Discriminating foliar adhered from metabolised Pb when monitoring vegetation exposed to windborne contamination

• Published in: Journal of hazardous materials 2025-02, Vol.484, p.136807, Article 136807
• Main Authors: Tibbett, Mark, Lardner, Tim, De Oliveira, Vinicius H.
• Format: Article
• Language: English
• Subjects: Air pollution; Heavy metals; Lead; Leaf morphology; Particulate matter, soil, aeolian, dust particles
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.136807

Monitoring heavy metals in vegetation near mining or industrial sites is crucial for detecting plant contamination; requiring discrimination between metals adhered to foliar surfaces from the internal concentrations. We investigated key factors that might contribute to lead (Pb) accumulation in leaves of local vegetation near a Pb mine: (i) distance from the pollutant source, (ii) morphological characteristics of leaf surfaces, (iii) their susceptibility to Pb loss by washing, and (iv) the effect of contrasting washing reagents in Pb removal. Native plant species were sampled at three field locations, possessing different leaf surface morphologies: glabrous (smooth), resinous (waxy) and hirsute (hairy). After washing with Citranox, EDTA or deionised water, Pb contents were assessed by ICP-OES and SEM-EDX. We observed an order of Pb (and other metals) retention from hirsute > resinous > glabrous, and found: i) greater Pb accumulation in leaves near the mine due to particulate matter (PM) deposition; ii) hirsute leaves retain the highest PM-Pb; iii) higher Pb removal (10-fold) by Citranox and EDTA compared to water; and iv) hirsute leaves retained considerable PM-Pb underneath trichomes despite washing, leading to Pb overestimation. Therefore, for accurate Pb monitoring, washed glabrous leaves are best indicated due to their negligible PM retention. [Display omitted] •Pb retained on leaves of plants and can be wrongly assessed as metabolised Pb.•Foliar morphology is critical in Pb entrapment and retention in leaf surfaces.•Citranox washing can be 10 times more effective in surface Pb removal than water.•Hirsute leaves retain Pb-bearing minerals beneath trichomes, even after washing.•Glabrous leaves are best for monitoring internal Pb due to lower dust retention.