Hourly data from 3 photochemical assessment monitoring stations (PAMS) located in central Taiwan were analyzed for the photochemical evidence and its correction with the meteorological data to elucidate the mechanism behind ozone formation in downwind rural central Taiwan. Using ratios of ethylbenzene vs. xylene as an aging indicator along with meteorogical data simultaneously collected at the stations we have successfully explained the why and how high level of ozone is formed in Chushan area where little VOCs sources are known to exist. Prevailing winds from northwest carry aged air mass passing over Chushan area around noon can be regarded as a general qualitative description for elevating local ozone level. Dramatic seasonal effects in ozone formation have also been noticed in that more aged air mass accompanying by higher ozone is encountered more frequently in October and in July. It can be preliminarily concluded that meteorology is the dominant factor which affects the absolute concentrations as well as the degree of aging and hence the level of ozone in downwind rural areas of central Taiwan such as Chushan. The research methodology developed in this project is maturing along with the gradual improving in PAMS network over the past two years. Similar techniques are expected to be applicable elsewhere in northern and southern Taiwan once other PAM stations become fully functional.

Ozone、VOCs、Health Risk Assessment