The mechanism of inorganic carbon sink in the stabilization process of Zn<sup>2+</sup> contaminated red clay in karst area

SONG Yu; LAI Yewei; CHEN Guohuan; HUANG Yanan; WU Zeyan; JIANG Zhongcheng; HUANG Xiang

doi:10.11932/karst2026y041

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SONG Yu, LAI Yewei, CHEN Guohuan, HUANG Yanan, WU Zeyan, JIANG Zhongcheng, HUANG Xiang. The mechanism of inorganic carbon sink in the stabilization process of Zn2+ contaminated red clay in karst area[J]. CARSOLOGICA SINICA. doi: 10.11932/karst2026y041

Citation:

SONG Yu, LAI Yewei, CHEN Guohuan, HUANG Yanan, WU Zeyan, JIANG Zhongcheng, HUANG Xiang. The mechanism of inorganic carbon sink in the stabilization process of Zn²⁺ contaminated red clay in karst area[J]. CARSOLOGICA SINICA. doi: 10.11932/karst2026y041

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The mechanism of inorganic carbon sink in the stabilization process of Zn²⁺ contaminated red clay in karst area

doi: 10.11932/karst2026y041

SONG Yu^{1, 2
,},
LAI Yewei^{1, 2},
CHEN Guohuan^{1, 2},
HUANG Yanan^{1, 2},
WU Zeyan³,
JIANG Zhongcheng³,
HUANG Xiang^{1, 2
,
,}

1.
School of Civil Engineering, Guilin University of Technology, Guilin, 541004
2.
Guangxi Key Laboratory of Geotechnics and Geotechnical Engineering, Guilin, 541004
3.
Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin, 541004

Received Date: 2026-01-21
Accepted Date: 2026-05-15
Rev Recd Date: 2026-05-03

Available Online: 2026-10-19

Abstract

Abstract

The karst area exhibits both ecological vulnerability and hydrogeological complexity. The unique carbonate landform and the high-permeability underground runoff characteristics make pollutants spread rapidly. Long-term lead-zinc mining and processing have led to continuous accumulation of soil heavy metal pollution in karst areas, especially severe Zn²⁺ accumulation in red clay, which destroys soil structure and significantly weakens the potential of natural inorganic carbon sinks in the region. At the same time, it causes compound soil-groundwater pollution, surface subsidence, and other geological disasters. Traditional solidification/stabilization (S/S) technology mainly relies on materials such as cement and lime. Although it can reduce the leaching risk of heavy metals to some extent, it still has problems such as high carbon emissions, poor long-term stability, and a long construction period. It is difficult to achieve the goal of low carbon and environmental protection. It cannot meet the needs of green restoration in the complex karst environment.To address the above problems, this study proposes an active MgO-enhanced CO₂ inorganic carbon sink stabilization technology as a green, low-carbon remediation approach. This technology mainly uses low-temperature-prepared active MgO as a curing material to generate hydrated magnesium carbonate (HMCs) through an inorganic carbon sink reaction in a CO₂ environment, thereby stabilizing heavy metals and advancing the development of artificial inorganic carbon sinks. Compared with traditional high-temperature calcined MgO, active MgO has the advantages of a large specific surface area, high reactivity, and low energy consumption, and can be better utilized in the geological background of high magnesium in karst areas.In this study, the typical Zn²⁺-contaminated red clay in a karst area was taken as the research object. The effects of Zn²⁺ pollution concentration, active MgO content, and reaction time on Zn²⁺ stabilization were systematically investigated. The morphological transformation of Zn²⁺ was analyzed using the BCR sequential extraction method; phase identification was performed by X-ray diffraction (XRD); and the morphology of the reaction products and the evolution of soil microstructure were observed by scanning electron microscopy (SEM) to reveal the stabilization mechanism. The results show that increasing the content of active MgO and optimizing the reaction time can increase the sample's resistivity, significantly reduce the free Zn²⁺ content, and promote its conversion to a residual state. A large amount of hydrated magnesium carbonate (HMCs), such as hydromagnesite, spherulite, and trihydrate magnesite, is generated as the main carbon sink products. High-efficiency CO₂ mineralization and storage can be achieved by reacting active MgO with CO₂. At the same time, the adsorption and cementation of Zn²⁺ can form a stable carbonate mineral structure, and the coordination of Zn²⁺ stabilization and an artificial inorganic carbon sink can be achieved.Unlike the high carbon-emission characteristics of traditional solidification/stabilization (S/S) technology, this study focuses on the key constraint posed by a high-magnesium geological background in a karst area. It extends the active MgO-enhanced CO₂ inorganic carbon sink technology to the remediation of Zn²⁺ contaminated red clay. Through systematic research, the mechanism of action of hydrated magnesium carbonate (HMCs) in mediating heavy metal stabilization at the micro level is clarified, providing a new theoretical explanation and technical path for the green, low-carbon treatment of heavy metal pollution in karst areas and the realization of carbon neutrality goals.In addition to discussing the variation in the influence of different factors on the stabilization effect and carbon sink mechanism, this study also guides engineering restoration of complex geological environments in karst areas. The technology offers fast reaction speed, excellent stabilization, significant environmental benefits, and strong carbon-sink potential. It shows broad application prospects for addressing heavy metal pollution in karst areas, reducing geological disasters, and advancing carbon neutrality. The active MgO-enhanced CO2 inorganic carbon sequestration stabilization technology proposed in this study has significant green and low-carbon advantages. The current research is mainly based on laboratory experiments. In the future, it is necessary to further conduct relevant model tests or on-site long-term monitoring to comprehensively evaluate the long-term stability, ion migration laws, and actual CO2 sequestration efficiency of the technology, thereby promoting its practical application in the remediation of contaminated sites in karst areas.In summary, this study demonstrates significant potential for sustainable and ecological restoration of the fragile karst ecosystem through the active MgO-enhanced CO₂ inorganic carbon sink stabilization technology, providing new ideas and methods for low-carbon, efficient restoration of Zn²⁺ contamination in karst areas. It has important scientific significance and engineering value in promoting the coordinated development of heavy metal pollution control and artificial carbon sinks.
- Karst area,
- Inorganic carbon sink,
- Red clay,
- Zn²⁺ contaminated soil,
- Stabilization mechanism

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The mechanism of inorganic carbon sink in the stabilization process of Zn²⁺ contaminated red clay in karst area

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The mechanism of inorganic carbon sink in the stabilization process of Zn²⁺ contaminated red clay in karst area