New approach to real-time analysis of multi-site Volatile Organic Compound (VOC) observation data from an industrial zone in the South of France

Volatile Organic Compounds (VOCs), from anthropogenic or biogenic sources, participate in the formation of ozone and particulate matter (PM), impacting health, climate, and ecosystems. They can also be directly harmful, in particular anthropogenic VOCs such as vinyl chloride monomer (chloroethene), benzene or 1-3-butadiene, that are carcinogenic.¹ In the southern region of France, the French thresholds for ozone (240 µg m³ hourly) and for PM_2.5 (10 µg m³ annual) are regularly exceeded. A 2018-study showed an exceedance for O₃ on 144 days and for PM on 28 days during a 14 month period.² These exceedances contributed to over 1,800 hospitalizations in the region from 2010 to 2019.³

To better understand the drivers behind these exceedances and anticipate the population’s exposure, a detailed study in an impacted industrial area is conducted. The study area is located in the south of France, around a brackish lake called the Étang de Berre. This area includes three major industrial complexes (Berre l'Étang, Martigues Lavéra and Port-de-Bouc), where major metallurgical and petrochemical industries are located, known to be high emitters of VOCs. Notably, the region has a high industrial density, with 56 SEVESO high-threshold sites and the Fos/Berre zone presenting the second largest site concentration in France. Further, a petrochemical plant in Lavéra is particularly noteworthy, as it produces 25% of France's chlorine and 40% of its vinyl chloride monomer (VCM).⁴ The region's VOC dynamics are influenced by the orography and specific meteorological conditions, particularly a regime of land and sea breezes, that advects relatively clean marine air during the nighttime. In this complex region, three observation stations, run by the local air quality organization AtmoSud are monitoring continuously the concentrations of 68 VOCs since January 2022. The stations are installed in strategic locations close to the industrial complexes and in a residential area in proximity of school.

The observations reveal distinct behaviors for specific VOCs, that show a transient variability with very high intensity peaks. For example, at the Berre l’Etang station, cyclohexane exhibits baseline concentrations below 50 µg m^-³, punctuated by peaks reaching up to 218 µg m^-³. Similarly, VCM concentrations are typically below 20 µg m^-³, with occasional spikes up to 600 µg m^-³. For other VOCs, such as ethane and acetylene, more stable levels are observed following regional dynamics. We use a source-receptor approach to better characterize the sources of VOCs in this challenging area and developed an online uncertainty tool to ensure quality-controlled entry data for the Positive Matrix Factorization (PMF).  Preliminary results reveal notable chemical signatures, including a pronounced cyclohexane profile and an aromatic profile, we attributed to emissions from the industrial platform northeast of the monitoring station. Further source apportionment results, including seasonal trends, will be discussed.

References:

(1) Report: 1,3-Butadiene, Ethylene Oxide and Vinyl Halides, (IARC, Lyon, 2008).

(2) Chazeau, B. et al.. Atmospheric Chem. Phys. 21, 7293–7319 (2021).

(3) Khaniabadi, Y. O. & Sicard, P. A Chemosphere 278, 130502 (2021).

(4) KEM ONE - Site KEM ONE de Lavéra. https://www.kemone.com/A-propos/Implantations/Lavera.