The atmospheric cycling of radiomethane and the "fossil fraction" of the methane source
The atmospheric cycling of radiomethane and the "fossil fraction" of the methane source
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DOI：
10.5194/acp-7-2141-2007
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发表时间：
2007-01-01
影响因子：
6.3
通讯作者：
Smith, A. M.
中科院分区：
文献类型：
--
作者：
Lassey, K. R.;Lowe, D. C.;Smith, A. M.
（CH4）-C-14（“放射性甲烷”）在大气中的循环在工业时代受到地质储层释放的不含c -14的甲烷（“化石甲烷”排放）的强烈干扰，在核时代，特别是自1970年左右以来，受到核电设施直接释放的核源性放射性甲烷的强烈干扰。大气辐射甲烷的当代测量已被用于估计化石甲烷在全球甲烷源中的比例（“化石部分”），但由于核动力源的不确定，这种估计具有很高的不确定性。在一篇配套论文中的质量平衡公式的指导下，我们应用当代大气辐射甲烷的时间序列来量化化石组分和核动力源的强度。我们推断，1986 - 2000年全球甲烷源的30.0 +/- 2.3% （1 s.d）是化石来源，其中一部分可能包括一些c -14耗尽的难熔碳，如来自古老的泥炭矿床。由于这一估计取决于基于线性回归模型的假设的有效性，因此它应被视为提供了一个合理的重新估计，而不是一个确定的修订。这样的化石部分将比普遍接受的要大得多（50%），这对清单编制有影响。全球放射性甲烷核动力源的共同估计强度与从当地核设施独立推断的值是一致的。
The cycling of (CH4)-C-14 ("radiomethane") through the atmosphere has been strongly perturbed in the industrial era by the release of C-14-free methane from geologic reservoirs ("fossil methane" emissions), and in the nuclear era, especially since ca 1970, by the direct release of nucleogenic radiomethane from nuclear power facilities. Contemporary measurements of atmospheric radiomethane have been used to estimate the proportion of fossil methane in the global methane source ( the "fossil fraction"), but such estimates carry high uncertainty due to the ill-determined nuclear-power source. Guided by a mass-balance formulation in a companion paper, we apply a contemporary time series of atmospheric radiomethane to quantify both the fossil fraction and the strength of the nuclear power source. We deduce that 30.0 +/- 2.3% ( 1 s.d.) of the global methane source for 1986 2000 has fossil origin, a fraction which may include some C-14-depleted refractory carbon such as from aged peat deposits. Since this estimate depends upon the validity of assumptions underlying a linear regression model, it should be seen as providing a plausible re-estimate rather than a definitive revision. Such a fossil fraction would be much larger ( by 50%) than is commonly accepted, with implications for inventory compilation. The co-estimated strength of the global nuclear-power source of radiomethane is consistent with values inferred independently from local nuclear facilities.