Spatial and seasonal distributions of carbonaceous aerosols over China

Abstract

[1] Simultaneous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during winter and summer seasons at 2003 in 14 cities in China. Daily PM 2.5 samples were analyzed for OC and EC by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance protocol. Average PM 2.5 OC concentrations in the 14 cities were 38.1 mg m À3 and 13.8 mg m À3 for winter and summer periods, and the corresponding EC were 9.9 mg m À3 and 3.6 mg m À3 , respectively. OC and EC concentrations had summer minima and winter maxima in all the cities. Carbonaceous matter (CM), the sum of organic matter (OM = 1.6 Â OC) and EC, contributed 44.2% to PM 2.5 in winter and 38.8% in summer. OC was correlated with EC (R 2 : 0.56-0.99) in winter, but correlation coefficients were lower in summer (R 2 : 0.003-0.90). Using OC/EC enrichment factors, the primary OC, secondary OC and EC accounted for 47.5%, 31.7% and 20.8%, respectively, of total carbon in Chinese urban environments. More than two thirds of China's urban carbon is derived from directly emitted particles. Average OC/EC ratios ranged from 2.0 to 4.7 among 14 cities during winter and from 2.1 to 5.9 during summer. OC/EC ratios in this study were consistent with a possible cooling effect of carbonaceous aerosols over China.

Radiocarbon-based impact assessment of open biomass burning on regional carbonaceous aerosols in North China

“…OC and EC concentrations accounted for 5.8% and 2.0% of the TSP mass concentration, while 5.6% and 2.2% for PM 2.5 . The contributions of carbonaceous species to particulate matter were notably lower than that in Chinese cities (Cao et al, 2007), and comparable with that at coastal background region, such as at Tuoji Island . The contribution of OC in PM 2.5 was slightly lower than that in TSP, while the contribution of EC was slightly higher.…”

Molecular distribution and seasonal variation of hydrocarbons in PM2.5 from Beijing during 2006

“…The high PM 2.5 concentrations in spring can be attributed to the annual influx of mineral dust from Inner Mongolia and the Xinjiang Autonomous Region (He et al, 2001). In contrast, the burning of coal and biomass for residential heating in winter likely causes the OC concentrations to be much higher than those in the non-heating seasons (Cao et al, 2007). The EC concentration in winter was lower than in autumn, however, and the seasonal differences between OC and EC may be explained not only by differences in their sources but also by the high wind speeds in winter which can disperse the aerosols around the city.…”

“…Organic compounds compose a substantial fraction of the atmospheric aerosol, especially fine PM (Cao et al, 2004(Cao et al, , 2007Kanakidou et al, 2005;Seinfeld and Pankow, 2003). It is well known that many organic species can be used as makers for source identification.…”

Spatial-temporal characteristics of PM2.5 in China: A city-level perspective analysis

“…On the one hand, the increase of PM 2.5 concentration can not only reduce atmospheric visibility (Kan et al, 2012), have negative impact on human health (Krewski et al, 2000), but also cause climate change by changing the radiation balance (Pan et al, 2014). On the other hand, PM 2.5 concentration, affected by the intensity of emission source, reliefs and climatic factors, is featured by spatial-temporal variability (Cao et al, 2007). Therefore, understanding the variations of PM 2.5 concentrations at the national scale is beneficial to us to assess their impact on human health and the environment, and carry out targeted control measures.…”