Measurements of OH, HO₂ and RO₂ radicals and also OH reactivity were made at a UK coastal site and compared to calculations from a constrained box model utilising the Master Chemical Mechanism. The model agreement displayed a strong dependence on the NO concentration. An experimental budget analysis for OH, HO₂, RO₂ and total RO_x demonstrated significant imbalances between HO₂ and RO₂ production rates. Ozone production rates were calculated from measured radicals and compared to modelled values.

As ozone can be transported across countries, efficient air quality management and regulatory policies rely on the assessment of local ozone production vs. transport. In our study, we investigate the origin of surface ozone in the UK and the contribution of the different source regions to regulatory ozone metrics. It is shown that emission controls would be necessary over western Europe to improve health-related metrics and over larger areas to reduce impacts on ecosystems.

We measured radicals (OH, HO₂, RO₂) and OH reactivity at a UK coastal site and compared our observations to the predictions of an MCMv3.3.1 box model. We find variable agreement between measured and modelled radical concentrations and OH reactivity, where the levels of agreement for individual species display strong dependences on NO concentrations. The most substantial disagreement is found for RO₂ at high NO (> 1 ppbv), when RO₂ levels are underpredicted by a factor of ~10–30.