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Use of rockets ans spinach as indicators of metallic trace element bioavailability: Are pollution standards valid for plant and soil ?

par Vermeulen, Valentine
Président du jury Roisin, Yves
Promoteur Noret, Nausicaa ;Drouet, Thomas
Publication Non publié, 2023-09-06

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Résumé :

The multifactorial nature of trace metal bioavailability has long been established.However, current soil pollution standards still often exclusively rely on total soil concentrationsto establish target, clean-up and intervention thresholds. This can represent a risk for humanhealth in the context of vegetable cultivation in agricultural and urban areas. The aim of ourstudy was to assess the relevance of trace metal pollution standards and thresholds in evaluatinghealth risks associated with growing vegetables in contaminated soils. In this context, leafyvegetable biomonitors Spinacia oleracea (spinach), Eruca vesicaria, and Diplotaxis tenuifolia(rockets) were chosen to represent the highest risk of contamination through plant consumption.These three species were cultivated on a variety of soils displaying a range of contamination incadmium, lead, and zinc. The bioavailability values obtained in these vegetables were comparedto standardized chemical extractions according to current Belgian, German, Swiss, and Dutchstandards, as well as commonly applied chemical extractions. A second objective was to definethe soil variables involved in trace metal bioavailability to determine the ones that should beconsidered in soil pollution standards. Our results show a general inability of soil standards toassess Cd contamination risks for the studied leafy vegetables. Our findings also emphasize aweak relation between the individual extractants used, especially aqua regia, andconcentrations of Cd, Cu, Ni, Pb, and Zn in rockets and spinach. This confirms that consideringonly total concentrations in soils does not lead to consistent pollution standards for soils. Ourstudy also shows the significant influence of pH and organic matter content on foliar Cd andZn concentrations in rockets and spinach within the range of considered soils, which haveneutral to alkaline pH. Among the considered chemical extraction methods, DTPA-TEAextraction, coupled with pH and organic matter content, showed the best relationship with leafCd and Zn concentrations.