Ecological risk assessment of heavy metals pollution on irrigated soil along Salanta River Valley, Kano State Nigeria

Abstract

This paper assessed the heavy metals pollution in irrigated soil of salanta river valley of Sharada industrial area with aim of assessing the potential ecological risk of Cd, Cu, Cr and Zn. Soil samples were collected from five plots randomly selected along the stream and heavy metals (Cd, Cu, Cr and Zn) and pH were analyzed using Atomic Absorption Spectrophotometer and pH meter respectively. The mean values and standard deviation of heavy metals in the study area shows that there is variation in the mean values among the heavy metal in the study area in which Cr recorded mean values of 2.30mg/kg ± 0.45, Cu 1.01 mg/kg ±0.78, Cd 3.02 mg/kg ± 0.66, Zn 26.4 mg/kg± 5.45 and mean pH 6.8 ± 0.51. The Cd, Cu and Zn were found below European regulatory values, the mean value of Cd (3.02mg/kg) is found above EU regulatory values (3.0mg/kg) and the pH value of the study area shows that the soil is slightly acidic and can influence the availability and solubility of the heavy metals in the area. The assessment also show that Cd (Pij,= 1.0), Cu (Pij,= 0.007) and Zn (Pij,= 0.088) are heavily polluted the soil of the area, and also slightly polluted with Cr (Pij,= 0.025). However, the potential ecological risk assessment show that Cr (Eri = 0.005) and Cu (Eri = 0.003) have low potential ecological risk in the area; Zn (Eri = 0.04) has moderate potential ecological risk while Cd (Eri = 0.088) is considerable potential ecological risk in the soil of study area. It was recommended that the industries should treat their waste water before  discharge and farmers should avoid using waste water directly, sewage sludge and effluent for watering and manure respectively.

Key words: Heavy metals, pollution, soil, ecological risk