Evidence of New Particle Formation Within Etna and Stromboli Volcanic Plumes and Its Parameterization From Airborne In Situ Measurements

Abstract

Volcanic emissions can significantly affect the Earth's radiation budget by emitting aerosol particles and gas‐phase species that can result in the new particle formation (NPF). These particles can scatter solar radiation or modify cloud properties, with consequences on health, weather, and climate. To our knowledge, this is the first dedicated study detailing how gas‐phase precursors emitted from volcanic plumes can influence the NPF. A series of airborne measurements were performed around the Etna and Stromboli volcanoes within the framework of the CLerVolc and STRAP projects. The ATR‐42 aircraft was equipped with a range of instrumentation allowing the measurement of particle number concentration in diameter range above 2.5 nm and gaseous species to investigate the aerosol dynamics and the processes governing the NPF and their growth within the volcanic plumes. We demonstrate that NPF occurs within the volcanic plumes in the free troposphere (FT) and boundary layer (BL). Typically, the NPF events were more pronounced in the FT, where the condensational sink was up to two orders of magnitude smaller and the temperature was ~20 °C lower than in the BL. Within the passive volcanic plume, the concentration of sulfur dioxide, sulfuric acid, and N2.5 were as high as 92 ppbV, 5.65 × 108 and 2.4 × 105 cm−3, respectively. Using these measurements, we propose a new parameterization for NPF rate (J2.5) within the passive volcanic plume in the FT. These results can be incorporated into mesoscale models to better assess the impact of the particle formed by natural processes, that is, volcanic plumes, on climate.

Volcanic Plume Aging During Passive Degassing and Low Eruptive Events of Etna and Stromboli Volcanoes

“…Unlike ETNA15, the number of aerosols observed in STRO16 is mainly composed of aerosols with diameters greater than 10 nm, which is comparable with the number of simulated aerosols. This is explained by the higher condensation sink in the MABL than in the FT (supporting information Figure S1), which tends to inhibit nucleation and confirms through simulations the hypothesis proposed by Sahyoun et al (). The maximum aerosol concentration are localized close to the vent (Figure d), where SO 2 concentrations are highest (Figure b): Whether at 7 UTC or 8hr50 UTC, aerosol concentrations exceed 20,000 cm −3 .…”

“…For ETNA15 flight (Figure 4c), the observed number of aerosols is mainly composed of aerosols with diameters between 2.5 and 10 nm (in diameter), as described in Sahyoun et al (2019). The simulation does not represent this particle size because, as explained in the section 3, the simulated aerosol distribution is defined by only two modes: Aitken and accumulation, and the median diameter of these modes is too coarse to represent particle sizes with diameters lower than 20 nm.…”

“…In order to understand the processes involved in the atmospheric volcanic emission rates and in the composition of the gas and particles mixture erupted from the vent, two STRAP campaigns were conducted (the acronym STRAP means "Synergie Transdisciplinaire pour répondre aux Aléas liés aux Panaches volcaniques" in french and can be translated in english to "Transdisciplinary collaboration to investigate volcano plumes risks"). One of them was made around Piton de la Fournaise, in La Réunion (Tulet et al, 2017) and another around Etna and Stromboli volcanoes, in Italy (Sahyoun et al, 2019; this study). This study focuses on the latter campaign during which Etna volcano was in a phase of passive degassing and Stromboli volcano in a normal phase of strombolian activity, which are typical intereruptive conditions for both volcanoes.…”

“…Volcanic plumes are composed of several gaseous species (water vapor [H 2 O], sulfur dioxide [SO 2 ], carbon dioxide [CO 2 ], hydrogen sulfide [H 2 S], hydrogen chloride [HCl], … ) and aerosols (Allard et al, 2000). Since sulfur dioxide is one of the main precursor gases for new particle formation (Kerminen et al, 2018;Kulmala et al, 2000;Weber et al, 1995Weber et al, , 1999, volcanic plumes are also considered as an important source of nanometric-sized particles (Boulon et al, 2011;Sahyoun et al, 2019). They can additionally contain primary aerosols whose emission mechanism is not yet well understood (Mather et al, 2006;Roberts et al, 2018).…”

New particle formation in the volcanic eruption plume of the Piton de la Fournaise: specific features from a long-term dataset

“…Our incomplete knowledge of the pre-industrial conditions is responsible for a significant fraction of the uncertainty on the impact of aerosols on climate, since these conditions form the baseline to calculate the radiative forcing caused by anthropogenic emissions in climate model simulations (Carslaw et al, 2013;Gordon et al, 2016Gordon et al, , 2017. Specifically, substantial uncertainties in the pre-industrial baseline cloud radiative state related to the activity of continuously degassing volcanoes were reported by Schmidt et al (2012).…”