This field study measured gallium in couch grass, plantain, dandelion, and the soil on their roots at two uncontaminated sites in St. Petersburg. Plants took up gallium, leaves held much less than roots, and concentrations in soil and roots changed during a single day. The plants are weeds, not foods.
Key numbers
- Site 1, mean ± SD, mg/kg after washing and air drying to constant weight (Table 1): rhizosphere soil 6.55 ± 0.33 (couch grass) and 7.32 ± 0.73 (plantain); roots 1.52 ± 0.45 and 0.46 ± 0.14; leaves 0.058 ± 0.010 and 0.14 ± 0.05. Leaf differences between species were statistically significant (p < 0.05). Because 1 mg/kg equals 1,000 µg/kg, the leaf means are 58 and 140 µg/kg.
- During a day, gallium in rhizosphere soil could change by 20 percent, and gallium in roots by more than two times (Results).
- The paper cites other work for 0.001 to 0.30 mg/kg in plants on uncontaminated soils, mostly crops such as rice and wheat, and 3 to 300 mg/kg in soils (Results; secondary).
- Certified reference materials BCR-060 (aquatic plant) and NIST 1573a (tomato leaves): differences between measured and certified or informative values did not exceed 10 percent (Methods).
Methods (brief)
Two experiments in 2019 and 2020. Samples were taken every 4 hours from 6:00 to 22:00, or every 5 hours from 9:00 to 19:00, with three to six plants per species at each collection. Plants were washed and dried at room temperature to constant weight, microwave digested in nitric acid, and analyzed by ICP-MS (Agilent 8900).
Evidence fitness
Supports measured gallium in wild plants and rhizosphere soil, low leaf concentrations relative to soil, and short-term variability. Does not support gallium levels in food crops or a dietary intake.
Limitations
Two small urban sites and one author. The cited crop and soil ranges are from other papers. The basis is air-dry weight, not fresh weight.
Related evidence
Update history
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