scholarly journals Evaluation of the absorption Ångström exponents for traffic and wood burning in the Aethalometer-based source apportionment using radiocarbon measurements of ambient aerosol

2017 ◽  
Vol 17 (6) ◽  
pp. 4229-4249 ◽  
Author(s):  
Peter Zotter ◽  
Hanna Herich ◽  
Martin Gysel ◽  
Imad El-Haddad ◽  
Yanlin Zhang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Source Apportionment ◽  
Light Absorption ◽  
A Priori ◽  
Accurate Determination ◽  
Data Set ◽  
Near Ultraviolet ◽  
Wood Burning ◽  
Significant Difference

Abstract. Equivalent black carbon (EBC) measured by a multi-wavelength Aethalometer can be apportioned to traffic and wood burning. The method is based on the differences in the dependence of aerosol absorption on the wavelength of light used to investigate the sample, parameterized by the source-specific absorption Ångström exponent (α). While the spectral dependence (defined as α values) of the traffic-related EBC light absorption is low, wood smoke particles feature enhanced light absorption in the blue and near ultraviolet. Source apportionment results using this methodology are hence strongly dependent on the α values assumed for both types of emissions: traffic αTR, and wood burning αWB. Most studies use a single αTR and αWB pair in the Aethalometer model, derived from previous work. However, an accurate determination of the source specific α values is currently lacking and in some recent publications the applicability of the Aethalometer model was questioned.Here we present an indirect methodology for the determination of αWB and αTR by comparing the source apportionment of EBC using the Aethalometer model with 14C measurements of the EC fraction on 16 to 40 h filter samples from several locations and campaigns across Switzerland during 2005–2012, mainly in winter. The data obtained at eight stations with different source characteristics also enabled the evaluation of the performance and the uncertainties of the Aethalometer model in different environments. The best combination of αTR and αWB (0.9 and 1.68, respectively) was obtained by fitting the Aethalometer model outputs (calculated with the absorption coefficients at 470 and 950 nm) against the fossil fraction of EC (ECF ∕ EC) derived from 14C measurements. Aethalometer and 14C source apportionment results are well correlated (r  =  0.81) and the fitting residuals exhibit only a minor positive bias of 1.6 % and an average precision of 9.3 %. This indicates that the Aethalometer model reproduces reasonably well the 14C results for all stations investigated in this study using our best estimate of a single αWB and αTR pair. Combining the EC, 14C, and Aethalometer measurements further allowed assessing the dependence of the mass absorption cross section (MAC) of EBC on its source. Results indicate no significant difference in MAC at 880 nm between EBC originating from traffic or wood-burning emissions. Using ECF ∕ EC as reference and constant a priori selected αTR values, αWB was also calculated for each individual data point. No clear station-to-station or season-to-season differences in αWB were observed, but αTR and αWB values are interdependent. For example, an increase in αTR by 0.1 results in a decrease in αWB by 0.1. The fitting residuals of different αTR and αWB combinations depend on ECF ∕ EC such that a good agreement cannot be obtained over the entire ECF ∕ EC range using other α pairs. Additional combinations of αTR  =  0.8, and 1.0 and αWB  =  1.8 and 1.6, respectively, are possible but only for ECF ∕ EC between  ∼  40 and 85 %. Applying α values previously used in the literature such as αWB of  ∼  2 or any αWB in combination with αTR  =  1.1 to our data set results in large residuals. Therefore we recommend to use the best α combination as obtained here (αTR  =  0.9 and αWB  =  1.68) in future studies when no or only limited additional information like 14C measurements are available. However, these results were obtained for locations impacted by black carbon (BC) mainly from traffic consisting of a modern car fleet and residential wood combustion with well-constrained combustion efficiencies. For regions of the world with different combustion conditions, additional BC sources, or fuels used, further investigations are needed.

scholarly journals Evaluation of the absorption Ångström exponents for traffic and wood burning in the Aethalometer based source apportionment using radiocarbon measurements of ambient aerosol

2016 ◽  
Author(s):  
Peter Zotter ◽  
Hanna Herich ◽  
Martin Gysel ◽  
Imad El-Haddad ◽  
Yanlin Zhang ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Light Absorption ◽  
A Priori ◽  
Accurate Determination ◽  
Wood Combustion ◽  
Data Set ◽  
Near Ultraviolet ◽  
Wood Burning ◽  
Significant Difference

Abstract. Black carbon (BC) measured by a multi-wavelength Aethalometer can be apportioned to traffic and wood burning. The method is based on the differences in the dependence of aerosol absorption on the wavelength of light used to investigate the sample, parameterized by the source-specific Ångström absorption exponent (α). While the spectral dependence (defined as α values) of the traffic-related BC light absorption is low, wood smoke particles feature enhanced light absorption in the blue and near ultraviolet. Source apportionment results using this methodology are hence strongly dependent on the α values assumed for both types of emissions: traffic αTR, and wood burning αWB. Most studies use a single αTR and αWB pair in the Aethalometer model, derived from previous work. However, an accurate determination of the source specific α values is currently lacking and in some recent publications the applicability of the Aethalometer model was questioned. Here we present an indirect methodology for the determination of WB and αTR by comparing the source apportionment of BC using the Aethalometer model with 14C measurements of the EC fraction on 16 to 40 h filter samples from several locations and campaigns across Switzerland during 2005–2012, mainly in winter. The data obtained at eight stations with different source characteristics also enabled the evaluation of the performance and the uncertainties of the Aethalometer model in different environments. The best combination of αTR and αWB (0.9 and 1.68, respectively) was obtained by fitting the Aethalometer model outputs (calculated with the absorption coefficients at 470 nm and 950 nm) against the fossil fraction of EC (ECF/EC) derived from 14C measurements. Aethalometer and 14C source apportionment results are well correlated (r = 0.81) and the fitting residuals exhibit only a minor positive bias of 1.6 % and an average precision of 9.3 %. This indicates that the Aethalometer model reproduces reasonably well the 14C results for all stations investigated in this study using our best estimate of a single αWB and αTR pair. Combining the EC, 14C and Aethalometer measurements further allowed assessing the dependence of the mass absorption cross section (MAC) of BC on its source. Results indicate no significant difference in MAC at 880 nm between BC originating from traffic or wood burning emissions. Using ECF/EC as reference and constant a priori selected αTR values, αWB was also calculated for each individual data point. No clear station-to-station or season-to-season differences in αWB were observed, but αTR and αWB values are interdependent. For example, an increase in αTR by 0.1 results in a decrease in αWB by 0.1. The fitting residuals of different αTR and αWB combinations depend on ECF/EC such that a good agreement cannot be obtained over the entire ECF/EC range using other α pairs. Additional combinations of αTR = 0.8, and 1.0 and αWB = 1.8 and 1.6, respectively, are possible but only for ECF/EC between ~ 40 % and 85 %. Applying α values previously used in literature such as αWB of ~ 2 or any αWB in combination with αTR = 1.1 to our data set results in large residuals. Therefore we recommend to use the best α combination as obtained here (αTR = 0.9 and αWB = 1.68) in future studies when no or only limited additional information like 14C measurements are available. However, these results were obtained for locations impacted by BC mainly from traffic consisting of a modern car fleet and residential wood combustion with well-constrained combustion efficiencies. For regions of the world with different combustion conditions, additional BC sources or fuels used further investigations are needed.

scholarly journals A 2.5 year's source apportionment study of black carbon from wood burning and fossil fuel combustion at urban and rural sites in Switzerland

2011 ◽  
Vol 4 (7) ◽  
pp. 1409-1420 ◽  
Author(s):  
H. Herich ◽  
C. Hueglin ◽  
B. Buchmann
Keyword(s):  
Black Carbon ◽  
Source Apportionment ◽  
Cross Sections ◽  
Light Absorption ◽  
Fossil Fuel ◽  
Data Sets ◽  
Near Ultraviolet ◽  
Wood Burning ◽  
Multi Wavelength ◽  
Rural Sites

Abstract. The contributions of fossil fuel (FF) and wood burning (WB) emissions to black carbon (BC) have been investigated in the recent past by analysis of multi-wavelength aethalometer data. This approach utilizes the stronger light absorption of WB aerosols in the near ultraviolet compared to the light absorption of aerosols from FF combustion. Here we present 2.5 years of seven-wavelength aethalometer data from one urban and two rural background sites in Switzerland measured from 2008–2010. The contribution of WB and FF to BC was directly determined from the aerosol absorption coefficients of FF and WB aerosols which were calculated by using confirmed Ångstrom exponents and aerosol light absorption cross-sections that were determined for all sites. Reasonable separation of total BC into contributions from FF and WB was achieved for all sites and seasons. The obtained WB contributions to BC are well correlated with measured concentrations of levoglucosan and potassium while FF contributions to BC correlate nicely with NOx. These findings support our approach and show that the applied source apportionment of BC is well applicable for long-term data sets. During winter, we found that BC from WB contributes on average 24–33 % to total BC at the considered measurement sites. This is a noticeable high fraction as the contribution of wood burning to the total final energy consumption is in Switzerland less than 4 %.

scholarly journals The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

2015 ◽  
Vol 8 (5) ◽  
pp. 1965-1979 ◽  
Author(s):  
L. Drinovec ◽  
G. Močnik ◽  
P. Zotter ◽  
A. S. H. Prévôt ◽  
C. Ruckstuhl ◽  
...  
Keyword(s):  
Real Time ◽  
Black Carbon ◽  
Source Apportionment ◽  
Accurate Determination ◽  
Optical Measurements ◽  
Quality Data ◽  
Loading Effect ◽  
Adverse Health Effects ◽  
Compensation Algorithm

Abstract. Aerosol black carbon is a unique primary tracer for combustion emissions. It affects the optical properties of the atmosphere and is recognized as the second most important anthropogenic forcing agent for climate change. It is the primary tracer for adverse health effects caused by air pollution. For the accurate determination of mass equivalent black carbon concentrations in the air and for source apportionment of the concentrations, optical measurements by filter-based absorption photometers must take into account the "filter loading effect". We present a new real-time loading effect compensation algorithm based on a two parallel spot measurement of optical absorption. This algorithm has been incorporated into the new Aethalometer model AE33. Intercomparison studies show excellent reproducibility of the AE33 measurements and very good agreement with post-processed data obtained using earlier Aethalometer models and other filter-based absorption photometers. The real-time loading effect compensation algorithm provides the high-quality data necessary for real-time source apportionment and for determination of the temporal variation of the compensation parameter k.

scholarly journals The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

2014 ◽  
Vol 7 (9) ◽  
pp. 10179-10220 ◽  
Author(s):  
L. Drinovec ◽  
G. Močnik ◽  
P. Zotter ◽  
A. S. H. Prévôt ◽  
C. Ruckstuhl ◽  
...  
Keyword(s):  
Real Time ◽  
Black Carbon ◽  
Source Apportionment ◽  
Accurate Determination ◽  
Optical Measurements ◽  
Quality Data ◽  
Loading Effect ◽  
Adverse Health Effects ◽  
Compensation Algorithm

Abstract. Aerosol black carbon is a unique primary tracer for combustion emissions. It affects the optical properties of the atmosphere and is recognized as the second most important anthropogenic forcing agent for climate change. It is the primary tracer for adverse health effects caused by air pollution. For the accurate determination of mass equivalent black carbon concentrations in the air and for source apportionment of the concentrations, optical measurements by filter-based absorption photometers must take into account the "filter loading effect". We present a new real-time loading effect compensation algorithm based on a two parallel spot measurement of optical absorption. This algorithm has been incorporated into the new Aethalometer model AE33. Intercomparison studies show excellent reproducibility of the AE33 measurements and very good agreement with post-processed data obtained using earlier Aethalometer models, and other filter-based absorption photometers. The real-time loading effect compensation algorithm provides the high-quality data necessary for real-time source apportionment, and for determination of the temporal variation of the compensation parameter k.

scholarly journals A two year's source apportionment study of wood burning and traffic aerosols for urban and rural sites in Switzerland

2010 ◽  
Vol 3 (6) ◽  
pp. 5313-5342 ◽  
Author(s):  
H. Herich ◽  
C. Hueglin ◽  
B. Buchmann
Keyword(s):  
Source Apportionment ◽  
Cross Sections ◽  
Light Absorption ◽  
Data Sets ◽  
Near Ultraviolet ◽  
Wood Burning ◽  
Multi Wavelength ◽  
High Fraction ◽  
Final Energy Consumption ◽  
Rural Sites

Abstract. The contributions of fossil fuel (FF) and wood burning (WB) emissions to black carbon (BC) have been investigated in the past by analysis of multi-wavelength aethalometer data. This approach utilize the stronger light absorption of WB aerosols in the near ultraviolet compared to the light absorption of aerosols from FF combustion. Here we present two years of seven-wavelength aethalometer data from one urban and two rural background sites in Switzerland measured from 2008–2010. The contribution of WB and FF to BC was directly determined from the absorption coefficients of FF and WB aerosols which were calculated by using confirmed absorption exponents and aerosol light absorption cross-sections that were determined for all sites. Reasonable separation of total BC into contributions from FF and WB was achieved for all sites and seasons. The obtained WB contributions to BC are well correlated with measured concentrations of levoglucosan and potassium while FF contributions to BC correlate nicely with NOx. These findings support our approach and show that the applied source apportionment of BC is well applicable for long-term data sets. During winter, we found that BC from WB contributes on average 24–29% to total BC at the considered measurement sites. This is a noticeable high fraction as the contribution of wood burning to the total final energy consumption is in Switzerland less than 4%.

scholarly journals Wintertime aerosol chemical composition and source apportionment of the organic fraction in the metropolitan area of Paris

2013 ◽  
Vol 13 (2) ◽  
pp. 961-981 ◽  
Author(s):  
M. Crippa ◽  
P. F. DeCarlo ◽  
J. G. Slowik ◽  
C. Mohr ◽  
M. F. Heringa ◽  
...  
Keyword(s):  
Black Carbon ◽  
Source Apportionment ◽  
Metropolitan Area ◽  
Organic Fraction ◽  
Organic Mass ◽  
Aerosol Composition ◽  
Mass Spectrometers ◽  
Particulate Pollution ◽  
Aerosol Mass ◽  
Wood Burning

Abstract. The effect of a post-industrial megacity on local and regional air quality was assessed via a month-long field measurement campaign in the Paris metropolitan area during winter 2010. Here we present source apportionment results from three aerosol mass spectrometers and two aethalometers deployed at three measurement stations within the Paris region. Submicron aerosol composition is dominated by the organic fraction (30–36%) and nitrate (28–29%), with lower contributions from sulfate (14–16%), ammonium (12–14%) and black carbon (7–13%). Organic source apportionment was performed using positive matrix factorization, resulting in a set of organic factors corresponding both to primary emission sources and secondary production. The dominant primary sources are traffic (11–15% of organic mass), biomass burning (13–15%) and cooking (up to 35% during meal hours). Secondary organic aerosol contributes more than 50% to the total organic mass and includes a highly oxidized factor from indeterminate and/or diverse sources and a less oxidized factor related to wood burning emissions. Black carbon was apportioned to traffic and wood burning sources using a model based on wavelength-dependent light absorption of these two combustion sources. The time series of organic and black carbon factors from related sources were strongly correlated. The similarities in aerosol composition, total mass and temporal variation between the three sites suggest that particulate pollution in Paris is dominated by regional factors, and that the emissions from Paris itself have a relatively low impact on its surroundings.

scholarly journals Sources and contributions of wood smoke during winter in London: assessing local and regional influences

2014 ◽  
Vol 14 (19) ◽  
pp. 27459-27530 ◽  
Author(s):  
L. R. Crilley ◽  
W. J. Bloss ◽  
J. Yin ◽  
D. C. S. Beddows ◽  
R. M. Harrison ◽  
...  
Keyword(s):  
Black Carbon ◽  
Source Apportionment ◽  
Biomass Burning ◽  
Traffic Emissions ◽  
Total Carbon ◽  
Local Source ◽  
Wood Smoke ◽  
Biomass Smoke ◽  
Domestic Heating ◽  
Wood Burning

Abstract. Determining the contribution of wood smoke to air pollution in large cities such as London is becoming increasingly important due to the changing nature of domestic heating in urban areas. During winter, biomass burning emissions can exceed the contributions from traffic emissions, and have been identified as a major cause of exceedences of European air quality limits. The aim of this work was to quantify the contribution of biomass burning in London to concentrations of PM2.5 and determine whether local emissions or regional contributions were the main source of biomass smoke. To achieve this, a number of biomass burning chemical tracers were analysed at a site within central London and two sites in surrounding rural areas. Concentrations of levoglucosan, elemental carbon (EC), organic carbon (OC) and K+ were generally well correlated across the three sites. At all the sites, biomass burning was found to be a source of OC and EC, with the largest contribution of EC from traffic emissions, while for OC the dominant fraction likely included contributions from secondary organic aerosols, primary biogenic and cooking sources. Source apportionment of the EC and OC using average source ratios from published data was found to give reasonable estimation of the total carbon from non-fossil and fossil fuel sources based upon comparison with estimates derived from 14C analysis. Black carbon (BC) data from 2 and 7 wavelength Aethalometers were also apportioned into the contributions from biomass burning and traffic, based upon the enhanced absorption of wood smoke at UV wavelengths compared to BC. While the source apportionment of BC using this approach found similar trends to that observed for EC, higher percentage contributions of wood burning to BC were estimated. Based on a wood smoke mass conversion factor for levoglucosan, mean wood smoke mass at the sites was found to range from 0.78–1.0 μg m−3 during the campaign in January–February 2012. Measurements on a 160 m tower in London suggested a similar ratio of brown to black carbon (reflecting wood burning and traffic respectively) in regional and London air. Peaks in the levoglucosan and K+ concentrations were observed to coincide with low ambient temperature, consistent with domestic heating as a major contributing local source in London. Overall, the source of biomass smoke in London was concluded to be a background regional source overlaid by contributions from local domestic burning emissions. This could have implications when considering future emission control strategies during winter and may be the focus of future work in order to better determine the contributing local sources.

Long-term observations of the strongest inflow branch of warm water to the Arctic Mediterranean

2020 ◽  
Author(s):  
Bogi Hansen ◽  
Karin M. H. Larsen ◽  
Hjálmar Hátún ◽  
Svein Østerhus
Keyword(s):  
Satellite Altimetry ◽  
Saline Water ◽  
Accurate Determination ◽  
Volume Transport ◽  
High Accuracy ◽  
The Arctic ◽  
Boundary Current ◽  
Data Set

<p>Warm and saline water from the North Atlantic enters the Arctic Mediterranean through three gaps. The strongest of these three flows is the inflow between Iceland and Faroes, which is focused into a narrow boundary current north of the Faroes. This boundary current, the Faroe Current, has been observed with regular CTD cruises since 1988 and with moored ADCPs since 1997, as well as satellite altimetry since 1993. Once calibrated by the long-term ADCP measurements, the satellite altimetry is found to yield high-accuracy determination of the velocity field and volume transport down to fixed depth. Due to geostrophic adjustment, satellite altimetry combined with CTD data also allow fairly accurate determination of the depth of the Atlantic layer. From the combined data set, monthly transport time series have been generated for the period Jan 1993 to April 2019. Over the period, the annually averaged volume transport of Atlantic water in the Faroe Current seems to have increased slightly, while the heat transport relative to an outflow temperature of 0°C increased by 13%, significant at the 95% level. The salinity increased from the mid-1990s to around 2010, after which it has decreased, especially after 2016, leading to the lowest salinities in the whole period since 1988. To stay updated on a possible inflow reduction due to reduced thermohaline ventilation caused by this freshening, the future monitoring system of the Faroe Current is planned to be expanded with moored PIES (Pressure Inverted Echo Sounders). An experiment with two PIES in 2017-2019 has documented that these instruments allow high-accuracy monitoring of the depth of the Atlantic layer on the section, which combined with satellite altimetry and CTD observations should give more accurate transport estimates.</p>

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