scholarly journals Concerted measurements of lipids in seawater and on submicron aerosol particles at the Cape Verde Islands: biogenic sources, selective transfer and high enrichments

2020 ◽  
Author(s):  
Nadja Triesch ◽  
Manuela van Pinxteren ◽  
Sanja Frka ◽  
Christian Stolle ◽  
Tobias Spranger ◽  
...  
Keyword(s):  
Enrichment Factor ◽  
Surface Activity ◽  
Aerosol Particles ◽  
High Surface ◽  
Cape Verde ◽  
Lipid Classes ◽  
Surface Microlayer ◽  
Atmospheric Concentration ◽  
Submicron Aerosol ◽  
Sea Surface Microlayer

Abstract. Measurements of lipids as representative species for different lipid classes in the marine environment have been performed to characterize their oceanic sources and their transfer from the ocean into the atmosphere to marine aerosol particles. To this end, a set of lipid classes (hydrocarbons (HC), fatty acid methyl esters (ME), free fatty acids (FFA), alcohols (ALC), 1,3-diacylglycerols (1,3 DG), 1,2-diacylglycerols (1,2 DG), monoacylglycerols (MG), wax esters (WE), triacylglycerols (TG), phospholipids (PP) including phosphatidylglycerols (PG), phosphatidylethanolamine (PE), phosphatidylcholines (PC), glycolipids (GL) including sulfoquinovosyldiacylglycerols (SQDG), monogalactosyl-diacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG) and sterols (ST)) is investigated in both the dissolved and particulate fraction in seawater, differentiated between underlying water (ULW) and the sea surface microlayer (SML), and in ambient submicron aerosol particle samples (PM1) at the Cape Verde Atmospheric Observatory (CVAO) applying concerted measurements. The different lipids are found in all marine compartments but in different compositions. At this point, a certain variability is observed for the concentration of dissolved (∑DLULW: 39.8–128.5 μg L−1, ∑DLSML: 55.7–121.5 μg L−1) and particulate (∑PLULW: 36.4–93.5 μg L−1, ∑PLSML: 61.0–118.1 μg L−1) lipids in seawater of the tropical North Atlantic Ocean along the campaign. Only slight SML enrichments are observed for the lipids with an enrichment factor EFSML of 1.1–1.4 (DL) and 1.0–1.7 (PL). On PM1 aerosol particles, a total lipid concentration between 75.2–219.5 ng m−3 (averaged: 119.9 ng m−3) is measured with high atmospheric concentration of TG (averaged: 21.9 ng m−3) as a potential indicator for freshly emitted sea spray. Besides phytoplankton sources, bacteria influence the lipid concentrations in seawater and on the aerosol particles, so that the phytoplankton tracer (chlorophyll-a) cannot sufficiently explain the lipid abundance. The concentration and enrichment of lipids in the SML is not related to physicochemical properties describing the surface activity. For aerosol, however, the high enrichment of lipids (as a sum) corresponds well with the consideration of their high surface activity, thus the EFaer (enrichment factor on submicron aerosol particles compared to SML) ranges between 9 × 104–7 × 105. Regarding the single lipid groups on the aerosol particles, a weak relation between EFaer and lipophilicity (expressed by the KOW value) was identified, which was absent for the SML. However, overall simple physico-chemical descriptors are not sufficient to fully explain the transfer of lipids. As our findings show that additional processes such as formation and degradation influence the ocean-atmosphere transfer of both OM in general and of lipids in particular, they have to be considered in OM transfer models. Moreover, our data suggest that the extend of enrichment of lipid classes constituents on the aerosol particles might be related to the distribution of the lipid within the bubble-air-water-interface. Lipids, which are preferably arranged within the bubble interface, namely TG and ALC, are transferred to the aerosol particles to the highest extend. Finally, the connection between ice nucleation particles (INP) in seawater, which are active already at higher temperatures (−10 °C to −15 °C), and the lipid classes PE and FFA suggests that lipids formed in the ocean have the potential to contribute to (biogenic) INP activity when transferred to the atmosphere.

scholarly journals Concerted measurements of lipids in seawater and on submicrometer aerosol particles at the Cabo Verde islands: biogenic sources, selective transfer and high enrichments

2021 ◽  
Vol 21 (6) ◽  
pp. 4267-4283
Author(s):  
Nadja Triesch ◽  
Manuela van Pinxteren ◽  
Sanja Frka ◽  
Christian Stolle ◽  
Tobias Spranger ◽  
...  
Keyword(s):  
Enrichment Factor ◽  
North Atlantic Ocean ◽  
Methyl Esters ◽  
Aerosol Particles ◽  
Lipid Classes ◽  
Surface Microlayer ◽  
Physicochemical Descriptors ◽  
Sea Surface Microlayer ◽  
The One ◽  
The Individual

Abstract. In the marine environment, measurements of lipids as representative species within different lipid classes have been performed to characterize their oceanic sources and their transfer from the ocean into the atmosphere to marine aerosol particles. The set of lipid classes includes hydrocarbons (HC); fatty acid methyl esters (ME); free fatty acids (FFA); alcohols (ALC); 1,3-diacylglycerols (1,3 DG); 1,2-diacylglycerols (1,2 DG); monoacylglycerols (MG); wax esters (WE); triacylglycerols (TG); and phospholipids (PP) including phosphatidylglycerols (PG), phosphatidylethanolamine (PE), phosphatidylcholines (PC), as well as glycolipids (GL) which cover sulfoquinovosyldiacylglycerols (SQDG), monogalactosyl-diacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG) and sterols (ST). These introduced lipid classes have been analyzed in the dissolved and particulate fraction of seawater, differentiating between underlying water (ULW) and the sea surface microlayer (SML) on the one hand. On the other hand, they have been examined on ambient submicrometer aerosol particle samples (PM1) which were collected at the Cape Verde Atmospheric Observatory (CVAO) by applying concerted measurements. These different lipids are found in all marine compartments but in different compositions. Along the campaign, certain variabilities are observed for the concentration of dissolved (∑DLULW: 39.8–128.5 µg L−1, ∑DLSML: 55.7–121.5 µg L−1) and particulate (∑PLULW: 36.4–93.5 µg L−1, ∑PLSML: 61.0–118.1 µg L−1) lipids in the seawater of the tropical North Atlantic Ocean. Only slight SML enrichments are observed for the lipids with an enrichment factor EFSML of 1.1–1.4 (DL) and 1.0–1.7 (PL). On PM1 aerosol particles, a total lipid concentration between 75.2–219.5 ng m−3 (averaged: 119.9 ng m−3) is measured. As also bacteria – besides phytoplankton sources – influence the lipid concentrations in seawater and on the aerosol particles, the lipid abundance cannot be exclusively explained by the phytoplankton tracer (chlorophyll a). The concentration and enrichment of lipids in the SML are not related to physicochemical properties which describe the surface activity. On the aerosol particles, an EFaer (the enrichment factor on the submicrometer aerosol particles compared to the SML) between 9×104–7×105 is observed. Regarding the individual lipid groups on the aerosol particles, a statistically significant correlation (R2=0.45, p=0.028) was found between EFaer and lipophilicity (expressed by the KOW value), which was not present for the SML. But simple physicochemical descriptors are overall not sufficient to fully explain the transfer of lipids. As our findings show that additional processes such as formation and degradation influence the ocean–atmosphere transfer of both OM in general and of lipids in particular, they have to be considered in OM transfer models. Moreover, our data suggest that the extent of the enrichment of the lipid class constituents on the aerosol particles might be related to the distribution of the lipid within the bubble–air–water interface. The lipids TG and ALC which are preferably arranged within the bubble interface are transferred to the aerosol particles to the highest extent. Finally, the connection between ice nucleation particles (INPs) in seawater, which are already active at higher temperatures (−10 to −15 ∘C), and the lipid classes PE and FFA suggests that lipids formed in the ocean have the potential to contribute to (biogenic) INP activity when transferred into the atmosphere.

scholarly journals Marine organic matter in the remote environment of the Cape Verde Islands – An introduction and overview to the MarParCloud campaign

2020 ◽  
Author(s):  
Manuela van Pinxteren ◽  
Khanneh Wadinga Fomba ◽  
Nadja Triesch ◽  
Heike Wex ◽  
Xianda Gong ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aerosol Particles ◽  
Cloud Water ◽  
Cape Verde ◽  
Back Trajectory ◽  
Surface Microlayer ◽  
Mercury Species ◽  
Biological Production ◽  
Cell Counts ◽  
Sea Surface Microlayer

<p>The project MarParCloud (marine biological production, organic aerosol particles and marine clouds: a process chain) aims at achieving a better understanding of the biological production of organic matter (OM)in the oceans, its export into marine aerosol particles and finally its ability to act as ice and cloud condensation nuclei (INP and CCN). The core of MarParCloud comprised a field campaign at the Cape Verde Atmosphere Observatory (CVAO) in autumn 2017, where a variety of chemical, physical, biological and meteorological approaches were applied. The investigations included concerted measurements of the bulk water, the Sea Surface Microlayer (SML), ambient aerosol particles on the ground (30 m a.s.l.) and in mountain heights (744 m) as well as cloud water. Important aspects of the ocean atmosphere Interactions focusing on marine OM have been addressed through detailed observation and modeling approaches.</p><p>Key variables comprised the chemical characterization of the atmospherically relevant OM components (e.g. lipids, proteins, sugars) in the ocean and the atmosphere as well as measurements of INP and CCN. Moreover, bacterial cell counts, mercury species and trace gases were analysed. To interpret the results, the measurements were accompanied by various auxiliary parameters such as air mass back trajectory analysis, vertical atmospheric profile analysis, cloud observations and pigment measurements in seawater. Additional modelling studies supported the experimental analysis.</p><p>Here we show the proof of concept of the connection between organic matter emission from the ocean to the atmosphere and up to the cloud level. A link between the ocean and the atmosphere was clearly observed as (i) the particles measured at the surface are well mixed within the marine boundary layer up to cloud level and (ii) ocean-derived compounds can be found in the aerosol particles at mountain height and in the cloud water. The organic measurements will be implemented in a new source function for the oceanic emission of OM. However, from a perspective of particle number concentrations, the marine contributions to both CCN and INP are rather limited.</p>

scholarly journals Glyoxal and methylglyoxal in Atlantic seawater and marine aerosol particles: method development and first application during the Polarstern cruise ANT XXVII/4

2013 ◽  
Vol 13 (23) ◽  
pp. 11791-11802 ◽  
Author(s):  
M. van Pinxteren ◽  
H. Herrmann
Keyword(s):  
Biological Activity ◽  
Method Development ◽  
Aerosol Particles ◽  
Global Radiation ◽  
Average Concentration ◽  
Surface Microlayer ◽  
Good Precision ◽  
Marine Aerosol ◽  
Sea Surface Microlayer ◽  
Significant Enrichment

Abstract. An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol particles is presented. The method is based on derivatization with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD < 10%), sensitivity (detection limits in the low ng L−1 range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the Polarstern cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulk water (BW) with average concentrations of 228 ng L−1 (GLY) and 196 ng L−1 (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng m−3) and MGLY (average concentration 0.15 ng m−3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosol particles could be a hint for interactions, in particular of GLY, between seawater and the atmosphere.

scholarly journals Characterization of aerosol particles at Cape Verde close to sea and cloud level heights – Part 2: ice nucleating particles in air, cloud and seawater

2019 ◽  
Author(s):  
Xianda Gong ◽  
Heike Wex ◽  
Manuela van Pinxteren ◽  
Nadja Triesch ◽  
Khanneh Wadinga Fomba ◽  
...  
Keyword(s):  
Cloud Water ◽  
Cape Verde ◽  
Surface Microlayer ◽  
Cloud Droplets ◽  
Clear Trend ◽  
Cold Temperatures ◽  
Biological Particles ◽  
Active Particles ◽  
Sea Surface Microlayer ◽  
Different Sources

Abstract. Ice nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (NINP) are not well characterized and although there is some understanding of their sources, it is still unclear to what extend different sources contribute, nor if all sources are known. In this work, we examined properties of INPs at Cape Verde from different sources, the oceanic sea surface microlayer (SML) and underlying water (ULW), the atmosphere close to both sea and cloud level as well as cloud water. Both enrichment and depletion of NINP in SML compared to ULW were observed. The enrichment factor (EF) varied from roughly 0.4 to 11, and there was no clear trend in EF with temperature. NINP in PM10 sampled at Cape Verde Atmospheric Observatory (CVAO) at any particular temperature spanned around 1 order of magnitude below −15 °C, and about 2 orders of magnitude at warmer temperatures (>−12 °C). NINP in PM1 were generally lower than those in PM10 at CVAO. About 83 ± 22 %, 67 ± 18 % and 77 ± 14 % (median ± standard deviation) of INPs had a diameter > 1 µm at ice activation temperatures of −12, −15, and −18 °C, respectively. Among the 17 PM10 samples at CVAO, three PM10 filters showed elevated NINP at warm temperatures, e.g., above 0.01 std L−1 at −10 °C. However, for NINP in PM1 at CVAO, this is not the case. At these higher temperatures, often biological particles have been found to be ice active. Consequently, the difference in NINP between PM1 and PM10 at CVAO, suggests that biological ice active particles were present in the super-micron size range. NINP in PM10 at CVAO was found to be similar to that on Monte Verde (MV, at 744 m a.s.l.) during non-cloud events. During cloud events, most INPs on MV were activated to cloud droplets. When highly ice active particles were present in PM10 filters at CVAO, they were not observed in PM10 filters on MV, but in cloud water samples, instead. This is direct evidence that these INPs which are likely biological are activated to cloud droplets during cloud events. In general, Cape Verde was often affected by dust from the Saharan desert during our measurement. For the observed air masses, atmospheric NINP in air fit well to the concentrations observed in cloud water. When comparing concentrations of both sea salt and INPs in both seawater and PM10 filters, it can be concluded that sea spray aerosol (SSA) only contributed a minor fraction to the atmospheric NINP. Therefore it can be said that, unless there would be a significant enrichment of NINP during the formation of SSA particles, NINP was mainly dominated by mineral dust at cold temperatures with few contributions from possible biological particles at warmer temperatures.

scholarly journals Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

2021 ◽  
Vol 21 (18) ◽  
pp. 13903-13930
Author(s):  
Robert Wagner ◽  
Luisa Ickes ◽  
Allan K. Bertram ◽  
Nora Els ◽  
Elena Gorokhova ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Ice Nucleation ◽  
Sea Surface ◽  
Ice Formation ◽  
Sea Spray ◽  
Surface Microlayer ◽  
Sea Surface Microlayer ◽  
Sea Spray Aerosol ◽  
Seawater Samples ◽  
Heterogeneous Ice Nucleation

Abstract. Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea spray aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 K are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (Skeletonema marinoi). The particles were suspended in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 K, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about 5×1010 m−2 at an ice saturation ratio of 1.3. Much smaller densities in the range of 108–109 m−2 were observed at temperatures between 220 and 235 K, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are 2 orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the number of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how instrumental parameters like the aerosolisation method and the ice nucleation measurement technique might affect the comparability of the results amongst different studies.

scholarly journals The influence of environmental drivers on the enrichment of organic carbon in the sea surface microlayer and in submicron aerosol particles – measurements from the Atlantic Ocean

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Manuela van Pinxteren ◽  
Stefan Barthel ◽  
Khanneh Wadinga Fomba ◽  
Konrad Müller ◽  
Wolf von Tümpling ◽  
...  
Keyword(s):  
Biological Activity ◽  
Organic Carbon ◽  
Chlorophyll A ◽  
Aerosol Particles ◽  
Enrichment Factors ◽  
Sea Surface ◽  
Environmental Drivers ◽  
Surface Microlayer ◽  
Marine Aerosol ◽  
Sea Surface Microlayer

The export of organic matter from ocean to atmosphere represents a substantial carbon flux in the Earth system, yet the impact of environmental drivers on this transfer is not fully understood. This work presents dissolved and particulate organic carbon (DOC, POC) concentrations, their enrichment factors in the sea surface microlayer (SML), and equivalent measurements in marine aerosol particles across the Atlantic Ocean. DOC concentrations averaged 161 ± 139 µmol L–1 (n = 78) in bulk seawater and 225 ± 175 µmol L–1 (n = 79) in the SML; POC concentrations averaged 13 ± 11 µmol L–1 (n = 80) and 17 ± 10 µmol L–1 (n = 80), respectively. High DOC and POC enrichment factors were observed when samples had low concentrations, and lower enrichments when concentrations were high. The impacts of wind speed and chlorophyll-a levels on concentrations and enrichment of DOC and POC in seawater were insignificant. In ambient submicron marine aerosol particles the concentration of water-soluble organic carbon was approximately 0.2 µg m–3. Water-insoluble organic carbon concentrations varied between 0.01 and 0.9 µg m–3, with highest concentrations observed when chlorophyll-a concentrations were high. Concerted measurements of bulk seawater, the SML and aerosol particles enabled calculation of enrichment factors of organic carbon in submicron marine ambient aerosols, which ranged from 103 to 104 during periods of low chlorophyll-a concentrations and up to 105 when chlorophyll-a levels were high. The results suggest that elevated local biological activity enhances the enrichment of marine-sourced organic carbon on aerosol particles. However, implementation of the results in source functions based on wind speed and chlorophyll-a concentrations underestimated the organic fraction at low biological activity by about 30%. There may be additional atmospheric and oceanic parameters to consider for accurately predicting organic fractions on aerosol particles.

scholarly journals Glyoxal and methylglyoxal in Atlantic seawater and marine aerosol particles: method development and first application during the Polarstern cruise ANT XXVII/4

2013 ◽  
Vol 13 (6) ◽  
pp. 15301-15331 ◽  
Author(s):  
M. van Pinxteren ◽  
H. Herrmann
Keyword(s):  
Biological Activity ◽  
Method Development ◽  
Aerosol Particles ◽  
Global Radiation ◽  
Average Concentration ◽  
Surface Microlayer ◽  
Good Precision ◽  
Marine Aerosol ◽  
Sea Surface Microlayer ◽  
Significant Enrichment

Abstract. An analytical method for the determination of the alpha dicarbonyls glyoxal (GLY) and methylglyoxal (MGLY) from seawater and marine aerosol samples is presented. The method is based on derivatisation with o-(2,3,4,5,6-Pentafluorobenzyl)-hydroxylamine (PFBHA) reagent, solvent extraction and GC-MS (SIM) analysis. The method showed good precision (RSD <10%), sensitivity (detection limits in the low ng L−1 range), and accuracy (good agreement between external calibration and standard addition). The method was applied to determine GLY and MGLY in oceanic water sampled during the POLARSTERN cruise ANT XXVII/4 from Capetown to Bremerhaven in spring 2011. GLY and MGLY were determined in the sea surface microlayer (SML) of the ocean and corresponding bulkwater (BW) with average concentrations of 228 ng L−1 (GLY) and 196 ng L−1 (MGLY). The results show a significant enrichment (factor of 4) of GLY and MGLY in the SML. Furthermore, marine aerosol particles (PM1) were sampled during the cruise and analyzed for GLY (average concentration 0.19 ng m−3) and MGLY (average concentration 0.15 ng m−3). On aerosol particles, both carbonyls show a very good correlation with oxalate, supporting the idea of a secondary formation of oxalic acid via GLY and MGLY. Concentrations of GLY and MGLY in seawater and on aerosol particles were correlated to environmental parameters such as global radiation, temperature, distance to the coastline and biological activity. There are slight hints for a photochemical production of GLY and MGLY in the SML (significant enrichment in the SML, higher enrichment at higher temperature). However, a clear connection of GLY and MGLY to global radiation as well as to biological activity cannot be concluded from the data. A slight correlation between GLY and MGLY in the SML and in aerosols could be a hint for interactions of especially GLY between seawater and the atmosphere.

scholarly journals Concerted measurements of free amino acids at the Cape Verde Islands: High enrichments in submicron sea spray aerosol particles and cloud droplets

2020 ◽  
Author(s):  
Nadja Triesch ◽  
Manuela van Pinxteren ◽  
Anja Engel ◽  
Hartmut Herrmann
Keyword(s):  
Amino Acids ◽  
Organic Carbon ◽  
Aspartic Acid ◽  
Water Samples ◽  
Free Amino Acids ◽  
Free Amino ◽  
Aerosol Particles ◽  
Cloud Water ◽  
Cape Verde ◽  
Atmospheric Concentration

Abstract. This study presents measurements of free amino acids (FAA) in the marine environment to elucidate their transfer from the ocean into the atmosphere to marine aerosol particles and to clouds. FAA were investigated in seawater (underline water (ULW), sea surface microlayer (SML)), in ambient marine size-segregated aerosol particle samples at two heights (ground based at the Cape Verde Atmospheric Observatory (CVAO) and at the Mt. Verde, 744 m height) and in cloud water using concerted measurements. The ∑FAA concentration in the SML varied between 0.13–3.64 µmol L−1, in the ULW between 0.01–1.10 µmol L−1 and a strong enrichment of ∑FAA in the SML (EFSML: 1.1–298.4, average of 57.2) was observed. In the submicron (0.05–1.2 µm) aerosol particles at the CVAO, the composition of FAA was more complex and higher atmospheric concentration of ∑FAA (up to 6.3 ng m−3) compared to the supermicron (1.2–10 µm) aerosol particles (maxima of 0.5 ng m−3) were observed. The total ∑FAA concentration (PM10) was between 1.8–6.8 ng m−3 and tended to increase during the campaign. Averaged ∑FAA concentrations on the aerosol particles at the Mt. Verde were lower (submicron: 1.5 ng m−3, supermicron: 1.2 ng m−3) compared to the CVAO. A similar percentage contribution of ∑FAA to dissolved organic carbon (DOC) in the seawater (up to 7.6&amp;tinsp;%) and to water-soluble organic carbon (WSOC) on the submicron aerosol particles (up to 5.3 %) indicated a related transfer process of FAA and DOC in the marine environment. The FAA were strongly enriched in the submicron aerosol particles (EFaer(∑FAA) 4∙102–3∙104, EFaer(WSOC) 2∙103–1∙104), possibly resulting from film droplet formation. The enrichment in supermicron aerosol particles was several orders of magnitude lower compared to supermicron size range with EFaer(∑FAA) 1∙101–2∙101, EFaer(WSOC) 3∙102–4∙102. A case study showed that several amino acids were transported from the ocean up to cloud level (e.g. aspartic acid, glutamic acid, proline) while other amino acids might not be transferred or quickly degraded (e.g. phenylalanine, tyrosine) or produced (e.g. GABA). The cloud water samples exhibited a similar composition of FAA compared to the SML but a strong variation of the atmospheric concentration of ∑FAA during the campaign (11.2–489.9 ng m−3). FAA in cloud water samples showed a strong enrichment by a factor of 4∙103 compared to the SML. The presence of high concentrations of FAA in general and of biologically produced FAA (aspartic acid) in particular together with the presence of inorganic marine tracers (sodium, methane sulfonic acid) demonstrates the influence of oceanic sources on marine clouds.

scholarly journals Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

2021 ◽  
Author(s):  
Robert Wagner ◽  
Luisa Ickes ◽  
Allan K. Bertram ◽  
Nora Els ◽  
Elena Gorokhova ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Ice Nucleation ◽  
Sea Surface ◽  
Ice Formation ◽  
Sea Spray ◽  
Surface Microlayer ◽  
Sea Surface Microlayer ◽  
Sea Spray Aerosol ◽  
Seawater Samples ◽  
Heterogeneous Ice Nucleation

Abstract. Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea salt aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 K are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (Skeletonema marinoi). The particles were suspended in a large cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 K, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about 5·1010 m−2 at an ice saturation ratio of 1.3. Much smaller densities in the range of 108–109 m−2 were observed at temperatures between 220 and 235 K, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are two orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the amount of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how far instrumental parameters like the aerosolisation method and the ice-nucleation measurement technique might affect the comparability of the results amongst different studies.

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