The environmental legacy of industrial coal combustion: tracing inorganic and organic contaminants in soils

As the world deal with the global climate and energy crises and energy transition, studies related to coal are still needed because, despite de phasing out of coal, the recognition of the environmental legacy left by fossil fuels is important to identify the influence of its use in the carbon cycle and to meet the main commitments of the European Green Deal. This study aims to identify the fingerprint in soil left by the past activity of Sines thermal power plant (S-TPP, Portugal), which lasted for decades. The multi-analytical approach (petrographic and geochemical techniques) used in the analysis of soil collected in the area surrounding the S-TPP allowed identification and quantification of inorganic and organic contaminants, their source, and allow the understanding of changes in the physic-chemical characteristics of soil induced by the contamination. The results reveal differentiated spatial distribution of changes and contaminants in soils, which are more intense in the south area, attributed to incorporation of contaminants through mobilization and dispersion influenced by predominant winds regime of the region. The incorporation of particles of coal and fly ash in soil enhances the concentration of some potentially toxic elements (As, Ba, Co, Cr, Ni, Se, U, V) beyond national reference values for healthy soil. The contaminants in soil also influence soil granulometric composition, alkalinity, electrical conductivity, total organic carbon and total sulphur. The sources of contaminants in soil are the fly ash and gaseous emission from smoke stacks and coal and fly ash particles mobilized during storage, handling and landfilling operations. • Assessment of soil quality surrounding a coal thermal power plant. • Application of a multi-technique approach combining petrographic and geochemical methods. • Mobilization of combustion by-products into soil enhanced concentration of toxic elements. • Petrographic observation provides unequivocal evidence of contamination.