UBC Faculty Research and Publications

Isotopic composition of CO2 in gasoline, diesel and natural gas combustion exhaust in Vancouver, BC, Canada Semmens, Caitlin; Ketler, Rick; Schwendenmann, Luitgard; Nesic, Zoran; Christen, Andreas


The isotopic composition (δ¹³ and δ¹⁸) in atmospheric carbon dioxide (CO₂) originating from gasoline and diesel vehicle exhaust and from natural gas combustion was determined. Gasoline and diesel samples were taken in the exhaust of representative vehicles of the fleet in Vancouver, BC, Canada between November 2013 and May 2014. The fleet average gasoline exhaust (which contained a fraction bioethanol) was determined with a δ¹³C of -27.27 (±0.93)‰ and a δ¹⁸O of -12.46 (±3.45)‰ (w.r.t. VPD-CO₂). The fleet average for diesel vehicles exhibited a slightly lower δ¹³C of -28.81 (±0.40)‰ and a δ¹⁸O of -18.63 (±0.72)‰ close to unfractionated combustion. For natural gas, samples were taken from a open torch using the city’s natural gas supply network at different dates over the year. The mean δ¹³C for natural gas samples was -41.64 (±0.82)‰, while the mean δ¹⁸O was lower than for internal combustion engines at -22.74 (±0.56)‰. In conclusion, δ¹³C depends on the fuel type and origin and there is evidence that δ¹⁸O is fractionated in the combustion process and presence and state of catalytic converters causes different δ¹⁸O.

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Attribution-NonCommercial-NoDerivs 2.5 Canada