Evolution of the Speciation and Mobility of Pb, Zn and Cd in Relation to Transport Processes in a Mining Environment

Intissar Elmayel, José María Esbrí, García-Ordiales Efrén, Eva-María García-Noguero, Zouhair Elouear, Bouzid Jalel, Alessandro Farieri, Nieves Roqueñí, Pablo Cienfuegos and Pablo Higueras
Additional contact information
Intissar Elmayel: Laboratoire Génie Environnement Ecotechnologie, Ecole Nationale d’Ingénieurs de Sfax, Université de Sfax, 3038 Sfax, Tunisia
José María Esbrí: Departamento de Ingeniería Geológica y Minera, Instituto de Geología Aplicada, Universidad de Castilla-La Mancha, 13400 Almadén, Spain
García-Ordiales Efrén: Departamento de Explotación y Prospección de Minas, Escuela de Ingeniería de Minas, Energía y Materiales de Oviedo, Universidad de Oviedo, 33004 Oviedo, Spain
Eva-María García-Noguero: Departamento de Ingeniería Geológica y Minera, Instituto de Geología Aplicada, Universidad de Castilla-La Mancha, 13400 Almadén, Spain
Zouhair Elouear: Laboratoire Génie Environnement Ecotechnologie, Ecole Nationale d’Ingénieurs de Sfax, Université de Sfax, 3038 Sfax, Tunisia
Bouzid Jalel: Laboratoire Génie Environnement Ecotechnologie, Ecole Nationale d’Ingénieurs de Sfax, Université de Sfax, 3038 Sfax, Tunisia
Alessandro Farieri: Dipartimento di Scienze della Terra, Università degli studi di Firenze, 50121 Firenze, Italy
Nieves Roqueñí: Departamento de Explotación y Prospección de Minas, Escuela de Ingeniería de Minas, Energía y Materiales de Oviedo, Universidad de Oviedo, 33004 Oviedo, Spain
Pablo Cienfuegos: Departamento de Explotación y Prospección de Minas, Escuela de Ingeniería de Minas, Energía y Materiales de Oviedo, Universidad de Oviedo, 33004 Oviedo, Spain
Pablo Higueras: Departamento de Ingeniería Geológica y Minera, Instituto de Geología Aplicada, Universidad de Castilla-La Mancha, 13400 Almadén, Spain

IJERPH, 2020, vol. 17, issue 14, 1-16

Abstract: Elements in mining extracts can be potentially toxic if they are incorporated into soils, sediments or biota. Numerous approaches have been used to assess this problem, and these include sequential extractions and selective extractions. These two methods have limitations and advantages, and their combined use usually provides a rough estimate of the availability or (bio)availability of potentially toxic elements and, therefore, of their real potential as toxicants in food chains. These indirect speciation data are interesting in absolute terms, but in the work described here, this aspect was developed further by assessing the evolution of availability-related speciation in relation to the transport processes from the emission source, which are mainly fluvial- and wind-driven. This objective was achieved by characterizing tailings samples as the source of elements in soils and sediments at increasing distances to investigate the evolution of certain elements. The standard procedures employed included a sequential five-step extraction and a selective extraction with ammonium acetate. The results show that the highest percentages of Zn and Pb in tailings, soils and sediment samples are associated with oxyhydroxides, along with a significant presence of resistant mineralogical forms. In the case of Cd, its association with organic matter is the second-most important trapping mechanism in the area. The physicochemical mechanisms of transport did not transform the main mineralogical associations (oxyhydroxides and resistant mineralogical forms) along the transects, but they produced a chaotic evolution pattern for the other minor matrix associations for Zn and a decrease in exchangeable and carbonate-bound forms for Pb in soils. Interestingly, in sediments, these mobile forms showed a decrease in Zn and a chaotic evolution for Pb. The most probable reason for these observations is that Zn 2+ can form smithsonite (ZnCO 3 ) or hydrozincite (Zn 5 (CO 3 ) 2 (OH) 6 ), which explains the retention of a carbonate-bound form for Zn in the soil transect. In contrast, Pb and Cd can appear as different mineral phases. The order of (bio)availability was Pb > Zn > Cd in tailings but Cd > Pb > Zn in soils. The physicochemical processes involved in transport from tailings to soils produce an increase in Cd (bio)availability. The trend is a decrease in bioavailability on moving away from the source (tailings), with maximum values obtained for Cd near to the source area (200–400 m).

Keywords: selective extractions; sequential extractions; (bio)availability; potentially toxic elements; Tunisia (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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