Development And Application Of The Technology Of Ecological And Health Risk Assessment For CO₂ Geological Sequestration Leakage

Carbon capture,utilization and storage(CCUS).as a large-scale emission reduction technology,is the most promising solution to achieve carbon neutrality.Analyzing the diffusion pattern of CO2 in near-surface space and exploring the hazards of potential CO2 leakage is one of the current research hotspots in the energy and environment field.In this study,we construct an ecological and human health risk assessment model for CO2 leakage from geological storage,and develop a large-scale complex terrain computational domain modeling and computational fluid dynamics(CFD)solution method.Firstly,we use the species sensitivity distribution(SSD)method to fit the toxicity data of typical species in terrestrial ecosystems,calculate the baseline value of CO2 ecological risk(HC5),and use the quotient model to calculate the ecological risk index;secondly,we analyze the health hazards of human exposure to CO2 indoors and outdoors,determine multiple levels of risk and corresponding CO2 concentration thresholds,and use the hazard quotient model to calculate the human health;Finally,we coupled common geographic information and 3D modeling software to establish a 3D computational domain,and analyzed and determined the turbulence model and discrete equation system solution method for CFD simulation of CO2 dispersion under complex terrain conditions.This study can not only efficiently simulate the gas diffusion characteristics of different leakage scenarios,but also quickly obtain the spatial and temporal patterns of leakage hazards,and apply them to the Xingzichuan oil field in Yan’an,Shaanxi Province.It was shown that the best SSD fitting equations for acute and chronic toxicity effect data in the ecological risk assessment model were Weibull CDF and SGompertz,respectively,with ecotoxicity benchmark concentration values HC5 of 3.25vol.%and 0.98vol.%,respectively.In the human health risk assessment model,10 risk classes ranging from occupational exposure to immediate death were set based on hazard effects,with exposure concentration thresholds ranging from 0.5vol.%to 25vol.%.The spatial and temporal characteristics of the ecological and health risk levels are similar:the risk distribution of point source spill is influenced by seasonal wind direction and wind speed,the high risk range is influenced by high wind speed,the low risk range is influenced by wind speed,topography and gravity,and the risk range increases and then decreases with increasing wind speed;the risk of surface source spill expands along the downwind direction at low altitude,and the overall increases gradually with increasing spill time The minimum impact distance of the highest level ecological risk in point source dispersion is 160 m,and the maximum impact distance of the risk of immediate lethal health hazard is 30 m.The maximum impact distance of the immediate lethal hazard in surface source dispersion is 39 m,which occurs only one day after the spill.This study investigates the spatial and temporal distribution and ecological and human health risks of potential CO2 leakage from geological storage,and proposes risk mitigation and control measures,which can effectively improve the level of CO2 leakage monitoring and early warning and emergency response,provide complete theoretical and data support for CCUS-related research,help CCUS to be applied safely on a large scale,and promote the implementation of China’s carbon neutrality initiative and the achievement of the dual carbon goal.