The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara

Year 2025, Volume: 1 Issue: 2, 48 - 68, 20.12.2025

Istocescu Mihaela , Viorel Roman , Aniela Pop

https://izlik.org/JA35RX76AF

Abstract

This this study, the volatile organic compounds (VOCs) and nitrogen oxides (NOx) were analyzed during two monitoring campaigns conducted in the spring season, using a mobile laboratory equipped with automatic pollutant measurement devices and sensors for meteorological parameters monitoring. The objective was to assess the characteristics of these pollutants and their potential to act as precursors to tropospheric ozone formation under the recorded weather conditions.
A comparison of the maximum VOC values recorded during the two monitoring campaigns shows low concentrations at night (between midnight and 6:00 a.m.) and relatively stable levels in the early morning. These patterns are attributed to reduced human activity and limited atmospheric dispersion, followed by noticeable differences in the hourly variation of VOC concentrations later in the day.
The daily maximum concentrations of VOCs may be attributed to both traffic in the area and potential industrial emissions originating from the southwest (SV) and northeast (NE) sectors of Timișoara, as indicated by the toluene/benzene (T/B) ratio. The recorded values reflect the activity within the monitored areas but show relatively low VOC emissions to the atmosphere, remaining well below the legislative limit for benzene. Despite these low levels, this information is crucial for assessing the role of VOCs in tropospheric ozone formation. NOx concentrations also stayed below the maximum limits set by current legislation, indicating low nitrogen oxide pollution during the monitoring period. Nonetheless, the VOCs/NOx ratio offered valuable insights into the potential for ozone formation, generally suggesting a VOC-sensitive chemical regime for ozone production.
This study offers improved insight into volatile organic compound (VOC) and nitrogen oxide (NOx) emissions in areas characterized by heavy traffic and industrial activity at the selected monitoring sites, as well as the conditions that contribute to tropospheric ozone formation in urban environments.

Keywords

Volatile organic compounds (VOCs) , ozone (O₃) , urban area of Timisoara , T/B ratio , VOCs/NOx ratio , air quality monitoring , mobile laboratory

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