Abstract

Purpose

Carbon capture and storage (CCS) has been frequently discussed as a strategy for meeting CO₂ emission reduction and its targets. However, some critical issues have been raised with regard to the potential hazards to near-surface environments by CO₂ leakage. Hence, this study was conducted to examine the effects of soil moisture content on the potential risks associated with a high concentration of CO₂ to change physicochemical properties of a near-surface soil.

Materials and methods

Soil samples for a batch experiment were collected from an abandoned gold mine, South Korea. Batch experiments were conducted in a specially designed CO₂ glove box (95–99 vol.% CO₂) at four different moisture contents (0, 15, 27.5 wt.%, and a suspension of soil to water ratio 1:10) and different reaction times up to 30 days. A control experiment was conducted at the ambient conditions open to the atmosphere otherwise the same conditions. Physicochemical properties of the soil samples (i.e., pH, mineralogy, organic matter (OM), inorganic carbon (IC), and cation exchange capacity (CEC)) as well as leachability of metal(loid)s were examined before and after the CO₂ incubation.

Results and discussion

Results showed that the pH of the CO₂-incubated partially wet (15 and 27.5 wt.%) and suspension samples rapidly decreased by about one unit (P < 0.01) in 2 h and gradually recovered in 10 days. It was noteworthy that CO₂ was adsorbed to the dry soil (0 wt.%) and led to acidification as the soil pH dropped from 5.56 ± 0.02 to 4.5 ± 0.03. Soil organic matter content and cation exchange capacity decreased with increasing moisture content in the CO₂-incubated samples. A noticeable increase in the leachability of Fe, Al, Ca, Mg, Mn, K, and Zn were observed in the CO₂-incubated soil suspensions. In contrast, the leachability of metal(loid)s in the dry and partially wet samples were not remarkable, although the soil pH decreased significantly.

Conclusions

Our findings highlighted the effect of CO₂ exposure on the soil acidification, even to soils in unsaturated zones, and stressed to monitor simultaneously soil physicochemical properties and metal(loid)s leaching induced by CO₂ exposure in the near-surface environment.

Graphical abstract

中文翻译：

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土壤水分对近地表CO 2触发土壤理化性质的影响

摘要

目的

碳捕集与封存（CCS）已被广泛讨论为实现CO ₂减排及其目标的一种策略。然而，关于CO ₂泄漏对近地表环境的潜在危害，已经提出了一些关键问题。因此，本研究旨在研究土壤水分含量对与高浓度CO ₂改变近地表土壤理化特性相关的潜在风险的影响。

材料和方法

从韩国一个废弃的金矿中收集了用于批量实验的土壤样品。在专门设计的CO ₂手套箱（95–99 vol。％CO ₂）中以四种不同的水分含量（0、15、27.5 wt。％和土壤与水的比例为1:10的悬浮液）进行批量实验不同的反应时间长达30天。在通向大气的环境条件下进行对照实验，否则在相同条件下进行。在CO之前和之后，检查了土壤样品的理化性质（即pH，矿物学，有机物（OM），无机碳（IC）和阳离子交换容量（CEC））以及金属（胶体）的浸出性。₂孵化。

结果和讨论

结果表明，CO ₂孵育的部分潮湿（15和27.5 wt。％）和悬浮液样品的pH 在2小时内迅速降低了约一个单位（P <0.01），并在10天后逐渐恢复。值得注意的是，当土壤pH从5.56±0.02降至4.5±0.03时，CO ₂被吸附到干燥的土壤（0 wt。％）并导致酸化。随着CO ₂培养样品中水分含量的增加，土壤有机质含量和阳离子交换能力降低。在CO ₂中观察到Fe，Al，Ca，Mg，Mn，K和Zn的浸出率显着提高-培养的土壤悬浮液。相比之下，尽管土壤pH值明显降低，但在干燥和部分潮湿的样品中金属（金属）的浸出性并不明显。

结论

我们的发现强调了CO ₂暴露对土壤酸化的影响，甚至对不饱和地区的土壤酸化也有影响，并强调要同时监测土壤物理化学性质和在近地表环境中暴露于CO ₂引起的金属（胶体）浸出。