Ozone Trends in the United Kingdom over the Last 30 Years

Previous work regarding the behaviour of ozone surface concentrations over many years in the United Kingdom had predicted that the frequency and severity of ozone episodes would become less marked in the future as a response to environmental regulations. The aim of this study is to extend these studies and compare the results with their predictions. The ozone data of 13 rural and six urban sites in the UK collected from the Department for Environment, Food and Rural Affairs over a period from 1992 to mid-2019 were used to investigate this behaviour. The yearly ozone exceedances (the number of hours that the ozone concentration exceeded the 50 ppbv limit) in the United Kingdom were found to have decreased over the last 30 years regardless of the type of site (rural or urban), showing that the adopted emission controls have so far been successful in the abatement of pollutant emissions. In the past three decades, the highest numbers of exceedances were reached in May regardless of the type of site. Furthermore, these episodes have become less frequent and less severe in recent years. In fact, the number of hours of exceedance is lower than that in previous decades, and it is almost constant throughout the week.