es9b03453_si_001.pdf (1.45 MB)
Formation and Evolution of Solvent-Extracted and Nonextractable Environmentally Persistent Free Radicals in Fly Ash of Municipal Solid Waste Incinerators
journal contribution
posted on 2019-08-23, 13:46 authored by Song Zhao, Pin Gao, Duo Miao, Lan Wu, Yajie Qian, Shanping Chen, Virender K. Sharma, Hanzhong JiaEnvironmentally
persistent free radicals (EPFRs) are emerging contaminants
occurring in combustion-borne particulates and atmospheric particulate
matter, but information on their formation and behavior on fly ash
from municipal solid waste (MSW) incinerators is scarce. Here, we
have found that MSW-associated fly ash samples contain an EPFR concentration
of 3–10 × 1015 spins g–1,
a line width (ΔHp‑p) of ∼8.6
G, and a g-factor of 2.0032–2.0038. These
EPFRs are proposed to be mixtures of carbon-centered and oxygen-centered
free radicals. Fractionation of the fly ash-associated EPFRs into
solvent-extracted and nonextractable radicals suggests that the solvent-extracted
part accounts for ∼45–73% of the total amount of EPFRs.
Spin densities of solvent-extracted EPFRs correlate positively with
the concentrations of Fe, Cu, Mn, Ti, and Zn, whereas similar correlations
are comparatively insignificant for nonextractable EPFRs. Under natural
conditions, these two types of EPFRs exhibit different stabilization
that solvent-extracted EPFRs are relatively unstable, whereas the
nonextractable fraction possesses a long life span. Significant correlations
between concentrations of solvent-extracted EPFRs and generation of
hydroxyl and superoxide radicals are found. Overall, our results suggest
that the fractionated solvent-extracted and nonextractable EPFRs may
experience different formation and stabilization processes and health
effects.