Nine stationary photochemical assessment monitoring stations (PAMS) has been constructed since its first station being established in Taichung city in 2003. A set of quality assurance and control routines has gradually evolved into a standardized procedure to ensure data quality. Monitoring data of 54 target compounds from any one of the nine stations can now be assessable to users. For certain stations, data length of more than 10 years was achieved and readily assessable in the database with a data completion rate over 85%, which constitutes the most valuable asset in the systematic study of ozone problems in Taiwan. With the active implementation of total air pollution control by the Environmental Protection Administration, air quality is gradually improving in Taiwan. While the concentrations of primary pollutants are decreasing, the concentrations of secondary pollutants keep increasing especially ozone. In order to better understand the characteristics of ozone, including ozone precursors, nine stationary photochemical assessment monitoring stations and two mobile photochemical assessment monitoring laboratories were established for air monitoring to completely comprehend the pollution characteristics of the major photochemically polluted areas in Taiwan.
The Perkin Elmer Co. built automatic volatile organic compounds (VOCs) analytical systems are utilized in the PAMS as the primary photochemical monitoring equipment. The whole system consists of a pre-concentrating device, a thermal desorption unit, a gas chromatograph with flame ionization detector, gas generators, standard gas, an air compressor and a controlling computer. In addition to the internal quality control steps taken in the monitoring station, the operational effectiveness of the system in PAMS and the accuracy of the data generated by the instrument were assured by the scheduled and unscheduled external on-site quality assurance audits.
We used the data produced by this project from 104 to 108 years and analyzed and sorted by the annual average concentration, and the box-and-whisker diagram changes in the past five years are drawn using the average annual concentration of eight main compounds. Regardless of whether the station is located in a metropolitan area, an industrial area, or a type where the two regions coexist, each species has its own changing trend at different stations, but the main trend is to decline year by year. In addition, the data was converted through the maximum incremental reaction (MIR) of ozone to obtain the top five ozone-contributing compounds of each station. Toluene, m,p-xylene, ethylene and propylene have four major contributions. The fifth one has o-xylene and 1,2,4-trimethylbenzene, only Taixi and Chaozhou Station have isoprene, which is a special biological source emission material, and its total ozone generation potential has also been declining over the years.
