Kinetics and mechanism of OH oxidation of small organic dicarboxylic acids in ice: comparison to behavior in aqueous solution.

To better understand the oxidation of organic species by OH within frozen solutions, experiments were conducted with a simplified model system consisting of succinic acid (2.5, 5, and 10 mM), using H(2)O(2) (30 mM) as a condensed-phase OH precursor. Frozen (-20 °C) and aqueous (0 °C and room temperature) solutions were irradiated using a xenon arc lamp to study the differences between frozen and nonfrozen reaction media.

Evaluation of the effects of ozone oxidation on redox-cycling activity of two-stroke engine exhaust particles.

The effect of oxidation on the redox-cycling activity of engine exhaust particles is examined. Particles obtained from a two-stroke gasoline engine were oxidized in a flow tube with ozone on a one-minute time scale both in the presence and absence of substantial gas-phase exhaust components. Whereas ozone concentrations were high, the ozone exposures were approximately equivalent to 60 ppb ozone for 2-8 h.