Jakub Kierczak

Solid speciation and mobility of potentially toxic elements from natural and contaminated soils: A combined approach

The study area (Szklary Massif, SW Poland) comprises three sites of different soil provenance: (1) natural serpentine Cambisol, (2) anthroposol situated on waste dump and (3) cultivated Inceptisol developed on glacial tills next to the dump. Potentially toxic elements (PTE) have either lithogenic or anthropogenic origins in these sites. The chemical partitioning of Co, Cr, Cu, Ni, Pb and Zn among solid forms was determined by sequential extractions coupled with direct mineral identifications (SEM, electron microprobe analysis - EMPA, and XRD). Examination of solid residues after several extraction steps was conducted in order to discuss the indirect speciation obtained by the extraction method. Total concentrations of PTE having anthropogenic origin greatly exceed those of lithogenic origin. Mobility of studied PTE is variable in the different environments except for Cr which is always mostly found in residual fractions of extractions. Cu and Pb are more mobile than Cr and Co in all soils. Zn is more stable (Cu>Pb>Ni>Co>Zn>>Cr) in the serpentine soil and cultivated epipedon (Pb>Cu>Zn>Ni>Co>>Cr) than in the anthroposol (Zn>CuPb>Ni>Co>>Cr). PTE of lithogenic origin are generally less mobile than those from anthropogenic origin except Ni which is more mobile in the serpentine soil. Nonetheless, mineral forms of metals better determine their mobility than metal origin. Identification by direct methods of the PTE mineral form was not possible for metals present at low concentrations (Cu, Pb). However, direct mineralogical examinations of the solid residues of several extractions steps improved the assessment of the PTE solid speciation and mobility, particularly for Cr, Ni and Zn.

Rock-type control of Ni, Cr, and Co phytoavailability in ultramafic soils

Background and aimsUltramafic soils constitute an extreme environment for plants because of specific physico-chemical properties and the presence of Ni, Cr, and Co. We hypothesized that type of ultramafic parent rock depending on their origin affects the composition of soils and plants. Therefore, phytoavailability of metals would be higher in soil derived from serpentinized peridotite compared to serpentinite because of differences in susceptibility of minerals to weathering.ResultsBased on DTPA-CaCl2 extractions, we noted that soil derived from the serpentinized peridotite is characterized by a higher phytoavailability of Ni compared to soil derived from the serpentinite. On the contrary, plant species growing on soil derived from the serpentinite contain higher concentrations of metals.ConclusionsOur study suggests that the metal uptake by plants is controlled by the mineral composition of parent rocks, which results from both their original magmatic composition and later metamorphic processes. Chemical extractions show that the phytoavailability of Ni and Co is higher in soil derived from the serpentinized peridotite than the serpentinite. Surprisingly, plants growing on the soil derived from the serpentinite contain higher levels of metals compared to these from the serpentinized peridotite derived soil. This contrasting behavior is due to higher abundances of Ca and Mg, not only Ni and Co, in soil derived from the serpentinized peridotite as compared to those in the soil derived from the serpentinite. Calcium and Mg are favored by plants and preferably fill the available sites, resulting in low Ni and Co intake despite their higher abundances.

Weathering of historical copper slags in dynamic experimental system with rhizosphere-like organic acids

This study was undertaken to simulate experimentally the weathering of slags disposed nearby soil rhizosphere. The aim of the research was to differentiate the effect of pH and organics on slags dissolution as well as to indicate weathering sequence of phase components. The studied slags are mainly composed of Fe (34.5 wt%) and Si (17.9 wt%) and contain up to 3761 mg kg-1 of Cu and 3628 mg kg-1 of Zn. The main identified phases are fayalite and glass, whereas sulfides and metallic Cu are volumetrically minor. A 30 days long slag weathering experiment was carried out with artificial root exudates (43.7 mM) and demineralized water at initial pH = 3.5 and pH = 6.7. The highest metal release (up to 10.9% of Zn and 4.6% of Cu) was observed in ARE solution at initial pH 3.5. Dissolution of sulfides and fayalite was mainly driven by pH. Artificial root exudates enhance glass dissolution as compared to demineralized water regardless of initially fixed pH. Based on this study following weathering sequences are delineated: i) under ARE 3.5 conditions: silicates > glass > sulfides, ii) under DW 3.5 conditions: sulfides > silicates > glass, iii) under near-neutral conditions: sulfides > glass > silicates.

Dissolution of lead matte and copper slag upon exposure to rhizosphere-like conditions

Abstract Metallurgical wastes displaying various chemical and mineralogical properties may reveal different behaviour under exposure to weathering conditions. The latter impact the stability of the wastes, which often results in metal release and subsequent pollution problems. The aim of this study was to compare the weathering of two types of metallurgical wastes (i.e., copper slag and lead matte) exposed to artificial root exudates organic solutions and demineralized water. The results of experimental weathering demonstrated that the extent of waste dissolution depends on the composition of weathering solution as well as on the waste properties. Artificial root exudates rich in organic acids were found to enhance elements release from sulphide rich lead matte and copper glassy slag relative to demineralized water control. The release of elements from the wastes exposed to artificial root exudates for 7 weeks reached 17.8% of Pb and 4.97% of Cu, for lead matte and granulated slag respectively. The most leachable elements may result from the dissolution of intermetallic phases hosting these elements. The fraction size ranging from 0.25–0.5 mm to 1–2 mm was found to be a minor factor in elements release under studied conditions.

Response to the comment on “Copper metallurgical slags - current knowledge and fate: A review”

Anna Potysz, Eric D. van Hullebusch, Jakub Kierczak, Malgorzata Grybos, Piet N.L. Lens, and Gilles Guibaud Universit e Paris-Est, Laboratoire G eomat eriaux et Environnement (EA 4508), UPEM, Marne-la-Vall ee, France; Universit e de Limoges, Groupement de Recherche Eau Sol Environnement (EA 4330), Facult e des Sciences et Techniques, Limoges Cedex, France; UNESCO-IHE Institute for Water Education, DA Delft, The Netherlands; University of Wroclaw, Institute of Geological Sciences, Cybulskiego, Wroc»aw, Poland