Chemical characteristics and source apportionment of atmospheric particles during heating period in Harbin, China

Atmospheric particles (total suspended particles  (TSPs); particulate matter (PM) with particle size below 10 μm, PM₁₀; particulate matter with particle size below 2.5 μm, PM_2.5) were collected and analyzed during heating and non-heating periods in Harbin. The sources of PM₁₀ and PM_2.5 were identified by the chemical mass balance (CMB) receptor model. Results indicated that PM_2.5/TSP was the most prevalent and PM_2.5 was the main component of PM₁₀, while the presence of PM_10–100 was relatively weak. SO₄^2?  and NO₃^? concentrations were more significant than other ions during the heating period. As compared with the non-heating period, Mn, Ni, Pb, S, Si, Ti, Zn, As, Ba, Cd, Cr, Fe and K were relatively higher during the heating period. In particular, Mn, Ni, S, Si, Ti, Zn and As in PM_2.5 were obviously higher during the heating period. Organic carbon (OC) in the heating period was 2–5 times higher than in the non-heating period. Elemental carbon (EC) did not change much. OC/EC ratios were 8–11 during the heating period, which was much higher than in other Chinese cities (OC/EC: 4–6). Results from the CMB indicated that 11 pollution sources were identified, of which traffic, coal combustion, secondary sulfate, secondary nitrate, and secondary organic carbon made the greatest contribution. Before the heating period, dust and petrochemical industry made a larger contribution. In the heating period, coal combustion and secondary sulfate were higher. After the heating period, dust and petrochemical industry were higher. Some hazardous components in PM_2.5 were higher than in PM₁₀, because PM_2.5 has a higher ability to absorb toxic substances. Thus PM_2.5 pollution is more significant regarding human health effects in the heating period.