Characteristics of CO2 in unsaturated zone（～90 m） of loess tableland, Northwest China

In order to observe CO2 characteristics in the unsaturated zone of loess tableland and further understand the carbon cycle,a series of tubes for gas monitoring and sampling were installed in an approximately 90-m deep Qiushe loess section of Lingtai County,Northwestern China.The results show that the concentration of CO2 was higher in loess than in the atmosphere,reaching a maximum of 6970 lmol·mol^-1.CO2 concentrations in loess were higher in summer than in winter.The CO2 in loess was related to organic carbon decomposed by microbes,and to the CaCO3–H2O–CO2 system in the interface between the saturated and unsaturated zones.