The use of CFC-12, CFC-11 and CH3CCl3 to trace terrestrial airborne pollutant transport by land–sea breezes

Time-series observations of the atmospheric concentrations of the halocarbons, trichlorofluorocarbon (CFC-11), dichlorofluorocarbon (CFC-12), 1,2-trichlorofluoroethane (CFC-113), methyl chloroform (CH3CCl3) and carbon tetrachloride (CCl4) were conducted at a site in Lukang, in Central Taiwan between April and August 2004. Fluctuations in atmospheric concentrations of CFC-11, CFC-12 and CH3CCl3 were generally driven by diurnal land–sea breeze and anthropogenic activity in this area. Elevated levels of CFC-11, CFC-12, and CH3CCl3 frequently occurred when the air was stagnant and the prevailing seaward land breeze was dominant. Atmospheric concentrations of CFC-113 and CCl4 were much less variable relative to CFC-11, CFC-12 and CH3CCl3 during the same period, indicating that emissions of these two species from anthropogenic activities were small. The time-series distributions of atmospheric levels of CFC-12, CFC-11, CH3CCl3 and CO were characterized as a diurnal cycle with an elevated level at night and a low level during the daytime for most of the observed periods. As CFC-12, CFC-11 and CH3CCl3 behave as traffic- and industry-derived airborne pollutants in the urban atmosphere, they provide as a useful tracer in the application for the study of terrestrial airborne pollutants transport across the coastal area driven by land–sea breezes in this area.