Structure and thermal history of the Wełnowiec dump, Poland: A municipal dump rehabilitated with coal waste

Abstract

The Wełnowiec municipal dump, Katowice, Poland, rehabilitated with coal waste, is self-heating and igniting. This paper presents a novel application of the use of electrical-and resistivity geophysical methods in the investigation of burning coal waste to help explain why the heating occurred. Geoelectrical methods allowed the internal structure of the dump to be revealed, and the municipal wastes and their rehabilitation cover containing coal waste to be differentiated. Instead of a planned 2.2-m-thick multi-barrier system, the cover consists of irregularly distributed material of varying thickness (< 1 to 8 m) and organic carbon content (> 5%). This caused the fire to arise 3-4 years after the coal waste deposition. In areas where the rehabilitation layer is < 3 m thick, a landslide enabled oxygen access, initiating self-heating. Changes in conductivity clearly identify sites of active burning where measured conductivity values are more than twice those for parts of the dump with no thermal activity. Field observations in particular, complemented to a degree by petrographic, mineralogical and geochemical data, enabled four types of heating zones to be distinguished, namely, (1) initial zones of fire overtaking new volumes of coal waste, (2) active zones with temperatures < 400-500°C in exhalation vents, (3) overburned zones characterized by long-lasting high temperatures (800-900°C) and (4) short-lived zones, ephemeral (< 1-2 months) with temperatures between 70 and 100°C. The geophysical methods applied could not distinguish between these zones. The combined results strongly suggest that the use of coal waste as a remediation layer covering waste dumps should be prohibited. Coal waste which, by its nature, is too prone to unpredictable self-heating and self-ignition with the potential environmental consequences that follow. water (rain); these are pyrolytic or/and hydropyrolytic processes (Fabiańska et al., 2013; Misz-Kennan and Fabiańska, 2011). Factors that influence the self-heating process can be classified as internal and external. Internal factors relate to coal-waste composition and condition, e.g., of mineral matter (contents of quartz, feldspars, clay minerals, carbonates, and sulphides) and coal-bearing rocks (maceral composition, especially of oxidation-prone vitrinite), coal rank, moisture content, granulation, and degree of weathering. External factors include dump shape and height, convection related to atmospheric conditions, i.e., wind and rain, insolation and grain segregation (Krishnaswamy et al., 1996a, 1996b; Kaymakçi and Didari, 2002). Self-heating and self-ignition of coal waste can be triggered spontaneously within a dump. If preventative measures are not taken, or the

Selected ions and major- and trace elements as contaminants in coal-waste dump water from the Lower- and Upper Silesian Coal Basins (Poland)

“…Apart from the initial composition, a signi cant factor affecting the elemental composition of coal waste is weathering and self-heating. The wide occurrence of self-heating in the LSCB and USCB and its impact on coal waste and on the environment has been described earlier (e.g., Ciesielczuk et al 2014;Misz-Kennan et al 2013;Misz-Kennan and Fabiańska 2011;Nádudvari and Fabiańska 2016;Pierwoła et al 2018). In this study, it is assumed that the elements in the water come exclusively from the leaching of coal waste.…”

“…On the basis of recent research on the chemical-and mineralogical composition of Upper Silesia waste rocks (Ciesielczuk et al 2014) and on attempts to leach elements from Upper Silesian coal waste (Pierwoła et al, 2018), it can be concluded that elements in waters were leached from rocks and minerals transformed as a result of hypergenesis or dump res. Elements such as Mg, K, Ca, Na, Mn, Fe, Cu, Cd, Pb, and Co occur in coal waste in concentrations ranging from 12-98600 mg/kg.…”

“…On a larger scale, ssures and vents formed in dump surfaces allow rainwater to enter dump interiors. Apart from the increase of coal-waste surface accessible to water, heating also induces changes in mineral composition (Ciesielczuk et al 2014, Pierwoła et al 2018).…”

Selected ions and major and trace elements as contaminants in coal-waste dump water from the Lower and Upper Silesian Coal Basins (Poland)

“…There are numerous descriptions from coal basins worldwide of the behaviour during combustion of mainand trace elements in coal (e.g., Swaine 1990;Querol et al 1995;Pusz et al 1997;Baruah et al 2003;Xu et al 2003;Ketris 2002, 2015;Lewińska-Preis et al 2009;Dai et al 2012Dai et al , 2014Kolker 2012;Hower et al 2016). Due to much higher mineral contents, the mobility of trace elements in coal waste is expected to differ significantly from that in coal (Li et al 2011;Zhou et al 2014;Pierwoła et al 2018). However, there are relatively limited data about the behaviour of elements in coal waste during self-heating; some exceptions are Guo (2018), Kruszewski (2019a, b), Nowak et al (2017), Sokol et al (2005), and Zhao et al (2008).…”

“…Even less is known about the migration of these elements into soil and surface waters. Some leaching tests (e.g., Huggins et al 2011;Pierwoła et al 2018;Yang et al 2016 andZhang et al 2015) and research on gangue environmental impact (Li et al 2011) indicate that many factors such as pH, type of mineral matrix, mode of element occurrence (water-leachable, ion-exchangeable, organic-bound, carbonate-bound, silicate-bound, sulfidebound), associated elements or method of leaching can affect element mobility (Guo 2018).…”