Stable carbon δ13C analysis of automotive particulate matter emissions under controlled conditions

Excessive automotive engine exhaust emissions of gases and particulate matter (PM) pose a threat to public health and urban air quality. In an effort to reduce automotive emissions modern cars use a variety of engine modifications, catalytic systems and filters which in turn alter the isotope ratio of carbonaceous particles (isotope fractionation effect). Diesel engines are of particular interest due to higher production of particulates (soot) in comparison to gasoline engines [1].

The aim of this work was to examine particulate matter δ¹³C variation in automotive emissions using stable carbon isotope ratio measurements. Emission experiments were performed in dynamometer laboratory using four light passenger vehicles with differing liquid fuels - diesel, diesel with additives, 92 RON and 95 RON. Vehicles were tested with varying engine power and using simulated transient cycles in urban and rural areas. Engine exhaust particulate matter was collected on quartz filters. Later, isotope ratio δ¹³C values of fuel and exhaust carbonaceous particulates were measured using IRMS. δ¹³C values were then compared and level of isotope fractionation determined.

The obtained results show particulate matter δ¹³C values ranging from -28.8 ‰ to -27.2 ‰ during separate driving modes. Isotope fractionation Δ (particulates-fuel) values varied between 1.8 ‰ and 3.5 ‰. It was determined that δ¹³C values of automotive emissions depend on the type of fuel used, applied engine power, driving modes (urban, rural) and can be used to characterize automotive carbonaceous particle emissions.

 

[1]             M. V. Twigg, “Progress and future challenges in controlling automotive exhaust gas emissions,” Appl. Catal. B Environ., 2007.