Associate professor, Institute of Environmental and Occupational Health Sciences, National Yang Ming University, Taipei 112, Taiwan

Speech Title: Environmental Fate and Sinks of PCDD/Fs in Taiwan: Effects of Climate Change
Abstract
Aims: Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants (POPs) that are formed and released unintentionally from anthropogenic sources. The high persistence of PCDD/Fs results in the concentrations of these contaminants in environment decreasing only very slowly. In this study, tropical cyclone (typhoon) events were explored in terms of their influence on the environmental fate and transport of PCDD/Fs in Taiwan under a climate change scenario.
Methods: The deposition flux of PCDD/F in atmosphere, water bodies and sediments were measured in the two reservoirs in northern and southern Taiwan.
Results: Taiwan is heavily exposed to natural hazards such as tropical cyclones, landslides and floods. Recent extreme events, such as the 2001 Toraji Typhoon, the 2004 Mindulle Typhoon, and the 2009 Morakot Typhoon, all caused catastrophic damage. Based on the measurements from a dated sediment core collected at a reservoir in northern Taiwan, the sharp increases in input fluxes of PCDD/Fs and mineral-derived elements levels in 1990 (20 ng I-TEQ/m²/year), 2001 (17 ng I-TEQ/m²/year), 2004 (16 ng I-TEQ/m²/year) and 2005 (15 ng I-TEQ/m²/year) seem to be a result of a deep turbid layer formed upstream due to landslides and/or mud flows during the typhoon season. Before the Morakot typhoon event (June, 2009), the PCDD/F concentration of the surface sediments were 0.091 ng I-TEQ/kg as detected at the upstream of the Tsengwen Reservoir (TWR). In addition, the PCDD/F levels (11 to 12 fg I-TEQ/L) in the shell water (water depth: 0.5 m) were found to be uniform and well mixed within the upstream, central and lower reaches of the TWR. Interestingly, the PCDD/F content (0.222 ng I-TEQ/kg d. w.) of surface sediments increased somewhat after typhoon event (January, 2010).
Conclusion: This finding demonstrates the effect of typhoon events on the long-term remobilization of PCDD/Fs as well as supporting the hypothesis that such events such have the potential to reactivate pollutants that have been deposited previously.
Acknowledgement: The authors gratefully acknowledge the financial support provided by the Ministry of Science and Technology (MOST 103-2628-M-010-001 and MOST 104-2628-M-010-001-MY3) of Taiwan.