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

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.

Assessment of Contamination Potential of Groundwater Adjacent to the Waste Disposal Site at Khulna: Contamination Indices, Multivariate Statistics and Geostatistical Approach

This study aimed to evaluate the contamination potential of groundwater using various contamination indices available in the literature. To these attempts, fifteen groundwater samples were collected during rainy and dry seasons from the selected tubewells located nearby waste disposal site at Rajbandh, Khulna, Bangladesh. In the laboratory, the concentration of metal elements such as Fe, Mn, Cr, Cu, Pb, Zn, Ni, Cd, Na, K, Ca, As and Mg in groundwater were measured through stanadard methods. The contamination indices such as groundwater quality index (GWQI), degree of contamination (Cd), heavy metal evaluation index (HEI) and heavy metal contamination index (HPI) were used to quantify the level of contamination of groundwater. The values of GWQI, Cd, HEI and HPI of groundwater were found less in rainy season than that of dry season due to dilution of groundwater. GWQI reveals that 26.67% of tubewells yield very poor, while, 73.33% of poor water condition. The result of principal component analysis (PCA) indicates that As contamination in groundwater caused from anthropogenic activities, while, Na, Ca and Mg from natural sources. Pearson’s correlations indicates that most of the metal elements were in highly positive correlations with each other. The spatial distribution of various indices reveals that contamination of groundwater was found comparatively higher in the nearest tubewells and decreases in relation to the increasing of water sampling distances. The outcome of this study will further be helpful for other researchers to quantify the level of contamination of groundwater from tubewells. Journal of Engineering Science 12(1), 2021, 9-20

Status of soil heavy metals contamination using contamination indices in shallot fields

Monitoring and assessment of heavy metal concentrations in shallot fields are needed to evaluate the potential risk of contamination due to heavy metals. This study aims to define the status of heavy metal contamination in shallot fields using contamination indices. A total of 184 soil samples (0-20 cm) were taken from shallot fields in Brebes Regency, Central Java. The soil samples were analyzed for the concentration of five heavy metals (Cd, Pb, Ni, Cr, and Co) with HNO3 and HClO4 extracts and measured using AAS. Assessment of the status of heavy metals contamination in the soil using contaminant factor (CF), geo-accumulation index (I-geo), and pollution load index (PLI). The mean concentration in shallot fields showed the following order Cr > Ni > Pb > Co > Cd and the concentration were still below critical limit values. Four metals are Pb, Cr, Co, and Ni are low contamination (CF<1), while Cd is considerable until very high contamination factor. Based on I-geo values, shallot fields are practically uncontaminated of Pb, Co, Ni, and Cr (I-geo<1), meanwhile the status of Cd is uncontaminated to moderately contaminated (0<I-geo<1). Generally, the shallot fields in Brebes Regency, Central Java is unpolluted with five metals (PLI<1).