Investigation on the Characteristics of GHGs Emitted from Industrial Wastewater Treatment Processes and Natural Estuarine Wetlands by In-situ Continuous Monitoring Technology

Autor: Wen-Bin Yang, 楊文彬
Rok vydání: 2018
Druh dokumentu: 學位論文 ; thesis
Popis: 106
In the context of global warming and climate change, greenhouse gas (GHG) emission has received a considerable attention for the past decades. Of many natural GHG sources, wetland plays an important role in modulating the concentrations of GHGs in the atmosphere. This study aims to continuously monitor the emission of greenhouse gases (CO2, CH4, and N2O) from a constructed wetland. A self-designed dynamic floating chamber was applied to collect GHGs through a Teflon tube connected to the top of the chamber, and in-situ monitored the concentrations of GHGs with a non-dispersive infrared (NDIR) monitor to continuously measure GHG emissions, estimated its CO2 equivalent (CO2-e), and investigated the seasonal variation of GHGs. This study further correlated GHGs and water quality, and combined GHG data and net primary production data to understand GHG emission from a natural estuarine wetland and a wastewater treatment plant. The temporal variation of greenhouse gas (GHG) emission from petrochemical and integrated industry wastewater treatment plants (WWTP) was then investigated. Two approaches including an in-situ continuous monitoring and a typical grab sampling methods were further compared. The in-situ continuous monitoring method provided more detailed information regarding the temporal variation of GHG concentration. A sufficient sampling frequency (e.g., once every 6 hours) for the grab sampling method is required to effectively resolve the diurnal variation of GHG emission. This study highlights significant diurnal variation of GHG concentration in different wastewater treatment units. Only with proper and reliable sampling and analytical methods, it becomes possible to correctly identify the characteristics of GHG emissions and to develop strategies to curtail the GHG emissions from such an important source in response to regulatory measures and international treaties. This study revealed that N2O was the dominant species responsible for GHG emissions from the WWTPs and the emission factors of CH4, and N2O were higher in the equalization tank and final sedimentation tank compared to other units. We also compared the GHG emission factors of this study with other literatures, showing that the GHG emission factors were much lower than those measured in Netherlands, Australia, and IPCC, but similar to those measured in Japan. Wetland play a crucial role in modulating atmospheric concentrations of greenhouse gases (GHGs). Key factors controlling GHG emission from subtropical estuarine wetlands were investigated in this study, which continuously monitored the uptake/emission of GHGs by/from a subtropical estuarine wetland located in the Minjiang and Zhangjiang estuaries in the coastal region of southeastern China. A self-designed floating chamber was used to collect air samples on-site at three environmental habitats (P. australis, mangrove, mudflats, and river water). Based on its potential to increase global warming, N2O was the main contributor to the total GHG emission, with that emitted from the river water being the most considerable. Tidal water carried onto the marsh had its own GHG content and thus may act as a source or sink of GHGs. However, water quality had a large effect on GHG emissions from the riverwater whereas the tidal water height did not. Both high salinity and large amounts of sulfates in the wetlands explicitly inhibited the activity of CH4-producing bacteria, particularly at nighttime. This study also investigated the seasonal variation of GHG emissions and estimated their overall CO2 equivalent (CO2-e). The GHG emissions were further correlated with water quality to identify which water quality parameters dominated GHG emissions in an estuarine mangrove ecosystem. A positive correlation was found between CO2 emission and water temperature, dissolved oxygen (DO), and total phosphorus (TP) in the riverwater. CH4 emission was positively correlated with TP, DO, and NH4+-N, while N2O emission was significantly positively correlated with DO, TP, and total nitrogen (TN) in the riverwater.
Databáze: Networked Digital Library of Theses & Dissertations
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