Impact of household waste and uncontrolled landfills on soil quality in the municipalities of Godomey and Abomey-Calavi in Benin

Disposal of solid waste is a major concern in Benin. The treatment method most used remains the traditional setting discharge. This study aims to assess the impact of uncontrolled waste on soil quality in in the districts of Godomey and Abomey-Calavi in Benin characterized by the greatest population and the highest human density. After characterization of landfills, six uncontrolled discharge sites were selected and 27 soil samples were taken. Particle size analysis of the samples was carried out according to the standards NF P 94-056. Physico-chemical analysis of soil samples was also performed. The collected data were analyzed using SAS 9.2 software. It appears from this study that there are 142 major uncontrolled landfills including 34 in Abomey-Calavi and 108 in Godomey. 46.36% of the sites were located in the lowlands of Godomey, while in Abomey-Calavi, 76.47% of the sites are on land (p <0.01). The area of these sites varies between 9.8 and 2943.7m² with heights between 0.3 and 12m. Their distance from the first houses ranged from 0 to 30m. Sorting by category of waste was made according to the method recommended by MEDECOME and had revealed fourteen categories with a predominance of fine wastes, putrescible and plastics. Waste leachates flow into water bodies or seeps into the ground. They are low oxygen, rich in minerals, organic matter and metals then are polluted by oxidized organic matter (DCO), lead and copper. Landfill sites tend to influence soil quality even though they are currently only contaminated by cadmium in depth and by lead in surface. The near absence of pollution in soils is related to the recovery activity that led to the scarcity of these waste landfill sites containing these metals.