Impacts of leakage of stored CO2 to growth of trifolium hybridum L.

Abstract: In recent years, more than 12 demonstration projects of carbon capture and storage (CCS) have been developed in China. The CCS technology can provide the CO2 capture capacity of hundreds of billions of tons and has important significance for mid-long term mitigation of CO2 in China. However, there is leakage risk for the CO2 stored in the geological structure, which may lead to major threats for farmland ecosystem. Along with the development of carbon capture and storage technique, more attentions have been focused on the potential threats from the leakage of stored CO2, and the adaptation capacity of crops to CO2 leakage has not been well understood. This study assessed the response of Trifolium hybridum L., which is widespread and has strong acid resistance, to leakage of stored CO2. And 4 treatments were designed in the pot experiment, in which the CO2 with the airflow rate from 500 to 2 000 g/(m2·d) was added into the bottom of the cultivation box. The experiment simulated the process of the leakage of CO2 in surface soil, and tested if the crop with strong acid resistance would better adapt to the impacts of the leakage of stored CO2. The results revealed that the productive viabilities (biomass, height, root length and root activity) of Trifeolium hybridum L. increased slightly or remained stable under the leakage of 500 g/(m2·d) CO2, and it showed better adaptation capability under 500 g/(m2·d) CO2 leakage treatment. When the leakage of CO2 increased to over 1 000 g/(m2·d), Trifolium hybridum L. gradually presented environmental stress, and the biomass and root activity decreased quickly under the leakage of 1 500-2 000 g/(m2·d). However, the crude protein, crude fiber, ash, crude fat and calcium have no obvious change. The change of soil pH value, from 6.6 to 7.2, was not out of the optimum pH value range for Trifolium hybridum L. growth and development, and the acid resistance should not be the key factor of adaptation capability. The replacement of CO2/O2 in soil led to the decrease of O2 concentration from 20% to 6.7% in the 10-20 cm soil layer. Previous study showed that the seedling rate, net photosynthetic rate, transpiration rate and fresh weight of maize were significantly inhibited under 500 g/(m2·d) CO2 leakage treatment, while Trifolium hybridum L. showed a better tolerance to O2 concentration reduction in soil than the maize. This finding suggests that Trifolium hybridum L. can be the alternative crop for the potential mild leakage area and can be developed as a new technology for the leakage of stored CO2. However, the mechanism of Trifolium hybridum L. for the resistance to CO2 leakage is still unclear and further researches will be needed.