Ahmed et al. (2019) sampled irrigation water, soil, and vegetables at three sites adjacent to a multi-industry zone (textiles, dyeing, garments, pharmaceuticals) in Gazipur District, Bangladesh, comparing dry and wet season concentrations for Cr, Cu, Zn, As, Cd, and Pb. The study’s central finding is that heavy metal concentrations in irrigation water and vegetables exceeded FAO permissible levels in both seasons, with dry-season values consistently higher than wet-season values due to dilution effects, and that vegetable contamination was driven by irrigation water absorption in the wet season but soil absorption in the dry season. All vegetables analyzed were declared unsuitable for human consumption on the basis of exceeding FAO limits for Cr, Zn, As, and Pb in both seasons, and Cd in the dry season.
Key numbers
Irrigation water (dry season means, mg/L; FAO permissible levels in parentheses):
- Cr: 1.1–3.2 (limit 0.1) — 11–32× over limit
- Cu: 1.8–6.85 (limit 0.2) — 9–34× over limit
- Zn: 12.8–17.5 (limit 2.0) — 6–9× over limit
- As: 0.44–0.63 (limit 0.1) — 4–6× over limit
- Cd: 0.007–0.023 (limit 0.01) — up to 2.3× over limit in some areas
- Pb: 0.58–2.04 (limit 5.0) — within limit
- Wet season (Bang. area): Cr 0.45, Cu 1.4, Zn 8.6, As 0.62, Cd 0.007, Pb 1.75 mg/L — all lower than dry season
Vegetables (dry season means, mg/kg; n=24 per area):
- Cr: 14.7–22.6 mg/kg (all three areas; FAO limit unstated in text but exceeded)
- Pb: 5.50–6.68 mg/kg (dry season)
- As: 1.01–1.43 mg/kg
- Cd: 0.299–0.392 mg/kg
- Zn: 59.9–66.8 mg/kg
- Wet season vegetables: Pb 8.10 mg/kg (Banglabazar wet, higher than dry in that area — consistent with different source pathway)
Bioconcentration factor (BCF) from soil to vegetable: mostly >20% in dry season for multiple metals.
Methods (brief)
ICP-MS (Agilent 7500ce) at Kyushu University Center of Advanced Instrumental Analysis. Soil digestion per US EPA 3050B; vegetable digestion at 120–130°C for 14–16 h with concentrated HNO₃. Irrigation water analyzed directly. Cluster analysis (hierarchical, SPSS v21) plus ANOVA and paired t-test for seasonal and area comparisons. Three industrial zones: Banglabazar, Kashimpur, and Chandra. Limitation: vegetables not speciated by type (mixed market vegetables from farms adjacent to the zone); no speciation of As.
Implications
Certification: This study documents extreme contamination from industrial wastewater irrigation, with vegetable concentrations far exceeding any certification threshold. It is relevant background for the certification program’s supplier sourcing criteria and irrigation water specification requirements. The seasonal difference is practically important: dry-season testing captures worst-case contamination, which should be the basis for supply-chain risk assessment.
Courses: Provides a dramatic case study of irrigation-water-to-food-chain contamination for use in supply chain and sourcing modules. The BCF >20% finding illustrates rapid soil-to-plant transfer under high-load conditions.
App: Supports flagging vegetables from known industrial zones or untested irrigation water sources as high risk. Jurisdiction-level flag for Bangladesh industrial zones is supported.