Formation of acetone from the OH radical- and O-3-initiated reactions of aseries of monoterpenes

The formation yields of acetone from the gas-phase reactions of the OH radi cal tin the presence of NO) and O-3 with a series of monoterpenes have been measured at room temperature and atmospheric pressure of air. The acetone formation yields ranged from <2-3% for the OH radical reaction with limonen e and the O-3 reactions with limonene and alpha-phellandrene to 50% for the O-3 reaction with terpinolene. Combining these acetone formation yields wi th literature estimates of emission rates of monoterpenes from vegetation l eads to an estimate of acetone formation from the atmospheric photooxidatio n of monoterpenes of similar to 10-11 Tg yr(-1) globally, a significant fra ction of the global acetone source strength of 40-60 Tg yr(-1). Reaction me chanisms leading to acetone formation from these monoterpene reactions are discussed.