Carbonaceous aerosol is one of the important constituents of fine particulate matter (PM2.5) in Southern China, including Guangdong Province (GD) and Hong Kong (HK) in Pearl River Delta (PRD) region. During the study period (October and December of 2002, and March and June of 2003), organic carbon (OC) ranged from 3.52 - 7.87 ug m3 in Hong Kong and 4.14 - 20.19 ug m3 in Guangdong Province from simultaneous measurements at three sites in HK and four sites in GD province. Compared to GD province, the relative homogeneous distribution of carbonaceous aerosol in Hong Kong suggests that HK is more representative of the regional background in PRD region while carbonaceous PM in GD are the sum of regional background and local sources. This study examined the excess OC at GD province by looking into eight primary sources contributing to those local sources of OC with chemical mass balance modeling (CMB) in a combination with molecular markers analyzed by gas chromatography/mass spectrometry (GC/MS). Excess OC at Guangzhou, the capital city of GD province, was consistently high, ranging from 9.8 - 13.6 ug m3. Four primary sources including gasoline exhaust, diesel exhaust, biomass burning, and coal combustion accounted for more than 50% of excess OC in GD province, especially in December (76%). Mobile sources alone can contribute about 30% of excess OC, but it is very interesting to find that the split between diesel exhaust and gasoline exhaust are completely different in Guangzhou and Shenzhen, with gasoline exhaust as 77% in Guangzhou while diesel exhaust as 71% in Shenzhen. The unexplained or other excess OC was the highest at the rural site, but in general less than 20% at other sites. Coal combustion source was unique in that it exhibited relatively homogeneous spatial distribution, indicating it was still an important source of local carbonaceous aerosol in GD province (17% of excess OC) during the study period. This analysis revealed that primary emissions are important sources of excess OC in the PRD region and there is a need to reduce the emissions of mobile sources, biomass burning and coal combustion in order to improve air quality in Southern China, especially gasoline exhaust in Guangzhou.
Lynn Garry Salmon <>{