Metal(loid)s leaching from unregulated coal ash and slag deposit in Istria, Croatia

Coal is one of the world's most important energy sources and contributes to the production of almost 40% of the world's electricity. Unfortunately, there are a number of by-products produced by coal combustion, including fly ash, bottom ash, boiler slag, and flue gas desulfurization material. If not properly disposed, coal combustion products can become a serious environmental concern. Namely, under different environmental conditions, waste particles could be transported from these repositories by wind action or rainfall erosion and consequently pollute the soil around the disposal site, reach water bodies in the region, or even enter local groundwater. Raša coal is an example of superhigh-organic- sulfur coal (SHOS), as it contains exceptionally high levels of sulfur (up to 11–14%) present mainly in the organic form. Decades of its use in the nearby thermal power plant (TPP) and other local factories left an imprint on the local environment, reflected in elevated concentrations of various metal(loid)s in different environmental compartments, local streams, vegetables, soils, aquatic sediments, and bird tissue. Furthermore, chemical and toxicological evaluation of soil collected in the area showed cytotoxic and genotoxic effects. New data on the leaching potential of selected metal(loid)s from the unregulated waste deposit of Raša coal ash and slag located in Istria (Croatia) will be presented, bringing some new insights into the connection between individual elements and existing mineral phases, and the possibility of their release under different environmental conditions.