Field Study on Correlation between CO2 Concentration and Surface Soil CO2 Flux in Closed Coal Mine Goaf

Self-heating of coal mine goaf or shallow coal seams can release an outbreak of unimaginable pollution disaster under suitable circumstances. As an indicator gas, CO 2 is always used to determine the coal spontaneous combustion state during the self-heating process. Based on this, the paper investigated the influence of abandoned coal mine goaf CO 2 on the surface environment by measuring the CO 2 concentration in the borehole connected to the goaf and CO 2 flux on the soil surface. Furthermore, rainfall and atmospheric temperature effects are discussed to illustrate the correlation between the CO 2 concentration and surface soil CO 2 flux in the closed mine goaf. Subsequently, the tracer gas experimental method is employed to analyze the effect of air leakage from an open-pit slope on CO 2 flux. The experimental results demonstrated that the distribution of CO 2 concentration in the borehole confirms the continuous diffusion of goaf CO 2 onto the surface. The value of CO 2 flux in the goaf is significantly higher than that of a normal area. Temperature is one of the primary factors that affect the CO 2 flux on the field. Air leakage from the slope promotes the surface soil-overlying goaf CO 2 diffusion. The study provides important reference data for the assessment of the mining area field environment and the determination of the spontaneous combustion risk of the residual coal in the goaf.