Vertical concentration gradient of ambient ozone &#8211; insight into seven-year continuous measurements at a rural Central European site tall tower
Authors: Hůnová Iva , Brabec Marek , Malý Marek 
Published: March 2024

The vertical representativeness of ambient air pollutant concentration measurements is addressed rarely though it is a very important aspect influencing the use and correct interpretation of measured values. Presently not much information on the vertical distribution of ambient ozone (O3) from sites representing relatively unpolluted rural areas is available. We explored the daily mean O3 concentrations measured at four heights above the ground (2, 8, 50 and 230 m) at the rural Central European site Ko&#353;etice in 2015&#8211;2021. We aimed to explore in detail the O3 behaviour above the measuring point in close vicinity of the ground. We used the semiparametric GAM (generalised additive model) approach (with complexity or roughness-penalised splines implementation) to analyse the data with sufficient flexibility. Our models for both O3 concentration and O3 gradients used (additive) decomposition into annual trend and seasonality. Our results indicated consistently increasing O3 with increasing height above the ground. The vertical O3 concentration gradient in 2&#8211;230 m is not uniform, however, but changes substantially with increasing height and shows by far the highest dynamics near the ground between 2 and 8 m, differing in both the seasonal and annual aspects for all the air columns inspected. Study of O3 concentrations at one site at several different heights above the ground brings useful results complementing ground-based ambient air quality monitoring, provides a deeper insight into the 3D structure of the atmosphere and the pollution, and provides valuable information for environmental studies exploring processes above the ground (H&#367;nov&#225; et al., 2023).&#160; Knowledge on vertical distribution of O3 concentrations near ground is for example an important input to ecological and environmental studies associating the air pollution with its impact on birds flying tens or hundred meters above the ground or impacts on tree canopies localised some tens of meters above the ground (Reif et al., 2023).References:H&#367;nov&#225; I., Brabec M., Mal&#253; M., 2023. Ambient ozone at a rural Central European site and its vertical concentration gradient close to the ground. Environmental Science and Pollution Research 30, 80014&#8211;80028. https://doi.org/10.1007/s11356-023-28016-8.Reif J., Gamero A., Flousek J., H&#367;nov&#225; I., 2023. Ambient ozone &#8211; new threat to birds in mountain ecosystems? Science of the Total Environment 876, 162711. doi: 10.1016/j.scitotenv.2023.162711.&#160;Acknowledgements:Ozone concentration measurements at the tall tower used for the analysis were financially supported by the project ACTRIS-CZ LM2018122 and ACTRIS-CZ RI (CZ.02.1.01/0.0/0.0/16_013/0001315). This study was partially supported from the long-term strategic development financing of the Institute of Computer Science (Czech Republic RVO 67985807) and by the Czech Hydrometeorological Institute research project &#701;Dlouhodob&#225; koncepce rozvoje v&#253;zkumn&#233; organizace (DKRVO) &#268;esk&#253; hydrometeorologick&#253; &#250;stav&#8217; financed by the Czech Ministry of the Environment.