NIGHTTIME PEROXY RADICAL CHEMISTRY IN THE REMOTE MARINE BOUNDARY-LAYER OVER THE SOUTHERN-OCEAN

Peroxy radical measurements were made in the remote marine boundary la yer over the Southern Ocean at Cape Grim, Tasmania during January and February 1995. From the experimental peroxy radical data it is clearly demonstrated that there is little night-time oxidation chemistry tail ing place. In such an environment at night the sole type of peroxy rad ical that persists is CH3O2 (tau > 12 hours) and the only nocturnal ch emical process involving peroxy radicals appear to be the self-reactio n of CH3O2 coupled to either a small but finite deposition velocity (k (d) similar to 0.003 m s(-1)) or a slow reaction with O-3 (k(CH3O2 + O -3) less than or equal to 8 x 10(-18) cm(3) molecule(-1) s(-1)). A dev iation between experimentally determined peroxy radical levels and J(( OD)-D-1) in the late afternoon is discussed and modelled in terms of t he peroxy radical self-reactions.