What Are the Principal Factors Affecting Ambient Ozone Concentrations in Czech Mountain Forests?

Iva Hůnová,Marek Brabec,Marek Malý

doi:10.3389/ffgc.2019.00031

Abstract

The aim of our study was to identify the factors substantially affecting day-to-day variability in O3 concentrations in Czech mountain forests. We examined the effects of meteorology and ambient NOx recorded in regular long-term continuous monitoring at five mountain forest sites representing different regions, covering both polluted and relatively unpolluted areas over the time period of 1992–2018. To investigate the association between ambient O3 concentrations on one hand, and precursor NOx concentrations and meteorology on the other hand, we used a generalized additive model, GAM, with semiparametric (penalized-spline-based) components to capture properly the possible departures from linearity. Our results revealed that the O3 concentrations showed significant associations with all selected explanatory variables, i.e. air temperature, global solar radiation (GLRD), relative humidity, and NOx. Apparently, both meteorology and air pollution are highly important for day-to-day O3 concentrations, and this finding is consistent for all five rural sites, representing middle-elevated forested mountain areas in Central Europe. In addition to individual variables, we were able to detect interactions between three pairs of explanatory variables, namely temperature*GLRD, temperature*relative humidity, and GLRD*relative humidity. Moreover, we confirmed non-linear O3 behavior towards individual explanatory variables.

Highlights

Ground-level ozone (O3), an important constituent of the atmosphere (Prinn, 2003; Singh and Fabian, 2003; Monks et al, 2015), belongs among the major factors exerting negative impacts on forests (Ferretti et al, 2015; EEA, 2016), and remains a challenging problem for current and future timber production and the conservation of natural plant communities, including species diversity (Krupa et al, 2001)
We have investigated the association between ambient O3 concentrations on one hand, and precursor nitrogen oxides (NOx) concentrations and meteorology on the other hand, using a generalized additive model, GAM (Wood, 2006)
The generalized additive model confirmed that selected explanatory variables, i.e., air temperature, global solar radiation (GLRD), relative humidity, and NOx, significantly affect daily O3 concentrations in Czech forests

Summary

Introduction

Ground-level ozone (O3), an important constituent of the atmosphere (Prinn, 2003; Singh and Fabian, 2003; Monks et al, 2015), belongs among the major factors exerting negative impacts on forests (Ferretti et al, 2015; EEA, 2016), and remains a challenging problem for current and future timber production and the conservation of natural plant communities, including species diversity (Krupa et al, 2001). The chemistry of O3 is very complex (Finlayson-Pitts and Pitts, 1997; Seinfeldt and Pandis, 1998). Many processes—physical, chemical, and biological—affect the formation, transportation, and destruction of O3 and the final O3 concentrations (Colbeck and Mackenzie, 1994; Seinfeldt and Pandis, 1998; Fowler et al, 2009).

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