Abstract
Coal ash obtained by coal combustion in the “Nikola Tesla A” power plant in Obrenovac, near Belgrade, Yugoslavia, is mixed with water of the Sava river and transported to the dump. In order to assess pollution caused by leaching of some minor and major elements during ash transport through the pipeline, two sets of samples (six samples each) were subjected to a modified sequential extraction. The first set consisted of coal ash samples taken immediately after combustion, while the second set was obtained by extraction with river water, imitating the processes that occur in the pipeline. Samples were extracted consecutively with distilled water and a 1 M solution of KCl, pH 7, and the differences in extractability were compared in order to predict potential pollution. Considering concentrations of seven trace elements as well as five major elements in extracts from a total of 12 samples, it can be concluded that lead and cadmium do not present an environmental threat during and immediately after ash transport to the dump. Portions of zinc, nickel and chromium are released during the ash transport, and arsenic and manganese are released continuously. Copper and iron do not present an environmental threat due to element leaching during and immediately after the coal ash suspension and transport. On the contrary, these elements, as well as chromium, become concentrated during coal ash transport. Adsorbed portions of calcium, magnesium and potassium are also leached during coal ash transport.
Highlights
Coal can be defined as combustible sedimentary rock, consisting of at least 50% of an organic fraction (Wood et al, 1983), and the remainder of which is an inorganic fraction that consists of mineral fragments and variously associated microelements
We have investigated microelement, and major element leaching during and immediately after coal ash transport to the dump of theNikola Tesla A'' power plant in Obrenovac, Yugoslavia
While previous work done on samples from this power plant was aimed at establishing major associations and leaching characteristics of trace and major elements, this particular investigation was the first one addressing actual pollution occurring during coal ash suspension and transport processes
Summary
Coal can be defined as combustible sedimentary rock, consisting of at least 50% of an organic fraction (Wood et al, 1983), and the remainder of which is an inorganic fraction that consists of mineral fragments and variously associated microelements. The chemical and physical characteristics of coal are predetermined by the nature of precursor plants, the amount of inorganic materials and by the nature, intensity and duration of the biochemical and geochemical processes that are responsible for coal formation. Coal combustion in power plants generates large amounts of ash that is marginally used (construction industry, agriculture, glass production) (Nesic et al, 1997; Faber et al, 1995; Boccaccini et al, 1997) or, in most cases, stored more or less unprotected in the environment where it can represent a significant source of heavy metals, PAHs and other pollutants. We have investigated microelement, and major element leaching during and immediately after coal ash transport to the dump of the`Nikola Tesla A'' power plant in Obrenovac, Yugoslavia
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