The formation of spinel-group minerals in contaminated soils: the sequestration of metal(loid)s by unexpected incidental nanoparticles

Abstract

Mineralogical studies of contaminated soils affected by smelter emission and dust from mining activities indicate that minerals of the spinel group are one of the common hosts of metal-bearing contaminants. Spinel group minerals typically originate from high temperature processes, but an increasing number of studies indicate that metal-bearing spinel group minerals can also form under ambient Earth surface conditions in surficial soils. In this contribution to honor Donald Sparks, we show that the spinels Zn-bearing magnetite (Zn0.5Fe2.5O4) and minium (Pb3O4) form during low temperature alteration of Pb-bearing silica glass in surficial organic rich soils in proximity to a former Cu-smelter in Timmins, Ontario, Canada. The glass most likely formed during high-temperature processes and has been either emitted by the smelter or wind-blown from waste rock piles to near-by soils. The alteration of the glass by percolating pore solutions has resulted in the formation of large micrometer-size dendritic etch features and in nanometer-size dendritic alteration halos composed of nano-size prismatic crystals of Zn-rich magnetite and spherical nanoparticles of minium. Both spinel-type phases are embedded in an amorphous silica matrix which formed during the alteration of the glass at low temperature. A review on the occurrence of spinel-group minerals in smelter-affected soils or mine tailings indicates that the formation of these minerals under ambient Earth surface conditions is quite common and often results in the sequestration of contaminants such as Cu, Ni, Zn and Sb. The pedogenic spinels often occur as euhedral crystals in nano-size mineral assemblages within alteration features such as dendritic etch patterns, mineral surface coatings and mineralized organic matter. Their well-developed crystal forms indicate that (a) they have not formed during a rapid cooling process in a smelter or refinery which typically creates spherical particulate matter, and (b) they have not been part of particulate matter added via fluvial or Aeolian processes which most commonly yield anhedral morphologies. The formation of nano-size spinel-group minerals in low temperature environmental settings may lead to the long-term storage of metal(loid)s in mineral phases and their transport over vast distances via fluvial, alluvial and Aeolian processes.Electronic supplementary materialThe online version of this article (10.1186/s12932-019-0061-3) contains supplementary material, which is available to authorized users.

Atom probe tomography and transmission electron microscopy: a powerful combination to characterize the speciation and distribution of Cu in organic matter

“…39 They are of great signicance in geological, environmental and materials sciences due to their physical properties and their ability to incorporate a variety of mono-, di-, tri-, tetraand pentavalent cations. 39 Spinel-type minerals such as magnetite also occur as NPs in the upper horizons of soils, where they form through various abiotic and biotic processes. 39 Cuprite is a common oxidation product of Cu-suldes and occurs in association with Cu-carbonates (azurite and malachite) and metallic Cu.…”

“…39 Spinel-type minerals such as magnetite also occur as NPs in the upper horizons of soils, where they form through various abiotic and biotic processes. 39 Cuprite is a common oxidation product of Cu-suldes and occurs in association with Cu-carbonates (azurite and malachite) and metallic Cu. 40 Illite is known to neo-form in soils through the weathering of rock forming minerals.…”

NOM-assisted, amyloid-enriched, hierarchical self-assembled nanostructures of maghemite nanoparticles and their plastic deformation: role of magnetic fields, Pb2+, and biomolecular conformations

“…16,17 Moreover smelter emission and dust from the mining activities enrich soils with the magnetic spinel group minerals, one of the common hosts of metal-bearing contaminants including Pb. 18 Lascu et al reported that a qualitative estimate of the magnetic properties of the sediments can be evaluated from the χ measurements but requires the knowledge of magnetic particles grain size. 10 Therefore, the extent of surface modifications of magnetic NPs, biomolecular conformations, grain size, and the degree of magnetic dipolar interactions evolved from polydispersity may facilitate the growth of magnetic field-directed self-assembled nanostructures in the environment.…”

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“…Similar to microbes, nanoparticles (which are defined as clusters, crystals, and amorphous phases having at least one dimension of 1–100 nm, Caraballo et al ., 2015), have been found prevalent and abundant in a wide range of natural systems, from groundwater, soils, volcanic ashes, glaciers, thawing permafrost, to lacustrine, riverine, estuarine and marine settings (Hochella et al ., 2008; Gartman et al ., 2014; Johnson et al ., 2014; Tepe and Bau, 2014, 2015; Hirst et al ., 2017; Graca et al ., 2018; Hawkings et al ., 2018; Schindler et al ., 2019). In contrast to the consensus that microbial life is central to many geological and environmental processes on Earth, the integral role of nanoparticles in global biogeochemical cycles has only started to be recognized.…”