在全球气候变暖影响下,冻土带中保存的天然气水合物被逐渐分解释放进入大气,改变了冻土带上空的大气甲烷(CH_4)浓度。以地面甲烷遥感探测实验为基础,发现甲烷气体在380~2500 nm电磁波谱范围内存在2个明显的吸收谱段(1700 nm和2300 nm附近),从机理上解释了对大气甲烷的遥感检测能力,肯定了遥感探测天然气水合物的可行性。选择扫描成像吸收光谱大气制图仪(scanning imaging absorption spectrometer for atmospheric char-tography,SCIAMACHY)传感器反演的祁连山冻土带大气甲烷数据,分析了2003-2006年间冻土带大气甲烷的时空变化规律。结果表明:冻土带大气甲烷含量不仅随季节呈现单峰-单谷型的变化规律,而且总体上还随时间推移有明显的递增趋势,可初步认为是冻土带天然气水合物分解释放引起的。以2006年2月冻土带大气甲烷浓度异常图为依据,结合地理和地质资料,对祁连山冻土带天然气水合物的资源潜力进行了评价,认为木里煤田的江仓和热水矿区应该是潜在的天然气水合物赋存区。
英文摘要:
Gas hydrate in permafrost gradually decomposes and seeps to atmosphere because of global warming,and the seepage changes the methane (CH_4) concentration of permafrost's atmosphere. In this paper, the possibility of gas hydrate detection with remote sensing data is proved by the nature gas detection experiments performed with domestic nature gas and ASD portable spectrometer. The experimental results show that two feature absorptions,spectra around 1 700 nm and 2 300 nm,are founded in the electromagnetic wave range from 380 to 2500 nm. Supported by the experiment,the authors selected the remote sensing data retrieved from the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) sensor during the period from 2003 to 2006 to analyze temporal and spatial changes of atmospheric methane of the permafrost in the Qilian Mountain. In addition to the discovery of methane concentration's seasonal changes,the trend of its gradual increment characteristics was also detected. This phenomenon is considered to be the result of methane seepage from underground gas hydrate. Finally,in combination with the geological data, the atmospheric methane anomaly in February 2006 was used to evaluate the potential of gas hydrate of the permafrost in the Qilian Mountain and, as a result, a new prospecting area was recommended.