Laboratory scale experiments were conducted to study the formation and elemental concentration of PM2.5 burning three typical Chinese coals in a drop tube furnace (DTF).The reaction temperature was 1300℃.The combustion atmosphere was O2/CO2 and O2/N2.The oxygen content in the O2/CO2 combustion was 10%

20% and 30%

respectively

the combustion in O2/N2 mixture of 1∶4 was also performed for a comparison.PM10 was collected with a 13 stage low-pressure impactor (LPI）having an aerodynamic cutoff diameter ranging from 0.03 μm to 9.8 μm.The experimental results indicate that the tri-modally distribution are observed in the O2/CO2 combustion around 0.15 μm

1.58 μm and larger than 3 μm.In comparison with the O2/N2 combustion

the O2/CO2 combustion can be effective in reducing PM2.5 formation.Besides

decreasing the oxygen content causes a reduction of PM2.5.Iron and sulfur have the quite adverse health effects comparing with other dominating elements in the particulate matter

so their concentration in PM2.5 is non-ignorable. The sulfur concentration in the central mode of PM2.5 is slightly less or even larger than the sulfur concentration in the ultrafine mode

and iron mostly exists in the central mode of PM2.5.As the combustion condition changes

the sulfur concentration in PM2.5 from different coals presents a different characteristic.