| 1. |
- Beck, Lisa J., et al.
(författare)
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Differing Mechanisms of New Particle Formation at Two Arctic Sites
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 48:4
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the Arctic atmosphere is an important source of aerosol particles. Understanding the processes of Arctic secondary aerosol formation is crucial due to their significant impact on cloud properties and therefore Arctic amplification. We observed the molecular formation of new particles from low-volatility vapors at two Arctic sites with differing surroundings. In Svalbard, sulfuric acid (SA) and methane sulfonic acid (MSA) contribute to the formation of secondary aerosol and to some extent to cloud condensation nuclei (CCN). This occurs via ion-induced nucleation of SA and NH3 and subsequent growth by mainly SA and MSA condensation during springtime and highly oxygenated organic molecules during summertime. By contrast, in an ice-covered region around Villum, we observed new particle formation driven by iodic acid but its concentration was insufficient to grow nucleated particles to CCN sizes. Our results provide new insight about sources and precursors of Arctic secondary aerosol particles.
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| 2. |
- Bianchi, Federico, et al.
(författare)
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Highly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals : A Key Contributor to Atmospheric Aerosol
- 2019
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Ingår i: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 119:6, s. 3472-3509
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Forskningsöversikt (refereegranskat)abstract
- Highly oxygenated organic molecules (HOM) are formed in the atmosphere via autoxidation involving peroxy radicals arising from volatile organic compounds (VOC). HOM condense on pre-existing particles and can be involved in new particle formation. HOM thus contribute to the formation of secondary organic aerosol (SOA), a significant and ubiquitous component of atmospheric aerosol known to affect the Earths radiation balance. HOM were discovered only very recently, but the interest in these compounds has grown rapidly. In this Review, we define HOM and describe the currently available techniques for their identification/quantification, followed by a summary of the current knowledge on their formation mechanisms and physicochemical properties. A main aim is to provide a common frame for the currently quite fragmented literature on HOM studies. Finally, we highlight the existing gaps in our understanding and suggest directions for future HOM research.
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| 3. |
- Graeffe, Frans, et al.
(författare)
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Detecting and Characterizing Particulate Organic Nitrates with an Aerodyne Long-ToF Aerosol Mass Spectrometer
- 2023
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Ingår i: ACS Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 7:1, s. 230-242
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Tidskriftsartikel (refereegranskat)abstract
- Particulate organic nitrate (pON) can be a major part of secondary organic aerosol (SOA) and is commonly quantified by indirect means from aerosol mass spectrometer (AMS) data. However, pON quantification remains challenging. Here, we set out to quantify and characterize pON in the boreal forest, through direct field observations at Station for Measuring Ecosystem Atmosphere Relationships (SMEAR) II in Hyytiälä, Finland, and targeted single-precursor laboratory studies. We utilized a long time-of-flight AMS (LToF-AMS) for aerosol chemical characterization, with a particular focus to identify CxHyOzN+ (“CHON+”) fragments. We estimate that during springtime at SMEAR II, pON (including both the organic and nitrate part) accounts for ∼10% of the particle mass concentration (calculated by the NO+/NO2+ method) and originates mainly from the NO3 radical oxidation of biogenic volatile organic compounds. The majority of the background nitrate aerosol measured is organic. The CHON+ fragment analysis was largely unsuccessful at SMEAR II, mainly due to low concentrations of the few detected fragments. However, our findings may be useful at other sites as we identified 80 unique CHON+ fragments from the laboratory measurements of SOA formed from NO3 radical oxidation of three pON precursors (β-pinene, limonene, and guaiacol). Finally, we noted a significant effect on ion identification during the LToF-AMS high-resolution data processing, resulting in too many ions being fit, depending on whether tungsten ions (W+) were used in the peak width determination. Although this phenomenon may be instrument-specific, we encourage all (LTOF-) AMS users to investigate this effect on their instrument to reduce the possibility of incorrect identifications.
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| 4. |
- Hao, Liqing, et al.
(författare)
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Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods
- 2018
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:23, s. 17705-17716
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Tidskriftsartikel (refereegranskat)abstract
- Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols - Effects on Clouds and Climate) campaign was conducted during the spring 2014 at the SMEAR II station (Station for Measuring Forest Ecosystem-Aerosol Relations) in Finland. The particles were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A PBL (planetary boundary layer) dilution model was developed to assist interpreting the measurement results. Right before nucleation events, the mass concentrations of organic and sulfate aerosol species were both decreased rapidly along with the growth of PBL heights. However, the mass fraction of sulfate aerosol of the total aerosol mass was increased, in contrast to a decrease for the organic mass fraction. Meanwhile, an increase in LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the total organic mass was observed, in distinct comparison to a reduction of SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at the beginning of nucleation events, the observed sulfate aerosol mass was mainly driven by vertical turbulent mixing of sulfate-rich aerosols between the residual layer and the newly formed boundary layer, while the condensation of sulfuric acid (SA) played a minor role in interpreting the measured sulfate mass concentration. For the measured organic aerosols, their temporal profiles were mainly driven by dilution from PBL development, organic aerosol mixing in different boundary layers and/or partitioning of organic vapors, but accurate measurements of organic vapor concentrations and characterization on the spatial aerosol chemical composition are required. In general, the observed aerosol particles by AMS are subjected to joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in different boundary layers. During aerosol growth periods in the nighttime, the mass concentrations of organic aerosols and organic nitrate aerosols were both increased. The increase in SVOOA mass correlated well with the calculated increase in condensed HOMs' (highly oxygenated organic molecules) mass. To our knowledge, our results are the first atmospheric observations showing a connection between increase in SVOOA and condensed HOMs during the nighttime.
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| 5. |
- Hong, Juan, et al.
(författare)
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Estimates of the organic aerosol volatility in a boreal forest using two independent methods
- 2017
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 17:6, s. 4387-4399
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Tidskriftsartikel (refereegranskat)abstract
- The volatility distribution of secondary organic aerosols that formed and had undergone aging - i. e., the particle mass fractions of semi-volatile, low-volatility and extremely low volatility organic compounds in the particle phase - was characterized in a boreal forest environment of Hyytiala, southern Finland. This was done by interpreting field measurements using a volatility tandem differential mobility analyzer (VTDMA) with a kinetic evaporation model. The field measurements were performed during April and May 2014. On average, 40% of the organics in particles were semi-volatile, 34% were low-volatility organics and 26% were extremely low volatility organics. The model was, however, very sensitive to the vaporization enthalpies assumed for the organics (Delta H-VAP). The best agreement between the observed and modeled temperature dependence of the evaporation was obtained when effective vaporization enthalpy values of 80 kJ mol(-1) were assumed. There are several potential reasons for the low effective enthalpy value, including molecular decomposition or dissociation that might occur in the particle phase upon heating, mixture effects and compound-dependent uncertainties in the mass accommodation coefficient. In addition to the VTDMA-based analysis, semi-volatile and low-volatility organic mass fractions were independently determined by applying positive matrix factorization (PMF) to high-resolution aerosol mass spectrometer (HR-AMS) data. The factor separation was based on the oxygenation levels of organics, specifically the relative abundance of mass ions at m/z 43 (f43) and m/z 44 (f44). The mass fractions of these two organic groups were compared against the VTDMA-based results. In general, the best agreement between the VTDMA results and the PMF-derived mass fractions of organics was obtained when Delta H-VAP D 80 kJ mol(-1) was set for all organic groups in the model, with a linear correlation coefficient of around 0.4. However, this still indicates that only about 16% (R-2)of the variation can be explained by the linear regression between the results from these two methods. The prospect of determining of extremely low volatility organic aerosols (ELVOAs) from AMS data using the PMF analysis should be assessed in future studies.
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| 6. |
- Hultin, Kim, 1976-, et al.
(författare)
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In situ laboratory sea spray production during the Marine Aerosol Production 2006 cruise on the northeastern Atlantic Ocean
- 2010
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996 .- 0148-0227 .- 2156-2202. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- Bubbles bursting from whitecaps are considered to be the most effective mechanism for particulate matter to be ejected into the atmosphere from the Earth's oceans. To realistically predict the climate effect of marine aerosols, global climate models require process-based understanding of particle formation from bubble bursting. During a cruise on the highly biologically active waters of the northeastern Atlantic Ocean in the summer of 2006, the submicrometer primary marine aerosol produced by a jet of seawater impinging on a seawater surface was investigated. The produced aerosol size spectra were centered on 200 nm in dry diameter and were conservative in shape throughout the cruise. The aerosol number production was negatively correlated with dissolved oxygen (DO) in the water (r < -0.6 for particles of dry diameter D-p > 200 nm). An increased surfactant concentration as a result of biological activity affecting the oxygen saturation is thought to diminish the particle production. The lack of influence of chlorophyll on aerosol production indicates that hydrocarbons produced directly by the photosynthesis are not essential for sea spray production. The upward mixing of deeper ocean water as a result of higher wind speed appears to affect the aerosol particle production, making wind speed influence aerosol production in more ways than by increasing the amount of whitecaps. The bubble spectra produced by the jet of seawater was representative of breaking waves at open sea, and the particle number production was positively correlated with increasing bubble number concentration with a peak production of 40-50 particles per bubble.
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| 7. |
- Junninen, Heikki, et al.
(författare)
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Terpene emissions from boreal wetlands can initiate stronger atmospheric new particle formation than boreal forests
- 2022
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Ingår i: Communications Earth and Environment. - : Springer Science and Business Media LLC. - 2662-4435. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Aerosols and their interaction with clouds constitute the largest uncertainty in estimating the radiative forcing affecting the climate system. Secondary aerosol formation is responsible for a large fraction of the cloud condensation nuclei in the global atmosphere. Wetlands are important to the budgets of methane and carbon dioxide, but the potential role of wetlands in aerosol formation has not been investigated. Here we use direct atmospheric sampling at the Siikaneva wetland in Finland to investigate the emission of methane and volatile organic compounds, and subsequently formed atmospheric clusters and aerosols. We find that terpenes initiate stronger atmospheric new particle formation than is typically observed over boreal forests and that, in addition to large emissions of methane which cause a warming effect, wetlands also have a cooling effect through emissions of these terpenes. We suggest that new wetlands produced by melting permafrost need to be taken into consideration as sources of secondary aerosol particles when estimating the role of increasing wetland extent in future climate change.
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| 8. |
- Kulmala, Markku, et al.
(författare)
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Direct Observations of Atmospheric Aerosol Nucleation
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6122, s. 943-946
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation-more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.
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| 9. |
- Kurtén, Theo, et al.
(författare)
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α-Pinene Autoxidation Products May Not Have Extremely Low Saturation Vapor Pressures Despite High O : C Ratios
- 2016
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1089-5639. ; 120:16, s. 2569-2582
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Tidskriftsartikel (refereegranskat)abstract
- COSMO-RS (conductor-like screening model for real solvents) and three different group-contribution methods were used to compute saturation (subcooled) liquid vapor pressures for 16 possible products of ozone-initiated α-pinene autoxidation, with elemental compositions C10H16O4-10 and C20H30O10-12. The saturation vapor pressures predicted by the different methods varied widely. COSMO-RS predicted relatively high saturation vapor pressures values in the range of 10-6 to 10-10 bar for the C10H16O4-10 "monomers", and 10-11 to 10-16 bar for the C20H30O10-12 "dimmers". The group-contribution methods predicted significantly (up to 8 order of magnitude) lower saturation vapor pressures for most of the more highly oxidized monomers. For the dimers, the COSMO-RS predictions were within the (wide) range spanned by the three group-contribution methods. The main reason for the discrepancies between the methods is likely that the group-contribution methods do not contain the necessary parameters to accurately treat autoxidation products containing multiple hydroperoxide, peroxy acid or peroxide functional groups, which form intramolecular hydrogen bonds with each other. While the COSMO-RS saturation vapor pressures for these systems may be overestimated, the results strongly indicate that despite their high O:C ratios, the volatilities of the autoxidation products of α-pinene (and possibly other atmospherically relevant alkenes) are not necessarily extremely low. In other words, while autoxidation products are able to adsorb onto aerosol particles, their evaporation back into the gas phase cannot be assumed to be negligible, especially from the smallest nanometer-scale particles. Their observed effective contribution to aerosol particle growth may therefore involve rapid heterogeneous reactions (reactive uptake) rather than effectively irreversible physical absorption.
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| 10. |
- Lampilahti, Janne, et al.
(författare)
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Zeppelin-led study on the onset of new particle formation in the planetary boundary layer
- 2021
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:16, s. 12649-12663
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Tidskriftsartikel (refereegranskat)abstract
- We compared observations of aerosol particle formation and growth in different parts of the planetary boundary layer at two different environments that have frequent new particle formation (NPF) events. In summer 2012 we had a campaign in Po Valley, Italy (urban background), and in spring 2013 a similar campaign took place in Hyytiälä, Finland (rural background). Our study consists of three case studies of airborne and ground-based measurements of ion and particle size distribution from ∼1 nm. The airborne measurements were performed using a Zeppelin inside the boundary layer up to 1000 m altitude. Our observations show the onset of regional NPF and the subsequent growth of the aerosol particles happening almost uniformly inside the mixed layer (ML) in both locations. However, in Hyytiälä we noticed local enhancement in the intensity of NPF caused by mesoscale boundary layer (BL) dynamics. Additionally, our observations indicate that in Hyytiälä NPF was probably also taking place above the ML. In Po Valley we observed NPF that was limited to a specific air mass.
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