Mossbauer spectroscopy indicates that iron in an aluminosilicate glass phase is the source of the bioavailable iron from coal fly ash

Iron speciation by Mossbauer spectroscopy indicates that ferric iron in an aluminosilicate glass phase is the source of the bioavailable iron in coal fly ash and that this iron species is associated with combustion particles, but not with crustal dust derived from soil minerals. Urban particulate ha s been shown to be a source of bioavailable iron and has been shown to be a ble to induce the formation of reactive species in cell culture experiments . Crustal dust and laboratory-generated coal fly ash have been studied as s urrogates for two sources of metal-bearing particles in ambient air. As muc h as a 60-fold difference in the amount of iron mobilized by the chelator c itrate was observed between fly ash and crustal dust samples with similar t otal iron contents. The extent of iron mobilization by citrate in vitro has been shown to correlate with indirect measures of excess iron in cultured cells and with assays for reactive oxygen species generation in vitro. Moss bauer spectroscopy of coal fly ash, before and after treatment with the che lator desferrioxamine B, showed that the iron in an aluminosilicate glass p hase was preferentially removed. The removal of the glass-phase iron greatl y reduced the amount of iron that could be mobilized by citrate and prevent ed the particles from inducing interleukin-8 in cultured human lung epithel ial (A549) cells. Ferric iron in aluminosilicate glass is associated with p articles formed at high temperatures followed by rapid cooling. The observa tion that ferric iron in aluminosilicate glass is the source of bioavailabl e iron in coal fly ash suggests that particles from ambient sources and oth er specific combustion sources should be examined for the presence of this potential source of bioavailable iron.