The effect of local sources on aerosol particle number size distribution,
                        concentrations and fluxes in Helsinki, Finland

Ripamonti, Giovanna; Järvi, Leena; Mølgaard, Bjarke; Hussein, Tareq; Nordbo, Annika; Hämeri, Kaarle

doi:10.3402/tellusb.v65i0.19786

Cited by 47 publications

(48 citation statements)

References 65 publications

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“…While the Aitken mode dominated the number size distribution in HTF, the accumulation and Aitken modes were close to equal at the LTFs and BGs. Similar trends for the urban number distributions are shown also before (Hussein et al, 2005b;Ripamonti et al, 2013). Both Ripamonti et al (2013) and Hussein et al (2005b) show that the Aitken mode is related quite directly to traffic while the accumulation mode have also non-traffic related sources in the urban area.…”

Section: Spatial Characterization Of the Air Pollutionsupporting

confidence: 68%

“…Similar trends for the urban number distributions are shown also before (Hussein et al, 2005b;Ripamonti et al, 2013). Both Ripamonti et al (2013) and Hussein et al (2005b) show that the Aitken mode is related quite directly to traffic while the accumulation mode have also non-traffic related sources in the urban area. Further, the average distributions during three days does not show clear nucleation mode below 10 nm as shown in Fig 6(B).…”

Section: Spatial Characterization Of the Air Pollutionsupporting

confidence: 68%

See 1 more Smart Citation

Mobile Particle and NOx Emission Characterization at Helsinki Downtown: Comparison of Different Traffic Flow Areas

Lähde

Niemi

Kousa³

et al. 2014

Aerosol Air Qual. Res.

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A two weeks measurement campaign by a mobile laboratory van was performed at downtown Helsinki, Finland, in winter 2010. The characteristics of air pollutants such as fine particles in the size ranges of 7-40 nm (N p40 ) and 40-1000 nm (N p1000 ), black carbon (BC), fine particle mass (PM 2.5 ), as well as gaseous compounds NO, NO 2 , NO x , CO and CO 2 were studied. The statistical analysis showed that the air pollution conditions strongly depended on the traffic flow area; therefore, the street sections were classified as high traffic flow areas (HTF1-HTF4), low traffic flow areas (LTF1-LTF5), and urban background areas (BG1-BG3). Large variation of particle emissions was observed, and the momentary peak particle concentrations were 8 × 10 5 cm -3 . At the HTF areas exhaust emissions followed clearly daily average heavy duty vehicle counts rather than the average daily vehicle counts. Higher correlation coefficients were found between CO 2 and NO than between CO 2 and N tot . The dispersion studies indicated that the air pollution conditions strongly improved from high traffic flow areas to low traffic flow areas. Therefore, proper city planning and locating, for example, cycle tracks, schools and hospitals farther from busy city streets might significantly reduce exposure risk for humans.

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Section: Spatial Characterization Of the Air Pollutionsupporting

confidence: 68%

Section: Spatial Characterization Of the Air Pollutionsupporting

confidence: 68%

Mobile Particle and NOx Emission Characterization at Helsinki Downtown: Comparison of Different Traffic Flow Areas

Lähde

Niemi

Kousa³

et al. 2014

Aerosol Air Qual. Res.

View full text Add to dashboard Cite

show abstract

“…Helsinki, Finland, vehicles are a primary pollution source (Järvi et al, 2009). The temporal variation of the imaginary part of the ARISP is well correlated with the variation of the aerosol flux (Ripamonti et al, 2013). These pieces of evidence suggest that the imaginary part of the ARISP can be used to measure the aerosol flux via LAS.…”

Section: Conclusion and Discussionmentioning

confidence: 68%

A new method for measuring the imaginary part of the atmospheric refractive index structure parameter in the urban surface layer

et al. 2015

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Abstract. The atmospheric refractive index consists of both real and imaginary parts. The intensity of refractive index fluctuations is generally expressed as the refractive index structure parameter, with the real part reflecting the strength of atmospheric turbulence and the imaginary part reflecting absorption in the light path. A large aperture scintillometer (LAS) is often used to measure the structure parameter of the real part of the atmospheric refractive index, from which the sensible and latent heat fluxes can further be obtained, whereas the influence of the imaginary part is ignored or considered noise. In this theoretical analysis study, the relationship between logarithmic light intensity variance and the atmospheric refractive index structure parameter (ARISP), as well as that between the logarithmic light intensity structure function and the ARISP, is derived. Additionally, a simple expression for the imaginary part of the ARISP is obtained which can be conveniently used to determine the imaginary part of the ARISP from LAS measurements. Moreover, these relationships provide a new method for estimating the outer scale of turbulence. Light propagation experiments were performed in the urban surface layer, from which the imaginary part of the ARISP was calculated. The experimental results showed good agreement with the presented theory. The results also suggest that the imaginary part of the ARISP exhibits a different diurnal variation from that of the real part. For the wavelength of light used (0.62 µm), the variation of the imaginary part of the ARISP is related to both the turbulent transport process and the spatial distribution characteristics of aerosols.

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“…Measurements of aerosol vertical transport flux using the EC method have been carried out recently in many cities including Stockholm (Vogt et al, 2011b), Helsinki (Ripamonti et al, 2013), Lecce (Samain et al, 2012), Munster (Pauwels et al, 2008), and London (Harrison et al, 2012). The EC method has also been used to determine the aerosol particle number concentration flux at other sites, such as sea-salt aerosol concentration flux measurements in Northern Europe (Brooks et al, 2009;Sproson et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The vertical transport flux of aerosol particle number density (F p ) is expressed as the cross-correlation between vertical wind velocity (w ) and aerosol particle number density (N ) (Ripamonti et al, 2013). Fluctuations in the vertical velocity and aerosol particle number density must be measured simultaneously at high temporal resolutions to provide an aerosol particle number flux.…”

Section: Introductionmentioning

confidence: 99%

A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

et al. 2016

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Abstract. Atmospheric aerosol greatly influences human health and the natural environment, as well as the weather and climate system. Therefore, atmospheric aerosol has attracted significant attention from society. Despite consistent research efforts, there are still uncertainties in understanding its effects due to poor knowledge about aerosol vertical transport caused by the limited measurement capabilities of aerosol mass vertical transport flux. In this paper, a new method for measuring atmospheric aerosol vertical transport flux is developed based on the similarity theory of surface layer, the theory of light propagation in a turbulent atmosphere, and the observations and studies of the atmospheric equivalent refractive index (AERI). The results show that aerosol mass flux can be linked to the real and imaginary parts of the atmospheric equivalent refractive index structure parameter (AERISP) and the ratio of aerosol mass concentration to the imaginary part of the AERI. The real and imaginary parts of the AERISP can be measured based on the lightpropagation theory. The ratio of the aerosol mass concentration to the imaginary part of the AERI can be measured based on the measurements of aerosol mass concentration and visibility. The observational results show that aerosol vertical transport flux varies diurnally and is related to the aerosol spatial distribution. The maximum aerosol flux during the experimental period in Hefei City was 0.017 mg m −2 s −1 , and the mean value was 0.004 mg m −2 s −1 . The new method offers an effective way to study aerosol vertical transport in complex environments.

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The effect of local sources on aerosol particle number size distribution, concentrations and fluxes in Helsinki, Finland

Cited by 47 publications

References 65 publications

Mobile Particle and NOx Emission Characterization at Helsinki Downtown: Comparison of Different Traffic Flow Areas

Mobile Particle and NOx Emission Characterization at Helsinki Downtown: Comparison of Different Traffic Flow Areas

A new method for measuring the imaginary part of the atmospheric refractive index structure parameter in the urban surface layer

A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

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