| Environmentally persistent free radicals (EPFRs) are paramagnetic species stabilized by interaction with particulate matter (PM), which allows them to persist in the environment for days-weeks. Such species are important because when inhaled they can catalytically generate reactive oxygen species (ROS) which cause oxidative stress and cell death. EPFRs are typically generated during combustion processes, but there is evidence in the literature that semiquinone EPFRs are formed when PM is aged in ambient air. It is known that polycyclic aromatic hydrocarbons (PAH), a common combustion PM (CPM) constituent, react heterogeneously with ozone, and quinone species are major products. In this thesis, using a single experimental method, we find for the first time that the reaction of ozone with PAH and with CPM produce several species of EPFRs. Their formation and behaviour is dependent upon a number of environmental factors including humidity, light, other gas phase radicals, and organic coating materials. |
