Relación de los niveles de cadmio en raiz, hojas, testa y almendra de cultivares de theobroma cacao l

Abstract

The high concentration of cadmium (Cd) in cocoa beans above the critical level (0.5 mg/kg) has given rise to serious concerns as it is associated with chocolate consumption in human health. The accumulation of Cd in cocoa beans in Ecuador has been linked to soil contamination. From this point of view it is of vital importance to look for mitigation strategies for this heavy metal Cd. With the exposed the objectives were: a) to characterize the chemical properties of the soils where cocoa samples were taken for the study, b) to determine the level of cadmium (Cd) in leaves, testa and almond in the cocoa culture, c) to correlate the levels of Cd with the properties of the soil for the sites Shumiral and Rio Bonito. Two cocoa farms were selected for this purpose. F1 (National) and F2 (CCN51). In this work samples were taken where the approach directed towards the plant organs (root, leaf, testa and almond) was used to identify the relation of the levels of Cd present in these tissues and correlate them with the concentration of Cd in each sampling point and also the analysis of the chemical and physical properties of the soil was carried out to correlate the nutrients with the content of total Cd for each sample. The analysis for the determination of Cd was carried out by means of an acid digestion of plant tissues by means of the atomic absorption method in the laboratory. The statistical analysis was carried out by means of descriptive analyses (mean, standard deviation, maximum and minimum values). Pearson's correlation of the cadmium levels of each sample and the macro and micro nutrients present in the soil of each farm, considering the maximum probability of error of 0.05. The general average of CE of F1 was 0.33 dS/m ±0.07 and in F2, 0.16 dS/m ±0.03, but both with a low standard deviation which indicates a low presence of salts. On the other hand, the average pH in F1 was 6.19 in relation to F2, 4.46. In this way the pH is the main factor for the availability of the metals in the plants since most of them tend to be more available in acid pH and when a decrease of the same one takes place it benefits to the absorption of Cd by the roots towards all the plant. The results indicated that the levels of Cd according to the averages obtained in both farms are higher than the maximum level allowed, determining levels in F1, in leaf (0.79 mg/kg ±1.19), almond (1.15 mg/kg ±0.32) and shell (1.97 mg/kg ±0.48), in F2; they were in leaf (2.59 mg/kg ±1.48), almond (1.21 mg/kg ±0.46) and testa (3.30 mg/kg ±0.81). Given these results according to studies several mitigation techniques are recommended to reduce the levels of Cd, a main one to immobilize the Cd in the soil, since from here it enters the plant contaminating all its organs and in particular the almond with which the chocolate is elaborated, is to increase the levels of Zn and Mn, in view that when there is deficiency of these micronutrients the Cd tends to enter much faster to the plant and therefore to the cocoa bean. For this reason the present work was carried out in an environment exposed to possible sources of contamination such as in this case mining.