Abstract
Mining activities are one of the main contributors to metals contamination of soils, most often due to the inappropriate management of the mining residues. In Italy, hundreds of small mining sites are scattered around the mountainous areas, near small villages with fragile environments. Here, wastes and residues may have polluted the surrounding soils and become a threat to living organisms. We investigated two dismissed sites in Northern Italy with extractive wastes in unmanaged areas close to villages using bioaccessibility and size fractionation methods, focussing on particles that can potentially be eroded and/or ingested (< 10 µm and < 200 µm). In the Campello Monti site, Co, Cu and Ni showed high values in soils near the landfills, with the highest concentrations in the < 10 µm particles around the landfills and along the valley bottom. Lead and Ni were the most bioaccessible metals. In the Plassa site, Cd and Zn were the most important contaminants, with an average content of 118 and 34,000 mg/kg. They originated from mining wastes scattered through the slope and had a particularly high bioaccessible fractions, close to the 100% for Zn and above 80% for Cd in the fine particles. The study of the fine, more reactive and mobile particles offered a close insight into the lability of contaminants, as in both sites, a dispersion of metal contaminants through very fine particles in surrounding and downhill areas was observed, resulting in an increased risk to all living organism and for the environment.
Highlights
The extraction of metals for technological applications has had a considerable impact on the environment in terms of pollution, constituting one of the most important sources of localized metal contamination of soils (Alloway 2013)
Soil contamination around dismissed mines has been recently described throughout the world, e.g. in Tunisia (Khelifi et al 2019), France (Courtin-Nomade et al 2016), Spain (García-Carmona et al 2017), Czech Republic (Weissmannová et al 2019), Colombia (González-Martínez et al 2019) and China (Li et al 2014; Zhu et al 2019)
In Campello Monti (CM), the soils were acid (Table 1), ranging between ultra-acid and moderately acid (Soil Science Division Staff 2017). This could be ascribed to the leaching of the basic cations by the high precipitation, as there was no difference between the control soils (CM0102) and the rest of the samples
Summary
The extraction of metals for technological applications has had a considerable impact on the environment in terms of pollution, constituting one of the most important sources of localized metal contamination of soils (Alloway 2013). Soil contamination around dismissed mines has been recently described throughout the world, e.g. in Tunisia (Khelifi et al 2019), France (Courtin-Nomade et al 2016), Spain (García-Carmona et al 2017), Czech Republic (Weissmannová et al 2019), Colombia (González-Martínez et al 2019) and China (Li et al 2014; Zhu et al 2019). Due to the less than optimal management of the exploitation process in the past, and to the frequently abrupt ending of the mining activities, residues were often abandoned onsite and may have polluted the surrounding soils and water (Courtin-Nomade et al 2016; González-Martínez et al 2019).
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