Geochemistry of Soils from the Surrounding Area of a Coal Mine Waste Pile Affected by Self-Burning (Northern Portugal).

Abstract

Coal mining can generate organic and inorganic pollutants that can be disseminated in the sur-rounding soils by leaching and/or aerial deposition. This study aims to identify and characterize the physicochemical and geochemical changes, promoted in the soils that surround a self-burning waste pile from an abandoned coal mine. A soil geochemical campaign was conducted bordering the waste pile, comprising the main drainage areas as well as the areas uphill. The soils were characterized geochemically for major and trace elements and multivariate statistics was used in combination with geostatistical methodologies to study the statistical and spatial re-lations of the different elements and infer its Potentially Toxic Elements (PTEs) sources. The 16 priority pollutants Polycyclic Aromatic Hydrocarbons (PAHS) were identified and quantified in soils according to its spatial distribution, and their pyrogenic/petrogenic sources inferred. Dif-ferent elementary sources were identified as contributing to the soils geochemical signature, considering not only the mine but also anthropogenic urban contamination or naturally en-hanced regional geochemical background in multiple PTEs. PAHs tend to concentrate down-stream the waste pile, along the runoff areas, presenting greater variety of the 16 priority pollu-tants PAHs and increase of High Molecular Weight (HMW) PAHS pointing to its pyrogenic origin, possibly related with the self-combustion phenomenon occurring in the waste pile.