Particulates and particulates-bound mercury (Hg(p)) sizes (PM 18 , PM 10 , PM 2.5 , PM 1 , PM ) distributions study by using MOUDI sampler at a complex sampling site

The objectives of this study were to measure ambient air particles concentrations of different particulates sizes ranges (PM18, PM10, PM2.5, PM1, PM<1) at a complex (traffic, residential and commercial) site. Besides, particulates-bound mercury (Hg(p)) concentrations for various particulates sizes (PM18, PM10, PM2.5, PM1, PM<1) at mixed site were also studied. Finally, ambient air particulates and Hg(p) size distributions were also described at this complex sampling site. The results showed that the average PM18, PM10, PM2.5, PM1, PM<1 concentrations were 48.83, 41.78, 35.41, 19.89, and 11.86 μg/m3, respectively. And the average ambient air particulates-bound mercury (Hg(p)) which attached on PM18, PM10, PM2.5, PM1, PM<1 particles concentrations were 0.0838, 0.0867, 0.0790, 0.0546, and 0.0373 ng/m3, respectively, in the summer season. In addition, the average ambient air Hg(p) which attached on PM18, PM10, PM2.5, PM1, PM<1 particles concentrations were 0.0175, 0.0144, 0.0120, 0.0092, and 0.0057 ng/m3, respectively, in the autumn season. Finally, the average ambient air Hg(p) which attached on PM18, PM10, PM2.5, PM1, PM<1 particles concentrations were 0.0070, 0.0053, 0.0038, 0.0026, and 0.0014 ng/m3, respectively, in the winter season. And July has the average highest PM18 and PM10 concentrations. As for PM2.5, PM1 and PM<1 particulates, the average highest particulates concentrations all occurred in November. In addition, the highest average Hg(p) in PM18, PM10, PM2.5, PM1, and PM<1 concentrations all occurred in July. Moreover, the average particles and particulates-bound mercury m.m.d. values were ranged from 1.0 to 1.8 and 0.7 to 2.0 μm from July to December of 2018, respectively, at this mixed sampling site. As for monthly ambient air particles sizes distributions, the results further showed that the main peaks for July, September, and December all occurred in the sizes of 10–18 μm. The main peaks for October and November all occurred in the sizes of 2.5–10 μm. As for monthly Hg(p) sizes distributions, the results further showed that the main peaks for July occurred in the size of 0.3–1 μm. The main peak for September occurred in the size of 1–2.5 μm. The main peaks for October to December all occurred in the size of 10–18 μm. The above finding further concluded that the particulates-bound mercury (Hg(p)) was tended to be associated with the large particles sizes mode during the winter season. Finally, this study further shows that the Taichung Thermal Power Plant was responsible for the main emission source of Hg(p) especially in summer season of Central Taiwan.