Rarivoson et al. 2022 — Heavy metals in organic agricultural resources from Madagascar (soil amendment dataset)
A large dataset of 1,000 organic resource (OR) samples from Madagascar — including livestock manures (pig, poultry, cattle, rabbit, sheep), urban composts, and agro-industrial byproducts (bone, blood, cotton cake, peanut cake, tobacco ash) — was characterized by chemical analysis and VIS-NIR spectroscopy. Trace metal analysis (Cd, Cr, Cu, Pb, Ni, Zn) was performed on 39 samples by AFNOR standardized laboratory methods, revealing extreme variability: mean Pb 429 mg/kg DM (range <LOD to 3,982 mg/kg) and mean Cr 84 mg/kg DM (range 4.83 to 293 mg/kg), reflecting the mixed-origin and variable contamination of urban and agro-industrial waste streams used as soil amendments in Malagasy agriculture. The dataset is openly available via Cirad Dataverse (doi:10.18167/DVN1/YRMQ52) and is relevant to food-chain contamination via recycled organic materials as agricultural inputs.
Key numbers
- n=39 samples analyzed for trace metals (subset of 1,000 total)
- Zinc (Zn): mean 559 mg/kg DM, SD 576, min 39.38, max 2,220 mg/kg
- Copper (Cu): mean 109 mg/kg DM, SD 150, min 5.51, max 540 mg/kg
- Nickel (Ni): mean 23.29 mg/kg DM, SD 18.13, min 3.56, max 64.13 mg/kg
- Chromium (Cr): mean 84.18 mg/kg DM, SD 80.38, min 4.83, max 293 mg/kg
- Cadmium (Cd): mean 0.97 mg/kg DM, SD 0.81, min <LOD, max 3.28 mg/kg
- Lead (Pb): mean 429 mg/kg DM, SD 806, min <LOD, max 3,982 mg/kg
- Maximum Pb of 3,982 mg/kg DM is extremely elevated and is consistent with urban waste stream contamination (e.g., tobacco ash, mixed waste)
- All figures presented on dry matter (DM) basis
- Methods: AFNOR standardized laboratory methods; VIS-NIR spectrometer (LabSpec, ASD)
- Dataset includes 32 metadata descriptors per sample (origin, nature, farm type, animal feed, litter, age, bedding material)
Methods (brief)
Composite sampling from 5 districts in Madagascar; minimum 3 to 20 subsamples per site merged into composite. Samples dried and ground for both spectral and chemical analysis. Trace metals (Cd, Cr, Cu, Pb, Ni, Zn) measured following AFNOR standardized methods from 39 samples. VIS-NIR spectra acquired by LabSpec portable spectrometer (ASD, Boulder USA), standardized to XDS reference spectrometer (Foss) using chemometric transfer methods. Dataset deposited openly: https://dataverse.cirad.fr/dataset.xhtml?persistentId=doi:10.18167/DVN1/YRMQ52.
Implications
Certification: Documents that recycled organic materials (manure, compost, agro-industrial waste) applied to agricultural soils in Madagascar carry highly variable heavy metal loads, with some materials containing Pb at concentrations (up to 3,982 mg/kg DM) far exceeding EU soil amendment limits. Provides baseline for supply-chain contamination risk via organic fertilizer inputs, particularly for crops grown on land receiving urban or mixed-waste composts. Courses: Good example of how organic amendment quality control is essential in low-income country agricultural systems where urban and industrial waste streams may contaminate soil inputs. App: Provides context for soil-amendment contamination pathway in Malagasy-origin commodity risk profiles; relevant to cocoa, vanilla, and other Madagascar export crops.