Changes Induced by Self-Burning in Technosols from a Coal Mine Waste Pile: A Hydropedological Approach

Abstract

Coal mining originates environmental impacts on soil and water bodies, including the leaching of Potentially Toxic Elements (PTEs) and Polycyclic Aromatic Hydrocarbons (PAHs) in mine waste piles. This research aims to identify and characterize changes induced by self-burning in Technosols from a coal mine waste pile by means of a comprehensive hydropedological assessment encompassing geochemical, mineralogical, and hydrological data, bearing in mind the potential leaching of PTEs and PAHs. The soil profile from two contiguous areas (an area with normal pedological evolution vs. an area affected by self-burning) was characterized in terms of morphological features. Each soil horizon was sampled and analyzed for geochemical and mineralogical characterization. The unsaturated hydraulic conductivity (Ki) was also measured in all soil horizons. Finally, the leaching potential of PTEs and PAHs in water was evaluated. Several changes induced by self-burning were identified in the studied Technosols: development of specific soil horizons; destruction of humified organic matter; contrasting geochemical composition, especially in the deeper horizons; mineralogical modifications, pointing to clay minerals with higher ion exchange capacity and higher specific surface by sulphates of lower structural order; diverse Ki values in the intermediate and lower part of the soil profile; and specific susceptibility to leaching of PTEs and PAHs. The research demonstrated that self-burning causes severe changes of hydropedological relevance, with influence on the leaching of PTEs and PAHs.

Phytotoxicity of coal waste elutriates (Douro Coalfield, North Portugal) in Lactuca sativa

“…2 ). The environmental impact of coal waste depends on several factors, namely, the type, concentration, solubility, mobility, and potential release of chemical elements (Kalembkiewicz and Sitarz-Palczak 2015 ; Espinha Marques et al 2021 ). Some chemical elements are more easily leached and accessible for percolation and mobilization into the environment, namely, Ca, Mg, Na, Mn, Cd, Co, Ni, and Zn (Ribeiro and Flores 2021 ), and all these elements were quantified in high concentrations in the here-presented soil elutriates.…”

“…Some chemical elements are more easily leached and accessible for percolation and mobilization into the environment, namely, Ca, Mg, Na, Mn, Cd, Co, Ni, and Zn (Ribeiro and Flores 2021 ), and all these elements were quantified in high concentrations in the here-presented soil elutriates. Previous studies in coal mine waste piles (CMW) from the Douro Carboniferous Basin reported different concentrations of leachable elements found in self-burning coal waste samples vs unburned material since the leaching of elements can be temperature-dependent (Espinha Marques et al 2021 ). Querol et al ( 2008 ) reported the leaching potential of unburned and burned coal waste piles and concluded that the burned coal waste produces leachates with higher concentrations of Al, Ca, K, Mg, Mn, and Ni, which corroborates the results presented here.…”

“…Organic matter (OM) content and water holding capacity (WHC) of each soil were also measured according to SPAC ( 2000 ) and ISO ( 2008 ), respectively [for more details see Antunes et al ( 2008 )]. The bioavailable heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb), inorganic ions (Na + , K + , Mg 2+ , Ca 2+ , Li + , Cl, NO 3 − , F − , and SO 4 2+ ), and other components (Al, Fe, NO 2 − , NH 4 + , and SiO 2 ) in elutriates were quantified according to Espinha Marques et al ( 2021 ).…”

“…Despite these advantages, coal mining waste (CMW), generated by coal extraction, is a serious environmental issue (Wang et al 2020 ), and the proper management of CMW has become an important challenge (Liu et al 2018 ). The environmental degradation caused by waste disposal is considered a major concern by several governmental agencies since these materials are subjected to intense geochemical and mineralogical processes (Espinha Marques et al 2021 ) which can increase the dispersion of organic and inorganic pollutants (Ribeiro et al 2014 ), as well as the leaching of potentially toxic elements (PTE) to the different matrices (e.g., soil, groundwater, freshwater) (Galhardi and Bonotto 2016 ; Espinha Marques et al 2021 ). Furthermore, the possibility of bioaccumulation and biomagnification in the food web can also represent a high risk to the environment and wildlife (Stefaniak and Twardowska 2010 ).…”

Effects of Magmatic Fluids in Coals of São Pedro da Cova Coalfield, Douro Carboniferous Basin, Portugal: Insights from Inorganic Geochemistry

“…The São Pedro da Cova Coalfield is part of the Douro Carboniferous Basin (DCB), the most important coal-bearing basin in Portugal, and has been, since the early 1990s, the focus of several geological studies with emphasis on tectono-stratigraphic development, e.g., [1][2][3][4][5], paleobotany, e.g., [6][7][8][9][10][11][12], paleozoology, e.g., [6,7,[13][14][15][16], organic petrology and physical parameters of the coals, e.g., [17][18][19][20][21][22][23][24][25], and coal exploration and its environmental impacts (e.g., [26][27][28][29][30][31][32][33][34][35][36]).…”