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

Istocescu Mihaela; Viorel Roman; Aniela Pop

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

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

References

Atkinson, R. (2000). Atmospheric chemistry of VOCs and NOx. Atmospheric Environment, 34(12), 2063- 2101. doi:10.1016/S1352-2310(99)00460-4
Auditors, E. C. o. (2018). Air pollution Our health still insufficiently protected (23/2018). Air pollution, 23. https://op.europa.eu/webpub/eca/special-reports/air-quality-23-2018/en/
Barbara J. Finlayson-Pitts & James N. Pitts, J. (2000). Chemistry of the Upper and Lower Atmosphere Academic Press. doi:10.1016/B978-0-12-257060-5.X5000-X
Caviedes, Á., Bigazzi, A. Y., & Figliozzi, M. (2016). Modeled Effects of Traffic Fleet Composition on the Toxicity of Volatile Organic Compound Emissions. Transportation Research Record, 2570(1), 118-126. doi:10.3141/2570-13
Chen, N., Yang, Y., Wang, D., You, J., Gao, Y., Zhang, L., Zeng, Z., & Hu, B. (2024). Changing ozone sensitivity in Fujian Province, China, during 2012–2021: Importance of controlling VOC emissions. Environmental Pollution, 359, 124757. doi:10.1016/j.envpol.2024.124757
Commission, E. (2025). Energy, Climate change, Environment, Air. Retrieved April 27 from
Cui, L., Wu, D., Wang, S., Xu, Q., Hu, R., & Hao, J. (2022). Measurement report: Ambient volatile organic compound (VOC) pollution in urban Beijing: characteristics, sources, and implications for pollution control. Atmos. Chem. Phys., 22(18), 11931-11944. doi:10.5194/acp-22-11931-2022
Eurostat. (2024). Air pollutants by source sector aggregated for indicator sets. Uniunea Europeană. Retrieved April 21 from

Galvão, E. S., Santos, J. M., Goulart, E. V., Kumar, P., de Brito, J. F., & Junior, N. C. R. (2025). A novel approach to source apportionment of VOCs with high potential for ozone and SOA formation using highresolution data and intraday variability. Science of The Total Environment, 970, 179024. doi:10.1016/j.scitotenv.2025.179024
Gheorghe Frățilă, M. F., Sterian Samoilă. (2011). Automobile Construcţie, întreţinere şi reparare. Didactică și Pedagogică.
GmbH, A. I. (2020). Operating Manual Gas Chromatograph GC 4000 Series.
Gülüm, M. (2023). Prediction of Exhaust Gas Temperature of a Diesel Engine Running with Diesel Fuelbiodiesel-1-pentanol Ternary Blends. IOP Conference Series: Earth and Environmental Science, 1204(1), 012002. doi:10.1088/1755-1315/1204/1/012002
Han, S., Tan, Y., Gao, Y., Li, X., Ho, S. S. H., Wang, M., & Lee, S.-c. (2023). Volatile organic compounds at a roadside site in Hong Kong: Characteristics, chemical reactivity, and health risk assessment. Science of The Total Environment, 866, 161370. doi:10.1016/j.scitotenv.2022.161370
Hata, H., Okada, M., Funakubo, C., & Hoshi, J. (2019). Tailpipe VOC Emissions from Late Model Gasoline Passenger Vehicles in the Japanese Market. Atmosphere, 10(10). doi:10.3390/atmos10100621
H Hwang, K., An, J.G., Lee, S., Choi, W., & Yim, U. H. (2020). A Study on the Ozone Formation Potential of Volatile Organic Compounds in Busan using SIFT-MS. Journal of Korean Society for Atmospheric Environment, 41. doi:10.5572/KOSAE.2020.36.5.645
Khan, D., & Goga, G. (2023). A review on performance and emission characteristics of a diesel engine fueled with gaseous & liquid fuels. Materials Today: Proceedings, 80, A14-A22. doi:10.1016/j.matpr.2023.04.197
Laitinen, J., Liesivuori, J., Linnainmaa, M., & Kalliokoski, P. (1993). EVALUATION OF MONITORING METHODS FOR NITROGEN OXIDES. The Annals of Occupational Hygiene, 37(3), 307-314. doi:10.1093/annhyg/37.3.307
LAW 104 on ambient air quality, 76 (2011).
Methodology for developing air quality plans, short-term action plans, and air quality maintenance plans, 21 (2015).
Miao, C., Peng, Z.-R., Cui, A., He, X., Chen, F., Lu, K., Jia, G., Yu, S., & Chen, W. (2024). Quantifying and predicting air quality on different road types in urban environments using mobile monitoring and automated machine learning. Atmospheric Pollution Research, 15(3), 102015. doi:10.1016/j.apr.2023.102015
Order 1121 approving the lists of administrative-territorial units drawn up following the classification into management regimes of the areas in the zones and agglomerations provided for in Annex 2 to Law No. 104_2011, 2 (2024).
Saarikoski, S., Hellén, H., Praplan, A. P., Schallhart, S., Clusius, P., Niemi, J. V., Kousa, A., Tykkä, T., Kouznetsov, R., Aurela, M., Salo, L., Rönkkö, T., Barreira, L. M. F., Pirjola, L., & Timonen, H. (2023). Characterization of volatile organic compounds and submicron organic aerosol in a traffic environment. Atmos. Chem. Phys., 23(5), 2963-2982. doi:10.5194/acp-23-2963-2023
Sillman, S. (1999). The relation between ozone, NOx and hydrocarbons in urban and polluted rural environments. Atmospheric Environment, 33(12), 1821-1845. doi:10.1016/S1352-2310(98)00345-8
Sillman, S. (2002). Chapter 12 The relation between ozone, NOx and hydrocarbons in urban and polluted rural environments. In J. Austin, P. Brimblecombe, & W. Sturges (Eds.), Developments in Environmental Science (Vol. 1, pp. 339-385). Elsevier. doi:10.1016/S1474-8177(02)80015-8
Tan, Y., Han, S., Chen, Y., Zhang, Z., Li, H., Li, W., Yuan, Q., Li, X., Wang, T., & Lee, S.-c. (2021). Characteristics and source apportionment of volatile organic compounds (VOCs) at a coastal site in Hong Kong. Science of The Total Environment, 777, 146241. doi:10.1016/j.scitotenv.2021.146241
Tehnic, M. (2014). Chemiluminescence NH3 Analyzer. Thermo Fisher Scientific.
Won, S. R., Kim, Y. P., Sainjargal, M., Soyol-Erdene, T.-O., & Lee, J. Y. (2024). First measurement report for volatile organic compounds characteristics during winter in Ulaanbaatar, Mongolia. Heliyon, 10(22), e40085. doi:10.1016/j.heliyon.2024.e40085
Yang, W., Zhang, Q., Wang, J., Zhou, C., Zhang, Y., & Pan, Z. (2018). Emission characteristics and ozone formation potentials of VOCs from gasoline passenger cars at different driving modes. Atmospheric Pollution Research, 9(5), 804-813. doi:10.1016/j.apr.2018.01.002
Yue, T., Yue, X., Chai, F., Hu, J., Lai, Y., He, L., & Zhu, R. (2017). Characteristics of volatile organic compounds (VOCs) from the evaporative emissions of modern passenger cars. Atmospheric Environment, 151, 62-69. doi:10.1016/j.atmosenv.2016.12.008
Zhang, X., Ning, M., Chu, W., Dong, Y., Shi, X., Chen, T., Ma, Q., Wang, L., Wu, Y., Zheng, W., & Wu, Z. (2025). Increased VOC reactivity forcing ozone pollution in the Yangtze River Delta region, China: Evidence from an eight-year observation at an urban site and implications for future control strategies. Journal of Hazardous Materials, 492, 138127. doi:10.1016/j.jhazmat.2025.138127

Details

Primary Language

English

Subjects

Instrumental Methods, Physical Chemistry (Other)

Journal Section

Research Article

Authors

Istocescu Mihaela ^*
Romania

Viorel Roman
Romania

Aniela Pop This is me
Romania

Publication Date

December 20, 2025

Submission Date

June 26, 2025

Acceptance Date

July 15, 2025

Published in Issue

Year 2025 Volume: 1 Number: 2

IZ

https://izlik.org/JA35RX76AF

Cite

RIS / Bibtex

APA

Mihaela, I., Roman, V., & Pop, A. (2025). The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara. Smyrna Journal of Natural and Data Sciences, 1(2), 48-68. https://izlik.org/JA35RX76AF

AMA

1.Mihaela I, Roman V, Pop A. The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara. Smyrna Journal of Natural and Data Sciences. 2025;1(2):48-68. https://izlik.org/JA35RX76AF

Chicago

Mihaela, Istocescu, Viorel Roman, and Aniela Pop. 2025. “The Relation Between NOx, VOCs (BTEX) and Ozone in Urban Area of Timisoara”. Smyrna Journal of Natural and Data Sciences 1 (2): 48-68. https://izlik.org/JA35RX76AF.

EndNote

Mihaela I, Roman V, Pop A (December 1, 2025) The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara. Smyrna Journal of Natural and Data Sciences 1 2 48–68.

IEEE

[1]I. Mihaela, V. Roman, and A. Pop, “The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara”, Smyrna Journal of Natural and Data Sciences, vol. 1, no. 2, pp. 48–68, Dec. 2025, [Online]. Available: https://izlik.org/JA35RX76AF

ISNAD

Mihaela, Istocescu - Roman, Viorel - Pop, Aniela. “The Relation Between NOx, VOCs (BTEX) and Ozone in Urban Area of Timisoara”. Smyrna Journal of Natural and Data Sciences 1/2 (December 1, 2025): 48-68. https://izlik.org/JA35RX76AF.

JAMA

1.Mihaela I, Roman V, Pop A. The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara. Smyrna Journal of Natural and Data Sciences. 2025;1:48–68.

MLA

Mihaela, Istocescu, et al. “The Relation Between NOx, VOCs (BTEX) and Ozone in Urban Area of Timisoara”. Smyrna Journal of Natural and Data Sciences, vol. 1, no. 2, Dec. 2025, pp. 48-68, https://izlik.org/JA35RX76AF.

Vancouver

1.Istocescu Mihaela, Viorel Roman, Aniela Pop. The relation between NOx, VOCs (BTEX) and ozone in urban area of Timisoara. Smyrna Journal of Natural and Data Sciences [Internet]. 2025 Dec. 1;1(2):48-6. Available from: https://izlik.org/JA35RX76AF