Air quality in post-mining towns: tracking potentially toxic elements using tree leaves

Abstract

In this study, leaves of the evergreen holm oak Quercus ilex were used to assess airborne contamination of potentially toxic elements (PTEs) at five towns located on the slopes of the Mt. Amiata (central Italy), an area with a long history of mining and, more recently, an important district for the industrial exploitation of geothermal energy. PTE composition and covariance of washed and unwashed Q. ilex leaves of three different ages (6, 12 and 24 month-old) were used to identify atmospheric inputs of PTEs at residential areas, evaluate long-term adsorption and retention of PTEs by the leaves, thus providing an indication of potential human exposure. Moreover, the determination of foliar concentrations of major elements (C, N, S and P) allowed an assessment of the nutritional status of the investigated urban tree stands which excluded the existence of stress condition caused by air pollution or other disturbances. Results indicated that overall Pb, Cu, and Cd concentration were low in the investigated urban sites, if compared with similar studies conducted in larger Italian cities, denoting a low contribution of vehicular traffic to the atmospheric pathway. The five urban settlements were characterized by a specific profile of elements (Al, Ba, Hg and Sb) enriched in unwashed leaves, resulting from the distinct geochemical characteristics of the area and from diffuse (i.e., urban activity) and point sources of PTEs emission (i.e., brownfields, geothermal power plants). The latter sources primarily govern the distribution of Hg, whose contamination was found to be very localized close to a major abandoned mining area. Our data provided quantitative evidence of the spectrum of PTEs potentially impacting resident population and may prove useful in support of follow-up instrumental monitoring campaigns of air quality, as well as for human health and ecological risk assessments. Graphical abstract

Tree-rings analysis to reconstruct atmospheric mercury contamination at a historical mining site

“…After this period of intense industrial activity, the mine experienced years of uninterrupted crisis which led to an unrelenting decrease in production, up to the complete closure in 1984. Hg contents in tree rings reflected well the reduction of Hg emissions linked to the crisis of the 1970s and indicated the actual levels of pollution, attributable to the abandoned mining-smelting plants (decade 2012-2022), currently under clean up for a complete remediation ( Monaci et al., 2023 ). Linden tree data ( Figure 3 ) show current levels of atmospheric Hg emission from the Abbadia S.S. mine site are at least twenty times lower than those of the years when the plant was fully operational.…”

Non-Lethal Assessment of Land Use Change Effects in Water and Soil of Algerian Riparian Areas along the Medjerda River through the Biosentinel Bufo spinosus Daudin

“…Consequently, the evaluation of ecosystem health can be reflected by the organisms inhabiting it [3]. Different biomonitors are reported in the scientific literature, in detail: earthworms, arthropods, and land snails for soil [4][5][6][7]; fish or aquatic macroinvertebrates for water [8,9]; lichens and moss for air [3,10,11]; and also microorganisms and vascular plants (i.e., bacteria, fungi, herbs, and trees) [12][13][14][15][16].…”