Evaluation of Heavy Metals and Contamination Status of Soil around Abandoned and Active Nigerian Dumpsites

Abstract

Aim: The study evaluated the heavy metals and contamination status of soil around active and abandoned waste dumpsites in Port Harcourt Metropolis, Nigeria. Methodology: Five soil samples were collected at the topsoil (0-15cm depth) in a regular distance of 20m, 40m, 60m, 80m and 100m from the center of the dumpsites and control plot. The soil samples were analysed for heavy metals (Cu, Cr, Cd, Fe, Pb and Zn), pH and total Organic C (TOC) using standard laboratory analyses and contamination indices to determine the soil contamination status. Descriptive statistics involving mean and standard deviation were used for the data analysis. Results: The mean concentrations of Cu, Cr, Cd, Fe, Pb and Zn in active dumpsite was 3.2616mg/kg, 0.3983 mg/kg, 0.2027 mg/kg, 6.5785 mg/kg, 2.6991mg/kg and 12.4111mg/kg respectively while that of the abandoned dumpsite are 1.3913mg/kg, 0.3693mg/kg, 0.0882mg/kg, 3.6235mg/kg, 0.4158mg/kg and 4.0140mg/kg respectively. Hence, the soil samples in both dumpsites exceeded the allowable limit of World Health Organisation (WHO). The order of heavy metal concentrations in the dumpsites was Zn>Fe>Cu>Pb>Cr>Cd. The contamination factor of the heavy metals follows order: Pb > Cu > Cr > Zn > Fe for both dumpsites. The degree of contamination ranged from (1612.51 to 2286.83 for active dumpsite and 26.14 to 641.46 for abandoned dumpsite) indicating very high degree of contamination. Modified degree of contamination ranged from 46.09 to 381.14 for active dumpsite indicating “ultra-high degree of contamination” and 4.36 to 106.91 for abandoned dumpsite indicating high degree of contamination to ultra-high degree of contamination. Pollution Load Index ranged from (5.08 to 8.12 for active and 1.63 to 4.16 for abandoned dumpsite) indicating polluted soil with various heavy metals.   Conclusion: the concentration of heavy metals combined with the contamination indices revealed that the soils around the dumpsites are contaminated/polluted; hence, pose ecological and health-related risk.