engleski

Mineral and geochemical properties, including particle characteristics, of an old coal ash and slag deposit in Istria (Croatia)

Utilization of coal combustion by-products (CCB) has been a major goal in coal waste management as only 50-60% generated by-products are currently utilized. However, it is estimated that 1 billion tonnes of CCB are generated yearly, leaving half for disposal in landfills or ash impoundments. Today's regulations require proper lining and leachate collection which should ensure site safety. However, the disposal of coal combustion products in unlined landfills and ash ponds was a common practice in the past. Therefore, old and unmonitored landfills present a large threat to the environment. Several of those old landfills are located in historical mining and coal burning area in the Istrian peninsula (Croatia). Previous studies already reported elevated concentrations of metals in soils, waters, and biota, indicating contamination of local areas by leaching of elements from waste. However, the processes that govern the release of toxic elements have not been addressed. The composition of coal combustion by- products varies greatly, therefore elements can have different mobility depending on the sample. This presentation aims to address those processes by mineralogical and geochemical analysis of waste, with the addition of particle characterization. The mineralogical analysis indicated secondary mineral phases which could reduce the mobility of ions (As, Se, Mo). However, other contaminants may be transported by colloids, which are most stable under alkaline conditions. Besides giving insight into the geochemical processes of leaching, the findings are useful for today’s landfills predictions as they represent aged waste with altered intrinsic characteristics.

coal ash deposit ; geochemistry ; mineralogy ; Croatia

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