Heavy metal status in cocoa (Theobroma cacao L.) soils and beans: the case of Abuakwa North Municipality of Eastern Region, Ghana.

Abstract

In recent times, public concerns over the potential accumulation of heavy metals in agricultural soils and crops due to the excessive use of agrochemicals are increasing. This study was conducted in the Abuakwa North Municipality of Eastern Region, Ghana, to assess the status of heavy metals in cocoa soils and beans. Cocoa farms aged between 10 and 20years and have received agrochemicals for at least 5years were selected, and their adjacent forests were used as controls. Soil samples and cocoa pods were collected randomly and processed for laboratory analysis. The study discovered that across the sampling sites, heavy metal concentrations in soil were below permissible limits. However, contamination factor and geo-accumulation index results revealed that Tontro cocoa farms were considerably contaminated and moderately polluted respectively with Cu, probably due to long-term fungicide application. The concentrations of Fe (39.3-47.1mgkg-1) and Zn (54.8-70.0mgkg-1) in the cocoa beans across the communities were below the FAO/WHO's safe limit of 99.4mgkg-1 and 73.0mgkg-1 respectively. Lead (0.03-0.06mgkg-1) and Cd (0.12-0.20mgkg-1) concentrations were below the EU's maximum allowable level and Codex Alimentarius Commission's limit of 1.0mgkg-1 respectively. However, bean Cu content in the Tontro farm (51.5mgkg-1) was slightly above the EU's recommended maximum limit of 50.0mgkg-1, possibly due to the continuous application of copper-based fungicides. The study showed that, overall, agrochemicals used for cocoa farming in Abuakwa North Municipality of Ghana did not cause serious harm to the soils and beans, since the mean metal concentrations were not alarming and guarantee public health safety.