| 1. |
- Kulmala, M., et al.
(författare)
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General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 13061-13143
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.
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| 2. |
- Boy, M., et al.
(författare)
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Interactions between the atmosphere, cryosphere, and ecosystems at northern high latitudes
- 2019
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:3, s. 2015-2061
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Tidskriftsartikel (refereegranskat)abstract
- The Nordic Centre of Excellence CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, is the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual centre with the objectives of identifying and quantifying the major processes controlling Arctic warming and related feedback mechanisms, outlining strategies to mitigate Arctic warming, and developing Nordic Earth system modelling with a focus on short-lived climate forcers (SLCFs), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special issue of the journal Atmospheric Chemistry and Physics. This paper presents an overview of the main scientific topics investigated in the centre and provides the reader with a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Faced with a vast amount of scientific discovery, we do not claim to completely summarize the results from CRAICC within this paper, but rather concentrate here on the main results which are related to feedback loops in climate change-cryosphere interactions that affect Arctic amplification.
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| 3. |
- Laj, P., et al.
(författare)
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Measuring Atmospheric Composition Change
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 43:33, s. 5351-5414
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Tidskriftsartikel (refereegranskat)abstract
- Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in-situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions.
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| 4. |
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| 5. |
- Bilde, M., et al.
(författare)
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Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures
- 2015
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Ingår i: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 115:10, s. 4115-4156
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Forskningsöversikt (refereegranskat)abstract
- There are a number of techniques that can be used that differ in terms of whether they fundamentally probe the equilibrium and the temperature range over which they can be applied. The series of homologous, straight-chain dicarboxylic acids have received much attention over the past decade given their atmospheric relevance, commercial availability, and low saturation vapor pressures, thus making them ideal test compounds. Uncertainties in the solid-state saturation vapor pressures obtained from individual methodologies are typically on the order of 50-100%, but the differences between saturation vapor pressures obtained with different methods are approximately 1-4 orders of magnitude, with the spread tending to increase as the saturation vapor pressure decreases. Some of the dicarboxylic acids can exist with multiple solid-state structures that have distinct saturation vapor pressures. Furthermore, the samples on which measurements are performed may actually exist as amorphous subcooled liquids rather than solid crystalline compounds, again with consequences for the measured saturation vapor pressures, since the subcooled liquid phase will have a higher saturation vapor pressure than the crystalline solid phase. Compounds with equilibrium vapor pressures in this range will exhibit the greatest sensitivities in terms of their gas to particle partitioning to uncertainties in their saturation vapor pressures, with consequent impacts on the ability of explicit and semiexplicit chemical models to simulate secondary organic aerosol formation.
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| 6. |
- Donahue, N. M., et al.
(författare)
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Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:34, s. 13503-13508
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Tidskriftsartikel (refereegranskat)abstract
- The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.
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| 7. |
- Hong, J., et al.
(författare)
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Hygroscopicity, CCN and volatility properties of submicron atmospheric aerosol in a boreal forest environment during the summer of 2010
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:9, s. 4733-4748
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Tidskriftsartikel (refereegranskat)abstract
- A Volatility-Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA) was applied to study the hygroscopicity and volatility properties of submicron atmospheric aerosol particles in a boreal forest environment in Hyytiala, Finland during the summer of 2010. Aitken and accumulation mode internally mixed particles (50 nm, 75 nm and 110 nm in diameter) were investigated. Hygroscopicity was found to increase with particle size. The relative mass fraction of organics and SO42- is probably the major contributor to the fluctuation of the hygroscopicity for all particle sizes. The Cloud Condensation Nuclei Counter (CCNC)-derived hygroscopicity parameter kappa was observed to be slightly higher than kappa calculated from VH-TDMA data under sub-saturated conditions, potential reasons for this behavior are discussed shortly. Also, the size-resolved volatility properties of particles were investigated. Upon heating, more small particles evaporated compared to large particles. There was a significant amount of aerosol volume (non-volatile material) left, even at heating temperatures of 280 degrees C. Using size resolved volatility-hygroscopicity analysis, we concluded that there was always hygroscopic material remaining in the particles at different heating temperatures, even at 280 degrees C. This indicates that the observed non-volatile aerosol material did not consist solely of black carbon.
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| 8. |
- Fors, Erik, et al.
(författare)
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Hygroscopic properties of Amazonian biomass burning and European background HULIS and investigation of their effects on surface tension with two models linking H-TDMA to CCNC data
- 2010
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 10:12, s. 5625-5639
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Tidskriftsartikel (refereegranskat)abstract
- HUmic-LIke Substances (HULIS) have been identified as major contributors to the organic carbon in atmospheric aerosol. The term "HULIS" is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rondonia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) at relative humidity (RH) < 100%, and a cloud condensation nucleus counter (CCNC) at RH > 100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m) and 31% (50.3 mN/m) for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m) and 13% (63.3 mN/m).
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| 9. |
- Snider, J. R., et al.
(författare)
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Intercomparison of cloud condensation nuclei and hygroscopic fraction measurements: Coated soot particles investigated during the LACIS Experiment in November (LExNo)
- 2010
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Ingår i: Journal of Geophysical Research. - 2156-2202. ; 115, s. 11205-11205
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Tidskriftsartikel (refereegranskat)abstract
- Four cloud condensation nuclei (CCN) instruments were used to sample size-selected particles prepared at the Leipzig Aerosol Cloud Interaction Simulator facility. Included were two Wyoming static diffusion CCN instruments, the continuous flow instrument built by Droplet Measurement Technologies, and the continuous flow Leipzig instrument. The aerosols were composed of ammonium sulfate, levoglucosan, levoglucosan and soot, and ammonium hydrogen sulfate and soot. Comparisons are made among critical supersaturation values from the CCN instruments and derived from measurements made with a humidified tandem differential mobility system. The comparison is quite encouraging: with few exceptions the reported critical supersaturations agree within known experimental uncertainty limits. Also reported are CCN- and hygroscopicity-based estimates of the soot particles' solute fraction. Relative differences between these are as large as 40%, but an error analysis demonstrates that agreement within experimental uncertainty is achieved. We also analyze data from the Droplet Measurement Technologies and the two Wyoming static diffusion instruments for evidence of size distribution broadening and investigate levoglucosan particle growth kinetics in the Wyoming CCN instrument.
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| 10. |
- Castarède, Dimitri, et al.
(författare)
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Development and characterization of the Portable Ice Nucleation Chamber 2 (PINCii)
- 2023
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Ingår i: Atmospheric Measurement Techniques. - 1867-1381. ; 16:16, s. 3881-3899
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Tidskriftsartikel (refereegranskat)abstract
- The Portable Ice Nucleation Chamber 2 (PINCii) is a newly developed continuous flow diffusion chamber (CFDC) for measuring ice nucleating particles (INPs). PINCii is a vertically oriented parallel-plate CFDC that has been engineered to improve upon the limitations of previous generations of CFDCs. This work presents a detailed description of the PINCii instrument and the upgrades that make it unique compared with other operational CFDCs. The PINCii design offers several possibilities for improved INP measurements. Notably, a specific icing procedure results in low background particle counts, which demonstrates the potential for PINCii to measure INPs at low concentrations ( < 10 L (-1)). High-spatial-resolution wall-temperature mapping enables the identification of temperature inhomogeneities on the chamber walls. This feature is used to introduce and discuss a new method for analyzing CFDC data based on the most extreme lamina conditions present within the chamber, which represent conditions most likely to trigger ice nucleation. A temperature gradient can be maintained throughout the evaporation section in addition to the main chamber, which enables PINCii to be used to study droplet activation processes or to extend ice crystal growth. A series of both liquid droplet activation and ice nucleation experiments were conducted at temperature and saturation conditions that span the spectrum of PINCii's operational conditions ( 50 <= temperature <= 15 degrees C and 100 <= relative humidity with respect to ice <= 160 %) to demonstrate the instrument's capabilities. In addition, typical sources of uncertainty in CFDCs, including particle background, particle loss, and variations in aerosol lamina temperature and relative humidity, are quantified and discussed for PINCii.
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| 11. |
- Frosch, Mia, et al.
(författare)
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CCN activity and volatility of beta-caryophyllene secondary organic aerosol
- 2013
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 13:4, s. 2283-2297
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Tidskriftsartikel (refereegranskat)abstract
- In a series of smog chamber experiments, the cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) generated from ozonolysis of beta-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, kappa(CCN), from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with kappa(CCN) in the range 0.001-0.16), and in dark experiments with no OH scavenger present, kappa(CCN) decreased when particles were sent through the thermodenuder (with a temperature up to 50 degrees C). SOA was generated under different experimental conditions: In some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived kappa(CCN) consistently increased with time after initial injection of beta-caryophyllene, showing that chemical ageing increases the CCN activity of beta-caryophyllene SOA. kappa(CCN) was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol for particles aged for several hours.
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| 12. |
- Kulmala, Markku, et al.
(författare)
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Overview of the biosphere-aerosol-cloud-climate interactions (BACCI) studies
- 2008
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 300-317
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Forskningsöversikt (refereegranskat)abstract
- Here we present research methods and results obtained by the Nordic Centre of Excellence Biosphere-Aerosol-Cloud-Climate Interactions (BACCI) between 1 January 2003 and 31 December 2007. The centre formed an integrated attempt to understand multiple, but interlinked, biosphere-atmosphere interactions applying inter and multidisciplinary approaches in a coherent manner. The main objective was to study the life cycle of aerosol particles and their importance on climate change. The foundation in BACCI was a thorough understanding of physical, meteorological, chemical and ecophysiological processes, providing a unique possibility to study biosphere-aerosol-cloud-climate interactions. Continuous measurements of atmospheric concentrations and fluxes of aerosol particles and precursors and, CO2/aerosol trace gas interactions in different field stations (e.g. SMEAR) were supported by models of particle thermodynamics, transport and dynamics, atmospheric chemistry, boundary layer meteorology and forest growth. The main progress was related to atmospheric new particle formation, existence of clusters, composition of nucleation mode aerosol particles, chemical precursors of fresh aerosol particles, the contribution of biogenic aerosol particles on the global aerosol load, transport, transformation and deposition of aerosol particles, thermodynamics related to aerosol particles and cloud droplets, and the microphysics and chemistry of cloud droplet formation.
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| 13. |
- Laursen, K. R., et al.
(författare)
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Airway and systemic biomarkers of health effects after short-term exposure to indoor ultrafine particles from cooking and candles - A randomized controlled double-blind crossover study among mild asthmatic subjects
- 2023
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Ingår i: Particle and Fibre Toxicology. - 1743-8977. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThere is insufficient knowledge about the systemic health effects of exposure to fine (PM2.5) and ultrafine particles emitted from typical indoor sources, including cooking and candlelight burning. We examined whether short-term exposure to emissions from cooking and burning candles cause inflammatory changes in young individuals with mild asthma. Thirty-six non-smoking asthmatics participated in a randomized controlled double-blind crossover study attending three exposure sessions (mean PM2.5 & mu;g/m(;)(3) polycyclic aromatic hydrocarbons ng/m(3)): (a) air mixed with emissions from cooking (96.1; 1.1), (b) air mixed with emissions from candles (89.8; 10), and (c) clean filtered air (5.8; 1.0). Emissions were generated in an adjacent chamber and let into a full-scale exposure chamber where participants were exposed for five hours. Several biomarkers were assessed in relation to airway and systemic inflammatory changes; the primary outcomes of interest were surfactant Protein-A (SP-A) and albumin in droplets in exhaled air - novel biomarkers for changes in the surfactant composition of small airways. Secondary outcomes included cytokines in nasal lavage, cytokines, C-reactive protein (CRP), epithelial progenitor cells (EPCs), genotoxicity, gene expression related to DNA-repair, oxidative stress, and inflammation, as well as metabolites in blood. Samples were collected before exposure start, right after exposure and the next morning.ResultsSP-A in droplets in exhaled air showed stable concentrations following candle exposure, while concentrations decreased following cooking and clean air exposure. Albumin in droplets in exhaled air increased following exposure to cooking and candles compared to clean air exposure, although not significant. Oxidatively damaged DNA and concentrations of some lipids and lipoproteins in the blood increased significantly following exposure to cooking. We found no or weak associations between cooking and candle exposure and systemic inflammation biomarkers including cytokines, CRP, and EPCs.ConclusionsCooking and candle emissions induced effects on some of the examined health-related biomarkers, while no effect was observed in others; Oxidatively damaged DNA and concentrations of lipids and lipoproteins were increased in blood after exposure to cooking, while both cooking and candle emissions slightly affected the small airways including the primary outcomes SP-A and albumin. We found only weak associations between the exposures and systemic inflammatory biomarkers. Together, the results show the existence of mild inflammation following cooking and candle exposure.
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| 14. |
- Laursen, K. R., et al.
(författare)
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An RCT of acute health effects in COPD-patients after passive vape exposure from e-cigarettes
- 2021
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Ingår i: European Clinical Respiratory Journal. - : Informa UK Limited. - 2001-8525. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: E-cigarette use has been shown to have short-term acute effects among active users but less is known of the acute passive effects, particularly among individuals with existing respiratory diseases. Objective: To investigate local and systemic effects of short-term passive vape exposure among patients with mild or moderate chronic obstructive pulmonary disease (COPD). Methods: In a double-blinded crossover study 16 non-smoking COPD-patients (mean age 68) were randomly exposed for 4 h to passive vape (median PM2.5: 18 mu g/m(3) (range: 8-333)) and clean air (PM2.5 < 6 mu g/m(3)) separated by 14 days. Particles were measured using an ultrafine particle counter (P-TRAK) and a scanning mobility particle sizer (SMPS). Health effects including Surfactant Protein-A (SP-A) and albumin in exhaled air, spirometry, FeNO, and plasma proteins were evaluated before, right after, and 24 hours after exposure. Participants reported symptoms throughout exposure sessions. Data were analyzed using mixed models. Results: SP-A in exhaled air was negatively affected by exposure to vape and several plasma proteins increased significantly. Throat irritation was more pronounced during passive vape exposure, while FVC and FEV1 decreased, however, not significantly. Conclusions: SP-A in exhaled air and some plasma proteins were affected by passive vape in patients with COPD indicating inflammation, showing that passive vape exposure is potentially harmful.
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| 15. |
- Svenningsson, Birgitta, et al.
(författare)
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Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance
- 2006
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7324. ; 6:7, s. 1937-1952
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Tidskriftsartikel (refereegranskat)abstract
- The organic fraction of atmospheric aerosols contains a multitude of compounds and usually only a small fraction can be identified and quantified. However, a limited number of representative organic compounds can be used to describe the water-soluble organic fraction. In this work, initiated within the EU 5FP project SMOCC, four mixtures containing various amounts of inorganic salts (ammonium sulfate, ammonium nitrate, and sodium chloride) and three model organic compounds (levoglucosan, succinic acid and fulvic acid) were studied. The interaction between water vapor and aerosol particles was studied at different relative humidities: at subsaturation using a hygroscopic tandem differential mobility analyzer (H-TDMA) and at supersaturation using a cloud condensation nuclei spectrometer (CCN spectrometer). Surface tensions as a function of carbon concentrations were measured using a bubble tensiometer. Parameterizations of water activity as a function of molality, based on hygroscopic growth, are given for the pure organic compounds and for the mixtures, indicating van't Hoff factors around 1 for the organics. The Zdanovskii-Stokes-Robinson (ZSR) mixing rule was tested on the hygroscopic growth of the mixtures and it was found to adequately explain the hygroscopic growth for 3 out of 4 mixtures, when the limited solubility of succinic acid is taken into account. One mixture containing sodium chloride was studied and showed a pronounced deviation from the ZSR mixing rule. Critical supersaturations calculated using the parameterizations of water activity and the measured surface tensions were compared with those determined experimentally.
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| 16. |
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| 17. |
- Christiansen, Sigurd, et al.
(författare)
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Influence of Arctic Microlayers and Algal Cultures on Sea Spray Hygroscopicity and the Possible Implications for Mixed-Phase Clouds
- 2020
-
Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-8996 .- 2169-897X. ; 125:19
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Tidskriftsartikel (refereegranskat)abstract
- As Arctic sea ice cover diminishes, sea spray aerosols (SSA) have a larger potential to be emitted into the Arctic atmosphere. Emitted SSA can contain organic material, but how it affects the ability of particles to act as cloud condensation nuclei (CCN) is still not well understood. Here we measure the CCN-derived hygroscopicity of three different types of aerosol particles: (1) Sea salt aerosols made from artificial seawater, (2) aerosol generated from artificial seawater spiked with diatom species cultured in the laboratory, and (3) aerosols made from samples of sea surface microlayer (SML) collected during field campaigns in the North Atlantic and Arctic Ocean. Samples are aerosolized using a sea spray simulation tank (plunging jet) or an atomizer. We show that SSA containing diatom and microlayer exhibit similar CCN activity to inorganic sea salt with a κ value of ∼1.0. Large-eddy simulation (LES) is then used to evaluate the general role of aerosol hygroscopicity in governing mixed-phase low-level cloud properties in the high Arctic. For accumulation mode aerosol, the simulated mixed-phase cloud properties do not depend strongly on κ, unless the values are lower than 0.4. For Aitken mode aerosol, the hygroscopicity is more important; the particles can sustain the cloud if the hygroscopicity is equal to or higher than 0.4, but not otherwise. The experimental and model results combined suggest that the internal mixing of biogenic organic components in SSA does not have a substantial impact on the cloud droplet activation process and the cloud lifetime in Arctic mixed-phase clouds.
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| 18. |
- Grinsted, Lena, et al.
(författare)
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Diverging cooperative prey capture strategies in convergently evolved social spiders
- 2022
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Ingår i: Journal of Arachnology. - 0161-8202. ; 50:2, s. 256-264
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Tidskriftsartikel (refereegranskat)abstract
- Sociality in spiders has evolved independently multiple times, resulting in convergently evolved cooperative breeding and prey capture. In all social spiders, prey is captured by only a subset of group members and then shared with other, non-attacking group members. However, spiders' propensity to attack prey may differ among species due to species-specific trade-offs between risks, costs and benefits of prey capture involvement. We explored whether engagement in prey attack differs among three social Stegodyphus species, using orthopteran prey, and found substantial differences. Stegodyphus mimosarum Pavesi, 1883 had a low prey acceptance rate, was slow to attack prey, and engaged very few spiders in prey attack. In S. sarasinorum Karsch, 1892, prey acceptance was high, independently of prey size, but more spiders attacked when prey was small. While medium-sized prey had higher acceptance rate in S. dumicola Pocock, 1898, indicating a preference, the number of attackers was not affected by prey size. Our results suggest that the three species may have different cooperative prey capture strategies. In S. mimosarum and S. dumicola, whose geographical ranges overlap, these strategies may represent niche specialization, depending on whether their respective cautious and choosy approaches extend to other prey types than orthopterans, while S. sarasinorum may have a more opportunistic approach. We discuss factors that can affect social spiders' foraging strategy, such as prey availability, predation pressure, and efficiency of the communal web to ensnare prey. Future studies are required to investigate to which extent species-specific cooperative foraging strategies are shaped by ontogeny, group size, and plastic responses to environmental factors.
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| 19. |
- Ickes, Luisa, 1986, et al.
(författare)
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The ice-nucleating activity of Arctic sea surface microlayer samples and marine algal cultures
- 2020
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:18, s. 11089-11117
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, sea spray as well as the biological material it contains has received increased attention as a source of ice-nucleating particles (INPs). Such INPs may play a role in remote marine regions, where other sources of INPs are scarce or absent. In the Arctic, these INPs can influence water-ice partitioning in low-level clouds and thereby the cloud lifetime, with consequences for the surface energy budget, sea ice formation and melt, and climate. Marine aerosol is of a diverse nature, so identifying sources of INPs is challenging. One fraction of marine bioaerosol (phytoplankton and their exudates) has been a particular focus of marine INP research. In our study we attempt to address three main questions. Firstly, we compare the ice-nucleating ability of two common phytoplankton species with Arctic seawater microlayer samples using the same instrumentation to see if these phytoplankton species produce ice-nucleating material with sufficient activity to account for the ice nucleation observed in Arctic microlayer samples. We present the first measurements of the ice-nucleating ability of two predominant phytoplankton species: Melosira arctica, a common Arctic diatom species, and Skeletonema marinoi, a ubiquitous diatom species across oceans worldwide. To determine the potential effect of nutrient conditions and characteristics of the algal culture, such as the amount of organic carbon associated with algal cells, on the ice nucleation activity, Skeletonema marinoi was grown under different nutrient regimes. From comparison of the ice nucleation data of the algal cultures to those obtained from a range of sea surface microlayer (SML) samples obtained during three different field expeditions to the Arctic (ACCACIA, NETCARE, and ASCOS), we found that they were not as ice active as the investigated microlayer samples, although these diatoms do produce ice-nucleating material. Secondly, to improve our understanding of local Arctic marine sources as atmospheric INPs we applied two aerosolization techniques to analyse the ice-nucleating ability of aerosolized microlayer and algal samples. The aerosols were generated either by direct nebulization of the undiluted bulk solutions or by the addition of the samples to a sea spray simulation chamber filled with artificial seawater. The latter method generates aerosol particles using a plunging jet to mimic the process of oceanic wave breaking. We observed that the aerosols produced using this approach can be ice active, indicating that the ice-nucleating material in seawater can indeed transfer to the aerosol phase. Thirdly, we attempted to measure ice nucleation activity across the entire temperature range relevant for mixed-phase clouds using a suite of ice nucleation measurement techniques - an expansion cloud chamber, a continuous-flow diffusion chamber, and a cold stage. In order to compare the measurements made using the different instruments, we have normalized the data in relation to the mass of salt present in the nascent sea spray aerosol. At temperatures above 248K some of the SML samples were very effective at nucleating ice, but there was substantial variability between the different samples. In contrast, there was much less variability between samples below 248 K. We discuss our results in the context of aerosol-cloud interactions in the Arctic with a focus on furthering our understanding of which INP types may be important in the Arctic atmosphere.
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| 20. |
- King, Stephanie M., et al.
(författare)
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Investigating Primary Marine Aerosol Properties : CCN Activity of Sea Salt and Mixed Inorganic-Organic Particles
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:19, s. 10405-10412
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Tidskriftsartikel (refereegranskat)abstract
- Sea spray particles ejected as a result of bubbles bursting from artificial seawater containing salt and organic matter in a stainless steel tank were sampled for size distribution, morphology, and cloud condensation nucleus (CCN) activity. Bubbles were generated either by aeration through a diffuser or by water jet impingement on the seawater surface. Three objectives were addressed in this study. First, CCN activities of NaCl and two types of artificial sea salt containing only inorganic components were measured to establish a baseline for further measurements of mixed organic inorganic particles. Second, the effect of varying bubble residence time in the bulk seawater solution on particle size and CCN activity was investigated and was found to be insignificant for the organic compounds studied. Finally, CCN activities of particles produced from jet impingement were compared with those produced from diffuser aeration. Analyses indicate a considerable amount of organic enrichment in the jet-produced particles relative to the bulk seawater composition when sodium laurate, an organic surfactant, is present in the seawater. In this case, the production of a thick foam layer during impingement may explain the difference in activation and supports hypotheses that particle production from the two methods of generating bubbles is not equal.
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| 21. |
- Krieger, Ulrich K., et al.
(författare)
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A reference data set for validating vapor pressure measurement techniques : homologous series of polyethylene glycols
- 2018
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 11:1, s. 49-63
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Tidskriftsartikel (refereegranskat)abstract
- To predict atmospheric partitioning of organic compounds between gas and aerosol particle phase based on explicit models for gas phase chemistry, saturation vapor pressures of the compounds need to be estimated. Estimation methods based on functional group contributions require training sets of compounds with well-established saturation vapor pressures. However, vapor pressures of semivolatile and low-volatility organic molecules at atmospheric temperatures reported in the literature often differ by several orders of magnitude between measurement techniques. These discrepancies exceed the stated uncertainty of each technique which is generally reported to be smaller than a factor of 2. At present, there is no general reference technique for measuring saturation vapor pressures of atmospherically relevant compounds with low vapor pressures at atmospheric temperatures. To address this problem, we measured vapor pressures with different techniques over a wide temperature range for intercomparison and to establish a reliable training set. We determined saturation vapor pressures for the homologous series of polyethylene glycols (H-(O-CH2-CH2)(n)-OH) for n = 3 to n = 8 ranging in vapor pressure at 298 K from 10(-7) to 5 x 10(-2) Pa and compare them with quantum chemistry calculations. Such a homologous series provides a reference set that covers several orders of magnitude in saturation vapor pressure, allowing a critical assessment of the lower limits of detection of vapor pressures for the different techniques as well as permitting the identification of potential sources of systematic error. Also, internal consistency within the series allows outlying data to be rejected more easily. Most of the measured vapor pressures agreed within the stated uncertainty range. Deviations mostly occurred for vapor pressure values approaching the lower detection limit of a technique. The good agreement between the measurement techniques (some of which are sensitive to the mass accommodation coefficient and some not) suggests that the mass accommodation coefficients of the studied compounds are close to unity. The quantum chemistry calculations were about 1 order of magnitude higher than the measurements. We find that extrapolation of vapor pressures from elevated to atmospheric temperatures is permissible over a range of about 100 K for these compounds, suggesting that measurements should be performed best at temperatures yielding the highest-accuracy data, allowing subsequent extrapolation to atmospheric temperatures.
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| 22. |
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| 23. |
- Salter, Matthew E., et al.
(författare)
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On the seawater temperature dependence of the sea spray aerosol generated by a continuous plunging jet
- 2014
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 119:14, s. 9052-9072
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Tidskriftsartikel (refereegranskat)abstract
- Breaking waves on the ocean surface produce bubbles which, upon bursting, deliver seawater constituents into the atmosphere as sea spray aerosol particles. One way of investigating this process in the laboratory is to generate a bubble plume by a continuous plunging jet. We performed a series of laboratory experiments to elucidate the role of seawater temperature on aerosol production from artificial seawater free from organic contamination using a plunging jet. The seawater temperature was varied from -1.3 degrees C to 30.1 degrees C, while the volume of air entrained by the jet, surface bubble size distributions, and size distribution of the aerosol particles produced was monitored. We observed that the volume of air entrained decreased as the seawater temperature was increased. The number of surface bubbles with film radius smaller than 2 mm decreased nonlinearly with seawater temperature. This decrease was coincident with a substantial reduction in particle production. The number concentrations of particles with dry diameter less than similar to 1 mu m decreased substantially as the seawater temperature was increased from -1.3 degrees C to similar to 9 degrees C. With further increase in seawater temperature (up to 30 degrees C), a small increase in the number concentration of larger particles (dry diameter >similar to 0.3 mu m) was observed. Based on these observations, we infer that as seawater temperature increases, the process of bubble fragmentation changes, resulting in decreased air entrainment by the plunging jet, as well as the number of bubbles with film radius smaller than 2 mm. This again results in decreased particle production with increasing seawater temperature.
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| 24. |
- Schneider, J. M., et al.
(författare)
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Benefits of cooperation with genetic kin in a subsocial spider
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:31, s. 10843-10846
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Tidskriftsartikel (refereegranskat)abstract
- Interaction within groups exploiting a common resource may be prone to cheating by selfish actions that result in disadvantages for all members of the group, including the selfish individuals. Kin selection is one mechanism by which such dilemmas can be resolved This is because selfish acts toward relatives include the cost of lowering indirect fitness benefits that could otherwise be achieved through the propagation of shared genes. Kin selection theory has been proved to be of general importance for the origin of cooperative behaviors, but other driving forces, such as direct fitness benefits, can also promote helping behavior in many cooperatively breeding taxa. Investigating transitional systems is therefore particularly suitable for understanding the influence of kin selection on the initial spread of cooperative behaviors. Here we investigated the role of kinship in cooperative feeding. We used a cross-fostering design to control for genetic relatedness and group membership. Our study animal was the periodic social spider Stegodyphus lineatus, a transitional species that belongs to a genus containing both permanent social and periodic social species. In S. lineatus, the young cooperate in prey capture and feed communally. We provide clear experimental evidence for net benefits of cooperating with kin. Genetic relatedness within groups and not association with familiar individuals directly improved feeding efficiency and growth rates, demonstrating a positive effect of kin cooperation. Hence, in communally feeding spiders, nepotism favors group retention and-reduces the conflict between selfish interests and the interests of the group.
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| 25. |
- Schwager, Evelyn E., et al.
(författare)
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The house spider genome reveals an ancient whole-genome duplication during arachnid evolution
- 2017
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Ingår i: BMC Biology. - : BIOMED CENTRAL LTD. - 1741-7007. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The duplication of genes can occur through various mechanisms and is thought to make a major contribution to the evolutionary diversification of organisms. There is increasing evidence for a large-scale duplication of genes in some chelicerate lineages including two rounds of whole genome duplication (WGD) in horseshoe crabs. To investigate this further, we sequenced and analyzed the genome of the common house spider Parasteatoda tepidariorum.Results: We found pervasive duplication of both coding and non-coding genes in this spider, including two clusters of Hox genes. Analysis of synteny conservation across the P. tepidariorum genome suggests that there has been an ancient WGD in spiders. Comparison with the genomes of other chelicerates, including that of the newly sequenced bark scorpion Centruroides sculpturatus, suggests that this event occurred in the common ancestor of spiders and scorpions, and is probably independent of the WGDs in horseshoe crabs. Furthermore, characterization of the sequence and expression of the Hox paralogs in P. tepidariorum suggests that many have been subject to neo-functionalization and/or sub-functionalization since their duplication.Conclusions: Our results reveal that spiders and scorpions are likely the descendants of a polyploid ancestor that lived more than 450 MYA. Given the extensive morphological diversity and ecological adaptations found among these animals, rivaling those of vertebrates, our study of the ancient WGD event in Arachnopulmonata provides a new comparative platform to explore common and divergent evolutionary outcomes of polyploidization events across eukaryotes.
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