Mercury emissions from automobiles using gasoline, diesel, and LPG

Mercury (Hg) emissions from gasoline, diesel, and liquefied petroleum gas (LPG) vehicles were measured and speciated (particulate, oxidized, and elemental mercury). First, three different fuel types were analyzed for their original Hg contents; 571.1±4.5 ng L^-1 for gasoline, 185.7±2.6 ng L^-1 for diesel, and 1230.3±23.5 ng L^-1 for LPG. All three vehicles were then tested at idling and driving modes. Hg in the exhaust gas was mostly in elemental form (Hg⁰), and no detectable levels of particulate (Hg^p) or oxidized (Hg²⁺) mercury were measured. At idling modes, Hg concentrations in the exhaust gas of gasoline, diesel, and LPG vehicles were 1.5-9.1, 1.6-3.5, and 10.2-18.6 ng m^-3, respectively. At driving modes, Hg concentrations were 3.8-16.8 ng m^-3 (gasoline), 2.8-8.5 ng m^-3 (diesel), and 20.0-26.9 ng m^-3 (LPG). For all three vehicles, Hg concentrations at driving modes were higher than at idling modes. Furthermore, Hg emissions from LPG vehicle was highest of all three vehicle types tested, both at idling and driving modes, as expected from the fact that it had the highest original fuel Hg content.