Soil quality around a solid waste dumpsite in Port Harcourt, Nigeria

The levels of soil parameters and selected heavy metals around a solid waste dumpsite receiving untreated wastes from all sources and a control site within Port Harcourt, Nigeria have been examined. Top soil (0–15 cm) and sediment samples were collected and analysed for pH value, particle size, total nitrogen, potassium, available phosphorus, organic matter, effective cation exchange capacity, cadmium, nickel and lead using standard methods. The results showed that the waste dump contributed to the high levels of nutrients and heavy metals. The dry season mean concentrations were: organic matter (5.28 ± 1.34% or 132,422.4 kg ha −1 ), K (1.60 ± 0.52 meq per 100 g), N (0.09 ± 0.06% or 2257.2 kg ha −1 ), Av.P (15.11 ± 7.57 μ g g −1 ), Cd (1.34 ± 0.72 μ g g −1 ), Ni (4.10 ± 1.63 μ g g −1 ) and Pb (38.85 ± 22.18 μ g g −1 ) while the wet season mean concentrations were organic matter (5.46 ± 1.39% or 136,936.8 kg ha −1 ), K (2.79 ± 0.81 meq per 100 g), N (0.10 ± 0.05% or 2508 kg ha −1 ), Av.P (9.22 ± 2.69 μ g g −1 ), Cd (1.72 ± 1.22 μ g g −1 ), Ni (14.95 ± 14.94 μ g g −1 ) and Pb (53.50 ± 40.09 μ g g −1 ). There was efficient mineralization process in the area. The texture of soil on the main dumpsite was loamy sand, which suggests that the ground water in the area is susceptible to contamination by surface pollutants. The texture of soil at the control site is sandy loam while sediment has the textural class of sand. Decomposed organic materials and agricultural activities influenced the texture of soils. The soils from the main dump and sediment were slightly alkaline while the control soil was moderately acidic. In both seasons, a significant variation exists ( P < 0.05) between the metal concentrations in soil at the main dump and those in the sediments with a positive correlation ( r = 0.572149) in the wet season and ( r = 0.956647) in the dry season. The presence of liming materials and activities of microorganisms on the waste dump increased the pH of the soils. The accumulation of nutrients results in the luxuriant growth of plants/crops on the waste dump.