Heterogeneous nucleation as a potential sulphate-coating mechanism of atmospheric mineral dust particles and implications of coated dust on new particle formation

This abstract is dedicated to dual-wavelength polarization lidars (2&#946;+2&#948;) and related particles backscattering &#197;ngstr&#246;m exponents BAEp, as nowadays remotely evaluated by atmospheric multi-wavelength lidar instruments (Veselovskii et al., ACP, 2016). We here present two new lidar remote sensing developments applicable to every multi-wavelengths polarization lidars, as published in Miffre et al. (Rem. Sens. 2019, Opt. Lett. 2020).As a first development, we investigate the size, shape and complex refractive index dependence of measured backscattering &#197;ngstr&#246;m exponents (Miffre et al., Opt. Lett., 2020). If BAEp is generally considered as a particles size indicator, it actually depends on the particles size, shape (Mehri et al., Atm. Res., 2018) and complex refractive index as &#946;p does. From a precise analysis of the polarization state of the backscattered radiation and of its wavelength dependence, in two components particle mixtures (p) = {s, ns} involving spherical (s) and nonspherical (ns)-particles, we could establish the relationship between BAEp, BAEs and BAEns. Then, by numerically simulating the two latter, we could discuss on the range of involved particle sizes and complex refractive indices.The second development is related to the remote sensing observation of a new particle formation event with a dual-wavelength polarization lidar (Miffre et al. Rem. Sens. 2019). Where previous thoughts were that it is not feasible due to the small size of involved particles, we identified the requirements ensuring a (UV, VIS) polarization lidar to be sensitive to the subsequent particles growth following nucleation events promoted by nonspherical mineral dust particles. The presentation will explicit these optical requirements in terms of polarization and spectroscopy, as recently published in (Miffre et al., Rem. Sens., 2019).The oral presentation will first present our dual-wavelength polarization lidar remote sensing instrument (2&#946;+2&#948;), based on an unique laboratory Pi-polarimeter (Miffre et al., JQSRT, 2016). Special focus will be made on the (UV, VIS) calibration of the polarization lidar, as a decisive point for precise observations and interpretations. As an application case study, the oral presentation will then consider the lidar remote sensing observation of a nucleation event promoted by mineral dust. There, the involved particles sizes of freshly nucleated sulfuric acid particles and mineral dust will be retrieved by considering the above backscattering &#197;ngstr&#246;m exponents analysis. As expected, the retrieved involved particles sizes reveal the underlying physical-chemistry of the nucleation process promoted by mineral dust (Dupart et al., PNAS, 2012). We believe this work may then interest a wide community of scientists.Veselovskii, I., P. Goloub, D. N. Whiteman, A. Diallo, T. Ndiaye, A. Kolgotin, and O. Dubovik, ACP, 16(11), (2016). Dupart, Y., A. Wiedensohler, H. Hermann, A. Miffre, P. Rairoux, B. D&#8217;Anna and C. George, PNAS, 109, 51, (2012). Miffre, A., T. Mehri, M. Francis and P.&#160;Rairoux, JQSRT, 169, 79-90, (2016). Mehri, T., P. Rairoux, T. Nousiainen, A. Miffre, Atm. Res. 203, 44-61 (2018). Miffre A, D Cholleton, T. Mehri and P Rairoux, Rem. Sens., 11(15), 1761, (2019). Miffre, A., D. Cholleton, P. Rairoux, Opt. Lett. 45, 5, 1084-1087, (2020).

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Remote Sensing Observation of New Particle Formation Events with a (UV, VIS) Polarization Lidar

Remote Sensing ◽

10.3390/rs11151761 ◽

2019 ◽

Vol 11 (15) ◽

pp. 1761 ◽

Cited By ~ 2

Author(s):

Alain Miffre ◽

Danaël Cholleton ◽

Tahar Mehri ◽

Patrick Rairoux

Keyword(s):

Mineral Dust ◽

Particle Formation ◽

Light Polarization ◽

Dust Particles ◽

Free Troposphere ◽

New Particle Formation ◽

Particles Size Distribution ◽

The Cost ◽

Particle Backscattering ◽

First Time

Observations of new particle formation events in free troposphere are rather seldom and limited in time and space, mainly due to the complexity and the cost of the required on-board instrumentation for airplane field campaigns. In this paper, a calibrated (UV, VIS) polarization elastic lidar (2β + 2δ) is used to remotely sense new particle formation events in the free troposphere in the presence of mineral dust particles. Using very efficient (UV, VIS) light polarization discriminators (1:107) and after robust calibration, the contribution of mineral dust particles to the co-polarized (UV, VIS) lidar channels could be removed, to reveal the backscattering coefficient of the newly nucleated particles after these numerous particles have grown to a size detectable with our lidar. Since our polarization and wavelength cross-talks are fully negligible, the observed variation in the (UV, VIS) particle backscattering time–altitude maps could be related to variations in the particle microphysics. Hence, day and nighttime differences, at low and high dust loadings, were observed in agreement with the observed nucleation process promoted by mineral dust. While light backscattering is more sensitive to small-sized particles at the UV lidar wavelength of 355 nm, such new particle formation events are here for the first time also remotely sensed at the VIS lidar wavelength of 532 nm at which most polarization lidars operate. Moreover, by addressing the (UV, VIS) backscattering Angstrom exponent, we could discuss the particles’ sizes addressed with our (UV, VIS) polarization lidar. As nucleation concerns the lowest modes of the particles’ size distribution, such a methodology may then be applied to reveal the lowest particle sizes that a (UV, VIS) polarization lidar can address, thus improving our understanding of the vertical and temporal extent of nucleation in free troposphere, where measurements are rather seldom.

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Climatology of new particle formation at Izaña mountain GAW observatory in the subtropical North Atlantic

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-3865-2014 ◽

2014 ◽

Vol 14 (8) ◽

pp. 3865-3881 ◽

Cited By ~ 21

Author(s):

M. I. García ◽

S. Rodríguez ◽

Y. González ◽

R. D. García

Keyword(s):

Sulfuric Acid ◽

North Atlantic ◽

Growth Rates ◽

Particle Growth ◽

Particle Formation ◽

Dust Particles ◽

New Particle Formation ◽

Data Set ◽

Mean Values ◽

Condensation Sink

Abstract. A climatology of new particle formation (NPF) events at high altitude in the subtropical North Atlantic is presented. A 4-year data set (June 2008–June 2012), which includes number size distributions (10–600 nm), reactive gases (SO2, NOx, and O3), several components of solar radiation and meteorological parameters, measured at Izaña Global Atmosphere Watch (GAW) observatory (2373 m above sea level; Tenerife, Canary Islands) was analysed. NPF is associated with the transport of gaseous precursors from the boundary layer by orographic buoyant upward flows that perturb the low free troposphere during daytime. On average, 30% of the days contained an NPF event. Mean values of the formation and growth rates during the study period were 0.46 cm−3 s−1 and 0.42 nm h−1, correspondingly. There is a clearly marked NPF season (May–August), when these events account for 50–60% of the days per month. Monthly mean values of the formation and growth rates exhibit higher values in this season, 0.49–0.92 cm−3 s−1 and 0.48–0.58 nm h−1, respectively. During NPF events, SO2, UV radiation and upslope winds showed higher values than during non-events. The overall data set indicates that SO2 plays a key role as precursor, although other species seem to contribute during some periods. Condensation of sulfuric acid vapour accounts for most of the measured particle growth during most of the year (~70%), except for some periods. In May, the highest mean growth rates (~0.6 nm h−1) and the lowest contribution of sulfuric acid (~13%) were measured, suggesting a significant involvement of other condensing vapours. The SO2 availability seems also to be the most influencing parameter in the year-to-year variability in the frequency of NPF events. The condensation sink showed similar features to other mountain sites, showing high values during NPF events. Summertime observations, when Izaña is within the Saharan Air Layer, suggest that dust particles may play a significant role acting as coagulation sink of freshly formed nucleation particles. The contribution of dust particles to the condensation sink of sulfuric acid vapours seems to be modest (~8% as average). Finally, we identified a set of NPF events in which two nucleation modes, which may evolve at different rates, occur simultaneously and for which further investigations are necessary.

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Growth of atmospheric nano-particles by heterogeneous nucleation of organic vapor

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-6523-2013 ◽

2013 ◽

Vol 13 (13) ◽

pp. 6523-6531 ◽

Cited By ~ 14

Author(s):

J. Wang ◽

R. L. McGraw ◽

C. Kuang

Keyword(s):

Atmospheric Aerosols ◽

Heterogeneous Nucleation ◽

Particle Formation ◽

Nano Particles ◽

High Rate ◽

Vapor Concentration ◽

Strong Increase ◽

Initial Growth ◽

New Particle Formation ◽

Cluster Number

Abstract. Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosols is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (~3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here, the contribution of organics to the initial cluster growth is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size leads to positive cluster number flux. This positive flux drives the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered the minimum particle size that can be grown through condensation. The conventional approach neglects the contribution from the cluster concentration gradient, and underestimates the cluster survival probabilities by a factor of up to 60 if early growth of clusters is due to both condensation of sulfuric acid and heterogeneous nucleation of organic vapors.

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Atmospheric nanoparticle observations in the low free troposphere during upward orographic flows at Izaña Mountain Observatory

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-6319-2009 ◽

2009 ◽

Vol 9 (17) ◽

pp. 6319-6335 ◽

Cited By ~ 47

Author(s):

S. Rodríguez ◽

Y. González ◽

E. Cuevas ◽

R. Ramos ◽

P. M. Romero ◽

...

Keyword(s):

Surface Area ◽

Particle Formation ◽

Saharan Dust ◽

Dust Particles ◽

Formation Mechanisms ◽

High Mountain ◽

Type I ◽

Free Troposphere ◽

New Particle Formation ◽

Data Set

Abstract. This study investigates the processes and conditions favouring the formation of nanoparticles (diameter<10 nm) which are frequently observed on high mountains reaching the low free troposphere. This was done through an analysis of a data set collected at Izaña Global Atmospheric Watch Observatory (Canary Islands; 2367 m above sea level). This high mountain supersite is located well above the stratocumulus layer characteristic of the subtropical oceanic tropospheres. At night, when the catabic flow regime is well established, free troposphere aerosols were measured. The development of orographic buoyant upward flows during daylight resulted in an increase of water vapour, SO2 and NOy concentrations. These ascending airflows perturbed the free troposphere and resulted in high concentrations of 3–10 nm particles (N3–10) due to new particle formation. An analysis of the 5-min average time series allowed the identification of two main types of N3–10 event. In Type I events a linear relationship between N3–10 and SO2 was observed (r2 coefficients 0.70–0.95 and a mean slope of 11 cm−3 ppt−1 for 5-min averaged data; SO2 concentrations from tens to hundreds of ppt). These particles seem to be formed during upward transport (probably within or after the outflows of clouds typically located below Izaña). During Type II events, no correlation between SO2 and N3–10 was observed and 3–10 nm particles were formed in-situ at noon and during the afternoon due to the condensation of vapours linked to photochemistry. New particle formation was observed almost every day owing to the favourable conditions associated with the entry of boundary layer air in the low free troposphere, even if SO2 concentrations are rather low at Izaña (tens to hundreds of ppt). The low surface area of pre-existing particles, low temperature and high radiation intensity clearly favoured the formation of nanoparticles. The low surface area of pre-existing particles in the upward flows is furthered by in-cloud particles scavenging in the stratocumulus layer typically located below Izaña. The higher temperature and the presence of coarse Saharan dust particles decrease the efficiency of the new particle formation mechanisms in summer. Thus, the "N3–10 versus SO2" slope (for r2>0.7 cases) was higher in autumn and winter (~15 cm−3 ppt−1 as average) than in summer (2–8 cm−3 ppt−1). These field observations suggest that elevated mounts that reaches the free troposphere may act as source regions for new particles.

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New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-14253-2020 ◽

2020 ◽

Vol 20 (22) ◽

pp. 14253-14271 ◽

Cited By ~ 1

Author(s):

Juan Andrés Casquero-Vera ◽

Hassan Lyamani ◽

Lubna Dada ◽

Simo Hakala ◽

Pauli Paasonen ◽

...

Keyword(s):

High Altitude ◽

Growth Rates ◽

Mineral Dust ◽

Particle Formation ◽

Aerosol Size Distribution ◽

Urban Site ◽

Climate Modelling ◽

Special Importance ◽

New Particle Formation ◽

Mass Load

Abstract. A substantial fraction of the atmospheric aerosols originates from secondary new particle formation (NPF), where atmospheric vapours are transformed into particles that subsequently grow to larger sizes, affecting human health and the climate. In this study, we investigate aerosol size distributions at two stations located close to each other (∼ 20 km) but at different altitudes: urban (UGR; 680 m a.s.l., metres above sea level) and high-altitude remote (SNS; 2500 m a.s.l.) sites, both in the area of Granada, Spain, and part of AGORA observatory (Andalusian Global ObseRvatory of the Atmosphere). The analysis shows a significant contribution of nucleation mode aerosol particles to the total aerosol number concentration at both sites, with a contribution of 47 % and 48 % at SNS and UGR, respectively. Due to the important contribution of NPF events to the total aerosol number concentrations and their high occurrence frequency (> 70 %) during the study period, a detailed analysis of NPF events is done in order to get insight into the possible mechanisms and processes involved in NPF events at these contrastive sites. At SNS, NPF is found to be associated with the transport of gaseous precursors from lower altitudes by orographic buoyant upward flows. NPF events at the SNS site are always observed from the smallest measured sizes of the aerosol size distribution (4 nm), implying that NPF takes place in or in the vicinity of the high-altitude SNS station rather than being transported from lower altitudes. Although NPF events at the mountain site seem to be connected with those occurring at the urban site, growth rates (GRs) at SNS are higher than those at the UGR site (GR7−25 of 6.9 and 4.5 nm h−1 and GR4−7 of 4.1 and 3.6 nm h−1 at SNS and UGR, respectively). This fact could have special importance for the production of cloud condensation nuclei (CCN) and therefore for cloud formations which may affect regional/global climate, since larger GRs at mountain sites could translate to a larger survival probability of NPF particles reaching CCN sizes, due to the shorter time period needed for the growth. The analysis of sulfuric acid (H2SO4) shows that the contribution of H2SO4 is able to explain a minimal fraction contribution to the observed GRs at both sites (< 1 % and < 10 % for the 7–25 and 4–7 nm size ranges, respectively), indicating that other condensing vapours are responsible for the majority of particle growth, as well as the differing growth rates between the two sites. Results also show that the condensation sink (CS) does not play a relevant role in NPF processes at both sites and points to the availability of volatile organic compounds (VOCs) as one of the main factors controlling the NPF events at both sites. Finally, a closer analysis of the NPF events that were observed at the SNS site during a Saharan dust episode that occurred during the field campaign was carried out, evidencing the role of TiO2 and F2O3 together with VOCs in promoting new particle formation during this dust intrusion event. Although further investigation is needed to improve our understanding in this topic, this result suggests that climate effects of mineral dust and NPF are not disconnected from each other as it was commonly thought. Therefore, since mineral dust contributes to a major fraction of the global aerosol mass load, dust–NPF interaction should be taken into account in global aerosol-climate modelling for better climate change prediction.

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Atmospheric nanoparticle observations in the low free troposphere during upward orographic flows at Izaña Mountain Observatory

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-10913-2009 ◽

2009 ◽

Vol 9 (3) ◽

pp. 10913-10956 ◽

Cited By ~ 1

Author(s):

S. Rodríguez ◽

Y. González ◽

E. Cuevas ◽

R. Ramos ◽

P. M. Romero ◽

...

Keyword(s):

Surface Area ◽

Particle Formation ◽

Saharan Dust ◽

Dust Particles ◽

Formation Mechanisms ◽

High Mountain ◽

Type I ◽

Free Troposphere ◽

New Particle Formation ◽

Data Set

Abstract. This study investigates the processes and conditions favouring the formation of nanoparticles (diameter <10 nm) which are frequently observed on high mountains reaching the low free troposphere. This was done through an analysis of a data set collected at Izaña Global Atmospheric Watch Observatory (Canary Islands; 2367 m a.s.l.). This high mountain supersite is located well above the stratocumulus layer characteristic of the subtropical oceanic tropospheres. At night, when the catabic flow regime is well established, free troposphere aerosols were measured. The development of orographic buoyant upward flows during daylight resulted in an increase of water vapour, SO2 and NOy concentrations. These ascending airflows perturbed the free troposphere and resulted in high concentrations of 3–10 nm particles (N3-10) due to new particle formation. An analysis of the 5-min average time series allowed the identification of two main types of N3-10 event. In Type I events a linear relationship between N3-10 and SO2 was observed (r2 coefficients 0.70–0.95 and a mean slope of 11 cm−3· ppt−1 for 5-min averaged data; SO2 concentrations from tens to hundreds of ppt). These particles seem to be formed during upward transport (probably within or after the outflows of clouds located below Izaña). During Type II events, no correlation between SO2 and N3-10 was observed and 3–10 nm particles were formed in-situ at noon and during the afternoon due to the condensation of vapours linked to photochemistry. New particle formation was observed almost every day owing to the favourable conditions associated with the entry of boundary layer air in the low free troposphere, even if SO2 concentrations are rather low at Izaña (tens to hundreds of ppt). The low surface area of pre-existing particles, low temperature and high radiation intensity clearly favoured the formation of nanoparticles. The low surface area of pre-existing particles in the upward flows is furthered by in-cloud particles scavenging in the stratocumulus layer typically located below Izaña. The higher temperature and the presence of coarse Saharan dust particles decrease the efficiency of the new particle formation mechanisms in summer. Thus, the "N3-10 versus SO2" slope (for r2>0.7 cases) was higher in autumn and winter (~15 cm−3· ppt−1 as average) than in summer (2–8 cm−3· ppt−1). These field observations suggest that elevated mounts that reaches the free troposphere may acts as source regions for new particles.

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