Ozone (O3) observations in Saxony, Germany, for 1997-2020: trends, modelling and implications for O3 control

Abstract

Given its importance for human health, vegetation and climate, trends in ground-level ozone (O3) concentrations in eastern Germany were systematically analysed using the long-term O3 data from 16 measurement stations. The findings indicate that despite reductions in oxides of nitrogen (NOx = NO + NO2) concentrations across all sites, O3 pollution in Saxony has in fact worsened over the past decade, especially in densely populated urban areas. The strongest O3 trend is observed at a traffic-dominated station, with an annual ozone increase of 1.2 µg m−3 yr−1 (or 3.5 % yr−1), while urban and rural background stations show more moderate rises of, on average, 0.5 µg m−3 yr−1 (or 1.1 % yr−1) over the last decade. To diagnose O3 formation and the controlling effects of NOx and volatile organic compounds (VOCs) over the past decades in this region, for the first time, detailed photochemical box modelling was performed by means of the complex MCM (Master Chemical Mechanism). Analysis of isopleth diagrams for two seasons indicates that O3 formation was predominantly VOC-limited at traffic and urban sites from 2000 to 2019. The observed rise in O3 levels suggests that current efforts to reduce total non-methane volatile organic compound (TNMVOC, including NMVOCs and oxygenated VOCs) emissions and NOx from various sources unfortunately remain insufficient. Based on anthropogenic and biogenic emission data, we recommend that continued NOx abatement and further additional VOC controls, with a focus on solvent use, be implemented in densely populated areas to mitigate O3 pollution in the coming years.