Rapid growth of new atmospheric particles by nitric acid and ammonia condensation.
Used by CERN's CLOUD Experiment in the manuscript published in Nature Journal on 13th May 2020,
Summary of illustration: Ultrafine particles can be formed in the atmosphere in highly polluted megacities, where they can add to pollution but also influence both local meteorology as well as global climate. The climate effects especially require particles to grow many times over from their size at formation to a size where they can influence clouds; if they do not grow rapidly enough, they are consumed by larger particles. This work addresses growth driven by the abundant but volatile combination of nitric acid and ammonia vapors, which are formed and emitted in cities from traffic and other activities. They combine to form ammonium nitrate in particles, but this was not thought to make ultrafine particles grow because the ammonium nitrate is too volatile. However, the eddies and plumes associated with air circulation in cities can generate conditions where this growth can occur. We have shown that it does occur via experiments in the CLOUD chamber at CERN, and this figure depicts the conditions of those eddies over an amalgamated megacity environment.
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