Trends in tropospheric ozone concentrations and forest impact metrics in Europe over the time period 2000–2014

Abstract

In Europe, tropospheric ozone pollution appears as a major air quality issue, and ozone concentrations remain potentially harmful to vegetation. In this study we compared the trends of two ozone metrics widely used for forests protection in Europe, the AOT40 (Accumulated Ozone over Threshold of 40 ppb) which only depends on surface air ozone concentrations, and the Phytotoxic Ozone Dose which is the accumulated ozone uptake through stomata over the growing season, and above a threshold Y of uptake (PODY). By using a chemistry transport model, we found that European-averaged ground-level ozone concentrations (− 2%) and AOT40 metric (− 26.5%) significantly declined from 2000 to 2014, due to successful control strategies to reduce the emission of ozone precursors in Europe since the early 1990s. In contrast, the stomatal ozone uptake by forests increased from 17.5 to 26.6 mmol O3 m−2 despite the reduction in ozone concentrations, leading to an increase of potential ozone damage on plants in Europe. In a climate change context, a biologically-sound stomatal flux-based standard (PODY) as new European legislative standard is needed.

Climate Change in the Baltic Sea Region: A Summary

“…The exposure index AOT40 (sum of the hourly exceedances above 40 ppb, for daylight hours during the growing season) significantly declined in all European regions except for Northern Europe, for which a positive but not significant trend is seen. On the nation level among the six European countries showing a positive trend were Denmark, Germany, Sweden (Proietti et al, 2021). A clear difference in trends between rural sites and other station typologies is found for Europe for the period 2000 to 2017.…”

“…Ground-level ozone (O3) can damage crops, forests and other vegetation, impairing growth and reducing biodiversity. According to a recent study by Proietti et al (2021), assessed trends of the O3 mean concentration in Northern Europe were not statistically significant for the time period from 2000 to 2014. The annual mean ozone concentration is reported to be slightly below 35 ppb, as compared to 43 to 45 ppb in the Mediterranean Region, for which a significant decreasing trend is found.…”

Ethylenediurea (EDU) spray effects on willows (Salix sachalinensis F. Schmid) grown in ambient or ozone-enriched air: implications for renewable biomass production

“…Being also affected by transboundary long-range transport (Gao et al 2020;Erickson et al 2020), which downplays national efforts to decrease O 3 concentrations, O 3 levels may remain elevated for several decades to come (Sicard et al 2017). Such elevated O 3 levels can lead to inhibited photosynthesis and suppressed woody biomass production and yields (Paoletti 2006;Karnosky et al 2007a;Koike et al 2013;Jolivet et al 2016;Li et al 2017;Cotrozzi 2021), suggesting increased risks to tree productivity (Sicard et al 2017;Feng et al 2019a;Proietti et al 2021;Sacchelli et al 2021). Therefore, it is important to develop methodologies to protect plants against elevated O 3 -induced toxicity.…”

Temporal Changes in Ozone Concentrations and Their Impact on Vegetation

“…At 38 sites involved in the European Monitoring and Evaluation Programme (EMEP), there was a decrease of [O 3 ] reported in the 1990s, however later, around 2000, the [O 3 ] had increased; then, in the 2010s it decreased [33]. Interpretation of the trends and spatial patterns over several past decades has been challenging [34]; however in Europe, because of the successfully adopted measures to reduce O 3 precursors, O 3 surface concentration decreased by 2% from 2000 to 2014 [35].…”