Abstract:
This study aimed to investigate the vertical concentration profiles of PM2.5, PM2.5-10, and metals around a high-rise building in Bangkok. Both PM's indoor and outdoor concentrations were measured at 4.5, 51.5, and 138.5m height of the office building located in the urban area. The PM measurement was continuously performed for seven days consecutively during rainy (September 23 - 29, 2019), winter (January 13 - 19, 2020), and summer (March 2 - 8, 2020). The metals in PM, including As, Cd, Cr, Pb, Mn, Ni, Cu, Fe, Zn, Mg, K, Ca, and Ba, were analyzed by ICP-MS. The result showed that the average outdoor concentrations of PM2.5 and PM2.5-10 were highest in winter (43.5 ± 10.7 and 16.5 ± 2.4 µg/m3) followed by those of rainy (31.7 ± 12.8 and 14.6 ± 4.3 µg/m3) and summer (17.1 ± 5.8 and 12.8 ± 2.5 µg/m3), respectively. The outdoor concentrations of PM2.5 at the height of 4.5, 51.5, and 138.5m were not significantly different at each sampling height in all seasons at 95% confidence interval (p > 0.05). For PM2.5-10 observed during rainy and summer, there were no significant differences between all sampling heights at 95% confidence interval (p > 0.05). While the concentration at 138.5m in winter was significantly less than those of 4.5 and 51.5m, 37.4% decreased from a height of 4.5m. The averaged PM2.5/ PM10 ratios was highest in winter (0.72 ± 0.05), followed by rainy (0.68 ± 0.06) and summer (0.56 ± 0.08), respectively. The relationship between indoor and outdoor concentrations of PM2.5 showed significant positive correlations at all heights (r = 0.926, 0.907, and 0.976, respectively); however, for PM2.5-10, the significant positive correlations was only at 138.5m (r = 0.629). The average I/O ratios of both PM at the height of 51.5m were lower than those of 4.5 and 138.5m. The concentrations of total metals in PM2.5 and PM2.5-10 were also not significantly different between all sampling heights in all seasons. The average I/O ratios of metals were mostly higher than 1. The composition of metals in outdoor PM at all sampling heights were similar. K, Ca, Mg, Fe, and Zn were found as the dominant metal in both PM, while other metals lower than 1%, including Cr, As, Pb, Cu, Mn, Ba, Ni, and Cd, were considered as trace metals. For the composition of metals in Indoor PM, Ca was found the highest fraction. The principal component analysis (PCA) result showed that the possible sources of metals in PM2.5 were vehicle emission, soil dust and construction, biomass burning, brake and tires wear, and oil burning. Likewise, the possible sources of metals in PM2.5-10 were vehicle emission, oil burning and iron/steel industries, sea salt, biomass burning, and soil dust and construction.