Soil properties and agronomic factors affecting cadmium concentrations in cacao beans: A nationwide survey in Ecuador

Abstract

Recent cadmium (Cd) regulation in chocolate threatens the sustainability of cacao production in Southwest America. Cadmium contamination in cacao beans has not been assessed at a country level. A nationwide survey was conducted in Ecuador to identify the spatial distribution of Cd in cacao beans, as well as soil and agronomic factors involved. Paired soil and plant samples (pods and leaves) were collected at 560 locations. Information on agronomic practices was obtained through a prepared questionnaire for farmers. Total soil Cd averaged 0.44 mg kg which is typical for young and non-polluted soils. Mean Cd concentration in peeled beans was 0.90 mg kg and 45% of samples exceeded the 0.60 mg kg threshold. Bean Cd hotspots were identified in some areas in seven provinces. Multivariate regression analysis showed that bean Cd concentrations increased with increasing total soil Cd and with decreasing soil pH, oxalate-extractable manganese (Mn) and organic carbon (OC) (R = 0.65), suggesting that Cd solubility in soil mainly affects Cd uptake. Bean Cd concentration decreased a factor of 1.4 as the age of the orchard increased from 4 to 40 years. Bean Cd concentration was inconsistently affected by genotype (CCN-51 vs. Nacional), pruning or application of fertilizers. It is concluded that the relatively larger bean Cd concentrations in Ecuador are related to the high Cd uptake capacity of the plants combined with their cultivation on young soils, instead of Cd depleted weathered soils. Mitigation strategies should consider the application of amendments to modify such soil properties to lower soil Cd availability. There is scope for genetic mitigation strategy to reduce bean Cd, but this needs to be properly investigated.

Cadmium isotope fractionation in the soil – cacao systems of Ecuador: a pilot field study

“…[4][5][6][7][8][9][10][11][12][13] In these regions, the Cd concentrations of beans commonly exceed 0.6 to 0.8 mg kg À1 , 14 which is the approximate upper range for manufacturing cocoa products that are in accord with the new EU regulations. 8,15 For example, a recent study of more than 500 farms in Ecuador revealed that nearly 50% of the cacao beans had Cd concentrations that exceeded 0.6 mg kg À1 . 15 For Ecuador and other affected countries, these thresholds may have grave economic consequences, whereby the numerous small-hold farmers and their families, which grow and harvest the cacao beans, might be most severely affected.…”

“…8,15 For example, a recent study of more than 500 farms in Ecuador revealed that nearly 50% of the cacao beans had Cd concentrations that exceeded 0.6 mg kg À1 . 15 For Ecuador and other affected countries, these thresholds may have grave economic consequences, whereby the numerous small-hold farmers and their families, which grow and harvest the cacao beans, might be most severely affected.…”

“…16,17 In comparison to other food crops, however, cacao plants commonly take up signicantly more Cd, such that they have been termed a Cd 'accumulator'. 6,15 Whilst the ultimate causes of Cd enrichment in beans remain unclear, the issue is of particular relevance, as the development of feasible mitigation strategies requires a better understanding of both natural and anthropogenic Cd sources and of the mechanisms that govern Cd uptake by cacao as well as transfer and accumulation of the element within the plants.…”

Evaluación del contenido de metales pesados en almendras de cacao (Theobroma cacao L) durante el proceso de beneficiado

“…En lo que concierne, a la presencia de metales pesados como Cd +2 en las almendras de cacao, estudios realizados por Mite, et al (2016); acotan que este factor puede deberse potencialmente a la incineración de residuos sólidos urbanos, uso de lodos residuales urbanos en las labores agrícolas, agroquímicos, abonos orgánicos sin compostar. Otros estudios realizados a granos secos de cacao se encontraron que en siete provincias de Ecuador las concentraciones de Cd +2 son de 0,90 ppm (Argüello, et al, 2018). El contenido promedio de Cd +2 encontrado en este estudio en la almendra de cacao seco (0,95 ppm) está por debajo a los de 1,1 ppm (Gramlich., et al, 2018) Para establecer un análisis comparativo de los niveles de Cd +2 y Pb +4 reportados en la presente investigación con el Reglamento (CE) Nº 1881/2006, tenemos que para el caso de Cd +2 lo valores permitidos son de 0,3 ppm para chocolates con 30% de cacao y 0,8 ppm para chocolates con 70% de cacao (Figura 6).…”

Concentration, Source, and Total Health Risks of Cadmium in Multiple Media in Densely Populated Areas, China

“…At present, soil cadmium pollution has become a serious global environmental problem [7][8][9][10]. Cadmium pollution is found to varying degrees in the soils of Asia [2,9,11,12], North America [13,14], and Europe [10,15]. Cadmium appears in the soil after dissolution, condensation, chemical reaction, adsorption, complexation, and other reactions, thus affecting the migration and transformation of Cd in plants [16][17][18].…”