Species of Iron in Size-resolved Particle Emitted from Xuanwei Coal Combustion and Their Oxidative Potential

Abstract

Many reports have claimed that high lung cancer mortality rate in Xuanwei is associated with the residential coal combustion. Considering iron is the main chemical element in the particles emitted from Xuanwei coal combustion, and especially, reactive oxygen species (ROS) could be generated by redox-active transition metals (TM) such as iron (Fe) in particles, therefore, raw coal samples from 4 coal mines in Xuanwei were sampled, and size-resolved particles emitted from the raw coal samples were collected by using of Andersen Five-stage High Volume Sampler. Species of iron in the raw coal sample, size-resolved particles and bottom ashes were analyzed by BCR sequential extraction method (community bureau of reference, BCR). The generation potential of·OH free radicals from coal emission particles in the surrogate lung fluid (SLF) solution was measured by using high pressure liquid chromatography (HPLC). Our results demonstrated that a large fraction of oxidizable Fe could be found in raw coal samples. However, the acid extractable, reducible and oxidizable fractions of Fe in the fly ash particles accounted for a large proportion (46%-78%) in the size-resolved particles after coal combustion. There was difference in levels of·OH free radicals generated from coal emission particles in the SLF for 24 hours among particles with different sizes. The concentration of·OH increased in both fine particles (<1 μm, 1.1-2 μm, 2-3.3 μm) and coarse particles (3.3-7 μm, >7 μm) as the particles size decreased. Linear correlation could be found between the oxidizable fractions of iron and the generation of·OH in particles emitted from coal combustion (R2=0.32).