The study of Central Taiwan particles concentration variations during earthquake period

Abstract

Ambient particle concentration was taken on the traffic sampling site over the Chung-Chi Road over the bridge (CCROB) in front of Hungkuang Institute of Technology (HKIT). The sampling time was from August 1999 to December 1999. During the sampling period, Taiwan's biggest earthquake in more than a century registered 7.3 on the Richter scale (Taiwan Chi-Chi Earthquake). Besides, there are more than 20,000 aftershocks following the Taiwan Chi-Chi Earthquake within 3 months. Thus, the mass concentration of particles with aerodynamic diameters smaller than 2.5 μm (PM 2.5) and PM 2.5–10 was also collected then compared with the total mass concentration of suspended particles (TSP) in this study. The average TSP, PM 2.5–10, and PM 2.5 concentrations are 106, 24.6, and 58.0 μg/m 3, respectively, after the Taiwan Chi-Chi Earthquake. The average TSP concentrations before and after Taiwan Chi-Chi Earthquake were 69.6 and 127 μg/m 3, respectively. In addition, statistical analysis of the PM 10 data from this study and EPA in 1999 yielded a T statistic of 0.147, which is smaller than t (0.975,18)=2.101. It is indicated that there was no significant difference. So, the PM 10 concentrations measured after Taiwan Chi-Chi Earthquake in this study were also greater than those data previously obtained from Taiwan EPA in the same region of this area. The relationships between TSP, PM 10, PM 2.5–10, and PM 2.5 particle concentrations and wind speed ( R 2) are .77, .59, .58, .58, respectively. And the ratios of PM 2.5/PM 2.5–10, PM 2.5/PM 10, and PM 10/TSP are 221%, 67.2%, 58.0%, respectively. The average ratios of PM 2.5/PM 2.5–10 and PM 2.5/PM 10 increase by about 120% and 17%. It indicated that the fine-particles concentration increases compared to the coarse-particles concentration after 921 Taiwan Chi-Chi Earthquake. And the proposed reasons are that local motor vehicle emissions combined the fine particles transported from the Chi-Chi epicenter. More importantly, the wind direction was mainly blown from southeastern part. These two main factors enhance the fine-particles concentration in this area.