Air pollution is one of the largest environmental risks for society. Substantial effort is made to gain insight into the detrimental effects of air pollution for human health but the impact on plants and vegetation is much less understood. Despite the increasing pressure on agriculture to provide food security for a continuously growing population, details of the chemistry occurring in plants upon exposure to air pollutants are poorly known.
Ozone (O3) and nitrogen dioxide (NO2•) are important irritant gaseous air pollutants in the troposphere, which are formed through combustion of fossil fuels and transformations of natural and anthropogenous volatile organic compounds in the presence of sun light. As both O3 and NO2• can be transported over distances of hundreds of kilometres, these air pollutants also directly affect agricultural environments in rural regions far removed from the precursor sources.
Studies on human health effects using rat models showed that exposure to combined NO2• and O3 has significant synergistic effects compared to the isolated pollutants, such as increased lipid peroxidation and protein nitration. These findings suggest that highly reactive nitrate radicals (NO3•) could be formed in situ:
NO2• + O3 → NO3• + O2
NO3• is a strongly oxidising radical, which reacts with organic molecules through electron transfer (ET), addition to π systems or by hydrogen atom transfer (HAT). Results from kinetic and product studies involving model systems of plant biomolecules will be presented.