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Deposition fluxes of PCDD/Fs in a reservoir system in northern Taiwan.

Chi, Kai Hsien; Hsu, Shih-Chieh; Lin, Chuan-Yao; Kao, Shuh Ji; Lee, Tzu Yi.
Chemosphere; 83(6): 745-52, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21435679
In this study, polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations and depositions in ambient air, water column and sediment were measured at a coupled reservoir-watershed system in northern Taiwan. The atmospheric PCDD/F concentration measured in the vicinity of the reservoir ranged from 4.9 to 39 fg I-TEQ m(-3) and the Asian dust storm in February accounted for the peak value, which corresponded to a total suspended particle concentration of 128 µg m(-3). The atmospheric PCDD/F deposition ranged from 1.4 to 19 pg I-TEQ m(-2)d(-1), with higher deposition occurring during winter and spring (long-range transport events). During summer, when atmospheric deposition is lower, consecutive tropical cyclones (typhoons) bring heavy rainfall that enhances soil erosion and creates turbidity-driven intermediate flow. This results in significantly higher PCDD/F deposition in water column of the reservoir at 70 m water depth (179 pg I-TEQ m(-2)d(-1)) than at 20 m (21 pg I-TEQ m(-2)d(-1)) during typhoon event. The accumulation rate of PCDD/Fs (9.1 ng I-TEQm(-2)y(-1)) in the reservoir sediments (depth 0-2 cm) was consistent with PCDD/F deposition obtained from water column (6.1 and 8.3 ng I-TEQ m(-2)y(-1)); however, it is significantly higher when compared to the atmospheric deposition (2.0 ng I-TEQ m(-2)y(-1)). Based on the mass balance between the measurements of atmospheric deposition and sinking particles in water column, around 54-74% of PCDD/F inputs into the reservoir were contributed by the catchment erosion during normal period. However, the PCDD/F input contributed by the enhanced catchment erosion significantly increased to 90% during intensive typhoon events.