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Title: Heavy metal accumulations in cacao (Theobroma cacao L.) leaves and cocoa beans grown at three main cacao growing regions of Peru

Author
item AREVALO-GARDINI, E - Tropical Crop Institute (ICT)
item AREVALO-HERNANDEZ, CI - Tropical Crop Institute (ICT)
item Baligar, Virupax
item HE, Z - University Of Florida

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2017
Publication Date: 7/20/2017
Citation: Arevalo-Gardini, E., Arevalo-Hernandez, C., Baligar, V.C., He, Z. 2017. Heavy metal accumulations in cacao (Theobroma cacao L.) leaves and cocoa beans grown at three main cacao growing regions of Peru. Science of the Total Environment. 17(2):410-428.

Interpretive Summary: Peru is one of the leading exporters of organic cacao beans and success of export significantly influenced by quality of cacao beans. However, the accumulation of heavy metals in cacao beans represents a considerable problem for the cacao bean quality. Accumulation of these heavy metals in cacao beans results in considerable reduction in market value of this crop and drastically affects the economic wellbeing of resource poor cacao farmers. In this paper we report the range of heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) concentrations in leaf and beans of cacao grown on 70 farms in northern and central regions of Peru. The results show that the mean values of heavy metals with exception of Cd in leaf and bean samples were below the critical limits; however high levels of Cd in bean and leaf samples were found in cacao grown in Amazonas, Piura, San Martin, and Tumbes, districts of Peru. This information will be of use to farmers to avoid these regions with high levels of soil Cd. A better understanding of soil chemical properties and levels of these heavy metals will help to reduce their toxic levels in cacao beans.

Technical Abstract: Peru is one of the leading exporters of organic cocoa beans in the world. However, the accumulation of heavy metals in cacao beans represents a considerable quality problem. The aim of this study was to investigate the distribution and accumulation of heavy metals in cacao plants grown at three different cacao growing regions of Peru. The study was conducted in cacao plantations with trees ranging from 10 to 15 years old located in multiple districts in three regions of Peru: North (Tumbes, Piura, Cajamarca, and Amazonas); Center (Huánuco, San Martin and Junín) and South (Cuzco). Samples of leaf and cacao beans were collected from 70 cacao plantations, and at each location, the cacao genotype or variety sampled was recorded. The concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn in the leaves and beans were determined by atomic absorption spectrophotometer. Heavy metals assessments were below critical limits except for the presence of high levels of Cd in cacao grown in these districts Amazonas, Piura, San Martin, and Tumbes. Genotypic differences for high and low levels of Cd accumulation in cacao leaves and cacao beans could be exploited by grafting plants to reduce Cd risks. When correlating concentration of trace elements in leaves and beans, significant effects were found, indicating that the use of Zn for Cd mitigation is not advisable, and care should be taken with Zn deficiencies and high Mn and Ni applications.