Hydroxyl radical: A critical air quality cleaning agent

Smokestacks protrude above fog. Credit: Pixabay

Scientists supported by CPO’s Atmospheric Chemistry, Carbon Cycle and Climate (AC4) Program are investigating the hydroxyl radical (OH), a molecule that despite its short lifetime of a few seconds, reacts with harmful gases and acts as a cleaning agent in Earth’s atmosphere. AC4-funded scientist Loretta Mickley of Harvard University worked with a team of researchers to compile a review exploring how OH, influenced by climate and human activities, impacts air quality, climate, and public health. This study works toward an AC4 initiative to explain trends, patterns, and extremes detectable in the existing long–term observational records of atmospheric composition.

OH reacts with certain air pollutants and greenhouse gases, breaking them down to help maintain air quality. However, difficulties in directly observing OH responses to climate and uncertainties in models make it challenging to predict OH changes. Climate warming, emissions, and human choices contribute to this complexity. Moreover, in a warmer climate, OH concentration in the atmosphere will increase primarily because of its dependence on water vapor. To confidently project OH, scientists need to reduce uncertainties in reactions, measurements, and emissions.