Differential distribution of chemical and ecotoxicological levels of biomass ashes by size fractionation

The main aim of this work was to study the chemical and ecotoxicological properties of different particle size fractions of bottom and fly ashes coming from a biomass power plant. Bottom and fly ashes were sieved in different size fractions. The size fractions with higher mass percentages were submitted to an acidic digestion and water leaching. The acidic samples and eluates were chemically characterized. The eluates were also submitted to an ecotoxicological characterization. The highest concentrations of metals and metalloids were found in the lower particle size fractions of bottom and fly ashes. It was not observed any releasing pattern from the particle size fractions, except in the fly ashes in which the releasing rate of some earth and alkali-earth metals seemed to increase in the lower particle size fractions. No specific pattern on the toxicity distribution through the different particle size fractions of bottom and fly ashes was determined, except that the particle size fractions of bottom ashes of 4,000-10,000 μm and >10,000 μm have shown lower toxicity levels than the other particle size fractions.