Ecological Risk Assessment of Heavy Metals Concentrations in Topsoil of Makurdi and Its Environs

This work examined the concentrations of As, Cd, Cr, Hg and Pb pollution in soil and estimated the potential ecological risks of these metals in Makurdi and its environs, using established pollution indices. The information derived from pollution indices will help to assess the extent, and intensity of anthropogenic contaminant deposition on surface soil in the study area. The soil samples were collected from sixteen (16) locations across the investigated sites, sampled as appropriate and treated using established methods and analyzed using atomic absorption spectrometry (AAS). The findings have revealed that the concentrations of the metals in the topsoil samples were arranged in the sequence from increasing to decreasing order thus: Cr > Pb > Cd > Hg > As. It was observed that the pollution levels of As and Hg were insignificant, while, the level of pollution caused by Cd, Cr and Pb ranged from low level of contamination to high level of contamination across the investigated sites, except, for the control site (BZ) whose pollution level was insignificant with respect to the heavy metals studied. The results could be used as preliminary baseline data for heavy metal concentrations for future assessment and monitoring. Therefore, there is an urgent need to effect mitigation measures to reduce the ecological environmental risks, taking into consideration that human activities which are the main source of pollutants are still ongoing in the study area.

GIS Mapping, Biomonitoring and Distribution of Heavy Metal Concentrations Using Neem (Azadirachta indica) Bark in Makurdi Town, Benue State, Nigeria

The present work determined the concentration and spatial distribution of heavy metals (As, Hg, Cr, Cd and Pb) in soil samples from Makurdi and its environs using geographic information system (GIS). The specific objective is to produce the spatial distribution maps showing the spatial distribution of toxic heavy metals in the study area. Inverse Distance Weighting (IDW), a GIS technique was used to produce dotted maps showing the spatial distribution of heavy metals in neem bark for better visualization of contamination zones and non-contamination zones. The map reveals few hotspot areas showing areas of high concentrations of the heavy metals investigated which were identified in red colours, the following concentration ranges were obtained;As (4.71 - 6.43 mg/kg), Cd (13.9 - 16.84 mg/kg), Cr (46.3 - 60.84 mg/kg), Hg (3.70 - 5.05 mg/kg) and Pb (24.02 - 31.34 mg/kg). These hotspot areas were found close to business outlets, fuel filling and service stations, farm sites where the application of fertilizers and pesticides were persistent coupled with heavy traffic of vehicles and other machinery which was associated with As, Hg, Cd, Pb and Cr been released into the environment thus, suggesting anthropogenic activities controlling the concentration of these heavy metals in the study areas. The cumulative effect of these heavy metals into the barks of neem could pose as danger, because this plant is used as herbs in folk medicine.

Analysis of Selected Pesticide Residues and Heavy Metals in Honey Obtained from Plateau State, Nigeria

Honey bees derive their nutrients from nectars and other plant materials. These naturally available materials are affected by the residual presence of pesticides. The concentration of pesticides in honey comb then reflects the leftover after degradation. In this study, samples of honey were collected from five different farms in Plateau State and analyzed for pesticide residues (atrazine, cypermethrin) and heavy metals (Pb, Cd, Cr, Fe and Mn) using GC-MS and AAS techniques. Results of the analysis indicated that atrazine and cypermethrin were found in the range (0.01 - 0.36 and 0.11 - 0.26) mg/kg, respectively in all the samples. Mn and Fe were found across the samples while Cd was detected only in the sample obtained from Maraban Jos (0.0013 mg/kg). Except Bokkos and Maraban Jos, Pb was detected in other samples. This study revealed that all samples contained the selected pesticide residues above the maximum residue limits recommended by European Union, while concentration of heavy metals in all the samples except Mn was below the maximum concentration limits recommended by Food and Agriculture Organization. The high concentration of pesticide residues in the samples indicates contaminated environment in which the bees fed;therefore intermittent monitoring of the quality of honeys produced would be necessary as this calls for urgent attention.