A survey on the gas emissions and soil properties near the surface in a coal fire area

Abstract

In this study, a comprehensive survey was performed on the fire-induced landforms, belowground and near surface gas emissions, and soil properties. In addition, the effect of the soil cover on the gas emissions and soil properties was examined. The survey zone was divided into three areas based on the surface features. Sponges, vents and cracks, and the fissures dominated in area A, and area B exhibited no obvious features but was covered with a layer of sand soil. Area C was characterized by degraded vegetation. A comparison of the composition and concentration of belowground and near surface gases was performed among the three areas. Topsoil samples were collected at a 0–5-cm depth in the three areas, and soil properties were measured and analyzed. The average CO, CO2, CH4, and H2 concentrations below the ground surface in area B were lower than those in area A. The detected near surface CO and CH4 mainly originated from obvious openings. Damage to the soil ecology was primarily caused by the replacement of O2 by CO2. Soil thermal and humidity anomalies were obvious in area A, but scarcely occurred in areas B and C because of solar heating. The soil pH was the lowest in area A, which was closely related to the total soil contents. The organic matter contents in area B were higher than those in area A because of the increase in the particles released from underground coal fires, and area C attained the highest organic matter contents due to vegetation withering.