Variations of surface ozone concentration across the Klang Valley, Malaysia

Hourly air quality data covering the period 2004-2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O-3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O-3 across the Klang Valley. A high surface O-3 concentration is usually observed between January and April, while a low surface O-3 concentration is found between June and August. Analysis of daily variations in surface O-3 and the precursors - NO, NO2, CO, NMHC and UVb, indicate that the surface O-3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NO, particularly through tri-tration processes. Although results from our study suggested that NMHCs may influence the maximum O-3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O-3 around the Klang Valley. HYSPLIT back trajectories (-72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O-3 in the study area. Results show that 47% of the high O-3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast. (C) 2012 Elsevier Ltd. All rights reserved.