Observed and simulated effects of certain pollutants on small air ion spectra: I. Positive ions

Parts, Tiia-Ene; Luts, Aare

doi:10.1016/j.atmosenv.2003.11.030

Cited by 37 publications

(24 citation statements)

References 18 publications

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“…The composition of cluster ions strongly depends on the age of ions and on the concentration of trace species in the air, as well as on the thermodynamical properties of the clusters and the environment (Bricard et al, 1972;Castleman et al, 1978;Eisele and Tanner, 1990;Nagato and Ogawa, 1998;Parts and Luts, 2004).…”

Section: Resultsmentioning

confidence: 99%

Initial steps of aerosol growth

et al. 2004

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Abstract. The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent -mainly condensational -growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm (diameter) in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhanced growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors.

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Section: Resultsmentioning

confidence: 99%

Initial steps of aerosol growth

et al. 2004

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“…Luts and Parts, 2002;Parts and Luts, 2004). The mean mobility or size of small ions has thus been reported in the literature (see Hirsikko et al, 2010 and references therein).…”

Section: Mean Diameter and Concentration Comparisonmentioning

confidence: 95%

Intercomparison of air ion spectrometers: an evaluation of results in varying conditions

et al. 2011

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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.

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“…The mobility spectrum of small ions is sensitive to the content of many trace species (gases or vapors at concentrations below 1 part per billion) in the air giving rise to certain specific ion families with characteristic mobilities (Nagato and Ogawa, 1998;Parts and Luts, 2004). The positive and negative small ions exhibit very different chemical composition (Eisele and Tanner, 1990;Beig and Brasseur, 2000;Luts and Parts, 2002).…”

Section: Introductionmentioning

confidence: 99%

Variation and balance of positive air ion concentrations in a boreal forest

et al. 2008

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Abstract. Air ions are characterized on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. The air ions were discriminated as small ions (charged molecular aggregates of the diameter of less than 2.5 nm), intermediate ions (charged aerosol particles of the diameter of 2.5-8 nm), and large ions (charged aerosol particles of the diameter of 8-20 nm). Statistical characteristics of the ion concentrations and the parameters of ion balance in the atmosphere are presented separately for the nucleation event days and non-event days. In the steady state, the ionization rate is balanced with the loss of small ions, which is expressed as the product of the small ion concentration and the ion sink rate. The widely known sinks of small ions are the recombination with small ions of opposite polarity and attachment to aerosol particles. The dependence of small ion concentration on the concentration of aerosol particles was investigated applying a model of the bipolar diffusion charging of particles by small ions. When the periods of relative humidity above 95% and wind speed less than 0.6 m s −1 were excluded, then the small ion concentration and the theoretically calculated small ion sink rate were closely negatively correlated (correlation coefficient −87%). However, an extra ion loss term of the same magnitude as the ion loss onto aerosol particles is needed for a quantitative explanation of the observations. This term is presumably due to the small ion deposition on coniferous forest. The hygroscopic growth correction of the measured aerosol particle size distributions was also found to be necessary for the proper estimation of the ion sink rate. In the case of nucleation burst events, the concentration of small positive ions followed the general balance equation, no extra ion loss in addition to the deposition on coniferous forCorrespondence to: U. Hõrrak (urmas.horrak@ut.ee) est was detected, and the hypothesis of the conversion of ions into particles in the process of ion-induced nucleation was not proved. The estimated average ionization rate of the air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 6 ion pairs cm −3 s −1 . The study of the charging state of nanometer aerosol particles (diameter 2.5-8 nm) in the atmosphere revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles neutralized in the aerosol spectrometer and naturally positively charged particles (air ions) during nucleation bursts. The charged fraction of particles varied from 3% to 6% in accordance with the hypothesis that the particles are quasi-steady state charged.

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Observed and simulated effects of certain pollutants on small air ion spectra: I. Positive ions

Cited by 37 publications

References 18 publications

Initial steps of aerosol growth

Initial steps of aerosol growth

Intercomparison of air ion spectrometers: an evaluation of results in varying conditions

Variation and balance of positive air ion concentrations in a boreal forest

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