Contribution of traffic-originated nanoparticle emissions to regional and local aerosol levels

Abstract. Sub-50 nm particles originating from traffic emissions pose risks to human health due to their high lung deposition efficiency and potentially harmful chemical composition. We present a modelling study using an updated EUCAARI number emission inventory, incorporating a more realistic, empirically justified particle size distribution (PSD) for sub-50 nm particles from road traffic. We present experimental PSDs and CO2 concentrations, measured in a highly trafficked street canyon in Helsinki, Finland, as an emission factor particle size distribution (EFPSD), which was then used in updating the EUCAARI inventory. We applied the updated inventory in a simulation using the regional chemical transport model PMCAMx-UF over Europe for May 2008 to test the effect of updated emissions in regional and local scales and in contrast to atmospheric new particle formation (NPF). Updating the inventory increased simulated average total particle number concentrations by only 1 %, although the total particle number emissions were increased to a 3-fold level. The concentrations increased up to 11 % when only 1.3–3 nm-sized particles (nanocluster aerosol, NCA) were considered. These values indicate that the effect of updating overall is insignificant in a regional scale during this photochemically active period, during which the fraction of the total particle number originating through atmospheric NPF processes was 91 %. These simulations give a lower limit for the contribution of traffic to the aerosol levels. Nevertheless, the situation is different when examining the effect of the update spatially or temporally, or when focusing to the chemical composition or the origin of the particles. For example, daily average NCA concentrations increased by a factor of several hundreds or thousands in some locations on certain days. Overall, the most significant effects–reaching several orders of magnitude–from updating the inventory are observed when examining specific particle sizes (especially 7–20 nm), particle components, and specific urban areas. While the model still has a tendency to predict more sub-50 nm particles compared to the observations, the most notable underestimations in the concentrations of sub-10 nm particles are, after updating, overcome and the simulated distributions now agree better with the data observed at locations having high traffic densities. The findings of this study highlight the need to consider emissions, PSDs, and composition of sub-50 nm particles from road traffic in studies focusing on urban air quality. Updating this emission source brings the simulated aerosol levels particularly in urban locations closer to observations, which highlights its importance for calculations of human exposure to nanoparticles.

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Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-5513-2003 ◽

2003 ◽

Vol 3 (6) ◽

pp. 5513-5546 ◽

Cited By ~ 5

Author(s):

M. Ketzel ◽

P. Wåhlin ◽

A. Kristensson ◽

E. Swietlicki ◽

R. Berkowicz ◽

...

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Particle Number ◽

Size Range ◽

Urban Background ◽

Total Particle ◽

Urban Level ◽

20 Nm ◽

Traffic Source

Abstract. Particle size distribution (size-range 3–900 nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500 # cm−3, 4500 # cm−3 and 7700 # cm−3 at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10–200 nm particle size range. The maximum of the size distribution shifts from about 20–30 nm at kerbside to 50–60 nm at rural level. We also observe particle formation events in the 3–20 nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of pre-existing aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28 nm in the urban location compared to 22 nm at kerbside. Assuming NOx as an inert tracer on urban scale let us estimate that ToN at urban level is reduced by 15–30% compared to kerbside. Particle removal processes, e.g. deposition and coagulation, which are most efficient for smallest particle sizes (<20 nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.

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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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Particle size distribution and particle mass measurements at urban,near-city and rural level in the Copenhagen area and Southern Sweden

Atmospheric Chemistry and Physics ◽

10.5194/acp-4-281-2004 ◽

2004 ◽

Vol 4 (1) ◽

pp. 281-292 ◽

Cited By ~ 74

Author(s):

M. Ketzel ◽

P. Wåhlin ◽

A. Kristensson ◽

E. Swietlicki ◽

R. Berkowicz ◽

...

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Particle Number ◽

Size Range ◽

Urban Background ◽

Rural Location ◽

Total Particle ◽

Urban Level ◽

Traffic Source

Abstract. Particle size distribution (size-range 3-900nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500#cm, 4500#cm and 7700#cm at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10-200nm particle size range. The maximum of the size distribution shifts from about 20-30nm at kerbside to 50-60nm at rural level. Particle formation events were observed in the 3-20nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of pre-existing aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28nm in the urban location compared to 22nm at kerbside. Assuming NOx as an inert tracer on urban scale allows to estimate that ToN at urban level is reduced by 15-30% compared to kerbside. Particle removal processes, e.g. deposition and coagulation, which are most efficient for smallest particle sizes (20nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.

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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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Particle number size distribution from direct-injection premixed combustion engine fueled with gasoline/diesel blends

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407019838128 ◽

2019 ◽

Vol 234 (1) ◽

pp. 258-269

Author(s):

Qiao Wang ◽

Wanchen Sun ◽

Liang Guo ◽

Luyan Fan ◽

Peng Cheng ◽

...

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Particle Number ◽

Combustion Engine ◽

Injection Pressure ◽

Premixed Combustion ◽

Total Particle ◽

Hydrocarbon Emission ◽

Blended Fuel

The organizing of combustion process in the advanced internal combustion engine is developing toward unified combustion mode of gasoline-engine-like premixed gas formation and diesel-engine-like compression ignition. Gasoline/diesel blended fuel has received extensive attention for its suitability for this combustion characteristic, owing to its relatively poor ignitability and high volatility. In order to more comprehensively evaluate the application of the blended fuel on this combustion mode, an experiment was conducted to characterize the particle size distribution and total number concentration of exhaust particles from the gasoline/diesel blended fuel. The premixed combustion characteristics and relatively high hydrocarbon emission were confirmed first and their effects on the particle size distribution were determined subsequently. Combustion control parameters such as exhaust gas recirculation and injection pressure were also taken into account. Results indicated that gasoline/diesel blended fuel had significant effect on the particle size distribution due to the higher premixed combustion ratio and more unburned hydrocarbon emission. Under high load condition, as the proportion of gasoline blending increased, the accumulation mode particle decreased while the nucleation mode particle and total particle number increased significantly. The geometric mean diameter of exhaust particle decreased with the addition of gasoline. The effect of exhaust gas recirculation and injection pressure on the particle size distribution of gasoline/diesel blended fuel was less than that of pure diesel. That meant the gasoline/diesel blends were beneficial for carbonaceous particle (>22 nm) reduction. However, the nucleation mode as well as total particle number were still higher for gasoline/diesel blends than that for pure diesel.

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Undiluted Measurement of the Particle Size Distribution of Different Oxygenated Biofuels in a Gasoline-Optimised DISI Engine

Atmosphere ◽

10.3390/atmos12111493 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1493

Author(s):

Tara Larsson ◽

Ulf Olofsson ◽

Anders Christiansen Erlandsson

Keyword(s):

Particle Size ◽

High Temperature ◽

High Resolution ◽

Particle Size Distribution ◽

Size Distribution ◽

Urban Areas ◽

Internal Combustion Engines ◽

Particle Number ◽

Combustion Engines ◽

Engine Exhaust

The utilisation of internal combustion engines is one of the main causes of particle emissions in urban areas. As the interest for the utilisation of biofuels increases, it is important to understand their effect on particle number emissions. In this paper, the particle size distribution and the particle number emissions from a gasoline-optimised direct-injected spark-ignited (DISI) engine are investigated. The effects of five different biofuel alternatives on these emissions were evaluated and compared to gasoline. The utilisation of the high-resolution, high-temperature ELPI+ enabled undiluted measurements of the particle size distribution down to 6 nm, without extensive cooling of the engine exhaust. Contrary to other studies, the results show that the particle number emissions for the three measured cut-off sizes (23, 10 and 7 nm) increased with the utilisation of oxygenated biofuels. The results indicate that the decreased volatility and energy density of the alcohols has a more significant impact on the particle formation in a DISI engine than the increased oxygen content of these fuels.

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