ABSTRACT
This study assessed the impact of open dumpsites on the quality of groundwater within the vicinity of solid waste dumpsites in Maiduguri. The problem of rapid urbanization and poor waste management has resulted in an increased of hand dug wells with some located within the premises of an open dumpsites. The mean percentage composition of solid waste at the two dump sites were earth/garbage (26%), metal (21%), glass (20%), plastic (19%), polythene (13%), textile (7%), battery (5%) and paper (3%). Soil sampling was conducted using soil auger for dry and wet season. Total of 34 soil samples and 4 water samples were collected and analysed for physico-chemical characteristics; turbidity, temperature, total dissolved solids (TDS), electrical conductivity (EC), pH, nitrate (NO3), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), zinc (Zn) iron (Fe), copper (Cu), cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As) and manganese (Mn). Particles size analysis was carried out using Bonyoucos hydrometer method and the texture determined on the USDA triangle. The soil pH and electrical conductivity was measured using Turbo pH/mV/temp. and EC meter and the soil BOD was determined using Winkler method from the soil filtrate. Potassium chloride (KCl) extraction method was used to determine the soil nitrate (NO3). The heavy metals (Cu, Zn, Mn, Cd, Pb, As, Cr and Fe) of the soil extracts were analysed using the multi-wave plasma atomic emission spectrophotometer (MP-AES 4200). The textural class of soil samples analyzed for dumpsites A and B were sandy loam with mean percentage ranged from 75-77%, 15.25-17.25% and 6.75-7.757% for sand, silt and clay respectively. The mean concentrations of pH, EC, NO3 and BOD of the soil samples for dumpsite A and B ranged from 6.8-8.17, 0.2-1.27 ds/m, 0.01-0.24 mg/Kg and 68-1180 mg/Kg in dry and wet season respectively, and all the mean concentrations were within NES limit for soil quality. The mean concentrations of Zn, Fe, Cu and Pb for dumpsite A and B ranged from 103-1412 mg/Kg, 3226-9670 mg/Kg, 10.72-55.7 mg/Kg and 8.21-81.4 mg/Kg for dry and wet season respectively. The mean concentrations of As, Cd, Cr and Mn for dumpsite A and B ranged from 71-134 mg/Kg, 0.31-2.67 mg/Kg, 24.91-62.5 mg/Kg and 172-474 mg/Kg for dry and wet season respectively. All the mean concentrations were within NES limit for soil quality except Zn and As for both seasons, while Cd for wet season. The concentrations of temperature, turbidity, pH, EC, and TDS ranged from 24.2- 30oC, 0.28-4.73 NTU, 7.35-9.8, 131-1329 μs/cm and 70-906 mg/l for dry and wet seasons respectively. All the concentrations were within NSDWQ and WHO standard limit in the dry season except turbidity and pH in the wet season. The concentrations of DO, COD, BOD ranged from 25-70 mg/l, 150-2000 mg/l, 4-30 mg/l and 1.18-53.62 mg/l for dry and wet seasons respectively. All the concentrations were above NSDWQ and WHO standard limit except NO3. The concentrations of Zn, Fe, Cu, and Pb ranged from 0.01-0.122 mg/l, 0.11-0.812 mg/l, 0.011-0.226 mg/l and 0.003-0.3 mg/l for dry and wet seasons respectively. All the concentrations were within NSDWQ and WHO standard limit except Fe in the wet season. The concentrations of As, Cd, Cr and Mn ranged from 0.029-514 mg/l, 0.001-0.24 mg/l, 0.001-0.184 mg/l and 0.001-0.357 mg/l for dry and wet seasons respectively. All the concentrations were above NSDWQ and WHO standard limit. The results obtained in this study shows that the leachate generated from the solid waste dumpsites had impacted negatively on the soil.