Abstract
Suspended particles of PM2.5 in air were sampled concurrently at an urban site and a rural site in Pingtung County in southern Taiwan, in the spring, the summer and the fall of 2005. All samples were analyzed to identify eight water-soluble ions, carbonaceous contents, and 19 metal elements. Measurements reveal that the overall means of PM10 (and PM2.5) are 59.2 (47.4) μg/m^3 at Pingtung (urban) site, and 63.6 (45.7) μg/m^3 at Chao-Chou (rural) site. Although both sites exhibited strong correlations (R = 0.98 at Pingtung, and R=0.78 at Chao-Chou) between PM10 and PM2.5 masses, the mean PM2.5/PM10 ratio was 0.81 at Pingtung, higher than 0.68 at Chao-Chou, suggesting that relatively large bare lands and outdoor burning on farms may have caused more coarse particles to be present in PM2.5 at a rural site (Chao-Chou) than at an urban site (Pingtung). Results of CMB (chemical mass balance) modeling show that the main contributors to PM2.5 mass at Pingtung are vehicle exhaust (49.3-62.4%) and secondary aerosols (SO4(superscript 2-), NO3(superscript –) and NH4(superscript +) (31.2-37.8%), while those at Chao-Chou are the outdoor burning (25.3-50.4%) of agricultural waste, secondary aerosols (27.2-34.3%) and vehicle exhaust (12.0-26.9%), depending on the seasons.
Highlights
Primary particulate matter (PM) is introduced directly into the atmosphere by UTM - N ˖rr Pingtungrr Chao-Chou Taiwan Strait 20 km Legend UTM - EA: Pingtung County B Kaohsiung CityC: Kaohsiung County D Taitung County
The concentrations of PM10 and PM2.5 in the early spring, fall and winter were about two to three times those in the late spring and summer, because fall, winter and/or early spring are typically the worst periods of air quality in southern Taiwan, in which dryness, little rain and low mixing heights reduce the ability of the atmosphere to dilute the airborne pollutants (Chen et al, 2004)
The correlation coefficient (R) between PM2.5 and the PM10 masses was 0.98 at Pingtung site and 0.78 at Chao-Chou site, indicating that the mass of PM2.5 dominated that of PM10
Summary
This work presents measurements of concentrations and constituents in PM2.5, including water-soluble ions, carbonaceous contents and metal elements, at an urban site and an agricultural town in Pingtung County, made in the spring, summer and fall of 2005. Source profiles and sensitivity analysis Multivariate factor analysis was adopted to help identify dominant source categories, from which three principal factors were obtained that explained about 61% and 56% of the total variance at the Pingtung and the Chao-Chou sites, respectively (Chen et al, 2006). Based on the dominant species in individual factors and current source profiles, the three principal sources are considered to be vehicle exhaust, marine aerosols and incinerators in Pingtung, and vehicle exhaust, outdoor burning of agricultural plants and marine aerosol in Chao-Chou.
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