Pollution indices of heavy metal contaminants in typical agrarian soil samples in Ihiala, South-East Nigeria

Abstract

The contamination of soil with toxic metals poses serious threats to the survival of living organisms including humans. We determined the contamination levels of cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and nickel (Ni) in soil samples from a typical agrarian soil in Nigeria, using various single and complex geochemical indices along with principal component analysis (PCA) for source determination. Ten soil samples (S1-S10) were collected from depths of 20 cm, with a clean shovel and brush from farmlands in Ihiala, South-East Nigeria. Three single pollution indices: geoaccumulation index (Igeo), pollution index (PI) and ecological risk index (Er), as well as four complex indices: pollution load index (PLI), Nemerow pollution index (PINemerow), average single pollution index (PIave) and Potential ecological risk (RI) were used for the geochemical analysis. The mean soil levels of Cd (1.94ppm) and Pb (60.83ppm) exceeded their corresponding world averages. The results of the single pollution indices of the soil samples revealed heavy Cd, moderate Pb and low Ni, Cr and Cu contaminations, while the PIavg, PINemerow and RI graded the soil samples as moderately to seriously polluted. The correlation analysis revealed that the general contamination was mostly contributed by Cd and partly by Cr. The findings showed that Cd and Pb were the main heavy metal soil contaminants in the area. The levels of toxic metals found in the soils could pose health and ecological risks. The probable sources of these metals include pesticides use and poor waste disposal systems.