汶川M_s 8.0地震破裂带CO_2、CH_4、Rn和Hg脱气强度

Degassing of CO_2,CH_4,Rn and Hg in the rupture zones produced by Wenchuan M_s 8.0 earthquake

地震活动断裂带能够向大气释放大量的温室气体、放射性气体和有毒气体(CO_2、CH_4、Rn和Hg),并对大气环境的影响产生复杂的影响。利用静态暗箱法,对汶川M_s8.0地震破裂带CO_2、Rn和Hg脱气强度进行实地测量,并计算了CO_2和Hg脱气对大气的年贡献量。结果表明:(1)破裂带土壤气中CO_2、CH_4、Rn和Hg异常浓度最大值分别可以达到7.98%、2.38%、524.30k Bq/m^3和161.00ng/m^3;破裂带CO_2、Rn和Hg脱气平均通量是34.95g·m^(-2)d^(-1)、36.11m Bq·m^(-2)s^(-1)和26.56ng·m^(-2)h^(-1),最大值分别达到259.23g·m^(-2)d^(-1)、580.35m Bq·m^(-2)s^(-1)和387.67ng·m^(-2)h^(-1);(2)汶川Ms8.0地震破裂带向大气脱气的CO_2年贡献量是0.95Mt,Hg的年贡献量是15.94kg。汶川Ms8.0地震破裂带破裂CO_2、CH_4、Rn和Hg等的脱气强度,不仅与破裂带渗透率有关,还与断裂带浅部存在的气藏、煤层以及磷矿层等气体源有重要的联系。

Large amounts of greenhouse gases, radioactive gases and toxic gases （e.g. CO2, CH4, Rn and Hg） could be emitted from seismic active faults into the atmosphere with effect to the atmospheric environment. The flux of CO2, Rn and Hg along rupture zones were investigated by static chamber techniques and the total anualy output of CO2 and Hg to atmosphere were estimated. The results indicated （1） The maximum anomalies of CO2, CH4, Rn and Hg concentration in soil gas along co-seismic rupture zones reached values of 7.98%, 2.38%, 524.30kBq/m3 and 161.00ng/m3, respectively. The average flux of CO2, Rn and Hg from co-seismic rupture zones were 34.95g·m-2d-1, 36.11mBq·m-2s-1 and 26.56ng·m-2h-1, respectively. The maximum flux of CO2, Rn and Hg reached 259.23g·m-2d-1, 580.35mBq·m-2s-1 and 387.67ng·m-2h-1. （2） The total output of CO2 and Hg degassing estimated along siesmic ruptures were approximately 0.95Mt·y-1 and 15.94kg·y-1. The flux of CO2, Rn and Hg in soil gas were affected not only by the permeability of rupture zones, but also by gas sources from natural gas reservoir, coal seams and phosphat, etc.