Overview
This field study grew tomato, zucchini, lettuce, basil and several herbs in urban gardens in Bologna and at a rural site, and measured twelve trace elements, including lead, cadmium, arsenic and mercury, in leaf tissue and in leaf-surface washings by ICP-OES. It compared gardens 10 m and 60 m from a main road, a railway site, soil versus soilless growing and urban versus rural plots. Per-metal concentrations are tabulated only for tomato and zucchini leaves; the edible-crop results appear as summed metals in figures.
Key numbers
- Tomato leaves 10 m from the road: lead 0.28 and cadmium 0.20 mg/kg dry weight; at 60 m lead 0.40 mg/kg and cadmium below detection (Table 1).
- Arsenic and mercury were below detection in tomato and zucchini leaves at both distances (Table 1).
- Summed metals in tomato fruit were not changed by washing (mean 55.0 ± 2.6 mg/kg dry weight, data not shown; Section 3.4).
Methods (brief)
Leaves were oven-dried below 40 °C, ground in a titanium blender, digested with nitric acid and hydrogen peroxide in a microwave oven and read by ICP-OES. Accuracy was checked against CRM 060 (aquatic plants) and CRM 062 (olive leaves), run every 10 samples. Leaf washings gave a surface-deposition measure per leaf area.
Evidence Fitness
These are garden-grown experimental plants, not retail samples, and the tabulated values are for leaves of fruiting crops rather than the parts people eat. Edible-crop results exist only as summed metals in figures, so the findings store holds no food concentrations from this paper. It is useful as context for roadside growing, soilless culture and washing, but it gives no direct numbers for the non-root-vegetables page, which is therefore not linked.