Natural discharge of carbon from the extremely arid land: The mode and amount of CO2 emission based on earth-air exchange

Abstract

Carbon dioxide (CO₂) emission is a critical cause of global warming. At present, the quantity of CO₂ emitted by land is mainly assessed in terms of concurrent soil respiration. It is unclear whether there are any background terrestrial sources of CO₂. According to the closed system model, earth-air (the air in the vadose zone) and atmospheric air are widely exchanged at the land's surface due to the barometric pumping effect. In order to calculate the amount of CO₂ released from the extremely arid region, an inventive device was utilized to monitor the amount of earth-air and CO₂ flowing. The findings demonstrate that the concentration of CO₂ in the earth-air rises when atmospheric pressure falls and it is proportionate to the earth-air flow. The CO₂ emitted from the land is positively correlated with temperature, amplitude of atmospheric fluctuations, and thickness and porosity of the vadose zone. CO₂ continuously migrates upwards driven by barometric pumping. Emission of CO₂ from land is widespread due to earth-air exchange. The total CO₂ emission varies with the season, exhibiting a ‘γ-shaped’ profile over the course of a year. On a daily timescale, the CO₂ flow varies in a bimodal manner. The average yearly CO₂ concentration in the pipe outflowing earth-air is 789.2 ppm; that of the inflowing air is 594.5 ppm. This study provides a method for monitoring terrestrial CO₂ release. Determining the amount CO₂ emitted via the earth-air mechanism has great significance for the scientific evaluation of soil respiration, natural CO₂ emission effects on ambient.