The rapid industrial development and urbanization has lead to increasing particulate matter pollution over the region across the Taiwan Strait, which has significant impacts on atmospheric visibility degradation. Long...
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The rapid industrial development and urbanization has lead to increasing particulate matter pollution over the region across the Taiwan Strait, which has significant impacts on atmospheric visibility degradation. Long-term visibility trends in five typical cities across the Taiwan Strait(i.e., Xiamen and Fuzhou in the Western Taiwan Strait(WTS) region and Taipei, Taichung and Tainan in Taiwan) and its correlation with air quality and meteorological conditions were investigated by using visibility and meteorological data during 1973-2011 and critical air pollutant data during 2009-2011. Average visibilities in the WTS region were better than those in Taiwan for the period 1973-2011, with an average of 16.8, 16.6, 8.5, 10.3 and 9.0 km in Fuzhou, Xiamen, Taipei, Taichung and Tainan, respectively. Decline trends with decreasing rates of-0.5--0.1 km/yr existed in all the cities except Taipei, which had an improvement in visibility after 1992. All seasons had decreasing trends during the last 39-year period except in Taipei. The WTS region had the worse change trend comparing with Taiwan. No statistically significant weekend effect in visibility is found over the region. Visibilities were better in summer and autumn, while worse in winter and spring. Correlation analysis revealed the significant negative correlations existed between visibility and NO2 and particles PM10 and PM2.5;PM2.5 played an important role in visibility degradation. High temperature and low pressure is beneficial for better visibility. Principal component analysis further confirmed the impacts of high concentrations of air pollutants and stable synoptic systems with high pressure and low temperature on poor visibility in the region. In addition, case studies highlighted characteristics and potential causes of typical regional low visibility episodes over the region.
Accurate sampling and analysis of PM2.5 is essential to determine the compliance with promulgated ambient PM2.5 standards and identify the sources of PM2.5 pollutants. USA PM2.5 FRM(federal reference method) manual sa...
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Accurate sampling and analysis of PM2.5 is essential to determine the compliance with promulgated ambient PM2.5 standards and identify the sources of PM2.5 pollutants. USA PM2.5 FRM(federal reference method) manual samplers or FEM(federal equivalent method) monitors are commonly used but there are still rooms to improve the accuracy. In several air monitoring stations in Taiwan, it was found PM2.5 concentrations are over-estimated by the VEREWA-F701 BAM(beta attenuation monitor) by as much as 58.4 %, and 28.4-29.8 % by the earlier version of the Met-One BAM-1020s(without FEM designation). In this talk, reasons why PM2.5 concentrations are overestimated by automatic beta attenuation monitors, including positive artifacts due to acid gas adsorption by the glass fiber filter tapes used in the monitors, aerosol water content and volatilization loss of inorganic semi-volatile species will be presented(Liu et al., 2013a). Then the size-selective inlets of current manual PM samplers, including impactors and cyclones, will be reviewed and problems associated with particle bounce, evaporation loss, ambient relative humidity and substrate coating conditions will be discussed. It was found that the BGI VSCC(very sharp cut cyclone) has a better solid particle loading performance than that of the WINS impactor and oil-coated Teflon substrates are capable of resolving solid particle loading problems in impactors(Tsai et al., 2012). The results of using the newly developed MFPPS(multi-filter PM10-PM2.5 sampler) in NCTU(Liu et al., 2011) to determine artifacts during filter sampling and conditioning of PM2.5 manual samplers will be presented. The evaluation of PM2.5 monitoring accuracy of the Model 1405-DF TEOM-FDMS, which is capable of correcting for positive and negative PM2.5 artifacts, will also be presented. For obtaining accurate size-classified aerosol samples, a newly developed 10-stage NCTU micro-orifice cascade impactor(NMCI, 56 nm to 10 m) which contains new nozzle plate
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