This study provides a survey of PM2.5 in Taichung, based on sampling analysis. Sampling locations include environmental conditions, bus stations, motorways, in-stacks, construction sites and bare-land sites, which are responsible for fugitive emissions. Chemical analysis showed that PM2.5 is composed of 25% to 27% sulfate, 18% to 30% organic carbon, 3% to 5% nitrate, 4% to 7% elemental carbon, and 4% to 7% metal components. Active emission control of sulfates, organic carbon, and their precursors SO2 and VOC would be the most effective strategy for achieving PM2.5 air quality targets.
Data indicate that oil-burning boilers emit high levels of FPM and CPM. Further analysis shows that sulfate is the most significant component of FPM. This finding corresponds with the use of sulfur-containing heavy oil and the lack of desulfurization equipment. FPM emissions from electric arc furnaces are second only to FPM emissions from oil-burning boilers in Taichung. Therefore, after regulating coal-burning boilers and oil-burning boilers, the next sensible target would be electric arc furnaces.
Actual measurements of gas boiler emissions show that while FPM is low, CPM is high. Emission reduction of CPM is a challenge for all fossil-fuel-burning (coal, oil, and gas) boilers. To reduce emissions from boilers, switching from oil and coal to gas is insufficient because while burning gas improves FPM emissions, CPM emissions remain an issue. We suggest regulatory agencies to develop emission control strategies for CPM.
As for stable isotope tracer technique used in traceability study of sulfur in PM2.5 pollution, the FPM ẟ34S-value from the Taichung Power Plant was 3.85‰, the SO2 ẟ34S-value was 0.43‰ and the diluted total PM2.5 (FPM+CPM) ẟ34S-value was 0.4‰, indicating that the proportion of total filterable particulate matters in PM2.5 was rather low and it was primarily dominated by condensable particulate matters of converted SO2. We estimated relative contributions of sulfate in PM2.5 in Dali, Taichung, based on mass balance principle. In the spring scenario, 7% of sulfate was attributed to Taichung Power Plant, while 93% of sulfate was assigned to transport from the upwind area. In the summer scenario, 5% of sulfate was caused by Taichung Power Plant, while 95% was due to transport from the upwind area.
Using a tethersonde and an optical particle counter, we estimated the construction site emission factor to be 1.34 MT/ha/yr and the fugitive PM2.5 emission factor to be 0.97 MT/ha/yr, both of which were higher than the corresponding TEDS 9.0 emission coefficients. These findings suggest that the "actual" emissions would also be higher than values from TEDS 9.0. As a result, strengthening the control of construction sites and fugitive dust may yield more air quality improvements than what one might otherwise expect.
Results of hazardous air pollutant monitoring in Central Taiwan Science Park showed while concentrations of VOCs, aldehydes, and acidic gases at the Taichung site were slightly higher than measured values at the Houli site, levels of all controlled pollutants were much lower than regulatory standards. This finding suggests that air pollution control efforts at the Central Taiwan Science Park are effective.
The PM2.5 concentration at a bus station was 1.3 ~ 4.0 times higher than values at the general air quality station. The PM2.5 level at a motorway was about 2~3 times higher than measurements at the general air quality station. These findings indicate that PM2.5 is affected by traffic and that regional air quality is also an important determinant.
