African volcanic emissions influencing atmospheric aerosols over  the Amazon rain forest

Abstract. The long-range transport (LRT) of trace gases and aerosol particles plays an important role for the composition of the Amazonian rain forest atmosphere. Sulfate aerosols originate to a substantial extent from LRT sources and play an important role in the Amazonian atmosphere as strongly light-scattering particles and effective cloud condensation nuclei. The transatlantic transport of volcanic sulfur emissions from Africa has been considered as a source of particulate sulfate in the Amazon; however, direct observations have been lacking so far. This study provides observational evidence for the influence of emissions from the Nyamuragira–Nyiragongo volcanoes in Africa on Amazonian aerosol properties and atmospheric composition during September 2014. Comprehensive ground-based and airborne aerosol measurements together with satellite observations are used to investigate the volcanic event. Under the volcanic influence, hourly mean sulfate mass concentrations in the submicron size range reached up to 3.6 µg m−3 at the Amazon Tall Tower Observatory, the highest value ever reported in the Amazon region. The substantial sulfate injection increased the aerosol hygroscopicity with κ values up to 0.36, thus altering aerosol–cloud interactions over the rain forest. Airborne measurements and satellite data indicate that the transatlantic transport of volcanogenic aerosols occurred in two major volcanic plumes with a sulfate-enhanced layer between 4 and 5 km of altitude. This study demonstrates how African aerosol sources, such as volcanic sulfur emissions, can substantially affect the aerosol cycling and atmospheric processes in Amazonia.

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African volcanic emissions influencing atmospheric aerosol particles over the Amazon rain forest

10.5194/acp-2017-1152 ◽

2017 ◽

Cited By ~ 3

Author(s):

Jorge Saturno ◽

Florian Ditas ◽

Marloes Penning de Vries ◽

Bruna A. Holanda ◽

Mira L. Pöhlker ◽

...

Keyword(s):

Rain Forest ◽

Amazon Basin ◽

Dimethyl Sulfide ◽

Aerosol Particles ◽

Amazon Region ◽

Volcanic Emissions ◽

Airborne Measurements ◽

Amazon Rain Forest ◽

Sulfur Emissions

Abstract. Long-range transport (LRT) plays an important role in the Amazon rain forest by bringing in different primary and secondary aerosol particles from distant sources. The atmospheric oxidation of dimethyl sulfide (DMS), emitted from marine plankton, is considered an important sulfate source over the Amazon rain forest, with a lesser contribution from terrestrial soil and vegetation sulfur emissions. Volcanic sulfur emissions from Africa could be a source of particulate sulfate to the Amazonian atmosphere upon transatlantic transport but no observations have been published. By using satellite observations, together with ground‑based and airborne aerosol particle observations, this paper provides evidence of the influence that volcanic emissions have on the aerosol properties that have been observed in central Amazonia. Under the volcanic influence, sulfate mass concentrations reached up to 3.6 µg m−3 (hourly mean) at ground level, the highest value ever reported in the Amazon region. The hygroscopicity parameter was higher than the characteristic dry-season average, reaching a maximum of 0.36 for accumulation mode aerosol particles. Airborne measurements and satellite data indicated the transport of two different volcanic plumes reaching the Amazon Basin in September 2014 with a sulfate-enhanced layer at an altitude between 4 and 5 km. These observations show that remote volcanic sources can episodically affect the aerosol cycling over the Amazon rain forest and perturb the background conditions. Further studies should address the long-term effect of volcanogenic aerosol particles over the Amazon Basin by running long-term and intensive field measurements in the Amazon region and by monitoring African emissions and their transatlantic transport.

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Machine learning uncovers aerosol size information from chemistry and meteorology to quantify potential cloud-forming particles

10.21203/rs.3.rs-244416/v1 ◽

2021 ◽

Author(s):

Arshad Nair ◽

Fangqun Yu ◽

Pedro Campuzano Jost ◽

Paul DeMott ◽

Ezra Levin ◽

...

Keyword(s):

Climate Change ◽

Machine Learning ◽

Radiative Forcing ◽

Climate Models ◽

Cloud Condensation Nuclei ◽

Global Climate Models ◽

Aerosol Composition ◽

Airborne Measurements ◽

Aerosol Cloud ◽

Aerosol Cloud Interactions

Abstract Cloud condensation nuclei (CCN) are mediators of aerosol–cloud interactions, which contribute to the largest uncertainty in climate change prediction. Here, we present a machine learning/artificial intelligence model that quantifies CCN from variables of aerosol composition, atmospheric trace gases, and meteorology. Comprehensive multi-campaign airborne measurements, covering varied physicochemical regimes in the troposphere, confirm the validity of and help probe the inner workings of this machine learning model: revealing for the first time that different ranges of atmospheric aerosol composition and mass correspond to distinct aerosol number size distributions. Machine learning extracts this information, important for accurate quantification of CCN, additionally from both chemistry and meteorology. This can provide a physicochemically explainable, computationally efficient, robust machine learning pathway in global climate models that only resolve aerosol composition; potentially mitigating the uncertainty of effective radiative forcing due to aerosol–cloud interactions (ERFaci) and improving confidence in assessment of anthropogenic contributions and climate change projections.

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Supplementary material to "African volcanic emissions influencing atmospheric aerosol particles over the Amazon rain forest"

10.5194/acp-2017-1152-supplement ◽

2017 ◽

Author(s):

Jorge Saturno ◽

Florian Ditas ◽

Marloes Penning de Vries ◽

Bruna A. Holanda ◽

Mira L. Pöhlker ◽

...

Keyword(s):

Atmospheric Aerosol ◽

Rain Forest ◽

Aerosol Particles ◽

Volcanic Emissions ◽

Atmospheric Aerosol Particles ◽

Amazon Rain Forest ◽

Supplementary Material

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UVB-irradiated Laboratory-generated Secondary Organic Aerosol Extracts Have Increased Cloud Condensation Nuclei Abilities: Comparison with Dissolved Organic Matter and Implications for the Photomineralization Mechanism

CHIMIA International Journal for Chemistry ◽

10.2533/chimia.2020.142 ◽

2020 ◽

Vol 74 (3) ◽

pp. 142-148

Author(s):

Nadine Borduas-Dedekind ◽

Sergey Nizkorodov ◽

Kristopher McNeill

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Atmospheric Aerosols ◽

Secondary Organic Aerosol ◽

Cloud Condensation Nuclei ◽

Organic Aerosol ◽

Anthropogenic Source ◽

Cloud Droplets ◽

Experimental Conditions ◽

Aerosol Cloud Interactions

During their atmospheric lifetime, organic compounds within aerosols are exposed to sunlight and undergo photochemical processing. This atmospheric aging process changes the ability of organic aerosols to form cloud droplets and consequently impacts aerosol–cloud interactions. We recently reported changes in the cloud forming properties of aerosolized dissolved organic matter (DOM) due to a photomineralization mechanism, transforming high-molecular weight compounds in DOM into organic acids, CO and CO2. To strengthen the implications of this mechanism to atmospheric aerosols, we now extend our previous dataset and report identical cloud activation experiments with laboratory-generated secondary organic aerosol (SOA) extracts. The SOA was produced from the oxidation of α-pinene and naphthalene, a representative biogenic and anthropogenic source of SOA, respectively. Exposure of aqueous solutions of SOA to UVB irradiation increased the dried organic material's hygroscopicity and thus its ability to form cloud droplets, consistent with our previous observations for DOM. We propose that a photomineralization mechanism is also at play in these SOA extracts. These results help to bridge the gap between DOM and SOA photochemistry by submitting two differently-sourced organic matter materials to identical experimental conditions for optimal comparison.

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Influence of aerosol chemical composition on N<sub>2</sub>O<sub>5</sub> uptake: airborne regional measurements in northwestern Europe

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-973-2015 ◽

2015 ◽

Vol 15 (2) ◽

pp. 973-990 ◽

Cited By ~ 39

Author(s):

W. T. Morgan ◽

B. Ouyang ◽

J. D. Allan ◽

E. Aruffo ◽

P. Di Carlo ◽

...

Keyword(s):

Chemical Composition ◽

Ammonium Nitrate ◽

Water Content ◽

Atmospheric Aerosols ◽

Atmospheric Chemistry ◽

Organic Aerosol ◽

Atmospheric Composition ◽

Airborne Measurements ◽

The Usa ◽

Aerosol Chemical Composition

Abstract. Aerosol chemical composition was found to influence nighttime atmospheric chemistry during a series of airborne measurements in northwestern Europe in summer conditions, which has implications for regional air quality and climate. The uptake of dinitrogen pentoxide, γ (N2O5), to particle surfaces was found to be modulated by the amount of water content and ammonium nitrate present in the aerosol. The conditions prevalent in this study suggest that the net uptake rate of N2O5 to atmospheric aerosols was relatively efficient compared to previous studies, with γ (N2O5) values in the range 0.01–0.03. This is likely a consequence of the elevated relative humidity in the region, which promotes greater aerosol water content. Increased nitrate concentrations relative to particulate water were found to suppress N2O5 uptake. The results presented here contrast with previous ambient studies of N2O5 uptake, which have generally taken place in low-nitrate environments in the USA. Comparison of the N2O5 uptake derived from the measurements with a parameterised scheme that is based on the ratio of particulate water to nitrate yielded reasonably good agreement in terms of the magnitude and variation in uptake, provided the effect of chloride was neglected. An additional suppression of the parameterised uptake is likely required to fully capture the variation in N2O5 uptake, which could be achieved via the known suppression by organic aerosol. However, existing parameterisations representing the suppression by organic aerosol were unable to fully represent the variation in N2O5 uptake. These results provide important ambient measurement constraint on our ability to predict N2O5 uptake in regional and global aerosol models. N2O5 uptake is a potentially important source of nitrate aerosol and a sink of the nitrate radical, which is the main nocturnal oxidant in the atmosphere. The results further highlight the importance of ammonium nitrate in northwestern Europe as a key component of atmospheric composition in the region.

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Oxidant and particle photochemical processes above a south-east Asian tropical rain forest (the OP3 project): introduction, rationale, location characteristics and tools

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-18899-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 18899-18963 ◽

Cited By ~ 9

Author(s):

C. N. Hewitt ◽

J. Lee ◽

M. P. Barkley ◽

N. Carslaw ◽

N. A. Chappell ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Rain Forest ◽

Tropical Rain Forest ◽

Forest Canopy ◽

East Asian ◽

Anthropogenic Pollution ◽

Atmospheric Composition ◽

Forest Site ◽

Airborne Measurements ◽

Photochemical Processes

Abstract. In April–July 2008, intensive measurements were made of atmospheric composition and chemistry in Sabah, Malaysia, as part of the "Oxidant and particle photochemical processes above a South-East Asian tropical rain forest" (OP3) project. Fluxes and concentrations of trace gases and particles were made from and above the rain forest canopy at the Bukit Atur Global Atmosphere Watch station and at the nearby Sabahmas oil palm plantation, using both ground-based and airborne measurements. Here, the measurement and modelling strategies used, the characteristics of the sites and an overview of data obtained are described. Composition measurements show that the rainforest site was not impacted by significant sources of anthropogenic pollution, and this is confirmed by satellite retrievals of NO2 and HCHO. The dominant modulators of atmospheric chemistry at the rain forest site were therefore emissions of BVOCs and soil emissions of reactive nitrogen oxides. At the observed BVOC:NOx volume mixing ratio (~104 pptv/pptv), current chemical models suggest that daytime maximum OH concentrations should be ca. 105 radicals cm−3, but observed OH concentrations were an order of magnitude greater than this. We confirm, therefore, previous measurements which suggest that an unexplained source of OH must exist above tropical forests and continue to interrogate the data to find explanations for this.

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