Studies of Leachate in Dumpsites in Enugu Metropolis, Enugu State

Abstract

A study of leachates in dumpsites in Enugu metropolis, Enugu State was undertaken from July, 2018 to January, 2019. The aim was to determine the leachate characteristics of the various dumpsites in Enugu. A total of 9 residential areas’ major dumpsites (Emene, Abakpa, Trans-Ekulu, GRA, Gariki, Asata, New Haven, Uwani, and Achara Layout) were studied. Site selections along the vicinity of the dumpsite were areas where waters from the dumpsites drip to the ground. The collected leachate samples were taken to the laboratory in plastic bottles in an ice cooler, filtered through a 250 mm Whatman filter paper and then stored in polyethylene bottles and preserved in cold room at a temperature of 4 °C prior to the physicochemical and metallic analyses. The data obtained from the study were analyzed using SPSS for Windows version 20. From the result, the pH value of the dumpsites ranged from 6.77 – 7.66 in the wet season and 6.73 – 7.29 in the dry season. Seasonal differences in pH values were recorded in the dumpsites. Electrical conductivity of the dumpsites ranged from 12.22 – 437.33 in wet season and 26.00 – 457.33 in dry season respectively. Also, the total dissolved solids values for both seasons ranged from 53.44 – 1480.78 (wet season) and 78.89 – 1263.11 (dry season). The present study heavy metals evaluation showed significantly increased copper (wet season: 0.01 – 2.29; dry season: 0.00 – 2.54), manganese (wet season: 0.02 – 0.64; dry season: 0.12 – 4.54), lead (wet season: 0.00 – 0.02; dry season: 0.03 – 1.05), cadmium (wet season: 0.01 – 0.93; dry season: 0.11 – 2.31), chromium (wet season: 0.02 – 0.15; dry season: 0.04 – 0.84), arsenic (wet season: 0.01 – 2.17; dry season: 0.09 – 2.81), and nickel (wet season: 0.08 – 0.30; dry season: 0.13 – 0.92) levels during the dry season. The concentrations of the heavy metals in the wet season followed this sequence in decreasing order: Ar > Cd > Mn > Ni > Cu > Cr > Pb. Arsenic and chromium were highest in Uwani dumpsite, cadmium levels highest in New Haven, manganese levels highest in GRA, nickel was highest in Echara New Layout, copper was highest in Asata, and lead was highest in Abakpa dumpsites. The dry season sequence in decreasing order is as follows: Mn > Ar > Cu > Cd > Pb > Ni > Cr. The heavy metals highest values were recorded in Asata for manganese, Uwani for arsenic and nickel, Abakpa and Uwani for copper, Echara New Layout for cadmium and chromium, and New Haven for lead concentrations. Overall, the study showed that copper levels have strong positive correlations with manganese, lead, arsenic and nickel concentrations. Also, manganese correlated with lead, arsenic and nickel. Cadmium correlated with chromium, while arsenic correlated with nickel. All the metallic correlations were positively strong. Copper and manganese had negative correlations, but that of cadmium was positive. The results obtained in this study showed that the leachates generated from the dumpsites could have harmful impact on the groundwater quality in the study area. This suggested that the surface and groundwater of the study sites are unreliable for drinking purposes, with emphasis on the need to improve on waste management practices and construct properly an engineered leachate collecting system at dumpsites to curtail pollution of surface and/or groundwater. Other implications of the leachate and regimes were also discussed.