Abstract: | Although OH uptake by carbonaceous surfaces is very efficient, it is thought to be negligible to affect the OH and O3 balance in the lower troposphere. To estimate its contribution in the upper troposphere, we have studied the temperature
dependence of OH uptake by carbonaceous surfaces of atmospheric importance over the temperature range from 218 to 298 K. We
found that the OH uptake coefficient is weakly dependent of temperature, ranging from 0.1 to 1, as was measured under flow
conditions using chemical ionization mass spectrometry. This finding was further used to estimate OH loss on carbonaceous
aerosol under upper tropospheric conditions. Our calculations suggested that OH heterogeneous loss may represent a notable
sink for OH in the upper troposphere, which is due to both the significantly lower diffusion limitation and weakly temperature-dependent
OH uptake. The obtained results may be thus important for aerosol chemistry of the upper troposphere. |