| 摘要: | 本研究自2007年12月到2010年5月監測位於嘉南藥理科技大學人工溼地之進流及出流水流量、水質、植物體及底泥氮含量、N2O釋放通量。採樣頻率為每月一次，實際氣體採樣數據有27筆。嘉南藥理科技大學人工溼地主要是由SSF溼地(1,450 m2)及FWS溼地(2200m2)所組成，主要為淨化經由污水處理場所處理過之二級放流水。本研究目的為估算人工溼地N2O釋放通量，再利用統計分析找出主要影響N2O釋放通量的環境因子，並推估溼地的氮質量收支計算結果。
溼地之平均進流水流量為316m3/d，平均水利負荷0.087m/d，平均水力停留時間為3.14d。進流水總氮濃度介於2.95～52.66 mg/L，出流水總氮濃度0.99～22.27 mg/L，平均去除率達56±28％。
在SSF溼地所監測到N2O釋放通量範圍介於3.83～87.37 μg N2O/m2/h，FWS溼地所測得的N2O釋放通量介於－6.10～128.78 μg N2O/m2/h。SSF、FWS及整個SSF-FWS溼地的N2O平均釋放通量為33.58±11.32、30.78±14.41及32.38±11.75 μg N2O/m2/h。
為了能更準確估算出溼地中N2O實際釋放通量，因此將透過日夜N2O平均釋放通量校正係數(α )、有無植物存在係數(β )與植物覆蓋係數(γ )值，藉以估算N2O年平均釋放通量。研究中並發現在各個採樣點之N2O平均釋放通量有顯著差異，因此透過主成份分析法與逐步迴歸法求得主要影響因子為水中溫度、含氮類物質(NH4-N、NO2-N、NO3-N)、BOD、ORP與pH，最後再建立其函數式。研究結果並發現溫度與N2O平均釋放通量有顯著相關。因此經由Modified Arrhenius equation計算結果得溫度校正係數介於1.047～1.085。
經由地面上與地面下生物量的生產量，並透過植物體氮含量，估算出SSF、FWS及整個SSF-FWS溼地植物生長氮攝取量77.9、41和55.7 g N/m2/year。再利用氮質量收支計算結果估算出由硝化脫硝循環及氮累積通量和為737.9、158.9、388.9 g N/m2/year。
最後由本研究所估算出嘉南藥理科技大學SSF及FWS溼地每年的N2O釋放通量(1,336.67 mg N2O/m2/ year、575.94 mg N2O/m2/ year )與國內SSF及FWS溼地的面積，推估出國內人工溼地SSF及FWS溼地每年的N2O釋放通量為65,496 g N2O/year、866,213 g N2O/year。再將所得結果換算出國內人工溼地每年N2O釋放通量的GWP值為5,323,106 g CO2-C/ year、70,399,554 g CO2-C/ year。
This study monitored influent flow and effluent, water quality, nitrogen content of plant and sediment, and N2O flux in a constructed wetland system built in Chia Nan University of Pharmacy & Science from December 2007 to May 2010. Sampling frequency was once a month and twenty-seven data by actual gas sampling. The constructed wetland system in Chia Nan University of Pharmacy & Science which operated for tertiary treatment of campus wastewater was composed by subsurface flow (SSF) (1450 m2) and free water surface flow (FWS) wetland (2200 m2). The purpose of this study was to estimate N2O flux, to figure out the major environmental factors for influencing N2O fluxes by statistical analyses and to estimate the results of nitrogen budgets for wetland.
The average of influent flow was 316 m3/d, the average of hydraulic loading was 0.087 m/d, and the average of hydraulic retention time was 3.14 d for the wetland in this study. The TN concentrations of the influent ranged from 2.95 to 52.66 mg/L, 0.99 to 22.27 mg/L in effluent and the average of removal efficiencies reached 56±28％.
The N2O flux which ranged from 3.83 to 87.37 μg N2O/m2/h for the SSF wetland was monitored, and it was monitored from －6.10 to 128.78 μg N2O/m2/h for the FWS wetland. The average of N2O flux was 33.58±11.32, 30.78±14.41 and 32.38±11.75 μg N2O/m2/h for the SSF, FWS and SSF-FWS wetland.
In order to estimate the N2O flux accurately, it used the day and night correction factor ( α ), the existence of plants ( β ) and percentage coverage of plants ( γ ) to assess the Average flux of N2O. There are significant differences for the average flux of N2O for each sample, thus it discovered the main affected factors in water temperature, containing nitrogen substances (NH4-N, NO2-N, NO3-N) , BOD, ORP and pH by principal component analysis and stepwise multiple regression. Finally, it established the functions formula. The results were significantly related to the temperature and average fluxes of N2O. Therefore, it was calculated that the temperature correction factor between 1.047 and 1.085 by Modified Arrhenius equation.
The results demonstrated that the nitrogen content in plant were 77.9, 41 and 55.7 g N/m2/year by above-ground and below-ground primary production and the nitrogen rate in plant. It also estimated the result of nitrification and denitrification cycle with nitrogen accumulation flux which was 737.9, 158.9 and 388.9 g N/m2/year by nitrogen budgets.
Finally, the results estimated the average fluxes of N2O (1,336.67 mg N2O/m2/ year, 575.94 mg N2O/m2/ year) in Chia Nan University of Pharmacy & Science and the area of SSF and FWS in Taiwan. It predicted that the average fluxes of N2O were 65,496 g N2O/year and 866,213 g N2O/ year for SSF and FWS wetland in Taiwan. It transformed the results to the average fluxes of N2O for GWP were 5,323,106 g CO2-C/ year and 70,399,554 g CO2-C/ year for constructed wetland in Taiwan. |
