ASSESSING THE ENVIRONMENTAL RISK AND POLLUTION STATUS OF SOIL AND WATER RESOURCES IN THE VICINITY OF MAJOR DUMPSITES IN LAGOS, NIGERIA

Abstract

Management of solid waste in cities is the most pressing environmental challenge. While this issue is global, it is more dominant in low- and middle-income countries with constantly increasing population, little to no regulation of waste management and open dumping of waste being the most prevalent method of waste management. The deterioration of soil quality and altered water quality are major consequences of open waste dumping resulting in environmental and public health concerns. Release of pollutants through leachates from open dumpsites poses a high environmental risk to the nearby soil as well as surface and groundwater resources. The focus of this study is to assess the environmental risk and pollution status of soil and water resources in the vicinity of major dumpsites in Lagos and to quantify their risks to the Lagos metropolis' local ecosystem and public health. A two-season collection and analysis of soil and water samples from the three major dumpsites and within 2km from the dumpsite was conducted. Biological and physicochemical parameters were analyzed, and the results were used to evaluate several environmental indicators namely pollution load index, contamination factor, total ecological risk, geo accumulation and water quality index. The results indicated that important soil parameters including TN (11.89-13.83mg/kg), pH (6.45 – 7.35), sulfate (36.71-39.49mg/kg) phosphate (9.31-14.39mg/kg), and electrical conductivity (342-566µS/cm), were impacted by the dumpsites. Heavy metals concentrations from samples around the dumpsite and those collected distance away from the dumpsites also varied. Fe (52.74-75.78mg/kg), Cr (1.52-3.74mg/kg), Cd (0.03-0.08mg/kg), Cu (1.98-66.94mg/kg), Zn (1.76-6.92mg/kg), Pb (0.1-1.99mg/kg) and Mn (0.46-4.56mg/kg) were the most encountered heavy metals in all dumpsites. The recorded concentrations were lower than or slightly within acceptable limits for optimal ecological function in most instances, however the values around the dumpsites were higher than those recorded at sample locations 2 km aways from the dumpsite. Optimal soil quality that supports essential ecological functions is directly impacted by these altered parameters and if biomagnified could affect the food chain, crop yield and vegetation abundance. Analyzed parameters for water were mostly within acceptable limit indicating less impact of the waste dump on water resources. The Water quality index the water is of good quality. Effort should be intensified to ensure proper waste segregation from sources to ensure that wastes with hazardous composition are not disposed of in open dumps. Waste reduction sensitization and awareness should be carried out to enlighten Lagos residents and local industries operating in the state on the needs to reduce, re-use and recycle materials. A robust monitoring and remediation plan should also be developed to ascertain the extent of leachate leakage into the environment.