A novel inversion algorithm for mobility particle size spectrometers considering non-sphericity and additional aerodynamic/optical number size distributions

Abstract. Multiple charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (Differential or Scanning Mobility Particle Sizers) into true particle number size distributions. In this work, we present a new multiple charge inversion algorithm with extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS), or an optical particle counter (OPC). This feature can considerably improve the multiple charge inversion result in the upper size range of the mobility spectrometer, for example, when substantial numbers of coarse particles are present. The program also yields a continuous size distribution from both sensors as an output. The algorithm is able to calculate the propagation of measurement errors, such as those based on counting statistics, into on the final particle number size distribution. As an additional aspect, the algorithm can perform all inversion steps under the assumption of non-spherical particle shape, including constant or size-dependent shape factor profiles.

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A fast and easy-to-implement inversion algorithm for mobility particle size spectrometers considering particle number size distribution information outside of the detection range

Atmospheric Measurement Techniques ◽

10.5194/amt-7-95-2014 ◽

2014 ◽

Vol 7 (1) ◽

pp. 95-105 ◽

Cited By ~ 34

Author(s):

S. Pfeifer ◽

W. Birmili ◽

A. Schladitz ◽

T. Müller ◽

A. Nowak ◽

...

Keyword(s):

Particle Size ◽

Size Distribution ◽

Particle Number ◽

Inversion Algorithm ◽

Charge Inversion ◽

Final Particle ◽

Detection Range ◽

Number Size Distribution ◽

Particle Number Size Distribution ◽

Multiple Charge

Abstract. Multiple-charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (differential or scanning mobility particle sizers), into true particle number size distributions. In this work, we present a fast and easy-to-implement multiple-charge inversion algorithm with sufficient precision for atmospheric conditions, but extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS) or an optical particle counter (OPC). This feature can considerably improve the multiple-charge inversion result in the upper size range of the mobility spectrometer, for example, when substantial numbers of coarse particles are present. The program also yields a continuous size distribution from both sensors as an output. The algorithm is able to calculate the propagation of measurement errors, such as those based on counting statistics, into on the final particle number size distribution. As an additional aspect, the algorithm can perform all inversion steps under the assumption of non-spherical particle shape, including constant or size-dependent shape factors.

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Particle number size distributions in urban air before and after volatilisation

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-4643-2010 ◽

2010 ◽

Vol 10 (10) ◽

pp. 4643-4660 ◽

Cited By ~ 50

Author(s):

W. Birmili ◽

K. Heinke ◽

M. Pitz ◽

J. Matschullat ◽

A. Wiedensohler ◽

...

Keyword(s):

Particle Size ◽

Volatile Compounds ◽

Size Distribution ◽

Particle Number ◽

Volume Concentration ◽

Urban Atmosphere ◽

Anthropogenic Sources ◽

Particulate Emissions ◽

Size Distributions ◽

Before And After

Abstract. Aerosol particle number size distributions (size range 0.003–10 μm) in the urban atmosphere of Augsburg (Germany) were examined with respect to the governing anthropogenic sources and meteorological factors. The two-year average particle number concentration between November 2004 and November 2006 was 12 200 cm−3, i.e. similar to previous observations in other European cities. A seasonal analysis yielded twice the total particle number concentrations in winter as compared to summer as consequence of more frequent inversion situations and enhanced particulate emissions. The diurnal variations of particle number were shaped by a remarkable maximum in the morning during the peak traffic hours. After a mid-day decrease along with the onset of vertical mixing, an evening concentration maximum could frequently be observed, suggesting a re-stratification of the urban atmosphere. Overall, the mixed layer height turned out to be the most influential meteorological parameter on the particle size distribution. Its influence was even greater than that of the geographical origin of the prevailing synoptic-scale air mass. Size distributions below 0.8 μm were also measured downstream of a thermodenuder (temperature: 300 °C), allowing to retrieve the volume concentration of non-volatile compounds. The balance of particle number upstream and downstream of the thermodenuder suggests that practically all particles >12 nm contain a non-volatile core while additional nucleation of particles smaller than 6 nm could be observed after the thermodenuder as an interfering artifact of the method. The good correlation between the non-volatile volume concentration and an independent measurement of the aerosol absorption coefficient (R2=0.9) suggests a close correspondence of the refractory and light-absorbing particle fractions. Using the "summation method", an average diameter ratio of particles before and after volatilisation could be determined as a function of particle size. The results indicated that particles >60 nm contain a significantly higher fraction of non-volatile compounds, most likely black carbon, than particles <60 nm. The results are relevant for future health-related studies in that they explore the size distribution and time-dependent behaviour of the refractory component of the urban aerosol over an extended time period.

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Remarkable dynamics of nanoparticles in the urban atmosphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-6623-2011 ◽

2011 ◽

Vol 11 (13) ◽

pp. 6623-6637 ◽

Cited By ~ 77

Author(s):

M. Dall'Osto ◽

A. Thorpe ◽

D. C. S. Beddows ◽

R. M. Harrison ◽

J. F. Barlow ◽

...

Keyword(s):

Particle Size ◽

Size Distribution ◽

Urban Areas ◽

Particle Number ◽

Road Traffic ◽

Urban Atmosphere ◽

Size Distributions ◽

Particle Size Distributions ◽

Number Count ◽

Adverse Health Effects

Abstract. Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that adverse health effects of airborne particles may scale with airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20–30 nm diameter emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m aloft. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20–30 nm diameter is much reduced with a new mode at <10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and are indicative of loss of nanoparticles from air aged during less turbulent conditions. These results are suggestive of nanoparticle loss by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health.

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Intra-community spatial variability of particulate matter size distributions in southern California/Los Angeles

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-9641-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 9641-9672 ◽

Cited By ~ 1

Author(s):

M. Krudysz ◽

K. Moore ◽

M. Geller ◽

C. Sioutas ◽

J. Froines

Keyword(s):

Particle Size ◽

Los Angeles ◽

Spatial Variability ◽

Size Distribution ◽

Particle Number ◽

Number Concentration ◽

Particle Number Concentration ◽

Size Distributions ◽

Sampling Locations ◽

Concentration Measurements

Abstract. Ultrafine particle (UFP) number concentrations vary significantly on small spatial and temporal scales due to their short atmospheric lifetimes and multiplicity of sources. To determine UFP exposure gradients within a community, simultaneous particle number concentration measurements at a network of sites are necessary. Concurrent particle size distribution measurements aid in identifying UFP sources, while providing data to investigate local scale effects of both photochemical and physical processes on UFP. From April to December 2007, we monitored particle size distributions at 13 sites within 350 m to 11 km of each other in the vicinity of the Ports of Los Angeles and Long Beach using Scanning Mobility Particle Sizers (SMPS). Typically, three SMPS units were simultaneously deployed and rotated among sites at 1–2 week intervals. Total particle number concentration measurements were conducted continuously at all sites. Seasonal and diurnal size distribution patterns are complex, highly dependent on local meteorology, nearby PM sources, and times of day, and cannot be generalized over the study area nor inferred from one or two sampling locations. Spatial variation in particle number size distributions was assessed by calculating the coefficient of divergence (COD) and correlation coefficients (r) between site pairs. Results show an overall inverse relationship between particle size and CODs, implying that number concentrations of smaller particles (<40 nm) differ from site to site, whereas larger particles tend to have similar concentrations at various sampling locations. In addition, variations in r values as a function of particle size are not necessarily consistent with corresponding COD values, indicating that using results from correlation analysis alone may not accurately assess spatial variability.

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Intra-community spatial variability of particulate matter size distributions in Southern California/Los Angeles

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1061-2009 ◽

2009 ◽

Vol 9 (3) ◽

pp. 1061-1075 ◽

Cited By ~ 44

Author(s):

M. Krudysz ◽

K. Moore ◽

M. Geller ◽

C. Sioutas ◽

J. Froines

Keyword(s):

Particle Size ◽

Los Angeles ◽

Spatial Variability ◽

Size Distribution ◽

Particle Number ◽

Number Concentration ◽

Particle Number Concentration ◽

Size Distributions ◽

Number Size Distribution ◽

Sampling Locations

Abstract. Ultrafine particle (UFP) number concentrations vary significantly on small spatial and temporal scales due to their short atmospheric lifetimes and multiplicity of sources. To determine UFP exposure gradients within a community, simultaneous particle number concentration measurements at a network of sites are necessary. Concurrent particle number size distribution measurements aid in identifying UFP sources, while providing data to investigate local scale effects of both photochemical and physical processes on UFP. From April to December 2007, we monitored particle number size distributions at 13 sites within 350 m–11 km of each other in the vicinity of the Ports of Los Angeles and Long Beach using Scanning Mobility Particle Sizers (SMPS). Typically, three SMPS units were simultaneously deployed and rotated among sites at 1–2 week intervals. Total particle number concentration measurements were conducted continuously at all sites. Seasonal and diurnal number size distribution patterns are complex, highly dependent on local meteorology, nearby PM sources, and times of day, and cannot be generalized over the study area nor inferred from one or two sampling locations. Spatial variation in particle number size distributions was assessed by calculating the coefficient of divergence (COD) and correlation coefficients (r) between site pairs. Results show an overall inverse relationship between particle size and CODs, implying that number concentrations of smaller particles (<40 nm) differ from site to site, whereas larger particles tend to have similar concentrations at various sampling locations. In addition, variations in r values as a function of particle size are not necessarily consistent with corresponding COD values, indicating that using results from correlation analysis alone may not accurately assess spatial variability.

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Remarkable dynamics of nanoparticles in the urban atmosphere

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-30651-2010 ◽

2010 ◽

Vol 10 (12) ◽

pp. 30651-30689 ◽

Cited By ~ 6

Author(s):

M. Dall'Osto ◽

A. Thorpe ◽

D. C. S. Beddows ◽

R. M. Harrison ◽

J. F. Barlow ◽

...

Keyword(s):

Particle Size ◽

Size Distribution ◽

Urban Areas ◽

Particle Number ◽

Road Traffic ◽

Urban Atmosphere ◽

Size Distributions ◽

Particle Size Distributions ◽

Number Count ◽

Adverse Health Effects

Abstract. Nanoparticles emitted from road traffic are the largest source of respiratory exposure for the general public living in urban areas. It has been suggested that the adverse health effects of airborne particles may scale with the airborne particle number, which if correct, focuses attention on the nanoparticle (less than 100 nm) size range which dominates the number count in urban areas. Urban measurements of particle size distributions have tended to show a broadly similar pattern dominated by a mode centred on 20–30 nm diameter particles emitted by diesel engine exhaust. In this paper we report the results of measurements of particle number concentration and size distribution made in a major London park as well as on the BT Tower, 160 m high. These measurements taken during the REPARTEE project (Regents Park and BT Tower experiment) show a remarkable shift in particle size distributions with major losses of the smallest particle class as particles are advected away from the traffic source. In the Park, the traffic related mode at 20–30 nm diameter is much reduced with a new mode at <10 nm. Size distribution measurements also revealed higher number concentrations of sub-50 nm particles at the BT Tower during days affected by higher turbulence as determined by Doppler Lidar measurements and indicate a loss of nanoparticles from air aged during less turbulent conditions. These results suggest that nanoparticles are lost by evaporation, rather than coagulation processes. The results have major implications for understanding the impacts of traffic-generated particulate matter on human health.

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Improved Normalization of the Size Distribution of Atmospheric Particles Retrieved from Aureole Measurements Using the Diffraction Approximation

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-10-05010.1 ◽

2011 ◽

Vol 28 (8) ◽

pp. 1019-1027 ◽

Cited By ~ 1

Author(s):

J. G. DeVore

Keyword(s):

Particle Size ◽

Size Distribution ◽

Atmospheric Particles ◽

Numerical Inversion ◽

Size Distributions ◽

Inversion Algorithm ◽

Particle Size Distributions ◽

Model Calculations ◽

Large Particles ◽

Power Law Distributions

Abstract This paper describes an improvement in the diffraction approximation used to retrieve the size distribution of atmospheric particles from solar aureole radiance measurements. Normalization using total optical thickness based on measurement of the solar disk radiance is replaced with one based on the aureole profile radiance itself. Retrievals involving model calculations for power-law distributions of water droplets show significant improvement using the new algorithm. Tests involving two empirical particle size distributions, one for cirrus and another for aerosols, also show improvement using the new normalization algorithm. Comparisons of the diffraction approximation algorithms with a numerical inversion algorithm found that the accuracy of the latter was higher for two different bimodal aerosol distributions. The role envisioned for the diffraction approximation is in estimating the size distribution of large particles in clouds and especially cirrus.

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Particle number size distributions in urban air before and after volatilisation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-9171-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 9171-9220 ◽

Cited By ~ 1

Author(s):

W. Birmili ◽

K. Heinke ◽

M. Pitz ◽

J. Matschullat ◽

A. Wiedensohler ◽

...

Keyword(s):

Particle Size ◽

Volatile Compounds ◽

Size Distribution ◽

Particle Number ◽

Volume Fraction ◽

Anthropogenic Sources ◽

Particulate Emissions ◽

Average Particle ◽

Size Distributions ◽

Before And After

Abstract. Aerosol particle number size distributions (size range 0.003–10 μm) with and without using a thermodenuder are measured continuously in the city of Augsburg, Germany. Here, the data between 2004 and 2006 are examined with respect to the governing anthropogenic sources and meteorological factors. The two-year average particle number concentration in Augsburg was found to be 12 200 cm−3, similar to previous observations in other European cities. A seasonal analysis yielded twice the total particle number concentrations in winter as compared to summer, a consequence of more frequent inversion situations and particulate emissions in winter. The diurnal variation of the size distribution is shaped by a remarkable increase in the morning along with the peak traffic hours. After a mid-day decrease along with the onset of vertical mixing, an evening increase in concentration could frequently be observed, suggesting a re-stratification of the urban atmosphere. The mixed layer height turned out to be the most influential meteorological parameter on particle size distribution. Its influence was greater than that of the geographical origin of the synoptic-scale air masses. By heating every second aerosol sample to 300°C in a thermodenuder, the volume fraction of non-volatile compounds in the urban aerosol was retrieved. The obtained results compared well with an independent measurement of the aerosol absorption coefficient (R2=0.9). The balance of particle number upstream and downstream of the thermodenuder suggests that all particles >12 nm contain a non-volatile core at 300°C. As an artefact of the volatility analysis, nucleation of particles smaller than 6 nm was observed in the cooling section of the thermodenuder. An average diameter ratio of particles before and after volatilisation was determined as a function of particle size. It indicated that particles >60 nm contain significantly higher fractions of non-volatile compounds, most likely soot, than particles <60 nm.

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