广州地区稻田甲烷排放及中国稻田甲烷排放的空间变化

METHANE EMISSION FROM RICE FIELDS IN GUANGZHOU REGION AND THE SPATIAL VARIATION OF METHANE EMISSION IN CHINA

１９９３年在广州地区采用中国科学院大气物理研究所研制的自动采集和分析系统测量了稻田甲烷的排放率，首次获得了占我国２０～２５％左右水稻收获面积的华南地区稻田甲烷排放特征值。从而宏观地使我国五大主要水稻生态区的甲烷排放率都有了实测资料。稻田甲烷排放率的季节变化主要与气温及灌溉水状态的变化有较大关系，日变化规律以下午出现极大为主。本实验田的甲烷排放率低，其特有的耕作制度（稻田冬天闲置及两季稻期间的闲置）可能是重要原因之一；广州地区实际水稻耕作中施用少量甚至不施有机肥也促成该地区比较低的甲烷排放率。在实验中尽量保持当地的常规水管理方式，这样能更准确和实际地反映出稻田甲烷排放率。年平均气温和土壤的有机质含量不足以说明稻田甲烷排放的空间变化规律。广州地区甲烷排放卒相对较低，早晚稻的季节平均值分别为０．５±０．６ｍｇ／ｍ￣２·ｈ和０．４±０．４ｍｇ／ｍ￣２·ｈ。根据我国目前已有的各大区域、各种耕作制度的稻田甲烷排放率资料及相应的稻田面积推算出中国总体稻田甲烷排放率为１１．１（１０．２～１２．８）×１０￣（１２）ｇ／ａ。

Methane emission rate was measured in 1993 using an automatic measuring systembuilt by the Institute of Atmospheric Physics,Chinese Academy of Sciences,Methane e-mission factor is preliminary available for rice fields in South China region,which takesabout 20%of the total rice harvesting area in China. Then the methane emission factorsare already available in all the five major rice culture regions in China. The seasonal varia-tion of methane emission rate depends mainly on the variation of air temperature and flood-ing condition. The afternoon peak mode is dominant for diurnal variation. The methane e-mission rate form this experiment field is rather low,which may mainly due to the uniquecultivation system in Guangzhou that rice fields are normally kept free during winter timeand in the gap between early and late rice growing season. The low dosage or even withoutorganic manure may be another important reason.In our experiment the water floodingcondition was kept normal as in the local region so that the methane emission factor canrepresent more properly the real emission value from actual rice paddy fields。Annualmean temperature and soil organic matter are not the factors to explain the spatial varia-tion of methane emission rate from rice fields. The seasonal average of methane emissionrate was 0.5±0. 6 mg/m￣2·h.According to the available date set for methane emissionrate from various rice fields in China,and relevant area of rice cultivation , total methaneemission in Chinese rice paddies can be estimated 11.1(10.2～12.8)×10￣(12)g/a.