dc.description.abstract |
Yunlin is located in central-southern portion of western Taiwan. The local industrial emissions (Maliao industry), vehicle exhausts, and burnings of agriculture wastes all contribute to the poorer air quality in Yunlin. Besides, the emissions from nearby power plants, Taichung metropolitan area, and Changhua industrial park also contribute to the local air pollution problem in Yunlin County. The local circulation such as the land-sea breeze might transport the air pollutants toward the inland areas and induce high concentrations.
Source apportionment (SA) based on observation data or 3-Dimention air quality model can provide the relationship between emission sources and concentration of air pollutants. This study was conducted to investigate the main emission source that contributes to the PM2.5 concentration in Yunlin County using CMAQ SA technique.
The WRF version 3.7.1 are conducted and the observation nudging technique is applied in WRF modeling to nudge surface observed temperature, wind speed and wind direction data from Taiwan Central Weather Bureau and Environmental Protection Agency to improve the meteorological conditions. This study focused on the emission from Yunlin and Taichung power plants through BFM (Brute Force Method) and ISAM (Integrated Source Apportionment Method) technique. The emission contribution estimated by BFM and ISAM had high correlation with each other. Due to the less computational time from ISAM, CMAQ version 5.0.2 with ISAM SA technique were applied to investigate the contributions of emissions from Yunlin County and Taichung metropolitan area to concentration of pollutants.
Three air pollution episodes were studied. The first episode occurred from Nov 8, 2015 to Nov 9, 2015. Nov 8, 2015 was associated with a weak synoptic weather condition and PM2.5 mainly came from local emissions released within Yunlin County. Therefore, reducing the Yunlin local emissions could decrease concentration of PM2.5. Nov 9, 2015 was affected by a continental anticyclone and weak northeasterly monsoonal flow brings the pollutants from upwind Taichung metropolitan area. The second and third episodes occurred from Oct 27, 2016 to Oct 28, 2016 and Nov 18, 2016 to Nov 19, 2016, respectively. Oct 28, 2016 was slightly affected by the continental anticyclone and the continental anticyclone was moving away to the East of Taiwan on Nov 19, 2016. The average wind speed on Oct 28, 2016 and Nov 19, 2016 were weaker than Nov 9, 2015, but Taichung contributed more to PM2.5 concentration due to the long-lasting northerly wind. Due to the influence of northerly wind flow, there are still small portion of pollutants from near surface emissions from Yunlin and the majority are area and line sources. In addition, the emissions from Mailiao industrial complex could also affect the air quality in coastal area of Yunlin. | en_US |