Copper and Zinc Pollution in Cocoa Growing Areas in a Low-income Country

Abstract

The application of copper-based fungicides and inorganic fertilizers affects the integrity of the soil which can result in bioaccumulation of copper and zinc in the cocoa beans to levels that are of public health concern. Cocoa farmers over the years have applied these agrochemicals in the control of pets and disease. The concentration of copper and zinc in soils and cocoa beans in the East Akyem municipality was then determined. Soil pH was measured with a pH meter with a glass electrode using a 1:2.5 soil: water ratio whiles Walkley-black method was used to determine Organic Carbon. Copper and Zinc in the soil were extracted using Mehlich-3 Extractant. The concentrations were determined using Atomic Absorption Spectrometer (Spectra AA 220 FS model). Cocoa beans samples were acid digested and Varian AA-240FS was used to determine the concentration of Copper and Zinc. Pollution Indices was used to quantify the pollution status of the soil. The mean concentration of Cu and Zn at depth 0-15cm was generally higher than at depth 15-30cm.The concentration of Cu and Zn were higher in the cocoa farm soils than that of the control farms. Soil acidity was found to increase with decreasing Organic matter. However, the Cocoa beans were not polluted with Cu nor Zn as their concentrations were found within the permissible limits. Pollution Index analysis suggest agrochemicals to have serious impacts on the farm soil. The soil-cocoa bean correlation matrix reveals that the concentration of Cu and Zn in the cocoa beans depends on the amount in the soil.

Keywords: Ghana, Cocoa, Pollution, Copper, Zinc, Agrochemicals