川中丘陵区冬灌田甲烷和氧化亚氮排放研究

CH_4 and N_2O emission from a winter-time flooded paddy field in a hilly area of Southwest China

采用静态暗箱 /气相色谱法对川中丘陵区冬灌田CH4 和N2 O排放特征进行连续一年的田间原位测定 .结果表明 ,种植水稻区 (种植区 )在水稻生长季平均CH4 排放速率为 2 2 76± 2 76mg·m- 2 ·h- 1,休闲期平均为 1 4 3± 0 2 0mg·m- 2 ·h- 1,全年平均为 9 6 4± 1 1 7mg·m- 2 ·h- 1;全年CH4 排放主要集中在水稻生长季 ,其累计CH4 排放量占全年总CH4 排放量的 91 2 % 未种植水稻区 (对照区 )全年CH4 平均排放速率为 2 0 3± 0 1 8mg·m- 2 ·h- 1,水稻生长季CH4 排放量占全年总排放量的 86 2 % .N2 O的排放在稻田落干时呈现脉冲排放 .在水稻生长季 ,对照区CH4 和N2 O的季节排放速率分别为 4 53± 0 38mg·m- 2 ·h- 1和 32 0 1± 5 0 2 μg·m- 2 ·h- 1,而种植区则分别为 2 2 76± 2 76mg·m- 2 ·h- 1和 73 0 4± 5 0 3μg·m- 2 ·h- 1,植株参与导致CH4 和N2 O排放速率分别增加 30 2 %和 1 2 8% .CH4 和N2 O的排放随土壤水分条件的变化呈互为消长关系 .在冬灌田中 ,即使考虑 50 0年的时间尺度 ,全年N2 O排放产生的全球增温潜势也只有CH4 的 7 9% ,与CH4 相比 ,冬灌田排放的N2 O所产生的温室效应很小 .

By the method of static opaque chamber/ modified gas chromatography,a one year field experiment was conducted to measure in situ the CH 4 and N 2O emission from a winter time flooded paddy field in a hilly area of Southwest China.Gas samples were taken simultaneously from rice involved and rice uninvolved plots.The results showed that during rice growth period,the CH 4 emission from the winter time flooded paddy field was higher than that from other paddy fields,but largely lower than many previous reports for the similar regions in Southwest China.The average flux of CH 4 emission from rice involved plots was 22.76±2.76 mg CH 4·m -2 ·h -1 during rice growth period,9.64±1.17 mg CH 4·m -2 ·h -1 per year,and 1.43±0.20 mg CH 4·m -2 ·h -1 during non rice growth season; while that from rice uninvolved plots was only 2.03±0.18 mg CH 4·m -2 ·h -1 per year,markedly lower than those from rice involved plots.During rice growth season,the mean emission rate of CH 4 and N 2O was 4.53±0.38 mg CH 4·m -2 ·h -1 and 32.01±5.02 μg N 2O·m -2 ·h -1 from rice uninvolved plots,but reached to 22.76±2.76 mg CH 4·m -2 ·h -1 and 73.04±5.03 μg N 2O·m -2 ·h -1 from rice involved plots,respectively.Rice involvement resulted in 302% increment of CH 4 and 128% increment of N 2O emission.There was a clear trade off between CH 4 and N 2O emission in paddy fields.Even with a span of 500 years,our calculation showed that in this winter time flooded paddy field,the GWP contributed by N 2O production was 7 9% of the CH 4 contribution,and thus,the greenhouse effect of N 2O production from this field was very small.