Atmospheric oxidation of N-PAC and nitro substituted N-PAC in water droplets

A pulse radiolysis technique was used to study the formation of OH-adducts of quinoline (Q) and 5-nitroquinoline (5NQ) and the subsequent reactions of the OH-adducts with O-2 in both acidic and alkaline aqueous solution. The rate constants in alkaline solution were: k(Q+OH) = (9.0+/-1.0)lozenge 10(9 ) dm(3)mol(-1)s(-1), k(5NQ+OH)= (5.4+/-0.5)lozenge 10(9) dm(3)mol(-1)s(-1), k(Q-OH+O-2) = (9.9+/-0.9)?10(8) dm(3)mol(-1)s(-1) k(5NQ-OH+O-2) = (1.1+/-0 .1)lozenge 10(6) dm(3)mol(-1)s(-1). The rate constants in acidic solution w ere: k(Q+OH)= (4.0+/-0.5)lozenge 10(9) dm(3)mol(-1)s(-1), k(5NQ+OH)=(1.4+/- 0.1)lozenge 10(9) dm(3)mol(-1)s(-1), k(Q-OH+O-2) = (1.8+/-0.1)lozenge 10(7) dm(3)mol(-1)s(-1), k(5NQ-OH+O-2) = (8.7+/-0.6)lozenge 10(5) dm(3)mol(-1)s( -1). Absorption spectra of the OH-adducts were also measured. The results s uggest that the lifetime of quinoline and 5-nitroquinoline with respect to reaction with OH in water droplets in the atmosphere is less than 1 hour. I t is estimated that the degradation of Q is accelerated in the presence of aqueous droplets with comparable contributions from aqueous and gas phase c hemistry at neutral pH. Under acidic conditions the aqueous phase degradati on is predicted to dominate. For 5NQ the aqueous phase degradation is predi cted to dominate regardless of pH.