A seasonality study of polychlorinated dibenzo-p-dioxins and dibenzofurans in ambient air in Kaohsiung (Taiwan) clustered with metallurgical industries.

As a comprehensive monitoring survey on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Kaohsiung, 40 ambient air samples taken from 10 locations in four seasons were studied. PCDD/F concentrations at 0.312-4.58pgNm(-3) and I-TEQ values, ranging from 0.0319 to 0.256pgNm(-3) were determined for these samples, which were comparable to those of other urban cities. However, unlike studies on some other urban cities, the ambient air in Kaohsiung did not exhibit regular seasonality in PCDD/F concentrations. All samples were predominated, in common, by congeners OCDD, 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,6,7,8-HpCDD, OCDF and 2,3,4,7,8-PeCDF. The congener profiles of the samples generally did not display any seasonal trend, either. The insignificant seasonality and constancy of congener profiles with time were attributed to the constant influence by emission sources in a metal-producing center, thereby resulting in high atmospheric dioxin levels in the nearby district. Principal component analyses identified that dioxin emissions in ambient air of the city originated from electric arc furnaces (EAFs) and sinter plants in the center. Concentration isopleth analyses assessing pollution sources and ambient air of the district also confirmed that its atmosphere was affected largely by the EAFs and sinter plants.