Emission Characteristics of Greenhouse Gases and Their Correlation with Water Quality at an Estuarine Mangrove Ecosystem – the Application of an In-situ On-site NDIR Monitoring Technique

Greenhouse gas (GHG) emission from natural sources have received a considerable attention for the past decade due to their considerable effects on global warming and climate change. Of many natural GHG sources, wetland plays a crucial role in modulating the atmospheric GHGs. This study aims to continuously monitor the emission/uptake of GHGs from an estuarine mangroves in summer August at Southeastern China (23°53′45.32 N, 117°24′07.61E). A self-designed open dynamic floating chamber was applied to collect air samples for continuously measuring GHG concentration in-situ with a non-dispersive infrared (NDIR) monitor. Diurnal emission of GHGs (CO2, CH4, and N2O) from the mangroves, the mudflats, and the river water was characterized by considering tidal and solar radiation effects. This study also investigated the seasonal variation of GHG emission and estimated their overall CO2 equivalent (CO2-e). The GHG emission was further correlated with water quality to identify which water quality parameters dominated GHG emission in the estuarine mangroves. A positive correlation was found between CO2 emission and water temperature, dissolved oxygen (DO), and total phosphorus (TP) in water. The emission of CH4 positively correlated with TP, DO, and NH4-N. The emission of N2O was significantly positively correlated with DO, TP, and total nitrogen (TN) in water. This study revealed that N2O was the dominant contributor to the global warming effect in the subtropical estuarine mangroves while compared to CO2 and CH4.