Study On The Effects Of Geological Storage Of CO₂ Leakage On Paddy Soil And The Screening Of Monitoring Indexes

Carbon capture and storage（CCS）,as a recognized globally and high-efficiency carbon emission reduction measure,can permanently isolate CO₂from the atmosphere.However,as an emerging technology,there are still a series of hidden dangers for CCS that would restrict its development on a larger-scale.The sequestered CO₂may leak out due to the surrounding environment and other factors.This study aimed to evaluate the potential risk to the plant and soil ecological environment of CO₂leakage during the CCS by using the CO₂leakage simulation platform,and rice and paddy soil were taken as the experimental objects.A range of rice and paddy soil parameters were applied to characterize the adverse effects including rice growth,properties of paddy soil,soil enzymes and soil bacterial diversity and composition that caused by CO₂leakage at different leakage rates specifically.The main results are as follows:（1）With the increasing of the CO₂leakage rates,the pH of the paddy soil significantly reduced,while the electrical conductivity increased.The ratio of nitrate nitrogen to total nitrogen in the paddy soil reduced,while ammonium nitrogen increased significantly.Soil organic carbon,microbial biomass carbon and nitrogen showed a decreasing trend with CO₂leakage,and the concentration of divalent iron gradually increased.Among them,the changing trend of pH,electrical conductivity,microbial biomass carbon and nitrogen with CO₂leakage were larger and relatively stable compared to others.Therefore,the decrease of pH,microbial biomass carbon and nitrogen,and the increase of electrical conductivity could be recommended as indicators for monitoring CO₂leakage.（2）The soil enzyme activities of paddy soil were inhibited by CO₂leakage in different degrees.The dehydrogenase of paddy soil reduced gradually,both peroxidase and amylase increased firstly and then decreased,while ureaase showed an opposite trend.The results of the correlation analysis with soil physical and chemical properties showed that soil dehydrogenase was positively correlated with pH significantly,microbial biomass nitrogen was negatively correlated with the electrical conductivity and the concentration of divalent iron.Peroxidase was positively correlated with organic carbon significantly.Urease was positively correlated with ammonium nitrogen significantly,and.negatively correlated with nitrate nitrogen.There was no significant correlation between amylase activity and physicochemical properties.（3）With the increase of CO₂leakage rate,compared to the increase of the bacteria richness index and the diversity index of paddy soil,the evenness index decreased.Moreover,the bacterial composition of paddy soil was notably changed by CO₂leakage,the relative abundances of Proteobacteria,Bacteroidetes and Chloroflexi in the dominant bacteria phyla of paddy soil generally decreased,while those of Acidobacteria and Actinobacteria increased.At the genus level,the abundances of RB41,MND1,Anaeromyxobacter and Sphingomonas in the dominant genus of paddy soil increased,but Nitrospira decreased.Among the rare bacteria under the CO₂leakage,all the phyla of Lentisphaerae,Tenericutes and the genus of Labrys,Sulfurifustis appeared,and the genus Pseudohongiella all disappeared.Taken together,the decrease of Proteobacteria and the increase of Acidobacteria,and the increase of RB41,MND1 and Anaeromyxobacter could be used as markers for monitoring CO₂leakage in paddy soil.RDA analysis of soil physicochemical properties,soil enzymes and the abundance of dominant bacteria showed that organic carbon,microbial biomass nitrogen and carbon,pH,urease and peroxidase were the key physicochemical factors affecting the abundance of dominant phyla.The parameters that had the greatest influence on the dominant genus including pH,microbial biomass carbon,organic carbon and peroxidase.（4）The CO₂leakage inhibited the growth of rice to a certain extent.The plant height,leaf area,tiller number and heading number were all threatened to varying degrees.The plant height and tiller number decreased significantly with the increasing of CO₂leakage,respectively compared with CK.While the leaf area and heading number showed a trend of first increasing and then decreasing.The leaf area had a significant inhibitory effect when the CO₂leakage rate reaches 0.12 L·m^-2·min^-1.When the CO₂leakage rate increased to0.48 L·m^-2·min^-1,the number of heading number decreased by 6.45%compared with CK.