Near-surface soil gas and groundwater measurements can be helpful tools in assuaging concerns of potential out-of-zone migration of CO₂ from a geologic storage unit into the overlying near-surface environment. These data, therefore, help to build confidence with local stakeholders and regulators that stored CO₂ is not impacting surface/near-surface environments. Routine monitoring of soil gas concentrations in the vadose zone can be used to show a lack of change or effect. However, both air temperature modeling and the Romanak et al. (2012) process-based approach should be applied when soil gas data are evaluated, as increased CO₂ concentrations can occur naturally from changes in the soil environment. Laboratory testing of groundwater and formation rock (drill cuttings) samples, exposed to varying concentrations of CO₂ under in situ temperature and pressure conditions, yield valuable information with respect to water chemistry changes that could occur from a potential out-of-zone migration. Key field-measured groundwater monitoring parameters that change significantly in response to low levels of CO₂ are pH (rapid decrease), alkalinity (increase), and conductivity (increase). Empirical models that predict soil gas concentrations using routinely measured climatic data such as air temperature, as well as models that predict the magnitude and duration of potential CO₂ exposure in groundwater, should be employed as components of a broad surface and subsurface monitoring program.

近地表土壤气体和地下水的测量可以帮助解决潜在的CO ₂从地质存储单元向地表近地环境迁移的担忧。因此，这些数据有助于建立与当地利益相关者和监管者的信任，因为他们认为储存的CO ₂不会影响地表/近地表环境。可以对渗流带中的土壤气体浓度进行常规监测，以显示缺乏变化或影响。但是，无论是空气温度模拟还是Romanak等。（2012）当评估土壤气体数据时，应采用基于过程的方法，因为CO ₂增加土壤环境的变化自然会产生浓度。在原位温度和压力条件下暴露于变化的CO ₂浓度的地下水和地层岩石（钻屑）样品的实验室测试，可提供有关水化学变化的有价值的信息，这些化学信息可能由潜在的区域外迁移引起。响应于低水平的CO ₂显着变化的关键现场监测地下水监测参数是pH（快速下降），碱度（增加）和电导率（增加）。使用常规测量的气候数据（例如气温）预测土壤气体浓度的经验模型，以及预测潜在CO ₂的强度和持续时间的模型 应将其暴露在地下水中，作为广泛的地表和地下监测计划的组成部分。