土壤温室气体昼夜变化及其环境影响因素研究  

DIURNAL VARIATIONS OF SOIL TRACE GASES AND RELATED IMPACTING FACTORS

作　　者：秦小光[1] 蔡炳贵[1] 吴金水[1] 王国安[2] 刘东生[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国农业大学资源与环境学院,北京100094

出　　处：《第四纪研究》2005年第3期376-388,共13页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40472094;40021202;49894170;40024202);国家重点基础研究发展规划项目(批准号:G1999043402)共同资助

摘　　要：通过对北京东灵山草地和桦树林土壤气体CO2,N2O和CH4浓度及其排放通量的昼夜连续观测,探讨了生长季节草地和森林土壤温室气体昼夜变化及其环境影响因素。研究表明:1)土壤CO2排放通量昼高夜低,N2O排放通量有明显小时尺度波动,但昼夜变化不突出;土壤CO2和N2O浓度昼夜变化不明显,且与排放通量波动不一致;土壤是大气CH4的一个汇,相对厌氧的环境可能有利于土壤吸收CH4。2)无雨时气温昼夜变化通过影响土壤表层的气体扩散和CO2产生过程,来影响土壤CO2和N2O的地表排放通量,而对土壤10cm以下CO2和N2O的产生影响不大。小时尺度的土壤CO2和N2O浓度波动则可能还有其他影响因素或机制。3)降雨时土壤渗水引起的土壤空气对流取代气体浓度扩散成为土壤与大气空气交换的主要方式,导致土壤CO2和N2O排放通量的同步波动。降雨渗水较多时,较多的溶解氧随着雨水进入土壤内,会促进土壤CO2的生成和抑制N2O的产生。4)土壤CO2与N2O浓度存在显著的正相关关系,反映出土壤CO2和N2O有相对稳定的产率比。土壤有效碳可能是造成土壤CO2与N2O浓度正相关的主要原因,土壤空气的氧分压则可能是造成土壤CO2和N2O浓度波动不一致的重要因素。Diurnal variations of concentrations and surface fluxes of soil CO 2, N 2O, and CH 4, and soil temperatures at an untilled grassland site and a forest site in the Donglingshan, Beijing during the summer were introduced, and possible impacting factors were discussed in this paper. (1) The surface emission flux of soil CO 2 is large in day time and low in night time. The surface emission flux of soil N 2O fluctuates on an hourly scale not a semidiurnal scale. The fluctuation of soil CO 2 and N 2O concentrations is also on an hourly scale not a semidiurnal scale, and different from the fluctuation of their surface emission flux. Soil absorbs atmospheric CH 4 and is a sink for CH 4. (2) During the rainless period, the semidiurnal fluctuation of air temperature influences the surface fluxes of soil CO 2 and N 2O by affecting the gas diffusion process and soil CO 2-producing process in topsoils above 10 cm. There may be other factors or mechanisms inducing hourly-scaled variations of soil CO 2 and N 2O concentrations. (3) During the rainy period, soil seep-water leads air convection in soil that replaces the gas diffusion to be the major air-exchange manner between soil and atmosphere, resulting in the synchronal change of surface emission fluxes of soil CO 2 and N 2O. When rainwater dissolved more oxygen seeps into soil, more soil CO 2 is produced. (4) The soil CO 2 concentration is positively correlative with the soil N 2O concentration, demonstrating that their production ratio is relatively stable in soils. Soil available carbon (as dissolved organic carbon, DOC) may be an important factor resulting in the positive correlation between soil CO 2 and N 2O concentrations. The change of the oxygen concentration in soil air may lead the difference between fluctuations of soil CO 2 and N 2O concentrations.

关 键 词：土壤温室气体 昼夜变化 环境影响因素 北京东灵山 

分 类 号：X511[环境科学与工程—环境工程]