The hydrogeochemistry of methane: Evidence from English groundwaters
The hydrogeochemistry of methane: Evidence from English groundwaters
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DOI：
10.1016/j.chemgeo.2005.11.003
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发表时间：
2006-05-30
期刊：
影响因子：
3.9
通讯作者：
Gooddy, D. C.
中科院分区：
文献类型：
--
作者：
Darling, W. G.;Gooddy, D. C.
地下水中甲烷(CH4)的存在通常只有当甲烷浓度上升到高浓度时才会被注意到；到目前为止，人们对甲烷的产生或自然“基线”条件知之甚少。来自英格兰一系列非污染地下水环境，包括供水含水层、含水层和热水的证据表明，即使在有氧条件下，CH4几乎总是可以检测到。对白垩纪、侏罗纪和三叠纪碳酸盐岩和砂岩含水层饮用水的测量表明，甲烷浓度高达500mg/L，但平均值为10mg/L。然而，石炭纪和三叠纪的盖层和热水通常含有超过1500mg/L。到目前为止，只有在氧化还原电位(Eh)低于0 mV时才能发现如此高的浓度，但总的来说，甲烷浓度与Eh值相关性较差。通过比较由氧化还原对C(4)/C(-4)计算的pE值和由Eh得到的pE值，证实了热力学平衡的缺失。CH4的发生似乎有两个时间尺度：土壤中厌氧微环境中活性碳的快速产生速度(如果很低)，以及更难处理的碳产生的千年规模要长得多。在地下水中很少测量到甲烷；没有单一的离子决定因素，它起着普遍的替代作用，但高HCO3和低SO4浓度的组合，或者相反，表明可能存在大量的CH4。(C)2006年《国家环境政策纲要》。爱思唯尔出版公司版权所有。
The presence of methane (CH4) in groundwater is usually only noticed when it rises to high concentrations; to date rather little is known about its production or natural 'baseline' conditions. Evidence from a range of non-polluted groundwater environments in England, including water supply aquifers, aquicludes and thermal waters, reveals that CH4 is almost always detectable, even in aerobic conditions. Measurements of potable waters from Cretaceous, Jurassic and Triassic carbonate and sandstone aquifers reveal CH4 concentrations of up to 500 mu g/l, but a mean value of < 10 mu g/l. However, aquiclude and thermal waters from the Carboniferous and Triassic typically contain in excess of 1500 mu g/l. Such high concentrations have so far only been found at redox (Eh) potentials below 0 mV, but in general CH4 Concentration and Eh value are poorly correlated. This suggests a lack of thermodynamic equilibrium, which is confirmed by comparing pe values calculated from the redox couple C(4)/C(-4) with those derived from Eh. Genesis of CH4 appears to occur on two timescales: a rapid if low rate of production from labile carbon in anaerobic microsites in the soil, and a much longer, millennium scale of production from more refractory carbon. Methane is rarely measured in groundwater; there is no single ionic determinand which acts universally as a proxy, but a combination of high HCO3 and low SO4 concentrations, or the reverse, is an indication that high amounts Of CH4 may be present. (c) 2006 NERC. Published by Elsevier B.V All rights reserved.