Index Model Assessment of Heavy Metal Pollution in Soils Selected from Three Irrigated Farm Sites in Fct Abuja, Nigeria

Abstract

The study was undertaken to examine the concentrations and health risk of heavy metals in soil from selected irrigated sites within Mpape River in FCT, Abuja. The study was carried out in dry seasons between 2015 and 2017 simultaneously from three irrigated farm sites. Heavy metal levels were quantified using Atomic Absorption Spectrophotometer (AAS). Other parameters were determined using standard methods. The levels of heavy metals in soils varied according to sites. The mean levels of Fe (24.82±0.89), Pb (3.34±0.65) and Zn (2.23±0.27) were significantly higher (P≤0.05) while Ni (0.39±0.19) was generally low. These values did not exceed the WHO/FAO,EU and USEPA permissible limits. However, soil bioavailable form recorded considerably higher concentrations in Fe (22.30±0.84), Zn (0.79±0.25) and Pb (0.79±0.28) while Ni (0.09±0.05) was lowest. Using contamination factor (CF) classifications; showed that soils from different irrigated farm sites along Mpape River were not contaminated by Fe, Zn, Ni and Pb. Pollution index was also (PLI = 0) indicating no pollution of the soil by heavy metals. Geo-accumulation index (igeo) values exhibited a zero category which shows that soils from various irrigated farm sites were unpolluted. Enrichment factor indicated extremely severe enrichment with respect to Pb (66-68.05), very severe enrichment was recorded for Zn (26.5) in farm B while Ni was found to be at very severe enrichment status in all the farms. The pollution index from all the farms were found to be in the low potential risk categories (<40) which suggested that the soils from all the farms do not pose any ecological health risk to the environment. The correlation results showed strong and positive relationship with Zn/Fe (0.959), Ni/Zn (0.978), Pb/Fe (0.970) and Pb/ Ni (0.990) and strong and negative relationship with Ni/ Fe (-0.988) and Pb/Zn (-0.976).The strong positive correlations in the soil samples is an indication that they have common source of pollution while the strong negative correlations observed is an attribute of different origin and sources of pollution load.