Impact of turbulent mixing on isoprene chemistry

Isoprene, a volatile organic compound that is mainly emitted from trees, rapidly reacts with hydroxyl radical (OH) during daytime and subsequently forms ozone and aerosols in the troposphere. The isoprene-OH reaction can be affected by the interplay between chemistry and mixing because the two processes occur at a similar time scale. We investigate the impact of turbulent mixing on isoprene-OH reactivity with large eddy simulations (LES) coupled with comprehensive chemistry. Our results show that the covariance of isoprene and OH causes ~20% decrease to ~10% increase of the horizontal average reaction rate, depending on nitrogen oxides (NO_x = NO + NO₂) abundances, compared to the rate that neglects the covariance. This wide range of effects on reaction rates is caused by the primary production and loss reactions of OH in each NO_x regime. Our research promotes the use of LES for better understanding the role of turbulence in isoprene-OH reaction and parameterizations in large-scale models.