EVALUATION OF OZONE DEPLETION POTENTIALS FOR CHLOROBROMOMETHANE (CH2CLBR) AND 1-BROMO-PROPANE (CH(2)BRCH(2)CH(3))

Chlorobromomethane (CH2ClBr) and I-bromo-propane (CH2BrCH2CH3 or simpl ified as 1-C3H7Br) are being considered for use as solvents and potent ially in other applications. As with other chemicals that contain chlo rine and/or bromine, it is important to determine the potential enviro nmental effect From use and emissions of such compounds, including eff ects on stratospheric ozone. In this paper, the Ozone Depletion Potent ials (ODPs), an important measure of the potential effects on ozone, a re evaluated for these two compounds using our two-dimensional chemica l-transport model of the troposphere and stratosphere. This is the fir st time these compounds have, to our knowledge, been evaluated with at mospheric models. Our model results show that the main removal process (ca. 99%) in the atmosphere for these compounds is the reaction with OH radicals. Photolysis has only a minor (less than or equal to 1.%) e ffect on the atmospheric lifetimes of either compound. The atmospheric lifetimes of CH2ClBr and 1-C3H7Br due to atmospheric reactions are ev aluated to be 0.40 yr (146 d) and 0.03 y (11 d), respectively. However , oceanic losses are likely to be important for CH2ClBr. Because of li mited data on solubility and degradation in sea water, the lifetime fo r ocean loss currently has a range of 0.43-0.65 yr. This results in a total lifetime for CH2ClBr of 0.21-0.25 yr. An ocean sink for 1-C3H7Br is likely to have an insignificant effect on its atmospheric lifetime or ODP. The ODP for 1-C3H7Br is evaluated to be 0.006, while the ODP for CH2ClBr including the effects of the ocean sink is 0.11-0.13. Ther e are additional uncertainties in these values due to ambiguities in m easured reaction rates and in the model treatment of atmospheric proce sses. (C) 1997 Published by Elsevier Science Ltd.