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To ensure the safety of carbon capture and storage (CCS) technology, insight into the potential impacts of CO2 leakage on the ecosystem is necessary. We conducted a greenhouse experiment to investigate the effects of high soil CO2 on plant growth and the soil environment. Treatments comprised 99.99% CO2 injection (CG), 99.99% N2injection (NG), and no injection (BG). NG treatment was employed to differentiate the effects of O2 depletion from those of CO2 enrichment. Soil CO2 and O2 concentrations were maintained at an average of 53% and 11%, respectively, under CG treatment. We verified that high soil CO2 had negative effects on root water absorption, chlorophyll, starch content and total biomass. Soil microbial acid phosphatase activity was affected by CG treatment. These negative effects were attributed to high soil CO2 instead of low O2 or low pH. Our results indicate that high soil CO2 affected the root system, which in turn triggered further changes in aboveground plant tissues and rhizospheric soil water conditions. A conceptual diagram of CO2 toxicity to plants and soil is suggested to act as a useful guideline for impact assessment of CCS technology.

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Vegetation monitoring can be used to detect CO2 leakage in carbon capture and storage (CCS) sites because it can monitor a large area at a relatively low cost. However, a rapidly responsive, sensitive, and cost-effective plant parameters must be suggested for vegetation monitoring to be practically utilized as a CCS management strategy. To screen the proper plant parameters for leakage monitoring, a greenhouse experiment was conducted by exposing kale (Brassica oleracea var. viridis), a sensitive plant, to 10%, 20%, and 40% soil CO2 concentrations. Water and water with CO2 stress treatments were also introduced to examine the parameters differentiating CO2 stress from water stresses. We tested the hypothesis that chlorophyl fluorescence parameters would be early and sensitive indicator to detect CO2 leakage. The results showed that the fluorescence parameters of effective quantum yield of photosystem II (Y(II)), detected the difference between CO2 treatments and control earlier than any other parameters, such as chlorophyl content, hyperspectral vegetation indices, and biomass. For systematic comparison among many parameters, we proposed an indicator evaluation score (IES) method based on four categories: CO2 specificity, early detection, field applicability, and cost. The IES results showed that fluorescence parameters (Y(II)) had the highest IES scores, and the parameters from spectral sensors (380–800 nm wavelength) had the second highest values. We suggest the IES system as a useful tool for evaluating new parameters in vegetation monitoring.

Potential CO2 leakage from carbon capture and storage (CCS) facilities should be monitored and managed carefully. Biomonitoring technologies for CO2 leakage using plants could be very effective, especially in areas near transport pipelines, because of the extensive areas that they can cover. A greenhouse study was conducted to investigate whether early changes in plant parameters could be an effective indicator to detect leaked CO2. Corn (Zea mays), which was reported to be a CO2‐tolerant species, was selected to identify specific indicators of CO2 leakage. The mean soil CO2 concentration for soil treated with CO2 was 20–40%, which is similar to the concentration that could occur near transport pipelines through slow‐insidious seepage. In the soil treated with CO2, the number of yellow leaves at the canopy level was significantly increased from the sixth day of CO2 injection compared to the control. The chlorophyll content in green leaves was significantly reduced on the eighth day from CO2 injection. The soil water content in the treated soil was increased from the sixth day of injection due to reduced root adsorption. The results of this study implied that early changes in parameters of CO2‐tolerant species such as canopy‐level discoloration and chlorophyll content could be used as CO2‐specific indicators for the detection of soil CO2 leakage. We suggested that canopy‐level monitoring is a promising, useful technique for soil CO2 leakage in extensive areas, such as near CO2 transport pipelines. In addition, rhizosphere‐level parameters, such as soil water content, could be good subsidiary indicators together with the large‐scale collection of baseline data and statistical analysis. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.