稻田灌溉河流甲烷排放通量观测研究

Paddy field is one of major sources of global CH4 emissions. A large number of studies have shown that midseason drainage is one of the most effective option for mitigating CH4 fluxes from paddy field. Measurements of CH4 fluxes from rivers draining paddy field may be particularly important, where waters are subject to much organic and nutrient loads through rice paddy drainage, and soil leaching, runoff and erosion. Though many field measurements have been taken in paddy field in China, very little is known about the dynamic, magnitude and pathways of CH4 fluxes from rivers that draining paddy field. A two-year measurement of CH4 fluxes was taken from rivers draining a paddy field in Lixiahe area in southeast China. The fluxes of CH4 were determined by using floating chamber and diffusion model methods.The study will address the following items as listed: (i) To reveal the seasonal dynamics of CH4 fluxes as well as their magnitude. (ii)To gain an insight into the magnitude of annual CH4 fluxes separated into diffusive and ebullitive components from rivers draining paddy field. (iii) To examine the dependence of seasonal CH4 fluxes on water and soil/sediment parameters and its underlying driving mechanisms from rivers draining paddy field. The results of this study would be conducive to have a better understand of CH4 fluxes from rivers draining paddy field, it also can amplify and provide scientific basis on agricultural GHGs emissions budget in China .

稻田是大气温室气体甲烷（CH4）的重要排放源，大量研究表明稻田中期排水烤田是稻田CH4减排最有效的措施之一。然而，由于排水烤田、淋溶径流和水土侵蚀等过程中稻田大量碳氮流失进入灌溉河流，稻田灌溉河流可能成为我国农业CH4排放源的重要组成部分。虽然国内外对我国稻田CH4排放进行了大量观测研究，而有关稻田灌溉河流CH4排放特征、排放强度和排放途径了解甚少。本项目以江苏里下河地区典型的稻田灌溉河流为研究对象，采用漂浮箱法和扩散模型法对稻田灌溉河流CH4排放通量进行连续2年的观测研究。项目将完成：（1）阐明稻田灌溉河流CH4的排放特征和排放强度；（2）辨析稻田灌溉河流CH4通过气泡和扩散传输途径及其排放贡献份额；（3）揭示稻田灌溉河流CH4排放的水体和底泥理化及微生物学驱动机制。研究结果将为了解我国稻田灌溉河流CH4排放规律和完善我国农业源温室气体排放清单提供科学基础和数据支撑。

稻田是大气温室气体甲烷（CH4）的重要排放源，大量研究表明稻田中期排水烤田是稻田CH4减排最有效的措施之一。然而，由于排水烤田、淋溶径流和水土侵蚀等过程中稻田大量碳氮流失进入灌溉河流，稻田灌溉河流可能成为我国农业CH4排放源的重要组成部分。虽然国内外对我国稻田CH4排放进行了大量观测研究，而有关稻田灌溉河流CH4排放特征、排放强度和排放途径了解甚少。本项目以江苏里下河地区典型的稻田灌溉河流为研究对象，采用漂浮箱法和扩散模型法对稻田灌溉河流CH4排放通量进行连续2年的观测研究，研究发现漂浮箱法和扩散模型法观测的灌溉河流CH4排放具有相同的昼夜和季节变化规律，扩散模型法观测的CH4排放通量低于漂浮箱法。稻田灌溉河流CH4排放呈现“夏高冬低”的季节变化趋势，其年平均排放通量为19.68 mg m-2 h-2。两年气泡排放贡献的CH4排放通量占CH4排放总量的44-56%，其中夏季气泡排放占比约90%是稻田灌溉河流甲烷排放的主要途径。水温、DO、DOC、NO3--N以及底泥pH、EC、SOC、DOC等是驱动CH4排放的主要环境驱动因子。本研究阐明了稻田灌溉河流CH4的排放特征和排放强度；辨析了稻田灌溉河流CH4通过气泡和扩散传输途径及其排放贡献份额；揭示了稻田灌溉河流CH4排放的水体和底泥理化环境驱动因子。研究结果为了解我国稻田灌溉河流CH4排放规律和完善我国农业源温室气体排放清单提供了科学基础和数据支撑。