Gutiérrez et al. 2022 - Cadmium fractionation and cacao uptake in Ecuador

Gutiérrez and colleagues studied cadmium behavior in four Ecuadorian cacao farms after surface compost application. The paper is direct cacao-supply-chain evidence for cadmium mobility and mitigation rather than a finished-chocolate retail survey. It reports total soil Cd, compost rates, soil-fraction Cd, humic and fulvic acid-bound Cd, and correlations between soil Cd pools and cacao leaf and bean Cd.

Key numbers

The four cacao farms were in Manabi and Guayas provinces, Ecuador. Total soil Cd ranged from 0.37 to 0.92 mg/kg. The compost used in the trial contained 0.03 mg/kg Cd, and the treatment rates were 6.25 Mg/ha per year and 12.5 Mg/ha per year as described in Methods; Tables 2 and 3 label the low and high rates as 12.5 and 25 Mg/ha per year because farm 4 received two applications.

Table 3 reports Cd bound to humic acid and fulvic acid in micrograms per kilogram soil. Asterisks mark high-rate values that differed significantly from the control by Dunnett’s post-hoc test (p < 0.05) in the source table.

Across farms, the authors state that soil Cd distribution by sequential extraction generally followed EDTA > HNO3 > NaOH >> KNO3/H2O. Compost-amended soils tended to increase Cd bound to NaOH and EDTA fractions, and high-rate compost increased Cd bound to humic or fulvic acid pools in several farm-depth combinations.

For plant transfer, the authors report that leaf and bean Cd were negatively and significantly correlated with Cd extracted by EDTA, NaOH, HNO3, and fulvic-acid pools. In the below-surface (5-20 cm) correlation table, bean Cd was negatively correlated with soil organic carbon, NaOH-bound Cd, HNO3-bound Cd, and fulvic-acid-bound Cd. In the surface (0-5 cm) correlation table, humic-acid-bound Cd was positively correlated with both leaf and bean Cd (Cd-HA vs Leaf-Cd1 = 0.39, vs Leaf-Cd2 = 0.38, vs Bean-Cd = 0.36; all p < 0.05); the below-surface table does not reproduce that positive bean-Cd association. The main text does not print a simple per-farm cacao-bean Cd concentration table.

Methods (brief)

The trial used four cacao farms with three treatments: no compost, low compost, and high compost. Soil samples were collected at 0-5 cm and 5-20 cm. Leaf samples and ripe cacao pods were collected from each treatment; beans were digested from 300 mg aliquots. Soil Cd was fractionated into KNO3, H2O, NaOH, EDTA, and HNO3 extractable pools, with separate humic-acid and fulvic-acid extractions. Total soil Cd was quantified by ICP-OES; the KNO3, NaOH, and HNO3 sequential fractions plus the humic- and fulvic-acid fractions were quantified by graphite-furnace atomic absorption spectrometry; the H2O and EDTA sequential fractions were quantified by ICP-MS. Leaves and beans were quantified by ICP-OES for farms 1-3 and by ICP-MS for farm 4 after microwave-assisted digestion. Cacao-bean recovery was reported as 98.3 +/- 0.01% against FDA-CP36 across all farms, and 91.5 +/- 10.2% against NIST 2384 in the farm-4 cross-check. The coefficient of variation for replicate Cd measurements was 1.29% to 2.80% (average 2.04%) in beans, 2.09% to 2.75% (average 2.37%) in leaves, and 7.58% to 17.5% (average 11.5%) in soil.

Implications

Certification: This is Ecuador-market cacao supply-chain evidence for cadmium mitigation and soil-to-bean transfer, not a finished chocolate concentration distribution. It should support cocoa/chocolate cadmium routeability, mitigation evidence, and jurisdiction-specific context for Latin American cacao.

Courses: The paper is useful for explaining why cacao Cd risk is not only a finished-product testing problem. Soil pH, organic carbon, fulvic acid, humic acid, and compost quality can change the transfer pathway before beans enter chocolate manufacturing.

App: Ingredient-level cocoa and chocolate Cd risk should retain a geography and sourcing modifier for Ecuadorian cacao and for farms using validated Cd mitigation practices.

Wiki pages this source may touch

• Cocoa
• Chocolate
• Chocolate
• Cadmium

Verification notes

The PDF title, byline, DOI, journal, license, farm geography, treatment rates, analytical methods, total soil Cd range, compost Cd concentration, humus-fraction table values, recovery values, and correlation findings were read from the source PDF. The source reports total cadmium; it does not provide lead, arsenic, mercury, nickel, chromium, tin, aluminum, or uranium occurrence values. The main PDF text does not provide a simple cacao-bean Cd distribution table, so this page does not infer one.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.