Features of major greenhouse gases in loess,Shanxi Province,China

According to the investigations of five loess sections in Shanri Province, China, it was found that the concentrations of the major greenhouse gases CO2, CH4 and N2O in loess-paleosol sequences are generally high, even sometimes may be several times or scores of tunes higher than their atmospheric concentrations respectively. Although the CO2 concentration in the same loess section shows poor regularity among different layers, it increases slowly from north to south in space. The CH4 concentration in the layers under Malan Loess is much higher than that in the atmosphere, although it is not high in Malan Loess. Most of the δ13C values of CO2 in loess are -11.14‰-15.48‰, (relative to PDB standard). Analysis of carbon isotopic compositions of CO2 indicates that the main source of CO2 in loess section is decomposition of ’stable’ organic matters by microbes. The δ13Cg of CO2 is a little heavier than organic source for exchanging carbon isotope with carbonate in loess. The abundant carbonate in loess not