Beaton E D, Stuart Marilyne, Stroes-Gascoyne Sim, King-Sharp Karen J, Gurban Ioana, Festarini Amy, Chen Hui Q
Canadian Nuclear Laboratories (formerly Atomic Energy of Canada Limited), Chalk River Laboratories, Deep RiverON, Canada.
Department of Earth and Environmental Sciences, University of Ottawa, OttawaON, Canada.
Front Microbiol. 2017 Sep 19;8:1731. doi: 10.3389/fmicb.2017.01731. eCollection 2017.
Proposed radioactive waste repositories require long residence times within deep geological settings for which we have little knowledge of local or regional subsurface dynamics that could affect the transport of hazardous species over the period of radioactive decay. Given the role of microbial processes on element speciation and transport, knowledge and understanding of local microbial ecology within geological formations being considered as host formations can aid predictions for long term safety. In this relatively unexplored environment, sampling opportunities are few and opportunistic. We combined the data collected for geochemistry and microbial abundances from multiple sampling opportunities from within a proposed host formation and performed multivariate mixing and mass balance (M3) modeling, spatial analysis and generalized linear modeling to address whether recharge can explain how subsurface communities assemble within fracture water obtained from multiple saturated fractures accessed by boreholes drilled into the crystalline formation underlying the Chalk River Laboratories site (Deep River, ON, Canada). We found that three possible source waters, each of meteoric origin, explained 97% of the samples, these are: modern recharge, recharge from the period of the Laurentide ice sheet retreat (. ∼12000 years before present) and a putative saline source assigned as Champlain Sea (also . 12000 years before present). The distributed microbial abundances and geochemistry provide a conceptual model of two distinct regions within the subsurface associated with bicarbonate - used as a proxy for modern recharge - and manganese; these regions occur at depths relevant to a proposed repository within the formation. At the scale of sampling, the associated spatial autocorrelation means that abundances linked with geochemistry were not unambiguously discerned, although fine scale Moran's eigenvector map (MEM) coefficients were correlated with the abundance data and suggest the action of localized processes possibly associated with the manganese and sulfate content of the fracture water.
拟建的放射性废物处置库需要在深层地质环境中长时间留存，而我们对当地或区域地下动力学了解甚少，这些动力学可能会影响危险物质在放射性衰变期间的迁移。鉴于微生物过程对元素形态和迁移的作用，了解被视为宿主地层的地质构造内的当地微生物生态学，有助于预测长期安全性。在这个相对未被探索的环境中，采样机会很少且具有偶然性。我们将从一个拟建宿主地层内的多个采样机会中收集的地球化学和微生物丰度数据相结合，进行了多变量混合和质量平衡（M3）建模、空间分析和广义线性建模，以探讨补给是否可以解释地下群落如何在从钻孔进入查克里弗实验室场地（加拿大安大略省迪普里弗）下方结晶地层的多个饱和裂缝中获取的裂隙水中聚集。我们发现，三种可能的源水，均源自大气降水，解释了97%的样本，它们分别是：现代补给、劳伦泰德冰盖退缩时期（约距今12000年）的补给以及被认定为尚普兰海（同样约距今12000年）的假定盐源。分布的微生物丰度和地球化学提供了一个地下两个不同区域的概念模型，这两个区域与用作现代补给指标的碳酸氢盐和锰有关；这些区域出现在与地层中拟建处置库相关的深度处。在采样尺度上，相关的空间自相关意味着与地球化学相关的丰度无法明确识别，尽管精细尺度的莫兰特征向量图（MEM）系数与丰度数据相关，并表明可能存在与裂隙水中锰和硫酸盐含量相关的局部过程的作用。
