Effect of different leakage speeds on plants in carbon capture and storage by simulation in chamber

Abstract: Carbon capture and storage (CCS) is an effective means to reduce greenhouse gas emissions, which sequesters anthropogenic CO2 in deep geological formations and avoids emissions into the atmosphere while supporting coal use. Thus, the technology is an attractive way of controlling greenhouse gases in economies heavily dependent on coal energy, such as China, whose goal is to reach an emissions cap by 2030. Currently, more than 12 CCS demonstration projects are in development in China. Preliminary estimates show that reservoirs, such as saline aquifers, depleted oil and gas reservoirs, and un-mineable coal seams, have a CO2 storage capacity with hundreds of billions of tons. However, there are risk of CCS-stored CO2 leaking out of the storage reservoirs, and the quick leakage such as failure of injection wells and slow leakage from geological aisle, which shows different environmental impacts. The most visible impact of CCS leakage is the degradation of plant cover. To know the impact of elevated soil CO2 flux in near-surface ecosystems and the plants' responses to different CO2 leaking rates, and to assess and address the risks of elevated soil CO2 flux, we simulated quick and slow CO2 leakage, at a rate of 2000 g/(m·d) and 60% of the soil CO2 concentration, and compared the differences of maize plant height, root length, leaf number, leaf photosynthetic rate and soil pH value. The experimental device was the self-made combination with gas chambers and soil chambers on top. CO2 was injected into the bottom of the cultivation container at different flux rates by manually control. The results indicated that, under the quick CO2 leaking at a rate of 2000 g/(m·d), the maize photosynthetic rate was decreased from (22.86±0.89) μmol/(m·s) of CK treatment to (0.1±0.08) μmol/(m·s) , while the height of maize was dropped from (206±10.20) cm to (93.67±4.78) cm and maize root length was decreased by 75%, from (109±16.83) cm to (20.73±3.73) cm. And the number of plant leaves was decreased significantly, which was 16 in the control group, but only 9 to 11 in the rapid leakage control, and the withered leaf number were significantly increased in the rapid leakage test. Slow leakage under 60% of the soil CO2 concentration did not inhibit the growth of maize. The height of maize plants in the control group (SCK) was (153.25±13.27) cm, and the plant height at slow leakage treatment was (154 ± 8.09) cm. The root length, the number of leaves and net photosynthetic rate of maize also were not significant difference, separately. Only the soil pH value in the vicinity of leaking source was decreased slightly, however, soil pH value remained within a reasonable range of maize growth and therefore did not have a significant impact on maize growth. The different response of plant to quick and slow stored CO2 leakage will provide useful information for decision maker to formulate countermeasures.