This study describes the characteristics of particulate matter and carbonaceous species at different air quality levels. The concentrations of PM10, PM2.5, PM1, and carbonaceous species in PM2.5 were monitored on-line in Langfang City on March 1-22, 2016. The PM10, PM2.5, and PM1 concentrations were 204.1 μg·m-3, 107.9 μg·m-3, and 87.8 μg·m-3, respectively. Diurnal variations in particulate matter concentrations showed a bimodal distribution. In general, the mass concentrations of particulate matter and carbonaceous species (OC, EC, SOC, and POC) and the ratios of PM1/PM10 and PM2.5/PM10 were lower on better air quality periods. However, the mass concentration of PM10 was the highest on moderately polluted times. The ratios of PM1/PM10 and PM2.5/PM10 reached minimum values on moderately polluted times.The mass concentration of OC was slightly lower in moderately polluted periods than slightly polluted times; it was significantly lower in moderately polluted periods compared to severely polluted time periods. Hourly concentrations of OC and EC were lower between the hours of 13:00 and 23:00 compared to slightly polluted and severely polluted periods. The proportion of PM2.5 and PM1 decreased in moderately polluted time periods, consistent with the corresponding primary pollutants. Besides, the value of OC/EC was larger than 2.0. The concentrations of SOC and POC estimated using the minimum OC/EC ratio were 12.2 μg·m-3 and 5.0 μg·m-3, respectively.
Keywords: Langfang City; air quality levels; carbonaceous fraction; on-line monitoring; particulate matter.