Abstract
The status of heavy metal contamination of surface soils in two cocoa plantations of approximately 30 years in Cameroon was evaluated. The bioavailable fractions of Fe, Cu, Zn, Cd and Cr were used to assess the extent of heavy metal contamination using a selection of contamination indices. In addition, other physicochemical properties including organic matter, particle size, CEC and pH were assessed. One of the farms was dominated by sand (64.56 - 73.46% sand) in contrast to the other (2.56 to 37.51%) and the latter had a higher clay content. The order of abundance of heavy metals, as expressed by the mean values, is as follows: Fe > Cu > Zn > Cr > Cd in soils from the two areas. Contamination factors of Cu-, Zn- and Cd are considerable for clay-dominated soil. The potential ecological risk of the metals in both soils was low with the exception of Cd in the clayey soil. Results for hazard assessment showed Cu levels were within the low ISQC sediment criteria in the clay-dominated soil; possibly linked to the long-term application of Cu-fungicide. Key words: Heavy metal, contamination indices, cocoa plantation, Cameroon.
Highlights
In Cameroon, like in many other developing countries, agricultural practices rely heavily on agrochemicals to prevent and/or control the crops threatening diseases (Emoghene and Futughe, 2016)
The present study evaluates the status of heavy metal contamination in the surface soils of approximately 30 years old cocoa plantations
In fluvial and alluvial soils, the redistribution of heavy metals within fractions occurs relatively quickly; it is not retained in the exchangeable fraction, which considerably decreases the risk of its mobility and inclusion into the food chain
Summary
In Cameroon, like in many other developing countries, agricultural practices rely heavily on agrochemicals to prevent and/or control the crops threatening diseases (Emoghene and Futughe, 2016). Cocoa production is threatened by a range of pests and diseases. In Cameroon, among the most common and highly destructive cocoa pests are mirids (Bisseleua et al, 2011; Babin et al, 2010), which could be responsible for between 30 to 70% of cocoa yield losses (Anikwe et al, 2009). The emergence of climate change as a global environmental problem conspicuously undermines cocoa productivity with persistent droughts coupled with outbreak of pests and diseases (Oyekale, 2017).
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