【北冰洋中心海区储存大量甲烷】Xin He Liguang Sun Zhouqing Xie Wen Huang Nanye Long Zheng Li Guangxi Xing. Role of shielding and consumption of methane. Atmospheric Environment 2012 67: Pages 8–13.

Abstract

Sources and sinks of methane one of the most important greenhouse gases have attracted intensive attention due to its role in global warming. We show that sea ice in the Arctic Ocean regulates methane level through two mechanisms shielding of methane emission from the ocean and consumption of methane. Using a static chamber technique we estimated that the methane flux from under-ice water was 0.56 mg(CH4) m−2 d−1 on average in central Arctic Ocean relatively higher than that in other oceans indicating considerable methane storage in this region under sea ice. Average methane flux on under-ice water was higher than that above sea ice which suggests that sea ice could limit methane emission. In addition negative fluxes on sea ice suggest that there are methane consuming processes which are possibly associated with both photochemical and biochemical oxidation. Our results provide a general understanding about how sea ice in Arctic affects regional and global methane balance.

 

中国科大极地环境研究室孙立广、谢周清课题组，首次对北冰洋中心海域的甲烷排放进行了实地 采样分析。结果发现，该海域储存了大量甲烷，海冰对甲烷的区域循环具有双重作用：阻碍海水中甲烷的排放，同时海冰表面或内部存在消耗大气甲烷的过程。该研 究为科学评估北冰洋海域对温室气体甲烷的贡献提供了依据。英国《大气环境》杂志日前在线发表了该项成果。
 
甲烷是一种对气候有显著变暖效应的温室气体，其增温潜力值是二氧化碳的25倍。长期以来， 人们一直认为甲烷是一种浓度恒定的自然大气成分。直到20世纪80年代初，人们才发现，自工业革命以来大气对流层中甲烷含量在增加，目前的含量是工业革命 前的两倍多。甲烷含量的增长，引发了对甲烷来源和从大气中清除过程的调查研究。
 
2010年7～9月，极地环境研究室的科研人员在参加中国第四次北极科考时，采用密闭箱法 测定了北冰洋中心海域的甲烷通量（冰下海水每天每平方米的甲烷排放量）。结果显示，在该海域的海冰被打破后，甲烷呈现明显的排放趋势，冰下海水每天每平方 米约平均排放0.56毫克甲烷，远高于其他海域的海水甲烷通量，约为太平洋和大西洋的20倍以上。这表明，北冰洋中心海域的冰下海水中储存着大量的甲烷气 体，海冰的存在阻碍了海水甲烷的排放。他们在海冰表面还观测到负的甲烷通量，表明海冰表面存在吸收和消耗甲烷的过程。
 
论文并列第一作者、该校硕士生何鑫介绍说，海冰中可能存在消耗甲烷的甲烷氧化菌，同时在海 冰表面甲烷可以被光化学氧化消耗。该研究意味着气候变暖将加速北冰洋海冰的消融，导致大气中甲烷浓度增大，从而增强温室效应。这又反过来进一步加速海冰消 融，由此成为恶性循环。（来源：中国科学报 杨保国）

【Structural Biology】Adrian Cho. News Flash: X-ray Laser Produces First Protein Structure. Science 2012 338(6111): 1136 DOI: 10.1126-science.338.6111.1136.

For the first time an ultraintense x-ray laser has revealed the previously unknown atomic-scale structure of a protein researchers report online today in Science. The advance ushers in a new type of protein crystallography. However it’s too early to tell whether so-called x-ray free-electron lasers will supplant conventional x-ray sources known as synchrotrons which have cranked out tens of thousands of protein structures or merely serve niche applications s

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