The Stratospheric Ozone Layer

The stratospheric ozone layer results from the photolysis of molecular oxygen by ultraviolet (UV) solar radiation in the high atmosphere. This large atmospheric layer is stable and, therefore, affects the general atmospheric circulation by decreasing significantly the vertical motions of air parcels. In addition, ozone protects the Earth from harmful UV radiation. Therefore, its destruction by anthropogenic activities may lead to public health impacts. This chapter presents first some fundamentals of atmospheric chemical kinetics (i.e., the speed at which chemical reactions occur in the atmosphere), which are needed to understand the processes leading to the presence of the ozone layer. These notions are also needed to understand the formation of gaseous and particulate pollutants, which is presented in the following chapters. Next, the processes that govern the ozone layer are described in terms of its natural formation and its destruction by man-made substances. Finally, the public policies introduced to address the protection of the stratospheric ozone layer are summarized.