Study On The Diffusion And Impacts Of CO₂ Leakage In Soil From Geological Storage Point Source

With the accelerated development of global industrialization,a large amount of carbon dioxide is emitted into the atmosphere,causing an increase in the greenhouse effect and global warming.In order to effectively solve the problem of carbon dioxide emissions,the international community has made it a key research issue.Carbon Capture Utilization and Storage（CCS）technology can effectively improve carbon emissions,which is an important measure to mitigate global warming.As a responsible country,China is also accelerating the completion of CCUS projects,playing an important role in the process of establishing a green low-carbon development system in China.serious consequences.For this reason,it is necessary to consider the risk of leakage and study the specific ecological hazards to ensure the safety of CCUS projects.In this study,we simulated the CO₂point source leakage in CCUS project,studied the CO₂transport pattern in near-surface soil and the influencing factors,and investigated the CO₂transport characteristics under different soil structures by combining physical models and numerical simulations,and analyzed the effects of CO₂on soil and plant growth and development by monitoring soil,plant and atmospheric environment indicators.The main conclusions are as follows:（1）Under the condition of CO₂point source leakage,the CO₂concentration in shallow soil showed obvious spatial variation as well as temporal variation,and its lateral diffusion distance was 2.85 times of the burial depth of the leakage source.The correlation results showed that soil CO₂concentration was significantly correlated with soil temperature,soil water content,soil porosity and distance from the source,and a regression relationship model between soil CO₂concentration and each influencing factor was established.（2）The experimental process was numerically simulated by COMSOL Multiphysics software,based on the experimental results,three soil pore structure models were established:homogeneous soil,non-homogeneous soil and non-homogeneous soil affected by soil temperature and humidity changes,and the transport law of CO₂gas under different soil structures was analyzed.Finally,the model prediction results were compared with the experimental results,and the error range between the simulated and measured values was between-5.84 and 5.42,and the model prediction results were more accurate.（3）CO₂ leakage affects soil physicochemical properties,soil enzymes,greenhouse gas emissions from farmland and plant growth.The closer to the source,the lower the soil p H,the higher the organic carbon content,the higher the ammonium nitrogen content and the opposite of nitrate nitrogen;the high concentration of CO₂in the soil will stimulate the activity of some enzymes in the soil such as urease and amylase,thus changing the soil properties;the high concentration of CO₂in the soil will increase the enzymatic activity of soil enzymes such as urease and amylase;CO₂leakage will induce the emission of N₂O and CH₄greenhouse gases by affecting the microorganisms in the soil,thus aggravating the greenhouse effect.The global warming potential（GWP）of the three greenhouse gases before and after CO₂leakage was calculated,and it was found that CO₂leakage would increase the warming potential of N₂O and CH₄in the farmland,but this effect was much smaller than the warming effect brought by CO₂itself.Correlation analysis revealed that there were significant correlations among soil p H,soil organic carbon,ammonium nitrogen,nitrate nitrogen,urease,amylase and greenhouse gases（CH₄,N₂O）...