The occurrence of relevant amounts of potential toxic elements (PTEs) in the environment as a legacy of past extraction and metallurgical activities at decommissioned mining areas represents a worldwide concern, potentially posing a threat to ecosystems and human health. This aspect is strongly dependent on the mobility and bioavailability of PTEs once released in the environment (Favas et al., 2011). However, in addition to being sources of contamination, mine waste such as tailings ponds can potentially be a resource since they may still host notable amounts of various elements of economic interest such as those included in European Union’s list of Critical Raw Materials (CRMs) (Rosario-Beltré et al., 2023). This study is focused on the assessment of metal(loid) distribution and environmental impact related to past extraction activities on the soils at the Pb-Zn Raibl mining district (NE Italy), which ended in 1991. Concentrations of several PTEs (As, Cd, Fe, Pb, Tl, Zn) and CRMs (As, Ge, Mn, Sb) were determined on sub-surface samples of various solid matrices (soils, waste rocks, tailings) collected throughout the mining district. A single-step extraction with 0.5 M HCl solution was used to evaluate the labile fraction of PTEs, potentially more mobile and bioavailable in the environment. As expected, mine waste heaps, consisting of waste rocks and flotation tailings stored in tailings impoundments and scattered within the mining district, showed high concentrations of metal(loid)s (≤ 100 mg/kg for Sb, Cd and Ge; > 500 mg/kg for Tl and Mn; > 1,000 mg/kg for As; > 1 wt% for Zn; > 10 wt% for Fe and Zn). Notably low concentrations were found in samples collected upstream the former mine, which are considered representative of the natural background of the study area. Overall, the leachable metal(loid)s concentrations are well correlated with the total content, with the highest PTEs (i.e. Zn, Pb, Fe, Cd) values generally observed in unprocessed waste rock samples. The only exception is represented by Tl which showed the highest labile concentration in tailings (up to 255 mg/kg), confirming their potential impact on local water resources (Barago et al., 2023). However, the highest percentages of the metal(loid)s leachable fraction were generally found for soils with a greater organic matter (OM) content, due to the lower pH and the potential formation of soluble organometallic complexes during soil ageing. Considering that remediation of the en-tire area is not feasible due to the extension of the contamination, this potential in-creased in the mobility of PTEs as soil ages should be considered when evaluating appropriate management strategies aimed at limiting PTEs dispersion and impact on local ecosystems. These strategies may also include the reprocessing of mine wastes accumulated in tailings ponds, which could both reduce the risk to water resources and human health and to recover critical or strategic elements such as As or Ge. Fur-ther research is still ongoing with the aim of broadening knowledge on the residual content in CRMs and PTEs buried in tailings ponds and providing data to assess the feasibility of this approach. REFERENCES Barago, N., Pavoni, E., Floreani, F., Crosera, M., Adami, G., Lenaz, D., and Covelli, S., 2023. Hydrogeo-chemistry of thallium and other potentially toxic elements in neutral mine drainage at the decom-missioned Pb-Zn Raibl mine (Eastern Alps, Italy). Journal of Geochemical Exploration, 245, 107129. Favas, P.J.C., Pratas, J., Gomes, M.E.P., and Cala, V., 2011. Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity: environmental implications. Journal of Geo-chemical Exploration, 111, 160-171. Rosario-Beltré, A.J., Sánchez-España, J., Rodríguez-Gómez, V., Fernández-Naranjo, F.J., Bellido-Martín, E., Adánez-Sanjuán, P., and Arranz-González J.C., 2023. Critical raw materials recovery potential from Spanish mine wastes: a national-scale preliminary assessment. Journal of Cleaner Production, 407, 137163.
Environmental concerns and future perspectives related to the legacy of metal(loid) contamination in the vicinity of a dismissed Pb-Zn mining area (Raibl, NE Italy)
Floreani F.
;Pavoni E.;Marussi G.;Lenaz D.;Covelli S.
2025-01-01
Abstract
The occurrence of relevant amounts of potential toxic elements (PTEs) in the environment as a legacy of past extraction and metallurgical activities at decommissioned mining areas represents a worldwide concern, potentially posing a threat to ecosystems and human health. This aspect is strongly dependent on the mobility and bioavailability of PTEs once released in the environment (Favas et al., 2011). However, in addition to being sources of contamination, mine waste such as tailings ponds can potentially be a resource since they may still host notable amounts of various elements of economic interest such as those included in European Union’s list of Critical Raw Materials (CRMs) (Rosario-Beltré et al., 2023). This study is focused on the assessment of metal(loid) distribution and environmental impact related to past extraction activities on the soils at the Pb-Zn Raibl mining district (NE Italy), which ended in 1991. Concentrations of several PTEs (As, Cd, Fe, Pb, Tl, Zn) and CRMs (As, Ge, Mn, Sb) were determined on sub-surface samples of various solid matrices (soils, waste rocks, tailings) collected throughout the mining district. A single-step extraction with 0.5 M HCl solution was used to evaluate the labile fraction of PTEs, potentially more mobile and bioavailable in the environment. As expected, mine waste heaps, consisting of waste rocks and flotation tailings stored in tailings impoundments and scattered within the mining district, showed high concentrations of metal(loid)s (≤ 100 mg/kg for Sb, Cd and Ge; > 500 mg/kg for Tl and Mn; > 1,000 mg/kg for As; > 1 wt% for Zn; > 10 wt% for Fe and Zn). Notably low concentrations were found in samples collected upstream the former mine, which are considered representative of the natural background of the study area. Overall, the leachable metal(loid)s concentrations are well correlated with the total content, with the highest PTEs (i.e. Zn, Pb, Fe, Cd) values generally observed in unprocessed waste rock samples. The only exception is represented by Tl which showed the highest labile concentration in tailings (up to 255 mg/kg), confirming their potential impact on local water resources (Barago et al., 2023). However, the highest percentages of the metal(loid)s leachable fraction were generally found for soils with a greater organic matter (OM) content, due to the lower pH and the potential formation of soluble organometallic complexes during soil ageing. Considering that remediation of the en-tire area is not feasible due to the extension of the contamination, this potential in-creased in the mobility of PTEs as soil ages should be considered when evaluating appropriate management strategies aimed at limiting PTEs dispersion and impact on local ecosystems. These strategies may also include the reprocessing of mine wastes accumulated in tailings ponds, which could both reduce the risk to water resources and human health and to recover critical or strategic elements such as As or Ge. Fur-ther research is still ongoing with the aim of broadening knowledge on the residual content in CRMs and PTEs buried in tailings ponds and providing data to assess the feasibility of this approach. REFERENCES Barago, N., Pavoni, E., Floreani, F., Crosera, M., Adami, G., Lenaz, D., and Covelli, S., 2023. Hydrogeo-chemistry of thallium and other potentially toxic elements in neutral mine drainage at the decom-missioned Pb-Zn Raibl mine (Eastern Alps, Italy). Journal of Geochemical Exploration, 245, 107129. Favas, P.J.C., Pratas, J., Gomes, M.E.P., and Cala, V., 2011. Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity: environmental implications. Journal of Geo-chemical Exploration, 111, 160-171. Rosario-Beltré, A.J., Sánchez-España, J., Rodríguez-Gómez, V., Fernández-Naranjo, F.J., Bellido-Martín, E., Adánez-Sanjuán, P., and Arranz-González J.C., 2023. Critical raw materials recovery potential from Spanish mine wastes: a national-scale preliminary assessment. Journal of Cleaner Production, 407, 137163.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
