ABSTRACT
To evaluate the difference in hazardous air pollutants in PM2.5 between reference method (National Institute of Environmental Analysis;NIEAA205) and high-volume air sampler (European standard:EN14907 and Japan method), we set up a sampling station on the campus of National Yang-Ming Chiao Tung University, northern Taiwan, during 2014-2015. Both vapor and solid phases of dioxins were collected using high-volume samplers, according to EN14907 and Japan method. The flow rate was set at 500 L min(-1) and 1000 L min(-1), respectively. To compare the difference with the high-volume air sampler, we simultaneously used the reference air sampler based on Taiwan NIEA A205.11C, at the flow rate of 16.7 L min(-1) (BGI PQ200-FRM). The mass concentrations of PM2.5 measured with NIEA A205, EN14907, and Japan method were 20.2 +/- 8.79, 25.4 +/- 10.5 and 28.6 +/- 13.9 mu g m(-3), respectively. The difference of the mass concentration of PM2.5 obtained from two different methods was lower than 3.9%. Moreover, the concentrations of PCDD/F between solid and vapor phases were 56.9-1,090 and 38.6-67.1 fg m(-3) via EN14907 and 51.1-1,150 and 18.4-81.8 fg m(-3) via Japan method, respectively. Obviously, there is no significant difference between these two samplers. Compared to the method of NIEA, high volume air sampling method not only provided equivalently good quality data but offer a higher sample quantity for analyzing the trace level chemical component of hazardous air pollutants and the toxicity in different areas.
ABSTRACT
Long-range pollution transport (LRT) events have a wide impact across East Asia, but are often difficult to track due to imprecise emission inventories and changing domain scales as the plume moves from source to receptor locations. This study adjusts a bottom-up emission inventory based on changes in remotely sensed NO2 column densities for a source region of East Asia, then with CMAQv5.2.1 simulates transport of LRT plumes to Taiwan. Adjustment of an emissions inventory based on satellite measurements during the COVID-19 lockdown in China led to a -59% reduction in emissions over the relevant source area in China compared to base emissions. As a result, PM2.5 mass concentrations were reproduced to match observations (mean fractional bias, MFB of -13.9% and 18.5% at a remote and urban station) as the plume passed through northern Taiwan. Furthermore, the OMI-adjusted emissions simulation brought all of the major PM2.5 components to within -50% of the measured values. Another LRT event from 2018 with more subtle OMI-adjustments to the emissions was also simulated and with improved overall PM2.5 mass concentration at the northern tip of Taiwan (MFB: -91.5%) compared to the base model (MFB: -102.1%), and an acceptable index of agreement (0.78). For the 2018 event, non sea-salt sulfate concentrations were consistently underpredicted (0.2-0.4), while nitrate concentrations were overpredicted by up to factor of 11. Copernicus Atmosphere Monitoring Service (CAMS) reanalysis of the PM(2.)5 concentrations shows high sulfate concentrations in eastern China in the areas associated with 72-h back-trajectories from northern Taiwan during both events, lending support for future model investigations of sulfate source area production and transport to Taiwan. In order to better track these LRT events out of East Asia and optimize OMI-adjustment methodology, it is recommended to explore other satellite-based products to map unaccounted for SO2 sources upstream of Taiwan.