The search by SKB (Swedish Nuclear Fuel and Waste Management Co.) for a site to locate the deep geological repository for spent nuclear fuel in Sweden has involved geoscientific investigations at several locations since the 1970s. The objectives were to characterise geologically a bedrock volume as well as its hydrogeology and hydrochemistry. To acquire high-quality hydrogeochemical data, a complete system for groundwater sampling and analysis, as well as for interpretation strategies, has been developed through a continuous process of modification and refinement. Since the largest part of the Swedish bedrock is composed of granitoids, the site investigations had to adapt to the special difficulties of fractured crystalline rocks. This paper discusses the problems with groundwater sampling that are specific to fractured crystalline rocks and describes the solutions adopted and methods developed by SKB since the early 2000s during the site investigations. The methodology described in this paper for the characterisation of deep groundwaters in crystalline rocks is not only applicable in the context of radioactive waste disposal but also useful when sampling groundwaters for any purpose in such rocks. Sampling of groundwaters in fractured rocks at depth, often down to approximately 1,000 m, involves special challenges since the natural conditions of the groundwater are easily disturbed, especially by the initial drilling, but also by every subsequent activity performed in the borehole, including the actual groundwater sampling. The sampling strategy presented in this paper shows that planning of the sampling preferably starts already when the drilling procedure is decided. Each following step is described in detail and includes tracing the drilling fluid, selecting the best borehole sections to sample, procedures for the actual sampling, and selection of analytical protocol; all this with the goal of taking representative samples. Although the evaluation of the sampling uncertainties is not a straightforward procedure, an adequate categorisation routine has been established to classify groundwater samples regarding sample quality, representativeness, and suitability for further interpretations and modelling.

中文翻译：

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用于表征结晶基岩中地下水的水文地球化学采样方法：瑞典放射性废物项目的进展

自 1970 年代以来，SKB（瑞典核燃料和废物管理公司）在瑞典寻找用于定位乏核燃料深层地质处置库的地点的工作涉及在多个地点进行的地球科学调查。目标是从地质上表征基岩体积及其水文地质和水化学。为了获取高质量的水文地球化学数据，通过不断的修改和完善，开发了一套完整的地下水采样和分析系统以及解释策略。由于瑞典基岩的最大部分由花岗岩组成，因此现场调查必须适应破碎结晶岩的特殊困难。本文讨论了特定于裂缝结晶岩的地下水采样问题，并描述了 SKB 自 2000 年代初在现场调查期间采用的解决方案和开发的方法。本文中描述的用于表征结晶岩中深层地下水的方法不仅适用于放射性废物处理，而且在出于任何目的对此类岩石中的地下水进行采样时也很有用。对裂隙岩中的地下水进行采样，通常低至约 1,000 m，这涉及到特殊的挑战，因为地下水的自然条件很容易受到干扰，尤其是最初的钻探，而且还受到钻孔中进行的每一次后续活动的干扰，包括实际地下水取样。本文中提出的采样策略表明，采样计划最好在确定钻井程序时就已经开始。详细描述了以下每个步骤，包括跟踪钻井液、选择最佳钻孔段进行采样、实际采样程序和分析协议的选择；所有这一切都是为了采集有代表性的样本。虽然采样不确定性的评估不是一个简单的过程，但已经建立了一个适当的分类程序，以根据样品质量、代表性和进一步解释和建模的适用性对地下水样品进行分类。详细描述了以下每个步骤，包括跟踪钻井液、选择最佳钻孔段进行采样、实际采样程序和分析协议的选择；所有这一切都是为了采集有代表性的样本。虽然采样不确定性的评估不是一个简单的程序，但已经建立了一个适当的分类程序来根据样品质量、代表性和进一步解释和建模的适用性对地下水样品进行分类。详细描述了以下每个步骤，包括跟踪钻井液、选择最佳钻孔段进行采样、实际采样程序和分析协议的选择；所有这一切都是为了采集有代表性的样本。虽然采样不确定性的评估不是一个简单的过程，但已经建立了一个适当的分类程序，以根据样品质量、代表性和进一步解释和建模的适用性对地下水样品进行分类。