中国CH_4排放量的估算

Sources of Methane in China : Rice Fields , Agricultural Waste Treatment, Cattle , Coal Mines , and Other Minor Sources

1987—1989年用自动连续采样分析设备对杭州地区的稻田CH_4排放进行了三年连续观测,1988—1990年用定期采样、分析方法对四川乐山地区的稻田CH_4排放进行了三年观测.发现稻田CH_4排放率有很大的日变化、季节变化和年际变化,这些变化主要是由土壤特性、水稻生长状况以及气象条件的变化造成的.不同地区稻田CH_4排放率差别很大,变化规律也不同,这种差别主要是由土壤特性,水稻品种及气候条件的差别造成的.根据现有观测资料,估计中国稻田CH_4年排放总量为17×10^(12)g.对沼气池的CH_4泄漏进行了三年系统观测研究,发现沼气池泄漏变化范围很大,但泄漏量总起来都很小,中国1000万个沼气池不构成大气CH_4的重要源.根据沼气池的泄漏估计了农村堆肥的CH_4排放量为3.2×10^(12)g/a;根据城市、稻田附近和沙漠地区大气CH_4浓度的测量结果推算了城市CH_4排放量;根据反刍动物消耗食物总量估计了反刍家畜的CH_4排放量;根据瓦斯排放资料估计了煤矿CH_4排放量;根据文献资料估计了中国天然湿地的CH_4排放量.最后估计了中国各种源的CH_4排放总量及未来变化趋势.1988年中国CH_4排放总量为40×10^(12)g,其中一半以上来自稻田.2000年中国CH_4排放总量可达45×10^(12)g,主要是反刍动物和煤矿排放量增加.

Continuous measurements of the methane flux from rice fields were carried out by using chamber technique . The results show that the methane flux from rice fields has a strong diurnal variation , and that the day-mean flux has a large seasonal variation . Based on the experiments, we estimate that the total emission of methane from rice fields in China is (17 ± 2) t/yr. Methane leakage from biogas pits is very little on the whole, with a range of 61 - 490 mg/hr/pit. The total emission from biogas pits in China may be of the order of 0.01 t/yr. Total emissions of methane from cattle in China are estimated to be 5.5 t/yr . Coal and oil mining may emit 6 t methane per year. Emissions from natural wetland in China are estimated to be about 2 t/yr . There is an important source of methane in China that has not been measured . Agricultural waste in China is often treated in cesspools, which are similar to the biogas pits . However, no methane is recovered from such cesspools . We estimate that the total flux of methane from such sources may be of the order of 5 t/yr. The total emissions of methane from sources in China are estimated to be about 35 ± 5 t/yr.