The concentrations and particle size relationships of selected trace elements in fly ashes from U.K. coal-fired power plants and a refuse incinerator

Fly ash samples from 11 coal-fired power plants and a refuse incinerator in the U.K. were analyzed for total arsenic, cadmium, lead and selenium. Enrichment factor (EF) values calculated with respect to crustal abundance (EF_crust) were highest for cadmium and lead in refuse fly ash, with EFs of 2500 and 740, respectively. Enrichment factors for selenium were similar in both fly ash types; only arsenic was more enriched in coal fly ash compared with refuse fly ash. Despite the high EF_crust values of certain elements in the two fly ash types, the same elements showed EF values of about unity when expressed with respect to the starting material. Both materials displayed an inverse relationship between particle size and extent of enrichment for all the elements studied, but the degree of enrichment on the finest particles was lower than reported for coal fly ash by other workers. The EF_crust values estimated for arsenic, lead and selenium in suspended particulates from a refuse incinerator were similar to those calculated for the urban atmospheric aerosol, whereas cadmium was 10 times more enriched in the suspended particulates.Scanning electron microscopy revealed a marked contrast in the morphological features of the two fly ash types. Coal fly ash was almost entirely composed of cenospheres of < 20 μm diameter, whereas refuse fly ash consisted mostly of amorphous particles of < 50 μm diameter; some cenospheres were, however, noted in the refuse fly ash.