| dc.description.abstract | Abstract
The environmental impact and health effect of atmospheric aerosol has drawn a great attention. The first Taiwan aerosol supersite for continuous aerosol properties has been fully operated at Hsin-Chuang City in March 2002. Aerosol properties include PM2.5 and PM10 mass concentrations, size distribution, carbon content, sulfate, nitrate, light-scattering coefficient, black carbon, and polyaromatic hydrocarbons are monitored continuously. In addition, meteorological factors are collected collocatedly.
The annual average of PM2.5 mass concentrations ranging from 31 to 33 μg m-3 are found based on data collected from March 2002 to February 2005 at aerosol supersite. Concentrations of major aerosol properties are 3.4-8.2 μg m-3 for organic carbon, 2.5-4.1 μg m-3 for elemental carbon, 5.0-7.7 μg m-3 for sulfate, and 1.3-3.6 μg m-3 for nitrate, respectively. Back trajectory analysis from Hysplit model shows air masses arriving at Hsin-Chuang site can be divided into from mainland China’s coastline transport, oceanic transport, and anticyclonic outflow during the stidy period. The PM2.5 mass concentrations for these three types of air mass are 40 μg m-3, 28 μg m-3, and 56 μg m-3, respectively. Sulfate average for air masses from mainland China’s coastline transport and anticyclonic outflow is around 8 μg m-3. In contrast, the highest nitrate is at 6.1 μg m-3, which occurred only under anticyclonic outflow. The statistic of high aerosol concentration event (PM2.5> 65μg m-3) shows anticyclonic outflow is the most frequent occurring type for the occurrence of 63. The estimation of senondary aerosol formation at Hsin-Chuang site is conducted by using EC-tracer method for calculating secondary organic carbon and chlorine loss for secondary inorganic aerosol. The estimation of secondary aerosol can also be calculated by using the ratio of PM2.5/CO for estimating primary aerosol. The secondary aerosol from the latter method can reach as high as 30 μg m-3 when O3 > 120 pp.
In this study, an intensive aerosol collection for six days was conducted from April 4 to 9, 2005. The aerosol size-distribution analysis reveals that most aerosol water-soluble ions are unimodally distributed except for mass concentration and nitrate they are bimodally distributed. Peak aerosol diameter is either 0.56 μm for unimodal distribution or 0.56 and 3.2 μm for bimodal distribution. Aerosol carbonyl analysis shows major components at Hsin-Chuang site are formaldehyde, acetaldehyde, and acetone. Normal day concentrations for formaldehyde, acetaldehyde, and acetone are 4.4±2.0 μg m-3, 9.8±8.3 μg m-3, and 16.5±10.0 μg m-3, respectively. In contrast, event day concentrations for formaldehyde, acetaldehyde, and acetone are 11.0±6.3 μg m-3, 17.1±11.9 μg m-3, and 34.0±19.1 μg m-3, respectively. A positive correlation between aerosol carbonyl and daily maximum ozone concentration is found. Among carbon fractions, aerosol carbonyl has a better relationship with OC2 and is even better as aerosol diameter getting smaller. It suggests these small particles with OC2 composition are originated from photochemical reactions. | en_US |