This project surveyed the background level of contamination of PCDD/Fs in Taichung County in 2009. Three sites which were located in Mountain, Coast, and Reclamation regions (Houli, Dacha, and Wufeng Township) and one site near the TPC Taichung Power Plant (Longjing Township) were selected for monitoring the content of PCDD/Fs in environmental matrix. Three types of environmental matrix samples including ambient air, soil and plant (leaves of banyan trees) were seasonally sampled at each site for PCDD/Fs analysis. The annual average of PCDD/Fs toxic equivalency (TEQ) in ambient air was 0.043 pg I-TEQ/Nm3 in all sites. Long-jing Elementary School (Longjing Township) has the highest measured value of ambient air dioxin (0.070 pg I-TEQ/Nm3), especially in the 3rd season (0.128 pg I-TEQ/Nm3). The annual average TEQ in soil was 3.27 ng I-TEQ/kg in all sites. The measured value (7.79 ng I-TEQ/kg) in soil of Nei-pu Elementary School (Houli Township) was significantly higher than the other 3 areas. The annual average TEQ in banyan leaves was 2.65 pg I-TEQ/g in all sites. The measured values of plant samples were similar between 4 sites. Multivariate statistical analysis revealed that the ambient air in most sites was affected by vehicle exhaust, and the higher values in Longjing site might be related to burning of biomass materials. The relatively high content of soil PCDD/Fs in Houli site might be affected by local burning residuals or foreign soil according to the field observation. The estimation of annual PCDD/Fs emission of all running regulated factories in Taichung County was 7.47 g I-TEQ in 2009. The emission from 2 iron smelting electric arc furnace factories (3.29 and 0.57 g I-TEQ/year) and coal-fired TPC power plant (3.22 g I-TEQ/year) occupied about 95% of total emission of Taichung County. However, the emission of 2 municipal solid waste incinerations in Taichung County was few. Additionally, the PCDD/Fs emission is expect to growth because the steelmaking factory in Longjing Township will have two new sinter plants be going into operation in 3 years. Thus, it is suggested to enhance the monitoring works in the ambient area of steelmaking factories and coal-fired plants in the future.

Dioxin;Air pollution;environmental monitoring