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  • 1
    Online Resource
    Online Resource
    Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest
    Copernicus GmbH ; 2008
    In:  Atmospheric Chemistry and Physics Vol. 8, No. 1 ( 2008-01-14), p. 129-139
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 8, No. 1 ( 2008-01-14), p. 129-139
    Abstract: Abstract. Biogenic aerosol formation is likely to contribute significantly to the global aerosol load. In recent years, new-particle formation has been observed in various ecosystems around the world but hardly any measurements have taken place in the terrestrial Southern Hemisphere. Here, we report the first results of atmospheric ion and charged particle concentrations as well as of new-particle formation in a Eucalypt forest in Tumbarumba, South-East Australia, from July 2005 to October 2006. The measurements were carried out with an Air Ion Spectrometer (AIS) with a size range from 0.34 to 40 nm. The Eucalypt forest was a very strong source of new aerosol particles. Daytime aerosol formation took place on 52% of days with acceptable data, which is 2–3 times as often as in the Nordic boreal zone. Average growth rates for negative/positive 1.5–3 nm particles during these formation events were 2.89/2.68 nmh−1, respectively; for 3-7 nm particles 4.26/4.03, and for 7–20 nm particles 8.90/7.58 nmh−1, respectively. The growth rates for large ions were highest when the air was coming from the native forest which suggests that the Eucalypts were a strong source of condensable vapours. Average concentrations of cluster ions (0.34–1.8 nm) were 2400/1700 cm−3 for negative/positive ions, very high compared to most other measurements around the world. One reason behind these high concentrations could be the strong radon efflux from the soils around the Tumbarumba field site. Furthermore, comparison between night-time and daytime concentrations supported the view that cluster ions are produced close to the surface within the boundary layer also at night but that large ions are mostly produced in daytime. Finally, a previously unreported phenomenon, nocturnal aerosol formation, appeared in 32% of the analysed nights but was clustered almost entirely within six months from summer to autumn in 2006. From January to May, nocturnal formation was 2.5 times as frequent as daytime formation. Therefore, it appears that in summer and autumn, nocturnal production was the major mechanism for aerosol formation in Tumbarumba.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-8-129-2008
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2008
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  • 2
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    Online Resource
    EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events
    Copernicus GmbH ; 2010
    In:  Atmospheric Chemistry and Physics Vol. 10, No. 16 ( 2010-08-25), p. 7907-7927
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 10, No. 16 ( 2010-08-25), p. 7907-7927
    Abstract: Abstract. We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ~1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-10-7907-2010
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2010
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  • 3
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    Online Resource
    Intercomparison of air ion spectrometers: an evaluation of results in varying conditions
    Copernicus GmbH ; 2011
    In:  Atmospheric Measurement Techniques Vol. 4, No. 5 ( 2011-05-04), p. 805-822
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 4, No. 5 ( 2011-05-04), p. 805-822
    Abstract: Abstract. We evaluated 11 air ion spectrometers from Airel Ltd. after they had spent one year in field measurements as a part of the EUCAARI project: 5 Air Ion Spectrometers (AIS), 5 Neutral cluster and Air Ion Spectrometers (NAIS) and one Airborne NAIS (ANAIS). This is the first time that an ANAIS is evaluated and compared so extensively. The ion spectrometers' mobility and concentration accuracy was evaluated. Their measurements of ambient air were compared between themselves and to reference instruments: a Differential Mobility Particle Sizer (DMPS), a Balanced Scanning Mobility Analyzer (BSMA), and an Ion-DMPS. We report on the simultaneous measurement of a new particle formation (NPF) event by all 11 instruments and the 3 reference instruments. To our knowledge, it is the first time that the size distribution of ions and particles is measured by so many ion spectrometers during a NPF event. The new particle formation rates (~0.2 cm−3 s−1 for ions and ~2 cm−3 s−1 for particles) and growth rates (~25 nm h−1 in the 3–7 nm size range) were calculated for all the instruments. The NAISs and the ANAIS gave higher concentrations and formation rates than the AISs. For example, the AISs agreed with the BSMA within 11 % and 28 % for negative and positive ion concentration respectively, whereas the NAISs agreed within 23 % and 29 %. Finally, based on the results presented here, we give guidelines for data evaluation, when data from different individual ion spectrometers are compared.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-4-805-2011
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
    detail.hit.zdb_id: 2505596-3
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  • 4
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    Atmospheric ions and nucleation: a review of observations
    Copernicus GmbH ; 2011
    In:  Atmospheric Chemistry and Physics Vol. 11, No. 2 ( 2011-01-26), p. 767-798
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 11, No. 2 ( 2011-01-26), p. 767-798
    Abstract: Abstract. This review is based on ca. 260 publications, 93 of which included data on the temporal and spatial variation of the concentration of small ions (〈1.6 nm in diameter) especially in the lower troposphere, chemical composition, or formation and growth rates of sub-3 nm ions. This information was collected on tables and figures. The small ions exist all the time in the atmosphere, and the average concentrations of positive and negative small ions are typically 200–2500 cm−3. However, concentrations up to 5000 cm−3 have been observed. The results are in agreement with observations of ion production rates in the atmosphere. We also summarised observations on the conversion of small ions to intermediate ions, which can act as embryos for new atmospheric aerosol particles. Those observations include the formation rates (J2[ion]) of 2-nm intermediate ions, growth rates (GR[ion]) of sub-3 nm ions, and information on the chemical composition of the ions. Unfortunately, there were only a few studies which presented J2[ion] and GR[ion]. Based on the publications, the formation rates of 2-nm ions were 0–1.1 cm−3 s−1, while the total 2-nm particle formation rates varied between 0.001 and 60 cm−3 s−1. Due to small changes in J2[ion], the relative importance of ions in 2-nm particle formation was determined by the large changes in J2[tot], and, accordingly the contribution of ions increased with decreasing J2[tot]. Furthermore, small ions were observed to activate for growth earlier than neutral nanometer-sized particles and at lower saturation ratio of condensing vapours.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-11-767-2011
    DOI: 10.5194/acp-11-767-2011-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
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  • 5
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    Online Resource
    Results of the first air ion spectrometer calibration and intercomparison workshop
    Copernicus GmbH ; 2009
    In:  Atmospheric Chemistry and Physics Vol. 9, No. 1 ( 2009-01-09), p. 141-154
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 9, No. 1 ( 2009-01-09), p. 141-154
    Abstract: Abstract. The Air Ion Spectrometer (AIS) measures mobility and size distributions of atmospheric ions. The Neutral cluster and Air Ion Spectrometer (NAIS) can additionally measure neutral particles. The number of the (N)AIS instruments in the world is only 11. Nevertheless, they are already widely used in atmospheric ion studies, particularly related to the initial steps of new particle formation. There is no standard method applicable for calibrating the ion spectrometers in the sub-3 nm ion range. However, recent development of high resolution DMAs has enabled the size separation of small ions with good mobility resolution. For the first time, the ion spectrometers were intercompared and calibrated in a workshop, held in January–February 2008 in Helsinki, Finland. The overall goal was to experimentally determine the (N)AIS transfer functions. Monomobile mobility standards, 241-Am charger ions and silver particles were generated and used as calibration aerosols. High resolution DMAs were used to size-separate the smaller (1–10 nm) ions, while at bigger diameters (4–40 nm) the size was selected with a HAUKE-type DMA. Negative ion mobilities were detected by (N)AISs with slightly better accuracy than positive, nonetheless, both were somewhat overestimated. A linear fit of slope of one to the whole dataset of mobilities suggested that (N)AISs measured the negative mobilities 1.36±0.16 times larger compared with the reference instruments. Similarly, positive mobilities were measured 1.39±0.15 times larger compared with the reference instruments. The completely monomobile mobility standards were measured with the best accuracy. The (N)AIS concentrations were compared with an aerosol electrometer (AE) and a condensation particle counter (CPC). At sizes below 1.5 nm (positive) and 3 nm (negative) the ion spectrometers detected higher concentrations while at bigger sizes they showed similar concentrations as the reference instruments. The total particle concentrations measured by the NAISs were within ±50% of the reference CPC concentration at 4–40 nm sizes. The lowest cut-off size of the NAIS in neutral particle measurements was determined to be between 1.5 and 3 nm, depending on the measurement conditions and the polarity.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-9-141-2009
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2009
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  • 6
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    Characterisation of sub-micron particle number concentrations and formation events in the western Bushveld Igneous Complex, South Africa
    Copernicus GmbH ; 2012
    In:  Atmospheric Chemistry and Physics Vol. 12, No. 9 ( 2012-05-04), p. 3951-3967
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 12, No. 9 ( 2012-05-04), p. 3951-3967
    Abstract: Abstract. South Africa holds significant mineral resources, with a substantial fraction of these reserves occurring and being processed in a large geological structure termed the Bushveld Igneous Complex (BIC). The area is also highly populated by informal, semi-formal and formal residential developments. However, knowledge of air quality and research related to the atmosphere is still very limited in the area. In order to investigate the characteristics and processes affecting sub-micron particle number concentrations and formation events, air ion and aerosol particle size distributions and number concentrations, together with meteorological parameters, trace gases and particulate matter (PM) were measured for over two years at Marikana in the heart of the western BIC. The observations showed that trace gas (i.e. SO2, NOx, CO) and black carbon concentrations were relatively high, but in general within the limits of local air quality standards. The area was characterised by very high condensation sink due to background aerosol particles, PM10 and O3 concentration. The results indicated that high amounts of Aitken and accumulation mode particles originated from domestic burning for heating and cooking in the morning and evening, while during daytime SO2-based nucleation followed by the growth by condensation of vapours from industrial, residential and natural sources was the most probable source for large number concentrations of nucleation and Aitken mode particles. Nucleation event day frequency was extremely high, i.e. 86% of the analysed days, which to the knowledge of the authors is the highest frequency ever reported. The air mass back trajectory and wind direction analyses showed that the secondary particle formation was influenced both by local and regional pollution and vapour sources. Therefore, our observation of the annual cycle and magnitude of the particle formation and growth rates during nucleation events were similar to results previously published for a semi-clean savannah site in South Africa.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-12-3951-2012
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2012
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  • 7
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    Online Resource
    Atmospheric nucleation: highlights of the EUCAARI project and future directions
    Copernicus GmbH ; 2010
    In:  Atmospheric Chemistry and Physics Vol. 10, No. 22 ( 2010-11-18), p. 10829-10848
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 10, No. 22 ( 2010-11-18), p. 10829-10848
    Abstract: Abstract. Within the project EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions), atmospheric nucleation was studied by (i) developing and testing new air ion and cluster spectrometers, (ii) conducting homogeneous nucleation experiments for sulphate and organic systems in the laboratory, (iii) investigating atmospheric nucleation mechanism under field conditions, and (iv) applying new theoretical and modelling tools for data interpretation and development of parameterisations. The current paper provides a synthesis of the obtained results and identifies the remaining major knowledge gaps related to atmospheric nucleation. The most important technical achievement of the project was the development of new instruments for measuring sub-3 nm particle populations, along with the extensive application of these instruments in both the laboratory and the field. All the results obtained during EUCAARI indicate that sulphuric acid plays a central role in atmospheric nucleation. However, also vapours other than sulphuric acid are needed to explain the nucleation and the subsequent growth processes, at least in continental boundary layers. Candidate vapours in this respect are some organic compounds, ammonia, and especially amines. Both our field and laboratory data demonstrate that the nucleation rate scales to the first or second power of the nucleating vapour concentration(s). This agrees with the few earlier field observations, but is in stark contrast with classical thermodynamic nucleation theories. The average formation rates of 2-nm particles were found to vary by almost two orders of magnitude between the different EUCAARI sites, whereas the formation rates of charged 2-nm particles varied very little between the sites. Overall, our observations are indicative of frequent, yet moderate, ion-induced nucleation usually outweighed by much stronger neutral nucleation events in the continental lower troposphere. The most concrete outcome of the EUCAARI nucleation studies are the new semi-empirical nucleation rate parameterizations based on field observations, along with updated aerosol formation parameterizations.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-10-10829-2010
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2010
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  • 8
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    Online Resource
    Characterisation of corona-generated ions used in a Neutral cluster and Air Ion Spectrometer (NAIS)
    Copernicus GmbH ; 2011
    In:  Atmospheric Measurement Techniques Vol. 4, No. 12 ( 2011-12-16), p. 2767-2776
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 4, No. 12 ( 2011-12-16), p. 2767-2776
    Abstract: Abstract. We characterized size and chemical composition of ions generated by a corona-needle charger of a Neutral cluster and Air Ion Spectrometer (NAIS) by using a high resolution differential mobility analyzer and a time-of-flight mass spectrometer. Our study is crucial to verify the role of corona-generated ions in the particle size spectra measured with the NAIS, in which a corona charger is used to charge aerosol particles down to the size range overlapping with the size of generated ions. The size and concentration of ions produced by the corona discharging process depend both on corona voltage and on properties and composition of carrier gas. Negative ions were 〈1.6 nm (0.8 cm2 V−1 s−1 in mobility) in all tested gas mixtures (nitrogen, air with variable mixing ratios of water vapour), whereas positive ions were 〈1.7 nm (0.7 cm2 V−1 s−1). Electrical filtering of the corona generated ions and not removing all charged particles plays an important role in determining the lowest detection limit. Based on our experiments, the lowest detection limit for the NAIS in the particle mode is between 2 and 3 nm.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-4-2767-2011
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
    detail.hit.zdb_id: 2505596-3
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  • 9
    Online Resource
    Online Resource
    MODELLING OF ELECTRIC AND IONIC FIELD IN THE CHARGER OF THE ELECTRICAL AEROSOL SPECTROMETER
    Elsevier BV ; 2004
    In:  Journal of Aerosol Science Vol. 35 ( 2004-07), p. S949-S950
    Details
    In: Journal of Aerosol Science, Elsevier BV, Vol. 35 ( 2004-07), p. S949-S950
    Type of Medium: Online Resource
    ISSN: 0021-8502
    URL: Article
    DOI: 10.1016/S0021-8502(19)30212-5
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2004
    detail.hit.zdb_id: 242500-2
    SSG: 13
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  • 10
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    Atmospheric sub-3 nm particles at high altitudes
    Copernicus GmbH ; 2010
    In:  Atmospheric Chemistry and Physics Vol. 10, No. 2 ( 2010-01-19), p. 437-451
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 10, No. 2 ( 2010-01-19), p. 437-451
    Abstract: Abstract. Formation of new atmospheric aerosol particles is known to occur almost all over the world and the importance of these particles to climate and air quality has been recognized. Recently, it was found that atmospheric aerosol particle formation begins at the diameter of around 1.5–2.0 nm and a pool of sub-3 nm atmospheric particles – consisting of both charged and uncharged ones – was observed at the ground level. Here, we report on the first airborne observations of the pool of sub-3 nm neutral atmospheric particles. Between 2 and 3 nm, their concentration is roughly two orders of magnitude larger than that of the ion clusters, depending slightly on the altitude. Our findings indicate that new particle formation takes place throughout the tropospheric column up to the tropopause. Particles were found to be formed via neutral pathways in the boundary layer, and there was no sign of an increasing role by ion-induced nucleation toward the upper troposphere. Clouds, while acting as a source of sub-10 nm ions, did not perturb the overall budget of atmospheric clusters or particles.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-10-437-2010
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2010
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