GAS-PHASE ATMOSPHERIC CHEMISTRY OF DIBENZO-P-DIOXIN AND DIBENZOFURAN

Rate constants for the gas-phase reactions of dibenzofuran and dibenzo-p-dioxin with the OH radical and O3 have been determined at 297 +/- 2 K and atmospheric pressure of air. Using a relative rate method, rate constants for the OH radical reactions were 3.9 X 10(-12) cm3 molecule-1 s-1 for dibenzofuran and 1.48 x 10(-11) cm3 molecule-1 s-1 for dibenzo-p-dioxin. Upper limits to the rate constants for the O3 reactions of <8 x 10(-20) and <5 x 10(-20) cm3 molecule-1 s-1 were obtained for dibenzofuran and dibenzo-p-dioxin, respectively. These data, together with those previously obtained for the NO3 radical reactions, show that the OH radical reactions will be the dominant tropospheric chemical loss processes for dibenzofuran and dibenzo-p-dioxin, with calculated lifetimes of 3.7 and 1.0 day, respectively. The OH radical reactions, in the presence of NO(x), formed nitro products in low (approximately 0.4-2%) yields.