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

Jorge Espinha Marques,Deolinda Flores,Joana Ribeiro,Armindo Melo,Catarina Mansilha,Vítor Martins,Patrícia Santos,Fernando Rocha

doi:10.3390/geosciences11050195

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.

Highlights

The environmental degradation resulting from the leaching of Potentially Toxic Elements (PTEs) and compounds, such as Polycyclic Aromatic Hydrocarbons (PAHs) from mine waste piles, as well as from acid mine drainage, is considered a major concern by governmental agencies, mining companies, and citizens [7,8]
The objective of this research is 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 pollutants (PTEs and PAHs)
Coal mining usually generates waste piles containing inorganic and organic pollutants, including Potentially Toxic Elements and Polycyclic Aromatic Hydrocarbons. These pollutants may disperse in the environment and disturb the normal functioning of ecosystems and may cause severe damages to the health of living organisms, including humans

Summary

Introduction

Some of the most critical and widespread mining impacts are related to the pollution of soil and the aquatic environment by metals and metalloids, due to the severity of the negative effects on ecosystems and on human health [4,5,6]. The environmental degradation resulting from the leaching of Potentially Toxic Elements (PTEs) and compounds, such as Polycyclic Aromatic Hydrocarbons (PAHs) from mine waste piles, as well as from acid mine drainage, is considered a major concern by governmental agencies, mining companies, and citizens [7,8]. Coal mining activities originate waste piles, often of great volume, containing PTEs, that is, metals and metalloids, including Al, Mn, As, Cd, Ni, Cu, Cr, Zn, Fe, and Pb in concentrations frequently higher than background values [9,10,11,12]. The 16 PAHs defined as priority pollutants by the United

Objectives

Results

Discussion

Conclusion