The Fate of Isocyanic Acid (HNCO): Investigation into Aqueous Phase Chemistry of HNCO

Isocyanic acid (HNCO) is an organic acid pollutant emitted by various sources, including: biomass burning, coal combustion, vehicle exhaust from gasoline and diesel engines, cigarettes from pyrolysis of urea and oxidation of nicotine, and produced via photochemical reactions of amines and amides in the atmosphere. Because of slow gas phase losses, the predominant removal of HNCO from the atmosphere is thought to be through dry deposition and heterogeneous uptake and subsequent hydrolysis. This thesis explores the overall hydrolysis (combination of three reactions with rate constants k1, k2, and k3) of HNCO, khyd, and has re-evaluated its associated rate constants, k1 and k2, for atmospherically relevant temperatures and pH values. The Arrhenius equation for k2 was determined to be k2 = (2.4 ± 5.9) x 1010 exp(-9126 ± 695/T) s-1 but, more data was needed to confidently calculate k1. Additionally, the partitioning characteristics of HNCO in aqueous droplets were investigated through simulated evaporation events.M.Sc