Pollution of coal mine soils: global reference concentrations of chemical elements

Abstract

Despite global efforts to phase out coal, the world’s coal production and consumption reached a record high in 2022. Even though soil pollution around collieries stands in the shadow of greenhouse gas emissions, the anthropogenic geochemical impact of coal mining will persist for decades to centuries after the coal phaseout. Soils are of paramount significance when assessing the pollution of mining sites. This analysis provides a reference dataset for evaluating soil transformation in coal minescapes. Identification, screening, eligibility check, and extraction of data from articles published in peer-reviewed journals between 2000 and 2022 yielded a comprehensive dataset on the chemical composition of 13,925 soil samples from 55 mined coal fields in 32 countries of Eurasia, Africa, Australia, and the Americas. These carefully handpicked records allowed the calculation of mean concentrations for 41 chemical elements, alongside total organic carbon and a total of 15 rare-earth elements. The resulting dataset is of both fundamental geochemical and policy-relevant significance. The maximum enrichment of contaminated soils with As, Bi, Hg, Sb, and Se reveals the role of coals as the source of highly coalphile elements. Remediation guidelines can benefit from the dataset, e.g., for arsenic whose world average contents fall below the standards of Canada, Russia, and the USA. Regional soil quality criteria may incorporate these figures to update threshold levels for mining sites. Finally, for the areas of discovered coal reserves, the question “to mine, or not to mine” can be answered with higher certainty owing to the predicted levels of pollutant burden.