Nitrogen Budgets and Nitrous Oxide Flux from Constructed Wetland

• Main Authors: Po-Lin Li, 李博霖
• Other Authors: Ying-Feng Lin
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/d562c5

碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 99 === 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.