Biogenic volatile organic compounds (BVOCs) reactivity related to new particle formation (NPF) over the Landes forest

• Published in: Atmospheric research 2020-06, Vol.237, p.104869-11, Article 104869
• Main Authors: Kammer, J., Flaud, P.-M., Chazeaubeny, A., Ciuraru, R., Le Menach, K., Geneste, E., Budzinski, H., Bonnefond, J.M., Lamaud, E., Perraudin, E., Villenave, E.
• Format: Article
• Language: English
• Subjects: Biodiversity and Ecology; BVOCs; Environment and Society; Environmental Sciences; Global Changes; Landes forest; Monoterpenes; Nighttime NPF; Oxidation products
• ISSN: 0169-8095; 1873-2895
• DOI: 10.1016/j.atmosres.2020.104869

Atmospheric particles play a major role in both air quality and climate change. Formation of secondary particles in the atmosphere has been observed over many different environments and is believed to provide up to half of the atmospheric cloud condensation nuclei (CCN) at a global scale. However, high uncertainties are still remaining in the description of mechanisms involved in new particle formation (NPF). Especially, more evidences of the implication of biogenic volatile organic compounds (BVOCs) in NPF from field studies are still needed. To investigate this question, two field campaigns have been set up during July 2014 and July 2015, in the French Landes forest (south west of France). Summer 2015 was characterized by a strong hydric stress, whereas summer 2014 was rainy. In 2015, frequent nocturnal NPF was observed, reaching a frequency of occurrence of ~55% of the nights, while only one event was observed in 2014. In July 2015, monoterpene mixing ratios (dominated by α- and β-pinene) were higher, mostly due to high ambient temperatures and drought. A focus was made on the 2015 field campaign, where NPF was mostly observed. The mean diurnal variation of the ratio between α- and β-pinene mixing ratios highlighted in-canopy reactivity of monoterpenes with ozone in the early night. This hypothesis was reinforced by the increasing gas phase levels of pinonaldehyde and nopinone, the main first-generation products arising from α- and β-pinene ozonolysis, at night, before NPF started. It strongly suggests that monoterpene oxidation further generated very-low volatility gases involved in NPF. This finding is also supported by the high concentrations of the SOA traditional biogenic tracers, e.g. pinic and pinonic acids, quantified in the particulate phase. The role of BVOCs in NPF is thus highlighted, as well as the importance of nighttime NPF. •High monoterpene concentrations were related to high nighttime NPF frequency.•In canopy α- and β-pinene ozonolysis was highlighted in the evening.•Nopinone and pinonaldehyde levels increase before NPF started.•Biogenic tracer (pinic and pinonic acids) concentration levels were high in the particulate phase.•BVOC oxidation was strongly involved in nighttime NPF in the Landes forest.