CHARACTERISTIC FLY-ASH PARTICLES FROM OIL-SHALE COMBUSTION FOUND IN LAKE-SEDIMENTS

Fly-ash particles accumulate in sediments and can be used to assess sp atial distribution and temporal trends of atmospheric deposition of po llutants derived from high temperature combustion of fossil fuels. Pre vious work has concerned fly-ash derived from oil and coal. Oil-shale is the main fossil fuel used in Estonia and a major source of atmosphe ric pollution in the Baltic states. To assess if oil-shale power plant s produce specific fly-ash particles, we used scanning electron micros copy (SEM) and energy dispersive X-ray analysis (EDX) to compare fly-a sh particles from oil-shale combustion with particles from oil and coa l combustion. Two types were analysed, large black (10-30 mu m) and sm all glassy (<5 mu m) spheroidal particles. Although particle morpholog y to some extent is indicative of the fuel burnt, morphological charac ters are not sufficient to differentiate between particles of differen t origin. However, our results indicate that with EDX analysis the fly -ash from oil-shale can be distinguished from oil and coal derived par ticles in environmental samples. Concentrations of large black and sma ll glassy spheroidal fly-ash particles in a sediment core from an Esto nian lake showed similar trends to oil-shale combustion statistics fro m Estonian power plants.