Characterization of ozone precursors in the Pearl River Delta by time series observation

of non-methane hydrocarbons

Atmospheric Environment 42 (2008) 6233–6246

Jia-Lin Wanga, Chieh-Heng Wanga, Cheng-Hsun Laia, Chih-Chung Changb, Ying Liuc, Yuanhang Zhangc, Shaw Liub, Min Shao

Guangzhou (urban) and Xinken (rural) in the Pearl River Delta, China.

Site description

From 16 October to 5 November in 2004

Guangzhou

• urban center of Guangzhou city

• about 55m above ground

• wind direction ： NNE and NNW

Xinken

• rural area

• about 10m height

• wind direction ： NE and N

※ ES sea breeze was observed in late afternoon.

Instrumentation

Guangzhou ： Time-series observation of propane, toluene, isoprene

Guangzhou ： Time-series observation of VOC (TVOC), CO, and NO

Xinken： Time-series observation of propane, toluene, isoprene

Xinken： Time-series observation of VOC (TVOC), CO, and NO

Surface windflow patterns andPBL heights (m) over the PRD

Guangzhou & Xinken

Top 10 NMHCs ranked by their concentration ranges (ppbv)

isoprene versus 3-methylpentane

hourly averaged concentration of three categories of NMHCs

Composition of NMHCs

• LPG-related species ： propane, n-butane, and iso-butane

• Guangzhou

• 58% of total alkanes , 35% of total VOC

• Xinken

• 42% of total alkanes , 22% of total VOC

Car exhaustFuel/solvent evaporation

ethylbenzene versus m,p-xylene

conclusion

• Diurnal patterns and correlation between the concentrations of NMHCs, NO, and CO suggest that vehicle exhaust is the dominant source of ozone precursors in Guangzhou.

• A large portion of NMHCs in Guangzhou is found to be related to LPG used as fuel for motor vehicles.

• The use of PCA and E/X as age indicator reveals that the air masses observed in Xinken are well aged and photochemically processed, which explains the high level of ozone frequently observed in the coastal areas of PRD such as Xinken.