In this study, polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) levels and depositions in ambient air, water column and sediment were measured at background area of reservoir-watershed systems in Northern (Feitsui Reservoir), Central (Sun Moon Lake) and Southern (Tsengwen Reservoir) Taiwan from January 2008 to 2010.The results indicated that the atmospheric PCDD/F concentrations measured in the vicinity area of Feitsui Reservoir, Sun Moon Lake and Tsengwen Reservoir ranged were 13.610, 15.65.2 and 10.96.3 fg I-TEQ/m3, respectively. In addition, the PCDD/F deposition flux measured in the same area were ranged from 0.950~38.5, 0.613~2.95 and 0.206~2.42 pg I-TEQ/m2/day, respectively. The atmospheric PCDD/F concentrations and deposition fluxes measured at the background area in Southern Taiwan were considerably lower than those measured in this study. The sampling results also indicated that the PCDD/F levels in the surface water (water depth: 0.5 m) measured in Feitsui Reservoir, Sun Moon Lake and Tsengwen were 0.0100.001, 0.0100.003 and 0.0080.001 pg WHO-TEQ/L, respectively. The results indicated that the PCDD/F concentrations in the surface water were uniform and sufficiently mixed at different locations in the reservoir. The results conducted from sediment measurements indicated that the PCDD/F input flux to the reservoir were 9.18, 2.54 and 26.5 pg I-TEQ/m2/day in Northern, Central and Southern Taiwan, respectively. Based on the mass calculations, around 40 to 95% of the PCDD/F input flux was contributed by catchment erosion. These findings implied that the pollutants deposited in the watershed must be transported to the reservoir by typhoon runoff and related physical erosion and that both of these phenomena play a major role in PCDD/F accumulation in the downstream reservoir.

Dioxin；Deposition；Sediment core