Studies on impact of carbonaceous aerosol on atmospheric environment in large cities in China

Research Project , Research Report 2006

Yutaka Kondo Research Center for Advanced Science and Technology, The University of Tokyo

Abstract

Distributions of aerosols in Asia are determined by their emissions, transport, and removal processes. Emissions rates of primary aerosol in Asia estimated by previous studies are still very uncertain. It is even more difficult to estimate production rates of secondary aerosol. We aim to understand average levels, variabilities, and emission ratios of elemental carbon (EC) and organic carbon (OC) through measurements of concentrations of carbonaceous aerosol (EC and OC), which constitutes a major component of aerosols in Asia. These measurements will improve estimates of emission rates of EC and OC in source regions accurately and lead to accurate prediction of aerosol distributions. We developed a system for continuous measurements of EC, OC, CO, and CO2 in Beijing, China, which is one of representative mega-cities in Asia. We installed it in the campus of Peking University in October-November 2005 and conducted intensive measurements during the period of November 2005-March 2007.
 The EC and CO concentrations decreased with the increase in the wind speed (WS). The correlations of EC with CO and CO2 were generally compact throughout the measurement period and the slopes of the EC-CO and EC-CO2 correlations (ΔEC/ΔCO and ΔEC/ΔCO2) are therefore useful parameters in investigating EC sources. The average EC concentrations for each season ranged between about 6 and 8 μg/m3. CO showed minimum values of about 1.1 ppmv in spring-summer and maximum of about 2.1 ppmv in winter. On calm days (WS < 2m/s), the average EC concentrations started to increase at around 1800 LT and continued to increase until around 0200 LT. The ΔEC/ΔCO ratios also showed similar diurnal patterns except for winter, when they showed little diurnal variation. These results suggest that there are strong EC source in Beijing during the nighttime, possibly from diesel vehicles. The high CO in winter indicates strong source of CO due to domestic heating and this suppresses the diurnal variation in the ΔEC/ΔCO ratios.

Keywords:

carbonaceous aerosol, elemental carbon, organic aerosol, carbon monoxide, China