Ccopi et al. 2026 — Heavy metal bioaccumulation in Peruvian Andean crops: irrigated vs rainfed systems
This study assessed concentrations and bioaccumulation factors (BAF) for 11 heavy metals (Cd, Pb, As, Cr, Hg, Ni, Cu, Zn, Mn, Fe, Mo) in 88 soil samples, 88 foliar samples from seven crop types (potato, broad bean/Vicia faba, maize, quinoa, barley, carrot, alfalfa), and 42 surface water samples collected in the Mantaro Valley (Junín Department, Peru) in February–March 2023, comparing irrigated and rainfed agricultural systems. The valley has a long history of contamination from mining, industrial, and urban discharges into the Mantaro River. Irrigated soils had higher and more homogeneous Cd, Pb, and As concentrations than rainfed soils. Several crops exceeded Codex Alimentarius limits for Cd, Pb, and As — especially potato and broad bean. Quinoa, broad bean, and potato showed BAF > 1 for Cd, Zn, and Mn, indicating active accumulation.
Key numbers
Foliar concentrations (mean ± SD, mg/kg) for selected metals and crops (Table 2 — irrigated I, rainfed R):
Cadmium (Codex max 0.2 mg/kg for vegetables):
- Potato I: 0.55±0.55, Potato R: 0.53±0.24 — both near/above Codex limit
- Quinoa I: 0.30±0.45, Quinoa R: 0.16±0.12
- Broad bean I: 0.33±0.19, Broad bean R: 1.52±0.95 — rainfed broad bean substantially above Codex limit
Lead (Codex max 0.3 mg/kg for vegetables and legumes):
- Potato I: 11.1±24.5, Potato R: 5.14±5.67 — both substantially above Codex limit
- Broad bean I: 4.30±7.36, Broad bean R: 2.79±1.99
- Quinoa I: 1.07±0.07, Quinoa R: 1.54±0.47
- Carrot I: 1.27±0.52, Carrot R: 0.15±0.09
Arsenic (Codex max 0.1 mg/kg for cereals/vegetables):
- Maize I: 0.41±0.39, Maize R: 0.83±0.87
- Broad bean I: 1.46±0.46, Broad bean R: 1.88±1.46
Soil Cd concentrations (Table 1, mg/kg):
- Alfalfa I: 0.12±0.03, R: 0.05±0.01
- Potato I: 0.98±1.59, R: 4.86±5.68
- Quinoa I: 0.69±1.48, R: 0.20±0.5
BAF > 1 (active accumulation) observed: quinoa BAF Cd, Zn, Mn; broad bean BAF Cd, Zn, Mn; potato BAF Cd, Zn, Mn. Maize and barley BAF < 1 for most metals (conservative absorption).
Irrigation effect: irrigation significantly increased soil Pb and Fe concentrations in potato soils (P=0.048); also associated with higher foliar concentrations of several metals in potato.
Methods (brief)
Sampling February–March 2023 (active growth stage). 218 georeferenced samples across the Mantaro Valley using regularized grid (2–5 km intervals): 88 soil composites (0–30 cm, 5 sub-samples each), 88 foliar composites (5 plants per location, aerial tissue), 42 surface water samples. Heavy metal analysis at LABSAF-Lima (INIA laboratory), using AAS with flame and graphite furnace atomization (INACAL-accredited). Methods: EPA-validated acid digestion for soil and plant tissue; ISO/IEC 17025 compliance. Recovery rates 85–115% for all certified reference materials. Statistical: non-parametric Wilcoxon (Mann-Whitney) for irrigated vs rainfed comparisons; PCA (FactoMineR); spatial analysis in QGIS.
Limitations
The Mantaro Valley is a historically contaminated region (mining discharges, industrial effluents); findings may not generalize to less-contaminated Andean agricultural zones or global quinoa production regions. Total arsenic reported (not speciated iAs). Sampling covers a single growing season (2023). The distinction between irrigated and rainfed systems conflates water quality effects with soil management differences. Foliar (aerial tissue) concentrations reported, not edible-portion concentrations; for root crops like potato and carrot, the edible tuber/root may differ substantially from the leaf concentration reported.
Implications
- Certification: Quinoa sourced from historically mining-contaminated Andean regions (particularly irrigated systems in the Mantaro Valley) may carry elevated Cd and Pb. This is directly relevant for any HMT&C quinoa sourcing standard and for geographic variance documentation. Carrot sourced from irrigated Mantaro Valley shows elevated Pb (1.27 mg/kg leaf) vs rainfed (0.15 mg/kg).
- Courses: Demonstrates that irrigation source water from mining-contaminated rivers is a significant driver of crop heavy metal uptake in Andean agricultural systems — relevant for supply-chain risk education.
- App: Note only — contamination_profile for quinoa (Cd, Pb) and carrots (Pb). Important caveat: foliar concentrations reported, not edible portion. Edible quinoa grain and carrot root would need separate data.
- Microbiome: Not applicable.