Impact of flood damage on pollutant removal efficiencies of a subtropical urban constructed wetland |
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Authors: | Chun-Han Ko Tsai-Ming Lee Pen-Yuan Chen Hwey-Lien Hsieh |
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Affiliation: | a School of Forest and Resources Conservation, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, ROCb The Instrument Center of National Cheng Kung University, National Cheng Kung University, No.1, University Road, Tainan 70101, Taiwan, ROCc Department of Geography, Chinese Culture University, 55 Hwagang Rd., Taipei 11114, Taiwan, ROCd Department of Landscape Architecture, National Chiayi University, 300 Syuefu Rd., Chiayi City 60004, Taiwan, ROCe Biodiversity Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529, Taiwan, ROC |
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Abstract: | Typhoons and hurricanes in subtropical/tropical regions can induce significant environmental changes (e.g., mass flooding and inundations). However, the damage to the pollutant removal efficiencies of constructed wetlands brought about by these natural disturbances has been neglected in major studies conducted in temperate climates. Therefore, this study compares the pollutant removal performance of a constructed wetland in the Danshui River Basin, before and after the system was inundated with flooding from Typhoon Krosa in 2007. The pollutant removal performance of the free water surface (FWS) constructed wetland was investigated monthly from September 2006 to April 2008. Results of the study demonstrated that this FWS wetland effectively removed 64.3% BOD, 98.9% NH4-N, and 39.5% Total-P before Typhoon Krosa. However, the extensive flooding caused by Typhoon Krosa swept over most of the aboveground plant community and deposited the sediment onto the bottom of each compartment. Subsequently, reduced pollutant removal efficiencies were observed. Only 37.7% BOD, 35.1% NH4-N, and 31.8% Total-P were removed after this event, although the flow regime was immediately restored. Comparing the water quality data for the FWS wetland before and after Typhoon Krosa revealed the immediate, quantitative damage to the pollutant removal performance caused by the typhoon's inundation. Consequently, a high-flow bypass and additional preventive measures would protect any constructed wetland in areas subject to typhoons. |
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Keywords: | Free water surface constructed wetland Pollutant removal efficiency Subtropical weather Typhoon |
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