Overview
This greenhouse study characterized arsenic uptake and accumulation in two contrasting vegetable types — a fruit vegetable (bean, Phaseolus vulgaris) and a leafy vegetable (lettuce, Lactuca sativa) — across multiple developmental stages when irrigated with water containing 0.1, 0.25, and 0.5 mg As/L. Lettuce edible parts accumulated As concentrations of 0.30, 0.61, and 1.21 mg/kg DW at the three irrigation treatments respectively, substantially higher than bean fruits (0.008, 0.005, and 0.022 mg/kg DW), and the study found that health risks from As consumption were significant at all applied concentrations in lettuce.
Key numbers
Edible-part As concentrations (mg/kg DW) at irrigation levels of 0.1, 0.25, and 0.5 mg As/L respectively:
- Lettuce (mature): 0.30, 0.61, 1.21
- Bean fruit: 0.008, 0.005, 0.022
Transfer factor (TF = edible part / root):
- Lettuce young stage: 0.09–0.19 (control and 0.1 mg/L treatments)
- Bean flowering stage: 0.09–0.41 (all treatments)
Developmental stage effects:
- Lettuce As accumulation order: young > mature
- Bean As accumulation order: fruiting > young > flowering
The irrigation water threshold for comparison: WHO drinking water guideline 10 µg/L; FAO irrigation water threshold 100 µg/L; Hungarian groundwater geogenic As up to 220 µg/L.
Methods (brief)
Controlled growth chamber experiment (25–27 °C day / 17 °C night; 16 h lighting at 500 µmol/m²/s). Sodium arsenate (Na₂HAsO₄·7H₂O) dissolved in irrigation water. Plant samples digested with HNO₃ and H₂O₂; total As quantified by ICP-MS (Analytik Jena). Certified reference material NIST 1573a (tomato leaf) used for accuracy verification. All As measurements are total As (tAs); no speciation between inorganic and organic As was performed.
Implications
Certification: Lettuce is a high-risk vegetable for As accumulation from contaminated irrigation water; concentrations far exceed safe dietary intake thresholds under typical contaminated-irrigation scenarios. Relevant to supply-chain sourcing requirements for leafy vegetable ingredients.
Courses: Strong illustration of how irrigation water quality drives food-chain As exposure; the fruit-vs-leaf distinction is useful for teaching differential accumulation.
App: Lettuce contamination profile should note irrigation-water-source dependency; bean As is low even under high contamination scenarios.
Related evidence
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