Spatial Variability and Pollution Loads of Selected Heavy Metals in Cocoa Plantation Soils in Cross River State, Nigeria

Abstract

Understanding heavy metal concentrations and their spatial variability is crucial for improved soil health and increased crop productivity. This study assessed heavy metal concentrations and their pollution loads in soils of cocoa plantations in Ikom, Etung and Boki Local Government Areas of Cross River State. Sixty (60) composite soil samples were collected from the area and analyzed Cd, Cr, Pb and Al. The results obtained revealed that Cd was above the maximum permissible limit for soil. Lead had means of 0.011 mg/kg, 0.02 mg/kg and 0.010 mg/kg, Cd had means of 1.53 mg/kg, 1.45 mg/kg and 1.25 mg/kg while Cr was 0.05 mg/kg, 0.03 mg/kg and 0.02 mg/kg Ikom, Etung and Boki respectively. The contamination factor for Cr and Pb was low (CF < 1) while Cd was considerably contaminated (3≤ CF < 6). The results of PLI indicated an unpolluted condition (PLI<1). Apart from Cd, the values of Igeo for Cr, Pb and Al fell in class ‘0’, indicating practically uncontaminated conditions in these areas. The soils of the area are safe for crop production but measures should be taken to reverse the trend of high concentration of Cd in the soils.