[Seasonal Variation of Carbon Fractions in PM2.5 in Heze].

PM2.5 samples were collected in Heze from August 2015 to April 2016. Eight carbon fractions were analyzed by a thermal/optical carbon analyzer, and organic carbon (OC) and elemental carbon (EC) analyses were obtained. The OC/EC ratio and the correlation between OC and EC were analyzed. Secondary organic carbon (SOC) mass concentration was estimated by the OC/EC ratio method; and eight carbon fractions were analyzed using a principal component analysis. The results showed that:① The annual average mass concentrations of OC and EC were 1.2-60.6 µg·m-3 and 0.6-24.8 µg·m-3, respectively; and the characterization of OC and EC percentages in PM2.5 during different seasons were similar with winter > spring > autumn > summer. ② The annual average OC/EC ratio was 2.6±1.0, and the correlations between OC and EC during spring, summer, autumn, and winter were 0.91, 0.56, 0.86, and 0.75, respectively, and the estimated mass concentration of SOC was (4.7±5.0) µg·m-3. ③ The characterization of eight carbon fractions percentages in PM2.5 in the different seasons demonstrated similar seasonal variations, with EC1 having the highest percentage and EC3 having the lowest percentage. The result of the principal component analysis showed that coal burning, motor vehicle emissions, and biomass burning were the major sources of carbon.