One of the risks of geologic carbon sequestration (GCS) is the leakage of injected CO₂ into overlying groundwater resources, resulting in potential deterioration of the quality of the groundwater due to the increase in acidity, the release of trace metals and organic compounds, and potential changes in microbial activities. A large number of studies have been conducted to evaluate various aspects of the impact of CO₂ leakage on overlying aquifers using natural analog, laboratory experiments, field tests, and numerical models. In this paper, we conducted an exhaustive review of the published work, focusing on the statistical assessment of the risk posed by the trace elements including Pb, As, Cd, Ba, and U and identifying the knowledge gaps. Key observations from the review include the following: (1) Pb, As, and U are metals of primary concern because multiple cases showed their concentration higher than maximum contaminant level (MCL) or other regulatory standards, (2) carbonate aquifers seemed more vulnerable to Pb and As contamination but not to U, (3) Cd and Ba are less a concern, only one case showed Cd/Ba concentration higher than MCL, (4) none of the field studies showed the concentrations of Pb and As higher than MCL, although one push–pull field test showed the concentration of U higher than MCL, (5) the order of aggressiveness in terms of releasing trace metals was determined to be as follows: batch experiment > column experiment > field test, and (6) there is no clear correlation between metal release and type of sediments, type of aquifer, the content of carbonate and clay. Evaluation likely has to be done on a case-by-case basis. For further operations of CO₂ storage overview and screening of potential sites, we suggest the use of an eight-step environmental risk assessment procedure comprising laboratory experiment, screening modeling work, and field testing for assessing the vulnerability of the overlying aquifers to degradation from CO₂ leakage from the GCS site. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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CO2 泄漏对地质固碳点上覆含水层地下水质量的潜在影响：审查和建议的评估程序

地质固碳 (GCS) 的风险之一是注入的 CO ₂泄漏到上覆地下水资源中，由于酸度增加、微量金属和有机化合物的释放，导致地下水质量潜在恶化，以及微生物活动的潜在变化。已经进行了大量研究来评估 CO ₂影响的各个方面使用自然模拟、实验室实验、现场测试和数值模型研究上覆含水层的渗漏。在本文中，我们对已发表的工作进行了详尽的审查，重点是对包括 Pb、As、Cd、Ba 和 U 在内的微量元素所带来的风险进行统计评估，并确定了知识差距。审查的主要观察结果包括：(1) Pb、As 和 U 是主要关注的金属，因为多个案例表明它们的浓度高于最大污染物水平 (MCL) 或其他监管标准，(2) 碳酸盐含水层似乎更容易受到影响对 Pb 和 As 污染而不是对 U 的污染，(3) Cd 和 Ba 不太受关注，只有一个案例显示 Cd/Ba 浓度高于 MCL，(4) 没有一项实地研究表明 Pb 和 As 的浓度高于MCL，尽管一项推拉式现场测试显示 U 的浓度高于 MCL，但 (5) 释放痕量金属的侵袭性顺序确定如下：批量实验 > 柱实验 > 现场测试，以及 (6)金属释放与沉积物类型、含水层类型、碳酸盐和粘土含量之间没有明确的相关性。评估可能必须根据具体情况进行。用于 CO 的进一步操作₂存储概述和潜在地点的筛选，我们建议使用八步环境风险评估程序，包括实验室实验、筛选建模工作和现场测试，以评估上覆含水层对GCS 的CO ₂泄漏降解的脆弱性地点。© 2021 化学工业协会和 John Wiley & Sons, Ltd.