Research project BL/C/28 (Research action BL)
1/12/2004-21/12/2006
Context and objectives
Methane (CH4) and nitrous oxide (N2O) are two important atmospheric greenhouse gases. The abundance of CH4 and N2O in the atmosphere has been continuously increasing since industrialization, with current increasing rates of 7.0 and 0.8 ppb per year, respectively. Irrigated rice fields are considered major anthropogenic sources of atmospheric CH4 during the flooded (reduced) period of the fields and of N2O during the remaining non-flooded period. China has about 30 million ha of rice fields. Recently, Li et al. (2004), using a process oriented modelling approach, predicted that CH4 and N2O emissions from Chinese rice fields are in the order of 6.4 – 12.0 Tg C per year and 0.29 – 0.41 Tg N per year respectively. Methane emission from irrigated rice fields is controlled by production, oxidation and plant transport.
A significant amount of CH4 produced in the soil can be oxidized before escaping from the soil. Stable isotope techniques offer a potentially powerful tool to study and quantify the importance of the magnitude of in situ CH4 oxidation in irrigated rice soils (Krüger et al., 2002).
The objectives were as follows:
- Study in situ methane oxidation in irrigated rice fields using stable isotope techniques;
- Provide technical to start-up stable isotope facilities at the Institute of Applied Ecology;
- To evaluate methane emissions from rice fields on a regional scale using different management scenarios.
Methodology
The measurement and method development related to stable isotopes is not straightforward and requires state-of the art equipment and well trained technicians. The main emphasis during the prject is given to assisting the Chinese partners in the start up of their Isotope Ratio Mass spectrometer and in the set-up of state of the art field experiments.
The following methods and techniques were used: Laboratory incubations to study the kinetics of CH4 oxidation; CH4 measurements by gas chromatography; Stable isotope analysis from laboratory data.
Extensive experiences in the analysis of land use and management scenarios and evaluating their impact on greenhouse gas missions. The Chinese partners carry out a meta-analysis of the critical factors for greenhouse gas emissions in rice fields and relate these to management options. The distribution of the different management options within northern China and scenarios for future distribution will be investigated
