【摘要】 海底通过泥火山释放的富甲烷流体是海洋甚至大气重要的碳源之一,对该系统内甲烷迁移与转化过程开展研究,有助于精确估算其碳排放总量。系统调研了国内外文献,认识到泥火山的碳排放具有强烈的时、空变化特征。在时间上,甲烷的排放主要发生在泥火山的喷发期和平静期,而在其消亡之后只出现微量的渗漏;在空间上,一个单独的泥火山中心、翼部和外缘分别发育强甲烷气泡泄漏、中等强度富甲烷和溶解无机碳(DIC)的流体泄漏以及大面积的DIC微渗漏;甲烷厌氧氧化和碳酸盐岩沉淀作用在翼部最强,对碳排放的拦截最有效,而在中心和外缘均较慢。全球陆坡和深水盆地沉积物通过泥火山向上释放的深部来源的甲烷通量为0.02 Pg C·a-1,这些碳可能引发海水缺氧、酸化和影响海-气交换通量,从而在千年尺度甚至更短时间内影响海洋吸收大气二氧化碳的能力。将来需要进一步对海底泥火山的发育数目和喷发周期进行统计,对不同类型的泥火山开展精细调查,以准确评估沉积物中自下而上的碳排放对海洋碳循环的影响,完善全球碳循环模式。更多还原

【Abstract】 Submarine mud volcanoes contribute carbon to the hydrosphere and the atmosphere by releasing methane-rich fluids, and researches on the temporal and spatial distribution of methane migration and chemical transportation at submarine mud volcanoes are the keys to understanding the processes mentioned above. In this paper, a large number of domestic and foreign literatures are systematically investigated,and the strong heterogeneity of methane leakage was recognized in the mud volcano systems. Methane emissions mainly occur during the eruption and dormant periods of mud volcanoes, and only a small amount of leakage occurs in extinct periods. In space, strong methane bubble leakages are usually developed around the centers of mud volcanos, and the chemical transportation efficiencies of methane are low in sediments; the leakages of methane and DIC controlled by fluid flow are mainly developed in the wings, where the rates of anaerobic oxidation of methane and the precipitation rate of authigenic carbonate are the highest. Shallow sediments have the strongest interception to carbon emission; both the intensity and the transportation rate of methane in the edge area are low, and hence a large area of DIC microleakage is developed. Globally, the carbon flux from submarine mud volcanos into shallow sediments is ca. 0.02 Pg C·a-1. The methane and DIC coming from sediments could cause seawater anoxia, acidification, and change air-sea carbon exchange fluxes, which may affect the ocean’s ability to absorb atmospheric carbon dioxide on millennium scale or even in a shorter time, and thus impacts on the global climate environment. In the future, accurate statistics on the number and eruption cycle of submarine mud volcanoes, and detailed investigations on the migration and transportation of methane in typical submarine mud volcanoes with different sizes and development stages, will be helpful to further accurately estimate their total carbon emissions, to study the impacts of bottom-up mud volcanoes’ carbon emissions on the marine carbon cycle, and to improve the marine carbon cycle model.更多还原