Diurnal and seasonal cycles of ozone precursors observed from continuous measurement at urban site in Taiwan

Kuang-Ling Yang, Chien-Chung Ting, Jia-Lin wang, Oliver W. Wingenter, Chang-Chuan Chan

VOCs measurement

http://www.showmecleanair.com/images/ozone_chart.jpg2

Monitoring site description

Fig. (a) Satellite mapping of Taiwan. Fig. (b) The enlarged area in (a) shows the deployment of the three stations in central Taiwan.

Instrumental condition

• Auto-GC system in monitoring station (Perkin-Elmer, USA)

A cryogen-free sorbent trap (Peltier cooling device, -30)with dual columns and dual FIDs was configured to cope with wide volatility range of components.

Excess water vapor is removed by Nafion dryer.

Denas’ switchColumns : DB-1 (60m x 0.25mm x 1μm) C6-C12

PLOT (30m x 0.25mm x 8 μm) C2-C5

Dual-trap dual-column GC system

Aspect on data quality control

• 56 target compounds with absolute concentration range 20 to 40 ppb C prepared by gravimetric method (Spctra gases).

• The hourly measurement within a day comprised 23 ambient sample injections plus one standard gas injection.

Emission source

LPG leakage

Gasoline evaporation

Biogenic emission

Vehicular exhaust

Ethane, propane

benzene benzene

Isoprene

Results and discussion

Fig. (a) benzene in February; (b)m, p-xylene in February

Fig. (a) Propane in February; (b)ethane in February

Fig. (a) Isoprene in February; (b)Isoprene in August

Diurnal and seasonal

Conclusion

• For species such as ethane and propane with relatively constant source characteristics, the change in mixing height is the dominant factor modulating abundance to reveal characteristic diurnal patterns.

• Chemical removal is only important from the seasonal point of view, which together with temperature inversion caused the observed seasonal variations