Chemistry inside aerosol particles is important for smog forecasts
The chemical processes inside smog particles affect their size and mass much more than previously thought. The improved prediction of particle size leads to better evaluations of effects of smog on air quality and public health.
Los Angeles, London, New Delhi or Beijing - all are mega cities in which millions of people suffer from breathing problems and burning eyes. The cause is smog. Often it is so thick that the tops of the skyscrapers disappear and the sun cannot be seen for days.
Under certain weather conditions smog - a mixture of particles and gaseous pollutants like ozone - develops due to traffic, industrial activities, or combustion of biomass, coal and wood. The main component of urban smog is the so-called secondary organic aerosol (SOA). The SOA particles develop from organic compounds oxidized by ozone and hydroxyl radicals. The organic molecules are for example released by burning fossil and renewable fuels.
The processes and mechanisms for the formation of these smog particles are still poorly understood. It has been difficult to accurately predict size and mass of the particles, which determines atmospheric visibility, i.e. the smog thickness and the extent of adverse health effects.