Ecotoxicity evaluation of Coal Fly ash to Daphnia similis and Danio rerio

Abstract

Coal Fly ash is a major solid waste from coal-fired power stations. In Brazil, more than 4 million tons per year of fly ash are generated with a tendency to increase every year. Only 30% of fly ash is applied as raw material for cement and concrete production. The remaining is disposed in onsite ponds, nearby abandoned or active mine sites, or landfills. The inadequate disposal of fly ash may pose a significant risk to the environment due to the possible leaching of hazardous pollutants into the surrounding soil and groundwater. A combination of leaching tests and ecotoxicological analyses were used in this work for the evaluation of the adverse effects of coal fly in non-target organisms. Ashes were collected from coal-fired power plant located in South of Brazil. Acute toxicity tests were performed with Danio rerio embryos and Daphnia similis, according to OECD 236 and ABNT NBR 12713, respectively. Coal fly ash sample was subjected to a leaching procedure using USEPA SW 864 Method 1311. The leachate was prepared in seven dilutions: 1.56%, 3.12%, 6.25%, 12.5%, 25%, 50%, and 100%. The assays were performed in triplicates and the results showed lethality of Danio rerio after 96 hours of exposure to the leachate, and the calculated LC50 was 4.39%. The ecotoxicity tests with Daphnia similis, observed immobility after 48 hours of exposure to the leachate, and EC50 calculated was 7.25%. The results of these tests indicate toxicity of the coal fly ash leachate toward exposed organisms.