Assessment of Level of Heavy Metal in Soil and Their Environmental Effects from Three Mechanic Villages in Abuja

ABSTRACT

This research work is aimed at assessment of levels of heavy metals in soils and their environmental effects from three Mechanic Villages in Abuja namely; Apo, Kugbo and Zuba. To achieve the set target, soil samples were collected from five sampling points in each of the mechanic villages to a depth range of 0 - 15 cm with a stainless hand-dug auger. A control sample was also taken from a point of approximately 100 km where neither industrial nor commercial activities take place. Results of analyses of physicochemical properties: pH, % porosity, electrical conductivity, particle size distribution, sulphate, chloride, nitrate and microbial contents of the soil samples indicate that most of the values exceeded those of control values. Levels of heavy metals in soils were determined using Automated Atomic Absorption Spectrophotometer (AAS). Results of the analysis revealed a decreasing in trend of heavy metal contents (mg/kg) in soil in the three studied automobile repair sites as follows; Apo site: Cu (7668) > Zn (5360) > Cr (1174) > Fe (467) > Pb (333) > Ni > (196) > Cd (10.6); Kugbo site: Zn (1587) > Cu (1043) > Cr (783) > Ni (234) > Fe (217) > Pb (170) > Cd (9.47) and Zuba site: Zn (1190) > Cr (767) > Cu (512) > Fe (279) > Pb (250) > Ni (127) > Cd (10.4). Comparative analysis reveals that values of the studied heavy metals exceeded those of control and background values of some international regulatory bodies. Pearson’s correlation analyses reveal that some of the heavy metals had very strong correlations with one another and with some of the physicochemical properties of the soil. These indicate that the studied heavy metals have the same origin, mutual dependence and identical behaviours. Multiple ecological risk indices models explored in the study showed various ecological risk levels associated with heavy metal contamination of soils from the investigated sites with classes ranging from low to very high ecological risks. This could be traceable to anthropogenic activities like the indiscriminate discharge of heavy metal-containing waste in soil and poor waste management practice in the mechanic villages. This calls for urgent measures in curtailing indiscriminate waste discharge and the introduction of environmental friendly waste management in the mechanic villages so as to avert epidemics and environmental degradation due to heavy metal pollution.