Concentrations of heavy metals in fly ash from a coal-fired power plant with respect to the new Finnish limit values |
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Authors: | Olli Dahl Risto Pöykiö Hannu Nurmesniemi |
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Institution: | (1) Department of Forest Production Technology, Laboratory of Chemical Pulping and Environmental Technology, Helsinki University of Technology, Espoo, Finland;(2) City of Kemi, Town Planning and Building Committee, Environmental Research Division, Valtakatu 26, FI-94100 Kemi, Finland;(3) Stora Enso Oyj, Kemi, Finland |
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Abstract: | In Finland, the new limit values for heavy metals in fertilizers used in agriculture and in forestry came into force in March
2007, and for materials used as earth construction agents, in June 2006. From the utilization point of view, it was notable
that the total heavy metal concentrations (Cd, Cu, Pb, Cr, Mo, Zn, As, Ni, Ba, and Hg) in fly ash from a coal-fired power
plant were lower than those limit values. The concentrations of the easily soluble elements Ca, Mg, Na, P, and Zn in the fly
ash were between 3.5 and 35 times higher than those found in the coarse mineral soils of Finland. Fly ash is a potential agent
for soil remediation and for improving soil fertility. If inorganic materials and by-products are utilized in earthworks,
the content of harmful compounds must be low and the harmful components must be tightly bound to the matrix. Therefore, a
five-stage sequential extraction procedure was used to evaluate the extractability of different elements in fly ash into the
following fractions: (1) the water-soluble fraction, (2) the exchangeable fraction (CH3COOH), (3) the easily reduced fraction (NH2OH-HCl), (4) the oxidizable fraction (H2O2 + CH3COONH4), and (5) the residual fraction (HF + HNO3 + HCl). |
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Keywords: | Ash Coal Extraction Fertilizer Heavy metals |
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