A Review on Ecosystem Monitoring for CO₂ Geological Storage

CO₂ geological storage is one of the most promising technologies for mitigating the greenhouse effect and achieving sustainable societal development. Ecosystem monitoring serves as a crucial technical approach for ensuring the safety, effectiveness, and long-term integrity of CO₂ geological storage projects. This paper reviews the impacts of CO₂ leakage on soil physicochemical properties, microbes, soil enzymes, water quality, and vegetation and analyzes the ecosystem monitoring methods for CO₂ geological storage, along with the associated challenges and future prospects. The results indicate that the CO₂ leakage alters soil physicochemical properties, soil microbial communities, and soil enzyme activities. Concurrently, it leads to an increase in the dissolved CO₂ content in water, a decrease in pH, and changes in ion composition and concentration. Changes in soil and water quality affect plant growth, manifested as stunted plant height, leaf chlorosis, and slow growth. The main ecosystem monitoring methods include soil gas flux monitoring, soil and water quality sampling monitoring, and vegetation stress monitoring. Commonly monitored soil parameters include soil gas concentration and flux, microbial species and abundance, organic carbon, moisture content, conductivity, etc. For surface water and shallow groundwater, key monitoring parameters include dissolved CO₂ concentration, mineralization degree, pH, conductivity, ion concentrations (e.g., Ca²⁺, HCO₃ ^-), etc. The normalized difference vegetation index (NDVI) and chlorophyll fluorescence parameters can serve as important indicators for monitoring the leakage of CO₂ from geological storage. The development of remote sensing technologies with high spatial and temporal resolution, the accurate discrimination of factors driving ecosystem changes, the reduction of ecosystem monitoring costs, and the development of multisource data fusion methods represent four major challenges and future research directions requiring urgent attention in the field of ecosystem monitoring for CO₂ leakage.