Sources and Deposition Fluxes of PCDD/Fs in the Largest Reservoir System in Taiwan before and after Typhoon Morakot

Kai Hsien Chi,Shuh Ji Kao,Shangde Luo,Tzu Yi Lee,Wei-Ting Hsu

doi:10.4209/aaqr.2014.10.0235

Abstract

The Tsengwen Reservoir (TWR) is located at 23°16′N, 120°34′E and is the largest reservoir in Taiwan. During 2009 to 2010, deposition of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) in ambient air, water bodies and sediments were measured in the TWR area for this study. The monthly atmospheric PCDD/F deposition in the vicinity of the TWR was found to range from 0.206 to 2.43 pg I-TEQ/m2/day. In addition, the PCDD/F levels (11 to 12 fg I-TEQ/L) in the surface water (water depth: 0.5 m) were found to be uniform and well mixed within the upstream, middle and lower reaches of the TWR. The PCDD/F input flux into the reservoir was investigated together with the PCDD/F concentrations at 1–2 cm intervals in two sediment cores collected at the TWR. The year dating within the sediment cores at different depths was estimated from the sedimentation rate (> 17 cm/y) and calculated by 210Pb analysis. The PCDD/F content at different depth within the sediment cores ranged from 0.136 ng I-TEQ/kg d. w. to 0.413 ng I-TEQ/kg d. w. Before the Morakot Typhoon event (June, 2009), the PCDD/F content of the surface sediments ranged from 0.091 to 0.187 ng I-TEQ/kg d. w. as measured at the upstream, middle and lower reaches of the TWR. Interestingly, the PCDD/F content (0.132 to 0.222 ng I-TEQ/kg d. w.) of surface sediments increased somewhat after typhoon event (January, 2010). The PCDD/F input contributed by the enhanced catchment erosion significantly increased to 99% during intensive typhoon periods.

Highlights

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are characterized as the persistent organic pollutants (POPs) that have been aimed for international source reduction by the Stockholm Convention
The results (Fig. 3) regarding to the deposition flux of atmospheric PCDD/Fs indicated that around 0.435 to 1.86 pg I-Toxic Equivalence (TEQ)/m2/day and 0.206 to 2.42 pg I-TEQ/m2/day, respectively, at Sites A and B measured in the vicinity of the Tsengwen Reservoir (TWR)
Relevant measurements regarding to the deposition fluxes of atmospheric PCDD/Fs conducted in other Asian countries (Seike et al, 1998; Ogura et al, 2001; Sakai et al, 2001; Moon et al, 2005; Ren et al, 2007; Fang et al, 2011) demonstrated that the deposition flux of atmospheric PCDD/Fs measured in the vicinity of the TWR in southern Taiwan was considerably lower

Summary

Introduction

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are characterized as the persistent organic pollutants (POPs) that have been aimed for international source reduction by the Stockholm Convention. Another study (Chi et al, 2013a) demonstrated that the considerably lower PCDD/F contents (3.45–49.1 pg I-TEQ/gTSP) in total suspended particles (TSPs) and ambient air concentrations (1.24–7.75 fg I-TEQ/m3) were measured at background areas in Taiwan and remote islands around

Results

Conclusion