Migration of Trace Elements from Pyrite Tailings in Carbonate Soils

Abstract

In the carbonate soils contaminated by a toxic spill from a pyrite mine (Aznalcóllar, southern Spain), a study was made of a thin layer (thickness = 4 mm) of polluted soil located between the pyrite tailings and the underlying soil. This layer, reddish-yellow in color due to a high Fe content, formed when sulfates (from the oxidation of sulfides) infiltrated the soil, causing acidification (to pH 5.6 as opposed to 8.0 of unaffected soil) and pollution (in Zn, Cu, As, Pb, Co, Cd, Sb, Bi, Tl, and In). The less mobile elements (As, Bi, In, Pb, Sb, and Tl) concentrated in the uppermost part of the reddish-yellow layer, with concentration decreasing downward. The more mobile elements (Co, Cd, Zn, and Cu) tended to precipitate where the pH was basic, toward the bottom of the layer or in the upper part of the underlying soil. The greatest accumulations occurred within the first 6 mm in overall soil depth, and were negligible below 15 mm. In addition, the acidity of the solution from the tailings degraded the minerals of the clay fraction of the soils, both the phyllosilicates as well as the carbonates. Also, within the reddish-yellow layer, gypsum formed autigenically, together with complex salts of sulfates of Fe, Al, Zn, Ca, and Mn, jarosite, and oxihydroxides of Fe.

Geochemical background of potentially toxic trace elements in reclaimed soils of the abandoned pyrite–uranium mine (south-central Poland)

“…The highest concentrations of trace elements have been found in samples revealing circumneutral pH (except for sample R55). This can be explained by increased mobility of metal(loid)s in acidic soils and their stabilization at a circumneutral pH (Dorronsoro et al 2002).…”

Arsenic Behaviour in Polluted Soils After Remediation Activities

“…In all cases, the As pollution concentrated in the uppermost 10 cm of the soils and decreased sharply in depth, without significantly affecting the subsoil or groundwater (Simón et al, 2001Dorronsoro et al, 2002). To study the As retention in the soil, we made extractions with selective reagents (water, calcium chloride, acetic acid, EDTA, oxalic-oxalate).…”

High-resolution studies on vegetation succession, hydrological variations, anthropogenic impact and genesis of a subrecent lake in southern Ecuador

“…Chemical diagenesis seems to be of minor importance as above the peak in LC-I the Fe/Ti ratio varies only little. If Pb had migrated upwards in the profile, variations would have been observed in the Fe/Ti ratio as Pb is less mobile than Fe (Charlatchka and Cambier 2000;Dorronsoro et al 2002). There is also a growing body of information for ombotrophic peat bogs suggesting that Pb is immobile in this environment (Shotyk et al 2005).…”