scholarly journals Aerosol dynamics in the Copenhagen urban plume during regional transport

2010 ◽  
Vol 10 (4) ◽  
pp. 8553-8594 ◽  
Author(s):  
F. Wang ◽  
P. Roldin ◽  
A. Massling ◽  
A. Kristensson ◽  
E. Swietlicki ◽  
...  
Keyword(s):  
Satisfactory Agreement ◽  
Particle Number ◽  
Meteorological Data ◽  
Atmospheric Dispersion ◽  
Emission Factors ◽  
Anthropogenic Sources ◽  
Minor Role ◽  
Size Distributions ◽  
Aerosol Dynamics ◽  
Urban Plume

Abstract. Aerosol particles in the submicrometer size range (PM1) have serious impacts on human health and climate. This work aims at studying the processes relevant for physical particle properties in and downwind Copenhagen and evaluating the capability of a detailed aerosol dynamics and chemistry model (ADCHEM) to describe the submicrometer aerosol dynamics in a complex urbanized region, subjected to a variety of important anthropogenic sources. The study area is the Oresund Region with Copenhagen (about 1.8 million people) as the major city, including the strait separating Denmark and Sweden with intense ship traffic. Modeled aerosol particle number size distributions and NOx concentrations are evaluated against ground-based measurements from two stations in the Copenhagen area in Denmark and one station in southern Sweden. The measured and modeled increments in NOx concentrations from rural background to the urban area showed satisfactory agreement, indicating that the estimated NOx emissions and modeled atmospheric dispersion are reasonable. For three out of five case studies, the modeled particle number concentrations and size distributions are in satisfactory agreement with the measurements at all stations along the trajectories. For the remaining cases the model significantly underestimates the particle number concentration over Copenhagen, but reaches acceptable agreement with the measurements at the downwind background station in Sweden. The major causes for this were identified as being the lack of spatial resolution in the meteorological data in describing boundary layer mixing heights and the uncertainty in the exact air mass trajectory path over Copenhagen. In addition, particle emission factors may also have been too low. It was shown that aerosol dynamics play a minor role from upwind to urban background, but are important 1–2 h downwind the city. Real-world size-resolved traffic number emission factors which take into account the initial ageing in the street canyon can be used to model traffic emissions in urban plume studies.

scholarly journals Particle number size distributions in urban air before and after volatilisation

2010 ◽  
Vol 10 (10) ◽  
pp. 4643-4660 ◽  
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.

scholarly journals Aerosol ageing in an urban plume – implication for climate

2011 ◽  
Vol 11 (12) ◽  
pp. 5897-5915 ◽  
Author(s):  
P. Roldin ◽  
E. Swietlicki ◽  
A. Massling ◽  
A. Kristensson ◽  
J. Löndahl ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Particle Number ◽  
Particulate Emissions ◽  
Aerosol Formation ◽  
Aerosol Dynamics ◽  
Cloud Properties ◽  
Total Particle ◽  
Physical Particle ◽  
Urban Plume ◽  
Phase Chemistry

Abstract. The climate effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmö city in southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind of Malmö, through the urban background environment and finally tens and hundreds of kilometers downwind of Malmö. The model results were evaluated using measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (~ 3 h) downwind, in the center of the Malmö plume, is about 3700 cm−3 of which the Malmö contribution is roughly 30%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmö increases the secondary aerosol formation with a maximum of 0.7–0.8 μg m−3 6 to 18 h downwind of Malmö. The secondary mass contribution dominates over the primary soot contribution from Malmö already 3 to 4 h downwind of the emission sources and contributes to an enhanced total surface direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from −0.3 to −3.3 W m−2 depending on the distance from Malmö, and the specific cloud properties.

scholarly journals Aerosol ageing in an urban plume – implications for climate and health

2010 ◽  
Vol 10 (8) ◽  
pp. 18731-18780 ◽  
Author(s):  
P. Roldin ◽  
E. Swietlicki ◽  
A. Massling ◽  
A. Kristensson ◽  
J. Löndahl ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Particle Number ◽  
Particulate Emissions ◽  
Aerosol Formation ◽  
Aerosol Dynamics ◽  
Cloud Properties ◽  
Total Particle ◽  
Physical Particle ◽  
Climate And Health ◽  
Urban Plume

Abstract. The climate and health effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmö city in Southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind Malmö, through the urban background environment and finally tens and hundreds of kilometers downwind Malmö. The model results were validated with measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (~3 h) downwind in the center of the Malmö plume is about 3800 cm−3 and the Malmö contribution is roughly 35%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmö increases the secondary aerosol formation with a maximum of 0.6–0.7 μg/m3 6 to 18 h downwind of Malmö. The secondary mass contribution dominates over the primary soot contribution from Malmö already 2 to 3 h after the emissions and gives an enhanced total top of the atmosphere direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from −0.3 to −2.3 W m−2 depending on the distance from Malmö, and the cloud properties. It also gives an increased respiratory tract deposited mass dose, which increases with the distance downwind Malmö.

scholarly journals Dispersion of traffic-related exhaust particles near the Berlin urban motorway: estimation of fleet emission factors

2008 ◽  
Vol 8 (4) ◽  
pp. 15537-15594 ◽  
Author(s):  
W. Birmili ◽  
B. Alaviippola ◽  
D. Hinneburg ◽  
O. Knoth ◽  
T. Tuch ◽  
...  
Keyword(s):  
Particle Number ◽  
Dispersion Model ◽  
Flow Simulation ◽  
Emission Factors ◽  
Size Distributions ◽  
Tracer Transport ◽  
Particle Volume ◽  
Traffic Emission ◽  
Atmospheric Particle ◽  
Particulate Number

Abstract. Atmospheric particle number size distributions of airborne particles (diameter range 10–500 nm) were measured over ten weeks at three sites in the vicinity of the A100 urban motorway in Berlin, Germany. The A100 carries about 180 000 vehicles on a weekday, and roadside particle size distributions showed a number maximum between 20 and 60 nm clearly related to the motorway emissions. The average total number concentration at roadside was 28 000 cm−3 with a total range between 1200 and 168 000 cm−3. At distances of 80 and 400 m from the motorway the concentrations decreased to mean levels of 11 000 and 9 000 cm−3, respectively. An obstacle-resolving dispersion model was applied to simulate the 3-D flow field and traffic tracer transport in the urban environment around the motorway. By inverse modelling, vehicle emission factors were derived, representative of a relative share of 6% lorry-like vehicles, and a driving speed of about 80 km h−1. Three different calculation approaches were compared, which differ in the choice of the experimental winds driving the flow simulation. The average emission factor per vehicle was 2.1(±0.2) · 1014 km−1 for particle number and 0.077(±0.01) · 1014 cm3 km−1 for particle volume. Regression analysis suggested that lorry-like vehicles emit 116 (± 21) times more particulate number than passenger car-like vehicles, and that lorry-like vehicles account for about 91% of particulate number emissions on weekdays. Our work highlights the increasing applicability of 3-D flow models in urban microscale environments and their usefulness in determining traffic emission factors.

scholarly journals Particle number emissions of motor traffic derived from street canyon measurements in a Central European city

2009 ◽  
Vol 9 (1) ◽  
pp. 3763-3809 ◽  
Author(s):  
S. Klose ◽  
W. Birmili ◽  
J. Voigtländer ◽  
T. Tuch ◽  
B. Wehner ◽  
...  
Keyword(s):  
Wind Direction ◽  
Urban Areas ◽  
Street Canyon ◽  
Particle Number ◽  
Emission Factors ◽  
Time Of Day ◽  
Traffic Emissions ◽  
Size Spectrum ◽  
Size Distributions ◽  
The Impact

Abstract. A biennial dataset of ambient particle number size distributions (diameter range 4–800 nm) collected in urban air in Leipzig, Germany, was analysed with respect to the influence of traffic emissions. Size distributions were sampled continuously in 2005 and 2006 inside a street canyon trafficked by ca. 10 000 motor vehicles per day, and at a background reference site distant at 1.5 km. Auto-correlation analysis showed that the impact of fresh traffic emissions could be seen most intensely below particle sizes of 60 nm. The traffic-induced concentration increment at roadside was estimated by subtracting the urban background values from the street canyon measurement. To describe the variable dispersion conditions inside the street canyon, micro-meteorological dilution factors were calculated using the Operational Street Pollution Model (OSPM), driven by above-roof wind speed and wind direction observations. The roadside increment concentrations, dilution factor, and real-time traffic counts were used to calculate vehicle emission factors (aerosol source rates) that are representative of the prevailing driving conditions, i.e. stop-and-go traffic including episodes of fluent traffic flow at speeds up to 40 km h−1. The size spectrum of traffic-derived particles was essentially bimodal – with mode diameters around 12 and 100 nm, while statistical analysis suggested that the emitted number concentration varied with time of day, wind direction, particle size and fleet properties. Significantly, the particle number emissions depended on ambient temperature, ranging between 4.8 (±1.8) and 7.8 (±2.9).1014 p. veh−1 km−1 in summer and winter, respectively. A separation of vehicle types according to vehicle length suggested that lorry-like vehicles emit about 80 times more particle number than passenger car-like vehicles. Using nitrogen oxide (NOx) measurements, specific total particle number emissions of 338 p. (pg NOx)−1 were inferred. The calculated traffic emission factors, considering particle number and size, are anticipated to provide useful input for future air quality and particle exposure modelling in densely populated urban areas.

scholarly journals Aerosol and NO<sub>x</sub> emission factors and submicron particle number size distributions in two road tunnels with different traffic regimes

2006 ◽  
Vol 6 (8) ◽  
pp. 2215-2230 ◽  
Author(s):  
D. Imhof ◽  
E. Weingartner ◽  
A. S. H. Prévôt ◽  
C. Ordóñez ◽  
R. Kurtenbach ◽  
...  
Keyword(s):  
Particle Size ◽  
Diurnal Variation ◽  
Particle Number ◽  
Emission Factors ◽  
Traffic Density ◽  
Size Distributions ◽  
Submicron Particle ◽  
Nucleation Mode ◽  
Road Tunnels ◽  
Vehicle Fleet

Abstract. Measurements of aerosol particle number size distributions (18–700 nm), mass concentrations (PM2.5 and PM10) and NOx were performed in the Plabutsch tunnel, Austria, and in the Kingsway tunnel, United Kingdom. These two tunnels show different characteristics regarding the roadway gradient, the composition of the vehicle fleet and the traffic frequency. The submicron particle size distributions contained a soot mode in the diameter range D=80–100 nm and a nucleation mode in the range of D=20–40 nm. In the Kingsway tunnel with a significantly lower particle number and volume concentration level than in the Plabutsch tunnel, a clear diurnal variation of nucleation and soot mode particles correlated to the traffic density was observed. In the Plabutsch tunnel, soot mode particles also revealed a diurnal variation, whereas no substantial variation was found for the nucleation mode particles. During the night a higher number concentration of nucleation mode particles were measured than soot mode particles and vice versa during the day. In this tunnel with very high soot emissions during daytime due to the heavy-duty vehicle (HDV) share of 18% and another 40% of diesel driven light-duty vehicles (LDV) semivolatile species condense on the pre-existing soot surface area rather than forming new particles by homogeneous nucleation. With the low concentration of soot mode particles in the Kingsway tunnel, also the nucleation mode particles exhibit a diurnal variation. From the measured parameters real-world traffic emission factors were estimated for the whole vehicle fleet as well as differentiated into the two categories LDV and HDV. In the particle size range D=18–700 nm, each vehicle of the mixed fleet emits (1.50±0.08)×1014 particles km-1 (Plabutsch) and (1.26±0.10)×1014 particles km-1 (Kingsway), while particle volume emission factors of 0.209±0.008 cm3 km-1 and 0.036±0.004 cm3 km-1, respectively, were obtained. PM1 emission factors of 104±4 mg km-1 (Plabutsch) and 41±4 mg km-1 (Kingsway) were calculated. Emission factors determined in this work were in good agreement with results from other studies.

scholarly journals Properties and emission factors of cloud condensation nuclei from biomass cookstoves – observations of a strong dependency on potassium content in the fuel

2021 ◽  
Vol 21 (10) ◽  
pp. 8023-8044
Author(s):  
Thomas Bjerring Kristensen ◽  
John Falk ◽  
Robert Lindgren ◽  
Christina Andersen ◽  
Vilhelm B. Malmborg ◽  
...  
Keyword(s):  
Particle Number ◽  
Potassium Concentration ◽  
Cloud Condensation Nuclei ◽  
Emission Factors ◽  
Effective Density ◽  
Biomass Combustion ◽  
Size Distributions ◽  
Condensation Nuclei ◽  
Fuel Ash ◽  
Ccn Activity

Abstract. Residential biomass combustion is a significant source of aerosol particles on regional and global scales influencing climate and human health. The main objective of the current study was to investigate the properties of cloud condensation nuclei (CCN) emitted from biomass burning of solid fuels in different cookstoves mostly of relevance to sub-Saharan east Africa. The traditional three-stone fire and a rocket stove were used for combustion of wood logs of Sesbania and Casuarina with birch used as a reference. A natural draft and a forced-draft pellet stove were used for combustion of pelletised Sesbania and pelletised Swedish softwood alone or in mixtures with pelletised coffee husk, rice husk or water hyacinth. The CCN activity and the effective density were measured for particles with mobility diameters of ∽65, ∽100 and ∽200 nm, respectively, and occasionally for 350 nm particles. Particle number size distributions were measured online with a fast particle analyser. The chemical composition of the fuel ash was measured by application of standard protocols. The average particle number size distributions were by number typically dominated by an ultrafine mode, and in most cases a soot mode was centred around a mobility diameter of ∽150 nm. The CCN activities decreased with increasing particle size for all experiments and ranged in terms of the hygroscopicity parameter, κ, from ∽0.1 to ∽0.8 for the ultrafine mode and from ∽0.001 to ∽0.15 for the soot mode. The CCN activity (κ) of the ultrafine mode increased (i) with increasing combustion temperature for a given fuel, and (ii) it typically increased with increasing potassium concentration in the investigated fuels. The primary CCN and the estimated particulate matter (PM) emission factors were typically found to increase significantly with increasing potassium concentration in the fuel for a given stove. In order to link CCN emission factors to PM emission factors, knowledge about stove technology, stove operation and the inorganic fuel ash composition is needed. This complicates the use of ambient PM levels alone for estimation of CCN concentrations in regions dominated by biomass combustion aerosol, with the relation turning even more complex when accounting for atmospheric ageing of the aerosol.

scholarly journals Particle number size distributions in urban air before and after volatilisation

2009 ◽  
Vol 9 (2) ◽  
pp. 9171-9220 ◽  
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.

scholarly journals Analysis of particle size distribution changes between three measurement sites in northern Scandinavia

2013 ◽  
Vol 13 (23) ◽  
pp. 11887-11903 ◽  
Author(s):  
R. Väänänen ◽  
E.-M. Kyrö ◽  
T. Nieminen ◽  
N. Kivekäs ◽  
H. Junninen ◽  
...  
Keyword(s):  
Mass Transport ◽  
Aerosol Particle ◽  
Growth Rates ◽  
Particle Number ◽  
Particle Growth ◽  
Size Distributions ◽  
Air Mass ◽  
Air Masses ◽  
Aerosol Dynamics ◽  
Particle Sizer

Abstract. We investigated atmospheric aerosol particle dynamics in a boreal forest zone in northern Scandinavia. We used aerosol number size distribution data measured with either a differential mobility particle sizer (DMPS) or scanning mobility particle sizer (SMPS) at three stations (Värriö, Pallas and Abisko), and combined these data with the HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) air mass trajectory analysis. We compared three approaches: analysis of new particle formation events, investigation of aerosol particle number size distributions during the air mass transport from the ocean to individual stations with different overland transport times, and analysis of changes in aerosol particle number size distributions during the air mass transport from one measurement station to another. Aitken-mode particles were found to have apparent average growth rates of 0.6–0.7 nm h−1 when the air masses traveled over land. Particle growth rates during the new particle formation (NPF) events were 3–6 times higher than the apparent particle growth during the summer period. When comparing aerosol dynamics for different overland transport times between the different stations, no major differences were found, except that in Abisko the NPF events were observed to take place in air masses with shorter overland times than at the other stations. We speculate that this is related to the meteorological differences along the paths of air masses caused by the land surface topology. When comparing air masses traveling in an east-to-west direction with those traveling in a west-to-east direction, clear differences in the aerosol dynamics were seen. Our results suggest that the condensation growth has an important role in aerosol dynamics even when NPF is not evident.

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