected were used to constitute vouchers for identification. Plants frequency occurrence was used to evaluate their relative importance, while the Shannon and evenness indices were calculated to characterize the diversity. The plant families and species identified were compared to those described as heavy metals phytoaccumulators in the literature. A total of 130 taxa belonging to 39 families have been recorded. The most frequent families (36.9% of the total taxa) were Poaceae, Euphorbiaceae and Cyperaceae. The dominant taxa on the old waste dumpsite having an average density superior to 5 plants/m2 and occurring less frequently on the control site were Alternanthera sessilis, Amaranthus spinosus, Cyperus rotundus, Cyperus iria, Eleusine indica, Euphorbia glomerifera, Ipomoea triloba, Portulaca oleracea and Trianthema portulacastrum. These plant species may be indigenous phytoaccumulators on the Akouedo landfill.Keywords: Heavy metals, landfill, phytoaccumulators, phytoremediation, plantsAfrican Journal of Biotechnology Vol. 12(3), pp. 253-26

Impacts of artisanal and small-scale gold mining on soils in northern regions of Côte d’Ivoire: cases of Boundiali, Korhogo and Tengrela

The development artisanal and small-scale gold mining in recent years in Côte d'Ivoire could pose a risk to soils and health of local communities. This study aimed at assessing the impacts of artisanal and small-scale gold mining on the soils in the areas in the northen localities (Boundiali, Korhogo and Tengrela) of Côte d’Ivoire, where those activities are accentuated. Field observation and physico-chemical parameters analysis (potential hydrogen (pH), cation exchange capacity (CEC), organic matter (OM)) and pollutants (mercury (Hg), copper (Cu), zinc (Zn), arsenic (As) and cyanide (CN)) in soil samples were carried out. The results indicate that artisanal gold mining create soils erosion and consequently, soil structure destruction. Trace metals concentrations were 0.0001-0.0051 mg/kg (Hg), 0.002-0.32 mg/kg (CN), 18.90-73.10 mg/kg (Cu), 16.40-50.1 mg/kg (As) and 10.20-26.60 mg/kg (Zn). Geoaccumulation index (Igeo) in soils showed uncontamination for Hg and Zn, uncontamination to moderate contamination for Cu and moderate to strong contamination for As. According to ecological risk index (Eri), As could pose considerable to high risks to biota in study area. This study highlights serious risks to soil biota and human health, from artisanal gold mining activities. Thus, it is necessary to clean-up arsenic-contaminated soils

Valorisation Energetique des Dechets Agricoles : cas de la Pomme de Cajou dans le Departement de Tanda (Côte d’Ivoire)

Cette étude s’est proposée de valoriser la pomme de cajou e combustible. Le matériel est constitué de pommes de cajou séchée non carbonisée (PCSNC), pommes de cajou fermentées séchées carbonisées (PCFSC),, pommes de cajou séchées et carbonisées (PCSC), briquettes comportant 100% de pommes carbonisées et 0% de sciure de bois carbonisée (BPC100), briquettes comportant 80% de pommes carbonisées et 20% de sciure de bois carbonisée (BPC80), briquettes comportant 70% de pommes carbonisées et 30% de sciure de bois carbonisée (BPC70), briquettes comportant 60% de pommes carbonisées et 40% de sciure de bois carbonisée (BPC60). Ces combustibles ont été caractérisés en déterminant la quantité de chaleur dégagée, la durée de combustion, le temps d’ébullition, le niveau de dégagement de fumée, la masse de suie après combustion et le taux de cendres. Les valeurs obtenues pour ces paramètres ont été comparées à celles du charbon de bois. Il ressort que les quantités de chaleur dégagées par PCFNC (963 KJ) et PCSNC (943 kJ) sont relativement proches de celle (1122 kJ) du charbon de bois. Pour la durée de combustion, ce sont les briquettes et le charbon de bois témoin qui mettent plus de temps à se consumer (60 minutes, environ). Le temps le plus court d’ébullition de l’eau est obtenu avec BPC100 (10,98 minutes contre 15,45 minutes pour le charbon de bois). Les combustibles à base de pommes de cajou ont tous dégagé de la fumée et ont favorisé un dépôt de suie après la combustion contrairement au charbon de bois. Au niveau de la cendre, BPC60 et BPC70 ont produit moins de cendre (10g) que le charbon de bois (12,5g). Au vu de ces résultats, si certaines caractéristiques de la pomme de cajou sont améliorées, sa valorisation énergétique est possible. This study intended to valorize the cashew apple or cashew nut into fuel. The material consists of cashew apples and sawdust, which allowed us to obtain 8 types of fuel. This includes dried cashew apples without carbonization (PCSNC), dried fermented cashew apples with carbonization (PCFSC), dried cashew apples with carbonization (PCSC), and briquettes with 100% carbonized apples and 0% sawdust with carbonization (BPC100), briquettes with 80% carbonized apples and 20% carbonized sawdust (BPC80), briquettes with 70% carbonized apples and 30% carbonized sawdust (BPC70), briquettes with 60% carbonized apples and 40% carbonized sawdust (BPC60). These fuels were characterized by determining the amount of released heat, combustion time, boiling time, level of smoke release, soot mass after combustion, and ash content. The values obtained for these parameters were compared with those of charcoal. The heat release of PCFNC (963 kJ) and PCSNC (943 kJ) is relatively close to that of charcoal (1122 kJ). The briquettes and the control charcoal take longer to burn (about 60 minutes, in terms of burning time. The shortest water boiling time was obtained with BPC100 (10.98 minutes versus 15.45 minutes for charcoal). Cashew apple fuels all gave off smoke and promoted soot deposition after combustion. This was not the same as charcoal’s case. Regarding ash generation, BPC60 and BPC70 produced less ash (10g) than charcoal (12.5g). Considering these results, if some characteristics of the cashew apple are improved, its energy valorization is possible

Influence de la hauteur du massif filtrant sur l’élimination des polluants organiques dans un filtre à sable à alimentation intermittente: Effect of sand depth on the removal of organic pollutants in an intermittent sand filter

La pollution des eaux de surface par les eaux usées urbaines est une préoccupation environnementale majeure. Cette étude a consisté à développer des filtres à sable intermittent en série en forme de U et à étudier l’influence de la hauteur et de la granulométrie du lit filtrant sur l’enlèvement des polluants organiques des eaux usées. Ainsi, deux hauteurs de lits filtrants (60 cm) et (70 cm) ont été utilisés. Les schistes grossiers, schistes moyens et le sable de lagune ont constitué le massif filtrant. Les résultats montrent que les rendements obtenus avec les filtres 70 cm de lit filtrant (FH70) sont relativement plus élevés (MES : 77,16%, DCO : 89,75% et DBO5: 92,96%). Cependant, les schistes moyens et le sable de lagune permettent d’obtenir une bonne réduction des MES, de la DCO et DBO5 dans les filtrats par rapport aux schistes grossiers. Les analyses du profil des polluants organiques dans le filtre de 70 cm de massif filtrant ont montré une diminution des teneurs de ces polluants de la surface au fond du filtre et elles restent élevées dans la couche de 0 à 20 cm. Les résultats obtenus montrent que les filtres FH70 contenant des schistes moyens et du sable de lagune constituent une technologie efficace d’épuration des eaux usées. Pollution of surface waters by urban wastewater is a major environmental concern. This study was conducted to develop intermittent sand filters in the shape of a “U” for organic pollutants treatment. In this study, the effect of both two sand depth (60 cm and 70 cm) and the filter media grain size on the removal of organic pollutants was studied. The coarsest shale medium (Sch1), mean shale (Sch2) and white lagoon sand constituting the filter media. The results show that the filter of 70 cm of sand (FH70) was the most efficient (TSS: 77.16%, COD: 89.75% and BOD5: 92.96%). However, the media grain size which removed optimum MES, DCO and DBO5 was observed to be mean shale and the white lagoon. Concerning the organic matter concentration in filter medium of filter 70 cm of sand, they decrease with depth and the sand layer from 0 to 20 cm show the highest concentration. The results obtained show that the filter of 70 cm of mean shale and with lagoon sand is an efficient technology for treating treat urban wastewater