Shanghai farm samples had lower reported lead and cadmium concentrations under hydroponic cultivation than conventional soil cultivation. The element-specific summaries combine four vegetables, while commodity-specific means combine lead with cadmium; neither split can be reconstructed into commodity-by-element concentrations from the preserved main paper.
Key numbers
| System | Element | Mean µg/kg | Median | Maximum | EDI µg/kg BW/day | THQ | Detected % | Paper exceedance % |
|---|---|---|---|---|---|---|---|---|
| hydroponic | Pb | 4.77 | 3.6 | 13.4 | 0.0192 | 0.00481 | 68.6 | 0 |
| hydroponic | Cd | 0.91 | 0.65 | 5.1 | 0.00367 | 0.00367 | 46.51 | 0 |
| conventional | Pb | 49.1 | 36.4 | 277 | 0.198 | 0.0495 | 79.12 | 1.1 |
| conventional | Cd | 11.5 | 8.48 | 33 | 0.0464 | 0.0464 | 81.32 | 0 |
Commodity-specific combined Pb+Cd means, conventional/hydroponic (µg/kg): lettuce 80.6/5.7; celery 51.3/3.2; cucumber 58.6/6.4; tomato 47.9/5.6. Soil lead (Pb)/cadmium (Cd): 13.02 ± 4.89 / 0.13 ± 0.02 mg/kg; hydroponic irrigation water: 0.036 ± 0.012 / 0.00017 ± 0.00008 mg/L (§3.3).
Methods (brief)
Fresh produce purchased directly from Shanghai farms in 2022–2023, vacuum freeze-dried for analysis. Pb and Cd measured by ICP-MS (Agilent 7500 CX); details refer to an earlier method. Means exclude results below LOQ (§2.5). Exposure model uses 242 g vegetables/day and 60 kg adult body weight. The preserved main PDF does not explicitly reconcile the reported concentration basis with freeze-dried preparation.
Implications
Supports a local cultivation-system comparison and the soil/irrigation pathway. It does not establish commodity-specific Pb or Cd distributions or universal hydroponic safety. Mixed-contaminant hazard indices include pesticides and phthalates; their interpretation remains source-reported.
Evidence Fitness: EF-2 for qualified comparative occurrence; EF-3 for the exposure model. Preserve summary statistics; require commodity-by-element data and basis clarification before narrower row admission.
Related evidence
- Lettuce
- Celery
- Tomato
- Cucumber
- Leafy / Green Vegetables, Other
- Non-Root Vegetables
- Irrigation water and soil amendments as anthropogenic inputs to cropland
- Lead
- Cadmium
Update history
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