The impact of long-range transport on the air quality of Taiwan was assessed by using measurements at stations of the air quality monitoring network of the Taiwan Environment Protection Administration over the winter monsoon periods of 2000 and 2001. The primary long-range transport process can be clearly identified to be the prevailing northeasterly following the cold front of winter monsoon that originates in the Asian continent. Based on pollutants concentration differences among different meteorological conditions, we estimate that the long-range transport of particulate pollutants contributes to about 30 μg m−3 to the PM10 concentrations in northern and eastern Taiwan. A smaller contribution is estimated for the western plain of Taiwan. Contributions of the long-range transport to CO and SO2 are about 230 and 0.5 ppb, respectively. The identified, dust events have the highest average inflow concentration (about 71±34 μg m−3) of PM10. The dust impacts on PM10 have been estimated to be nearly 100% at windward background stations along the north and northeast coast. In the northern cities of Taiwan, such as Taipei and Hsinchu, the impacts decrease to around 60–80% as local emission increase. Due to geographic blocking, a smaller impact is estimated for the western plain of Taiwan. However, the identified frontal pollution cases have significant impact on CO and SO2, which is more evident than the impact of dust events. In general, impacts of long-range transport on air pollutants at coastal stations are greater than those in urban areas.
