Laboratory studies of nitrate radical reactions with some atmospheric sulfur compounds

The reaction of nitrate radicals (NO/sub 3/) with CH/sub 3/SCH/sub 3/ (DMS), CH/sub 3/SH, CH/sub 3/SSCH/sub 3/ (DMDS), H/sub 2/S, and SO/sub 2/ have been studied at low pressures in a fast flow reactor with LIF detection of NO/sub 3/. All experiments were performed under pseudo-first-order conditions in NO/sub 3/, using thermolysis of N/sub 2/O/sub 5/ as a source of NO/sub 3/. The reaction of NO/sub 3/ with DMS (1) was studied between 0.46 and 4.5 Torr and as a function of temperature from 256 to 376 K. The rate coefficient for the reaction is k/sub 1/(T) = (1.79 +/- 0.22) x 10/sup -13/ exp(530 +/- 40/T) cm/sup 3/ molecule/sup -1/ s/sup -1/ with no dependence on pressure. All error limits are the 95% confidence levels and include a factor for systematic errors. The reaction of NO/sub 3/ with CH/sub 3/SH (2) was studied over the temperature range 254-376 K, and the rate constant was found to be k/sub 2/(T) = (1.09 +/- 0.17) x 10/sup -12/ cm/sup 3/ molecule/sup -1/ s/sup -1/ independent of temperature and pressure in the range 0.45-4.5 Torr. For both of these reactions, the authors determined that NO/sub 2/ was not a significant product, <5%.more » The reaction of NO/sub 3/ with DMDS (3) was studied at 382 and 334 K, and the rate constant is k/sub 3/ = (7.4 +/- 1.5) x 10/sup -13/ cm/sup 3/ molecule/sup -1/ s/sup -1/, independent of temperature. They have also determined upper limits for the rate coefficients at 298 K for the reactions of NO/sub 3/ with H/sub 2/S (4), k/sub 4/ < 8 x 10/sup -16/, and SO/sub 2/ (5), k/sub 5/ < 1 x 10/sup -15/ both in units of cm/sup 3/ molecule/sup -1/ s/sup -1/.« less