Characterization of inorganic elements within PM2.5 and PM10 fractions of fly ashes from coal-fired power plants

Abstract

In this study 15 fly ash samples were collected from 15 large-scale coal-fired power plants (CFPPs) in China. The samples were then re-suspended through PM2.5 and PM10 inlets and analyzed for the contents of 39 inorganic elements (IEs) using inductively coupled plasma-mass spectroscopy (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The results show that the particle size distributions for the 15 FAs samples exhibited bimodal patterns. The Ʃ39IEs (g g–1) for the PM2.5 (0.292–0.564) in all the 15 CFPPs were higher than that of PM10 (0.269–0.403). Except for Cu, all the other 38 IEs were more enriched in the PM2.5 with the PM2.5/PM10 ratios being 1.06–1.73. Considering 13 heavy metals, the same orders occurred between PM2.5 and PM10 with Al >> Cr > Zn > Mn > Cu > V > Pb > Sn > Co > As > Sb > Tl > Cd. More attention should be paid to the high contents of Cr in both PM2.5 (1310 mg g–1) and for PM10 (1240 mg g–1) from all 15 CFPPs. 23 IEs for PM10 and 26 IEs for PM2.5 had the geo-accumulation index (Igeo) values higher than 0, indicating different pollution levels for them. On the other hand, there was moderate to extreme levels of pollution for Cr, Zn, Cu, Pb, Sn, Sb, Tl, Cd and Al based on Igeo values. The element profiles for PM2.5 or PM10 from 15 CFPPs were similar based on low coefficients of divergence for PM2.5 (0.254 ± 0.038) and PM10 (0.244 ± 0.054) according to the comparison between any two CFPPs. Most elements with low relative enrichment factors (REF) as less than 0.70 or 0.70–1.30 indicated no or weak condensation occurred for them during coal combustion, while Cr, Cu, Zn, Sn, W and Pb had REF values higher than 1.30 indicated that significant condensation occurred for these elements.