Heavy Metals Contamination in Water, Soil and Plant Samples of Okomu National Park, Edo State, Nigeria.

Abstract

The pollution of the environment with a wide range of contaminants has become a matter of great concern over the last few 
decades. Heavy metals are considered to be one of the main contaminants in the environment, since they have a significant effect 
on ecological quality. They have the capability to move from contaminated soils and water and bioaccumulate in plant species 
that herbivores ingest causing health risks to various organisms in the food chain as a result of bioaccumulation. This study 
therefore assessed the levels of heavy metals in water, soil and plant samples of Okomu National Park, Edo State, Nigeria. Water 
samples were collected by grab sampling while top soil (0-15 cm) and plant samples were collected randomly. Samples of water 
(8), soil (8) and plant (6) were collected for two seasons (dry and wet) and analysed for heavy metals: Copper (Cu), Nickel (Ni), 
Chromium (Cr), Zinc (Zn), Iron (Fe), Lead (Pb), Manganese (Mn) and Cadmium (Cd) using Atomic Absorption 
Spectrophotometer after wet (acid) digestion. Data collected were subjected to descriptive (mean, standard deviation) and 
inferential (T-test) statistics using Statistical Package for Social Sciences with statistical significance set at α0.05. The mean values 
of heavy metals in the water samples revealed that all the heavy metals analysed (except Cu and Zn) were above the WHO 
guidelines for drinking water. The level of Cd in the soil samples was higher than the comparable maximum allowable limit 
while the mean values of all the analysed heavy metals (except Zn) in the sampled plant species were above the comparable 
WHO permissible limit. Significant seasonal variation in the concentration of heavy metals was observed in the study as there 
was more metal contamination in all the analysed samples during the wet season. The concentrations of analysed heavy metals 
and influence of seasonal variation observed in this study may have negative implication on wildlife health within Okomu 
National Park. As such, there is need to carry out the study (in sediments inclusive) over time so as to monitor heavy metal 
deposition and route of exposure in the park.