France: Growing Low Lead Vegetables While Cleaning Garden Soil

Study in Nantes, France found certain veggies like tomatoes and beans grow safely in lead-contaminated soil

By Jenn Hoskins
Natural Science News
5th April, 2024

Excerpt:

A recent study conducted by researchers from Nantes Université, Université d’Angers, Le Mans Université, and CNRS has shed light on this issue[1]. The research aimed to explore a cropping system that could produce safe-to-eat vegetables and simultaneously cleanse the soil of lead through a process called phytoextraction.

Phytoextraction involves using plants that can absorb contaminants from the soil and store them in their tissues. The idea is to harvest and dispose of these plants, thereby gradually removing the contaminants from the environment. The study took place in an allotment garden in Nantes, France, where the soil is known to be moderately enriched with geogenic lead.

The scientists selected four vegetables with a known low propensity to accumulate lead: tomato (Solanum lycopersicum), cabbage (Brassica oleracea cv. “Capitata”), potato (Solanum tuberosum), and bean (Phaseolus vulgaris). Alongside these, they planted Brassica juncea L., a species previously identified for its potential to accumulate lead from the soil[2].

The results were promising for urban gardeners. The analyses confirmed that the edible parts of the four vegetables contained minimal levels of lead, suggesting that they can be safely grown in moderately contaminated soils. However, the lead uptake by Brassica juncea was insufficient for effective phytoextraction, with the highest concentration reaching only about 1 mg/kg of dry matter.

This finding echoes earlier research which found that washing vegetables before consumption is an effective way to reduce exposure to certain contaminants[3]. While washing can significantly decrease the presence of lead on the surface of the vegetables, it is less effective for elements that are taken up by the plant and incorporated into its tissues. The study also reinforces the notion that the bioconcentration factors, which indicate how readily a plant will absorb a contaminant from the soil, are crucial in determining the effectiveness of washing and the potential risk of exposure[3].

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