Geochemical behaviour and mineralogical transformations during spontaneous combustion of a coal waste pile in Oslavany, Czech Republic

Abstract

Geochemical processes and mineralogical transformations in the spontaneously combusting coal waste pile of the Kukla mine in Oslavany, Czech Republic, were investigated. The aims of the study were:(1) the characterization of secondary minerals; and (2) determination of processes which influence the mobility of elements in the pile. The pile burned from the late 19th century until the 1990s and has acquired a zoned nature, with original black material in the core of the pile, red material produced by burning close to the pile slopes and grey and white efflorescent salts precipitated on the pile top and slopes. Several mineral assemblages have been identified including (1) primary minerals in the black material including bituminous coal to anthracite, micas, pyrite and goethite; (2) hematite, spinels and corundum in the red material produced by pyrometamorphism; and (3) hydrated sulphates of magnesium including hexahydrite, konyaite and picromerite in efflorescent precipitates on the slopes of the pile. A conceptual model of geochemical processes in the pile includes seasonal changes with mineral dissolution during the wet season and precipitation of efflorescent salt minerals during the dry season. Formation of secondary minerals such as hematite, which is resistant to weathering and immobilizes hydrolysable Fe, may have a positive environmental impact in the long term.

Geochemistry and mineralogy of Cu and Co in mine tailings at the Copperbelt, Zambia

“…This may cause release of previously adsorbed and co-precipitated metals (Langmuir, 1997, Lottermoser andAshley, 2006). However, once hematite is formed, it is very resistant to dissolution and iron and incorporated metals are very immobile (Dokoupilová et al, 2007). This is in good agreement with low pore water concentrations of Cu and Co (Table 2).…”

Secondary arsenic minerals and arsenic mobility in a historical waste rock pile at Kaňk near Kutná Hora, Czech Republic

“…Oxygen can get into waste rock material by diffusion and convection . Convection can be particularly important near a pile slope and especially in the case of increased temperature (Dokoupilová et al 2007). …”

“…Although OH−and H 3 O + contents were calculated, i.e., assuming (OH+ Cl)=6 and H 3 O + =1−(Na+K+Ca+Pb+Ba), the sums of oxides are usually significantly lower than 100 wt.% (Table 8); the low sums could result from poor crystallinity accompanied by high amounts of adsorbed water on the surface of mineral particles. Low sums of oxides in EMPA data for poorly crystalline minerals are common feature, but such data are only rarely published (e.g., Dokoupilová et al 2007;Filippi et al 2009). …”

Evolution of minesoils at a coal waste pile: A case study from Rosice-Oslavany (Czech Republic)

“…Subsequent biological reclamation was based on revegetation using hydroseeding and tree planting. The pile burned from the late 19 th century until the 1990s and has acquired a zoned nature recently investigated by Dokoupilová et al (2007) who reported (1) bituminous coal to anthracite, micas and goethite (i.e. primary minerals) in the black zone; (2) hematite, spinels and corundum in the red material produced by pyrometamorphism; and (3) hydrated Mg-sulphates on the slopes of the waste pile.…”

“…The color variability of subsurface horizons is a result of successive material accumulation and subsequent long-lasting pile burning. The colorimetrical analysis in visible reflectance spectra indicates the presence of the Fe 3+ bound in hematite (Fe 2 O 3 ), presence of which is a result of intensive oxidation process at waste pile burning (Dokoupilová et al, 2007). Although some horizons are intensively red colored, e.g.…”