Delineation of air-quality basins utilizing multivariate statistical methods in Taiwan

This study analyzed time-series data of air pollutants, O3 and PM10, to determine the division of air-quality basins in Taiwan by employing multivariate statistical methods, Varimax rotational method and cluster analysis. The databases of air pollutants, daily maximum 1-h O3 and daily mean PM10 concentrations, were obtained from the ROC Environmental Protection Administration (ROC EPA) for the period from 1 July 1993 to 30 June 1998. The Varimax rotational method allowed us to delineate five homogenous PM10 subregions that cumulatively accounted for 85.6% of the total variance. The time-series analysis of rotated component scores associated with the PM10 subregions revealed that all divided subregions presented a strong seasonal cycle. Four of five subregions had higher component scores and PM10 concentrations from November to January. One subregion experienced higher values from March to May. The use of Varimax approach and cluster analysis on the O3 and PM10 confirmed that O3 was more demonstrative of the air-quality basins in Taiwan. Both the Varimax rotational method and the cluster analysis have specific advantages for the division of air-quality basins. This study also proposes a delineation of five air-quality basins having homogenous O3 features as an alternative assignment of atmospheric carrying capacity control regions.