The carbon isotopic compositions of Non-methane Hydrocarbons in atmosphere

Carbon isotopic compositions of atmospheric Non-methane Hydrocarbons （NMHCs） in the urban areas of Taiyuan and Lanzhou in summer were reported and the sources of NMHCs are discussed. Carbon isotopic ratios （δ13C） of vehicle exhaust, coal-combustion exhaust, fuel volatiies and cooking exhaust were also measured with thermal desorption-gas chromatography-isotope ratio-mass spectrometry （TD-GC-IR-MS）. δ13C values of NMHCs in the urban areas of Lanzhou and Taiyuan range from -32.3‰ to -22.3‰ and from -32.8‰ to -18.1‰. δ13C values of vehicle exhaust, coal-combustion exhaust, fuel volatiles and cooking exhaust are -32.6‰---21.7‰, -24.5‰--22.3‰, -32.5‰--27.4‰ and -31.6‰-- -24.5‰, respectively. The data indicate that vehicle exhaust and cooking exhaust make a significant contribution to the atmospheric NMHCs. Therefore, to reduce emissions of vehicle exhaust and cooking exhaust is critical for controlling atmospheric NMHCs pollution in summer.