Title : Soil pollution in Central Africa: Implications of inadequate waste management practices
Abstract:
Urban expansion in developing countries is correlated with a significant increase in waste generation, presenting formidable challenges for effective waste management by both authorities and the local populace. The accumulation of waste in unauthorized dumpsites and landfills has pronounced adverse effects on soil quality, particularly in Brazzaville, Republic of Congo. Adverse weather conditions, notably precipitation, augment soil moisture levels, which in turn accelerates waste decomposition and facilitates the leaching of pollutants, including heavy metals. This scenario raises critical concerns regarding its implications for soil health and public health. To elucidate these impacts, a comprehensive study was conducted to evaluate metal contamination in soils at public landfills in Brazzaville. Three systematic sampling campaigns were executed across six landfill sites, with five samples collected at a
depth of 25 cm at each location, thereby enabling the formation of composite samples. The physicochemical analyses encompassed measurements of moisture content, pH, electrical conductivity, and concentrations of dissolved salts. Organic matter and organic carbon were quantified utilizing the Walkley and Black method, while sample mineralization adhered to the NF ISO 11466 standard. To investigate heavy metal speciation, a sequential extraction protocol was employed, and the concentrations of these metals were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). Statistical analyses, including ANOVA and mean comparison tests, unveiled significant correlations among various physicochemical and metallic parameters. The results indicate a substantial variation in the measured parameters : moisture content ranged from 9.57 % to 22.33 %, pH values fluctuated between 6.93 and 7.29, and alarming concentrations of heavy metals were observed, with lead levels varying from 120 to 173 mg/kg, nickel from 18 to 4028 mg/kg, zinc from 610 to 5500 mg/kg, chromium from 50 to 6664.67 mg/kg, mercury from 0.78 to 2.97 mg/kg, and cobalt from 2.33 to 80.67 mg/kg. Contamination indicators, such as the contamination factor and pollution index, reveal that the majority of landfill soils exhibit severe heavy metal pollution, confirming notable accumulation. Notably, the outcomes of sequential extractions indicate that chromium and nickel are associated with multiple fractions, underscoring the complexity of their environmental contamination and the challenges associated with remediation efforts.
