Photochemical smog modeling for air quality management of Bangkok metropolitan region | |
| Author | Zhang, Baoning |
| Call Number | AIT Diss no.EV-02-07 |
| Subject(s) | Photochemical smog--Thailand--Bangkok Air quality--Thailand--Bangkok |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Status and trend of 0 3 were studied in relation to the local meteorological conditions using 5-year monitoring data at 16 stations in the Bangkok Metropolitan Region (BMR). Meteorology-unadjusted trend shows a slight increase in 0 3 from 1998 to 2000. 0 3 production in BMR is effective when the ratio of peaks morning NOx to NMHC is in the range of 0.03-0.15 with optimum ratio of around 0.07. The ratio of 0.06 was observed in summer, 0.04 in winter, and 0.03 in rainy season. The seasonal variations of NOx/NMHC ratios are consistent with the seasonal variations of 0 3 concentration in Bangkok. Seasonal fluctuations of 0 3 were also found to relate to the regional transport associated with the Asian monsoon. Photochemical smog model systems, UAM-V/SAIMM and CHIMERE/ECMWF, were applied to gain an insight view of the formation and accumulation of the pollutants in the simulation domain of 88km x 72k. Horizontal grid of 4km x 4km was selected. The vertical structure of the SAIMM model consisted of 16 levels with the model top at 8500m, while the UAM-V model consisted of 6 layers with the top height of 50m, lOOm, 500m, 1500m, 2500m, and 4000m; CHIMERE model also consisted of 6 layers with the top height of 50m, 300m, 600m, 1200m, 2000m, and 3000m, while ECMWF consisted of 10 layers between 0 to 3000m. Daily gridded anthropogenic emission database including area sources (residential, petrol service station, airport, and refuse disposal), mobile sources, and point sources prepared by the Pollution Control Department for 1997 was used. Biogenic VOC emissions including isoprene and monoterpene were determined based on ecosystems. CBM-IV and MELCHIOR mechanisms were used for UAM-V and CHIMERE, respectively. Due to the lack of detail VOC emission profiles for major sources m Bangkok, the well developed European VOC emission profile was used in this study. 0 3 episodes of January 13 to 14 and April 28 to 29 in 1997 were selected for simulation study. The January episode was ofrepresentative meteorological conditions while the April episode was of abnormal conditions with El Nifio. Two start-up days were used to minimize the effects of the initial concentrations field. Observed pollutant concentrations were selected as surface boundary conditions; constant values were selected as upper layer lateral boundary conditions for UAM-V. Large scale CHIMERE model simulation results served as regional CHIMERE model upper lateral boundary inputs for this study. For April episode, the UAM-V model showed a reasonable good dispersion pattern of CO but there was no good agreement between simulated and observed 03 values. The El Nifio meteorological conditions with the intrusion of 0 3 and its precursors and lack of upper air measurement of 0 3 and other pollutants used for model lateral boundary conditions maybe the reason for the discrepancy. Besides, the April episode was associated with stronger sea breeze. The lack of surface and upper air meteorological data of the sea limited the model system UAM-V/SAIMM capacity to adequately simulate sea-land breeze. For the January episode, visual spatial and temporal comparisons between simulated results by two models and observations for 0 3, CO, NOy, and Ox, and statistical performance evaluations of the models were conducted. Both models produced reasonable good 0 3 predictions for the domain. However analyzing the pollutants concentrations (CO, NOy, and Ox) especially at periods of the day when no photochemical reactions occurred revealed anthropogenic emissions maybe overestimated by PCD. A series of test runs with CHIMERE and UAM-V were conducted and a modified emission data were proposed which has the mobile source NOx, CO, and VOC of 50%, 80%, and 40-50% of the original PCD emission data, respectively. 0 3 simulation result for January 14 (Tuesday) was better than January 13 (Monday). One of the reasons was the use of daily average of mobile sources for all days of the year without separating into different days of a week. Actually there could be higher traffic flow on Monday (Jan 13) than other weekday. Therefore for future study only conditions of Jan 14 was used. For UAM-V and CHIMERE models on Jan 14 based on the modified emissions, mean normalized bias error (MNBE) and mean normalized gross error (MNGE) for 0 3 have been improved and met the USEP A recommended values for 0 3 predictions. MNBE and MNGE for CO and NOy were also improved than original PCD data. Two model systems were used to simulate contributions of different emission sources to the 0 3 in Bangkok. It was found that Bangkok photochemical pollution is mainly caused by the city anthropogenic emission sources. Biogenic sources only contribute about 10- 20ppb of 03. Domain boundary areas contribute about 25-35% to the maximum ozone in Bangkok. To study the sensitivity of 03 formation to change in VOC and NOx precursors, isopleths of maximum diurnal ozone concentrations across Bangkok were constructed. Sensitivity analysis showed that 03 formation in Bangkok is more sensitive to VOC than to NOx emissions. voe emission should be at least reduced by around 60% to ensure that the highest ozone concentration in Bangkok is below the standard of 1 OOppb. Different management strategies including Stage I and Stage II control for HC from fuel distribution and service stations, phasing out 2-stroke motorcycles, 100% gas fired power plant in BMR, 100% CNG buses, and MTBE replacement by ethanol in gasoline have been studied to check the impacts on photochemical smog pollution. For CHIMERE and UAM-V models based on original PCD emissions, simulated 0 3 peak value would reduce by 1.5- 2.6% for scenario la (Stage I implementation), 2.8- 5.0% for scenario 1 b(Stage I and II implementation), 19- 25.3% for scenario 2 (replacement of 2- stroke motorcycles by 50% 4-stroke Honda and 50% 4-stroke Yamaha); and increase by 6.4% for scenario 3 (100% gas fired power plant with SNCR technology by UAM-V), 5.1- 6.6% for scenario 4 (100% CNG buses), 17% for scenario 5 (MTBE replacement by ethanol by UAM-V). UAM-V simulation alone based on modified emissions showed simulated 0 3 peak value reduce by 2.9%, 5.7%, and 17.9% for scenario la, lb, and 2; peak 0 3 value increase by 7.4%, 4.4%, and 12% for scenario 3, 4, 5, respectively. Development of strategies to reduce 0 3 pollution in Bangkok needs to take into account the complicated relationships of 03 and the precursors at the present situation of the city. Further development of the emission database for BMR as well as the suitable modeling system for real time forecast of photochemical pollution for the city is recommended. |
| Year | 2002 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Nguyen Thi Kim Oanh; |
| Examination Committee(s) | Suphat Vongvisessomjai;Fukushi, Kensuke;Mark, Ole; Supat Wangwongwatana;Fox,Douglas G. ; |
| Scholarship Donor(s) | State Education Commission of P.R. China; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2002 |