Using a Photochemical Index to Discuss the Ozone Formation and Estimate Hydroxyl Concentration at Downwind Area

Received: November 30, 2009
Revised: November 30, 2009
Accepted: November 30, 2009
Download Citation: RIS|BibTeX|https://doi.org/10.4209/aaqr.2009.05.0026  

Cite this article:
Tseng, K.H., Wang, J.L., Kuo, P.H. and Tsuang, B.J. (2009). Using a Photochemical Index to Discuss the Ozone Formation and Estimate Hydroxyl Concentration at Downwind Area. Aerosol Air Qual. Res. 9: 441-452. https://doi.org/10.4209/aaqr.2009.05.0026

ABSTRACT

Ozone problem is deteriorating in the mountainous areas in central Taiwan. High level of reactive ozone precursor coming from traffic, industrial activities and vegetation upwind produces ozone episodes in the downwind area. Continuously monitoring of ozone and its precursors with hourly resolution was performed by three photochemical assessment monitoring stations (PAMS) forming a line of upwind, midway and downwind observation. A ratio (ethylbenzene/m, p-xylene) which showed high agreement with ozone concentrations were used as a sensitive photochemical index to represent the degree of photochemical reaction. It was found that both the peaks of the photochemical index and the ozone concentration around noon exhibited a consistent descending order of Jhushan (downwind) > Caotun (midway) > Chonglun (upwind). Furthermore, when coupling photochemical index of the three PAMS with kinetic equations and the trajectory model, OH concentrations were estimated. The results showed that the OH concentration reached the maximum (2.1 × 10⁶ - 2.3 × 10⁶ molecule/cm³) at noon to early afternoon on a daily cycle.

Keywords: Volatile organic compounds; Photochemical index; Backward trajectory; OH concentration