scholarly journals Carbonaceous aerosols contributed by traffic and solid fuel burning at a polluted rural site in Northwestern England

2011 ◽  
Vol 11 (4) ◽  
pp. 1603-1619 ◽  
Author(s):  
D. Liu ◽  
J. Allan ◽  
B. Corris ◽  
M. Flynn ◽  
E. Andrews ◽  
...  
Keyword(s):  
Solid Fuel ◽  
Mass Fraction ◽  
Organic Aerosol ◽  
Radiative Properties ◽  
Rural Site ◽  
Specific Information ◽  
Carbonaceous Aerosols ◽  
Traffic Emission ◽  
Aerosol Mass ◽  
Fuel Burning

Abstract. The experiment presented in this paper was conducted at the Holme Moss site, which is located in the southern Pennines region in Northwestern England during November–December 2006. The strong southwesterly wind during the experimental period, which enhanced the transport of urban pollutants from the conurbations of Greater Manchester and Liverpool, in addition to the seasonally increased nearby residential heating activities, made this site a receptor for pollutants from a range of sources. A factor analysis is applied to the mass spectra of organic matter (OM) measured by the Aerodyne Aerosol Mass Spectrometer (AMS) to attribute the pollutant sources. Besides the oxygenated organic aerosol (OOA), this site was found to contain a considerable fraction of primary organic aerosols (POA, mass fraction 50–70% within total mass of OM). The POA sources are attributed to be traffic emission and solid fuel burning, which are identified as hydrocarbon-like organic aerosol (HOA) and solid fuel organic aerosol (SFOA) respectively. There were strongly combined emissions of black carbon (BC) particles from both sources. The refractory BC component (rBC) was characterized by a single particle soot photometer. This site began to be influenced during the late morning by fresh traffic emissions, whereas solid fuel burning became dominant from late afternoon until night. A covariance analysis of rBC and POA was used to derive source specific emission factors of 1.61 μgHOA/μgrBC and 1.96 μgHOA/μgrBC. The absorbing properties of aerosols were characterized at multiple wavelengths (λ), and a stronger spectral dependence of absorption was observed when this site was significantly influenced by solid fuel burning. The rBC was estimated to contribute 3–16% of submicron aerosol mass. The single scattering albedo at λ = 700 nm (SSA700 nm) was significantly anti-correlated with the rBC mass fraction, but also associated with the BC mixing state. The BC incorporation/removal process therefore may play a role in modulating the radiative properties of aerosols at the site under the influence of fresh sources. Given that traffic and residential combustion of solid fuels are significant contributors of carbonaceous aerosols over Europe, these results provide important source-specific information on modeling the anthropogenic carbonaceous aerosols.

scholarly journals Carbonaceous aerosols contributed by traffic and solid fuel burning at a polluted rural site in Northwestern England

2010 ◽  
Vol 10 (10) ◽  
pp. 25243-25286
Author(s):  
D. Liu ◽  
J. Allan ◽  
B. Corris ◽  
M. Flynn ◽  
E. Andrews ◽  
...  
Keyword(s):  
Solid Fuel ◽  
Mass Fraction ◽  
Organic Aerosol ◽  
Radiative Properties ◽  
Rural Site ◽  
Specific Information ◽  
Carbonaceous Aerosols ◽  
Traffic Emission ◽  
Aerosol Mass ◽  
Fuel Burning

Abstract. The experiment presented in this paper was conducted at the Holme Moss site, which is located in the southern Pennines region in Northwestern England during November–December 2006. The strong southwesterly wind during the experimental period, which enhanced the transport of urban pollutants from the conurbations of Greater Manchester and Liverpool, in addition to the seasonally increased nearby residential heating activities, made this site a receptor for pollutants from a range of sources. A factor analysis is applied to the mass spectra of organic matter (OM) measured by the Aerodyne Aerosol Mass Spectrometer (AMS) to attribute the pollutant sources. Besides the oxygenated organic aerosol (OOA), this site was found to contain a considerable fraction of primary organic aerosols (POA, mass fraction 50–70% within total mass of OM), which are source attributed as traffic emission and solid fuel burning, and are identified as hydrocarbon-like organic aerosol (HOA) and solid fuel organic aerosol (SFOA) respectively. There were strongly combined emissions of black carbon (BC) particles from both sources, as the refractory BC component (rBC) was characterized by the single particle soot photometer. This site began to be influenced during the late morning by fresh traffic emissions, whereas solid fuel burning became dominant from late afternoon until night. A covariance analysis of rBC and POA was used to derive source specific emission factors of 1.61 μgHOA/μgrBC and 1.96 μgSFOA/μgrBC. The absorbing properties of aerosols were characterized at multiple wavelengths (λ), and a stronger spectral dependence of absorption was observed when this site was significantly influenced by solid fuel burning. The rBC was estimated to contribute 3–16% of submicron aerosol mass. The single scattering albedo at λ=550 nm (SSA550 nm) was significantly anti-correlated with the rBC mass fraction, but also associated with the BC mixing state. The BC incorporation/removal process therefore plays an important role on modulating the radiative properties of aerosols at the site under the influence of fresh sources. Given that traffic and residential combustion of solid fuels are significant contributors of carbonaceous aerosols over Europe, these results provide important source-specific information on modeling the anthropogenic carbonaceous aerosols.

scholarly journals On the use of reference mass spectra for reducing uncertainty in source apportionment of solid-fuel burning in ambient organic aerosol

2021 ◽  
Vol 14 (10) ◽  
pp. 6905-6916
Author(s):  
Chunshui Lin ◽  
Darius Ceburnis ◽  
Anna Trubetskaya ◽  
Wei Xu ◽  
William Smith ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Solid Fuel ◽  
Mass Spectra ◽  
Organic Aerosol ◽  
Solid Fuels ◽  
Winter Period ◽  
Aerosol Mass ◽  
Eu Directive ◽  
A Value ◽  
Fuel Burning

Abstract. Reference mass spectra are routinely used to facilitate source apportionment of ambient organic aerosol (OA) measured by aerosol mass spectrometers. However, source apportionment of solid-fuel-burning emissions can be complicated by the use of different fuels, stoves, and burning conditions. In this study, the organic aerosol mass spectra produced from burning a range of solid fuels in several heating stoves have been compared using an aerosol chemical speciation monitor (ACSM). The same samples of biomass briquettes and smokeless coal were burnt in a conventional stove and Ecodesign stove (Ecodesign refers to a stove conforming to EU Directive 2009/125/EC), while different batches of wood, peat, and smoky coal were also burnt in the conventional stove, and the OA mass spectra were compared to those previously obtained using a boiler stove. The results show that although certain ions (e.g., m/z 60) remain important markers for solid-fuel burning, the peak intensities obtained at specific m/z values in the normalized mass spectra were not constant with variations ranging from < 5 % to > 100 %. Using the OA mass spectra of peat, wood, and coal as anchoring profiles and the variation of individual m/z values for the upper/lower limits (the limits approach) in the positive matrix factorization (PMF) analysis with the Multilinear Engine algorithm (ME-2), the respective contributions of these fuels to ambient submicron aerosols during a winter period in Dublin, Ireland, were evaluated and compared with the conventional a-value approach. The ME-2 solution was stable for the limits approach with uncertainties in the range of 2 %–7 %, while relatively large uncertainties (8 %–29 %) were found for the a-value approach. Nevertheless, both approaches showed good agreement overall, with the burning of peat (39 % vs. 41 %) and wood (14 % vs. 11 %) accounting for the majority of ambient organic aerosol during polluted evenings, despite their small uses compared to electricity and gas. This study, thus, accounts for the source variability in ME-2 modelling and provides better constraints on the primary factor contributions to the ambient organic aerosol estimations. The finding from this study has significant implications for public health and policymakers considering that it is often the case that different batches of solid fuels are often burnt in different stoves in real-world applications.

scholarly journals On the use of reference mass spectra for reducing uncertainty in source apportionment of solid fuel burning in ambient organic aerosol

2021 ◽  
Author(s):  
Chunshui Lin ◽  
Darius Ceburnis ◽  
Anna Trubetskaya ◽  
Wei Xu ◽  
William Smith ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Solid Fuel ◽  
Mass Spectra ◽  
Organic Aerosol ◽  
Solid Fuels ◽  
Winter Period ◽  
Aerosol Mass ◽  
A Value ◽  
Fuel Burning ◽  
Smoky Coal

Abstract. Reference mass spectra are routinely used to facilitate source apportionment of ambient organic aerosol (OA) measured by an aerosol chemical speciation monitor (ACSM). However. source apportionment of solid fuel burning emissions can be complicated by the use of different fuels, stoves and burning conditions. In this study, the organic aerosol mass spectra produced from burning a range of solid fuels in several stoves have been compared using an ACSM. The same samples of biomass briquettes and smokeless coal were burnt in a conventional and Ecodesign stove, while different batches of wood, peat, and smoky coal were also burnt in the conventional stove and the OA mass spectra compared to those previously obtained using a boiler stove. The results shows that although certain ions (e.g., m/z 60) remain important markers for solid fuel burning, the peak intensities obtained at specific m/z values were not constant with variations ranging from <5% to >100 %. Using the OA mass spectra of peat, wood and coal as anchoring profiles and the variation of individual m/z values for the upper/lower limits in ME-2 analysis (the limits approach), the respective contributions of these fuels to ambient sub-micron aerosols during a winter period in Dublin were evaluated and compared with the conventional a value approach. The ME-2 solution was stable for the limits approach with uncertainties in the range of 2–7 %, while relatively large uncertainties (8–29 %) were found for the a value approach. Nevertheless, both approaches showed good agreement overall, with the burning of peat (39 % vs 41 %) and wood (14 % vs 11 %) accounting for the majority of ambient organic aerosol during polluted evenings, despite their small uses. This study, thus, accounts for the source variability in ME-2 modelling and provides better constraints on the primary factor contributions to the ambient organic aerosol estimations. The finding from this study has significant implications for public health and policymakers considering that it is often the case that different batches of solid fuels are often burned in different stoves in real-world applications.

scholarly journals Wintertime aerosol chemical composition, volatility, and spatial variability in the greater London area

2016 ◽  
Vol 16 (2) ◽  
pp. 1139-1160 ◽  
Author(s):  
L. Xu ◽  
L. R. Williams ◽  
D. E. Young ◽  
J. D. Allan ◽  
H. Coe ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Solid Fuel ◽  
Field Studies ◽  
Rural Site ◽  
Urban Site ◽  
High Temporal Resolution ◽  
Volatile Organics ◽  
Aerosol Mass ◽  
Rural And Urban ◽  
Wide Range

Abstract. The composition of PM1 (particulate matter with diameter less than 1 µm) in the greater London area was characterized during the Clean Air for London (ClearfLo) project in winter 2012. Two high-resolution time-of-flight aerosol mass spectrometers (HR-ToF-AMS) were deployed at a rural site (Detling, Kent) and an urban site (North Kensington, London). The simultaneous and high-temporal resolution measurements at the two sites provide a unique opportunity to investigate the spatial distribution of PM1. We find that the organic aerosol (OA) concentration is comparable between the rural and urban sites, but the contribution from different sources is distinctly different between the two sites. The concentration of solid fuel OA at the urban site is about twice as high as at the rural site, due to elevated domestic heating in the urban area. While the concentrations of oxygenated OA (OOA) are well-correlated between the two sites, the OOA concentration at the rural site is almost twice that of the urban site. At the rural site, more than 70 % of the carbon in OOA is estimated to be non-fossil, which suggests that OOA is likely related to aged biomass burning considering the small amount of biogenic SOA in winter. Thus, it is possible that the biomass burning OA contributes a larger fraction of ambient OA in wintertime than what previous field studies have suggested. A suite of instruments was deployed downstream of a thermal denuder (TD) to investigate the volatility of PM1 species at the rural Detling site. After heating at 250 °C in the TD, 40 % of the residual mass is OA, indicating the presence of non-volatile organics in the aerosol. Although the OA associated with refractory black carbon (rBC; measured by a soot-particle aerosol mass spectrometer) only accounts for < 10 % of the total OA (measured by a HR-ToF-AMS) at 250 °C, the two measurements are well-correlated, suggesting that the non-volatile organics have similar sources or have undergone similar chemical processing as rBC in the atmosphere. Although the atomic O : C ratio of OOA is substantially larger than that of solid fuel OA and hydrocarbon-like OA, these three factors have similar volatility, which is inferred from the change in mass concentration after heating at 120 °C. Finally, we discuss the relationship between the mass fraction remaining (MFR) of OA after heating in the TD and atomic O : C of OA and find that particles with a wide range of O : C could have similar MFR after heating. This analysis emphasizes the importance of understanding the distribution of volatility and O : C in bulk OA.

scholarly journals Combined effects of boundary layer dynamics and atmospheric chemistry on aerosol composition during new particle formation periods

2018 ◽  
Author(s):  
Liqing Hao ◽  
Olga Garmash ◽  
Mikael Ehn ◽  
Pasi Miettinen ◽  
Paola Massoli ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Atmospheric Chemistry ◽  
Mass Fraction ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Sulfate Aerosol ◽  
Organic Mass ◽  
Night Time ◽  
Aerosol Mass

Abstract. Characterizing aerosol chemical composition in response to meteorological changes and atmospheric chemistry is important to gain insights into new particle formation mechanisms. A BAECC (Biogenic Aerosols-Effects on Clouds and Climate) campaign was conducted during the spring 2014 at SMEAR II station (Station for Measuring Forest Ecosystem-Aerosol Relations) in Finland. The particles were characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A PBL (planetary boundary layer) dilution model was developed to assist interpreting the measurement results. Right before nucleation events, the mass concentrations of organic and sulfate aerosol species were both decreased rapidly along with the growth of PBL heights. However, the mass fraction of sulfate aerosol of the total aerosol mass was increased, in contrast to a decrease for the organic mass fraction. Meanwhile, an increase of LVOOA (low-volatility oxygenated organic aerosol) mass fraction of the total organic mass was observed, in distinct comparison to a reduction of SVOOA (semi-volatile OOA) mass fraction. Our results demonstrate that, at the beginning of nucleation events, the observed sulfate aerosol mass was mainly driven by vertical turbulent mixing of sulfate-rich aerosols between the residual layer and the newly formed boundary layer, while the condensation of sulfuric acid played a minor role in interpreting the measured sulfate mass concentration. For the measured organic aerosols, their temporal profiles were mainly driven by dilution from PBL development, organic aerosol mixing in different boundary layers and/or condensation of organic vapors, but accurate measurements of organic vapor concentrations and characterization on the spatial aerosol chemical composition are required. In general, the observed aerosol particles by AMS are subjected to joint effects of PBL dilution, atmospheric chemistry and aerosol mixing in different boundary layers. During aerosol growth periods in the night time, the mass concentrations of organic aerosols and organic nitrate aerosols were both increased. The increase of SVOOA mass correlated well with the calculated increase of condensed HOMs (highly oxygenated organic molecules) mass. To our knowledge, our results are the first atmospheric observations showing a connection between increase in SVOOA and condensed HOMs during the night time.

scholarly journals Organic aerosol volatility and viscosity in North China Plain: Contrast between summer and winter

2020 ◽  
Author(s):  
Weiqi Xu ◽  
Chun Chen ◽  
Yanmei Qiu ◽  
Ying Li ◽  
Zhiqiang Zhang ◽  
...  
Keyword(s):  
Coal Combustion ◽  
North China Plain ◽  
North China ◽  
Organic Aerosol ◽  
Rural Site ◽  
Urban Site ◽  
Aerosol Mass ◽  
Effective Saturation ◽  
Formation And Evolution ◽  
Primary Emissions

Abstract. Volatility and viscosity have substantial impacts on gas-particle partitioning, formation and evolution of aerosol, and hence the predictions of aerosol related air quality and climate effects. Here aerosol volatility and viscosity at a rural site (Gucheng) and an urban site (Beijing) in North China Plain (NCP) in summer and winter were investigated by using a thermodenuder coupled with high resolution aerosol mass spectrometer. The effective saturation concentration (C*) of organic aerosol (OA) in summer was smaller than that in winter (0.55 μg m−3 vs. 0.71–0.75 μg m−3), indicating that OA in winter in NCP is more volatile due to enhanced primary emissions from coal combustion and biomass burning. The volatility distributions varied largely different among different OA factors. In particular, we found that hydrocarbon-like OA (HOA) contained more non-volatile compounds compared to coal combustion related OA. The more oxidized oxygenated OA (MO-OOA) showed overall lower volatility than less oxidized OOA (LO-OOA) in both summer and winter, yet the volatility of MO-OOA was found to be relative humidity (RH) dependent showing more volatile properties at higher RH. Our results demonstrated the different composition and chemical formation pathways of MO-OOA under different RH levels. The glass transition temperature (Tg) and viscosity of OA in summer and winter are estimated using the recently developed parameterization formula. Our results showed that the Tg of OA in summer in Beijing (291.5 K) was higher than that in winter (289.7–290.0 K), while it varied greatly among different OA factors. The viscosity suggested that OA existed mainly as solid in winter in Beijing, but as semi-solids in Beijing in summer and Gucheng in winter. These results have important implications that kinetically limited gas-particle partitioning may need to be considered when simulating secondary OA formation in NCP.

scholarly journals Photochemical processing of organic aerosol at nearby continental sites: contrast between urban plumes and regional aerosol

2011 ◽  
Vol 11 (6) ◽  
pp. 2991-3006 ◽  
Author(s):  
J. G. Slowik ◽  
J. Brook ◽  
R. Y.-W. Chang ◽  
G. J. Evans ◽  
K. Hayden ◽  
...  
Keyword(s):  
Organic Aerosol ◽  
Rural Site ◽  
Reaction Products ◽  
Mass Spectrometers ◽  
Mass Spectral ◽  
Rural Agriculture ◽  
Aerosol Mass ◽  
Atmospheric Processing ◽  
Show Evidence ◽  
Bear Creek

Abstract. As part of the BAQS-Met 2007 field campaign, Aerodyne time-of-flight aerosol mass spectrometers (ToF-AMS) were deployed at two sites in southwestern Ontario from 17 June to 11 July 2007. One instrument was located at Harrow, ON, a rural, agriculture-dominated area approximately 40 km southeast of the Detroit/Windsor/Windsor urban area and 5 km north of Lake Erie. The second instrument was located at Bear Creek, ON, a rural site approximately 70 km northeast of the Harrow site and 50 km east of Detroit/Windsor. Positive matrix factorization analysis of the combined organic mass spectral dataset yields factors related to secondary organic aerosol (SOA), direct emissions, and a factor tentatively attributed to the reactive uptake of isoprene and/or condensation of its early generation reaction products. This is the first application of PMF to simultaneous AMS measurements at different sites, an approach which allows for self-consistent, direct comparison of the datasets. Case studies are utilized to investigate processing of SOA from (1) fresh emissions from Detroit/Windsor and (2) regional aerosol during periods of inter-site flow. A strong correlation is observed between SOA/excess CO and photochemical age as represented by the NOx/NOy ratio for Detroit/Windsor outflow. Although this correlation is not evident for more aged air, measurements at the two sites during inter-site transport nevertheless show evidence of continued atmospheric processing by SOA production. However, the rate of SOA production decreases with airmass age from an initial value of ~10.1 μg m−3 ppmvCO−1 h−1 for the first ~10 h of plume processing to near-zero in an aged airmass (i.e. after several days). The initial SOA production rate is comparable to the observed rate in Mexico City over similar timescales.

scholarly journals Wintertime aerosol optical and radiative properties in the Kathmandu Valley during the SusKat-ABC field campaign

2017 ◽  
Vol 17 (20) ◽  
pp. 12617-12632 ◽  
Author(s):  
Chaeyoon Cho ◽  
Sang-Woo Kim ◽  
Maheswar Rupakheti ◽  
Jin-Soo Park ◽  
Arnico Panday ◽  
...  
Keyword(s):  
Black Carbon ◽  
Urban Areas ◽  
Regional Scale ◽  
Temperature Drop ◽  
Absorption Efficiency ◽  
Radiative Properties ◽  
Kathmandu Valley ◽  
Carbonaceous Aerosols ◽  
Brick Kilns ◽  
Aerosol Mass

Abstract. Particulate air pollution in the Kathmandu Valley has reached severe levels that are mainly due to uncontrolled emissions and the location of the urban area in a bowl-shaped basin with associated local wind circulations. The AERONET measurements from December 2012 to August 2014 revealed a mean aerosol optical depth (AOD) of approximately 0.30 at 675 nm during winter, which is similar to that of the post-monsoon but half of that of the pre-monsoon AOD (0.63). The distinct seasonal variations are closely related to regional-scale monsoon circulations over South Asia and emissions in the Kathmandu Valley. During the SusKat-ABC campaign (December 2012–February 2013), a noticeable increase in both aerosol scattering (σs; 313  →  577 Mm−1 at 550 nm) and absorption (σa; 98  →  145 Mm−1 at 520 nm) coefficients occurred before and after 4 January 2013. This can be attributed to the increase in wood-burned fires due to a temperature drop and the start of firing at nearby brick kilns. The σs value in the Kathmandu Valley was a factor of 0.5 lower than that in polluted cities in India. The σa value in the Kathmandu Valley was approximately 2 times higher than that at severely polluted urban sites in India. The aerosol mass scattering efficiency of 2.6 m2 g−1 from PM10 measurements in the Kathmandu Valley is similar to that reported in urban areas. However, the aerosol mass absorption efficiency was determined to be 11 m2 g−1 from PM10 measurements, which is higher than that reported in the literature for pure soot particles (7.5 ± 1.2 m2 g−1). This might be due to the fact that most of the carbonaceous aerosols in the Kathmandu Valley were thought to be mostly externally mixed with other aerosols under dry conditions due to a short travel time from their sources. The σs and σa values and the equivalent black carbon (EBC) mass concentration reached up to 757 Mm−1, 224 Mm−1, and 29 µg m−3 at 08:00 LST (local standard time), respectively but decreased dramatically during the daytime (09:00–18:00 LST), to one-quarter of the morning average (06:00–09:00 LST) due to the development of valley winds and an atmospheric bounder layer. The σs and σa values and the EBC concentration remained almost constant during the night at the levels of 410 Mm−1, 130 Mm−1, and 17 µg m−3, respectively. The average aerosol direct radiative forcings over the intensive measurement period were estimated to be −6.9 ± 1.4 W m−2 (top of the atmosphere) and −20.8 ± 4.6 W m−2 (surface). Therefore, the high atmospheric forcing (i.e., 13.9 ± 3.6 W m−2) and forcing efficiency (74.8 ± 24.2 W m−2 τ−1) can be attributed to the high portion of light-absorbing aerosols in the Kathmandu Valley, as indicated by the high black carbon (or elemental carbon) to sulphate ratio (1.5 ± 1.1).

scholarly journals Hygroscopic properties of smoke-generated organic aerosol particles emitted in the marine atmosphere

2013 ◽  
Vol 13 (19) ◽  
pp. 9819-9835 ◽  
Author(s):  
A. Wonaschütz ◽  
M. Coggon ◽  
A. Sorooshian ◽  
R. Modini ◽  
A. A. Frossard ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Marine Atmosphere ◽  
Hygroscopic Growth ◽  
Organic Mass ◽  
Aerosol Mass ◽  
Hygroscopic Properties ◽  
Mass Fractions

Abstract. During the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE), a plume of organic aerosol was produced by a smoke generator and emitted into the marine atmosphere from aboard the R/V Point Sur. In this study, the hygroscopic properties and the chemical composition of the plume were studied at plume ages between 0 and 4 h in different meteorological conditions. In sunny conditions, the plume particles had very low hygroscopic growth factors (GFs): between 1.05 and 1.09 for 30 nm and between 1.02 and 1.1 for 150 nm dry size at a relative humidity (RH) of 92%, contrasted by an average marine background GF of 1.6. New particles were produced in large quantities (several 10 000 cm−3), which lead to substantially increased cloud condensation nuclei (CCN) concentrations at supersaturations between 0.07 and 0.88%. Ratios of oxygen to carbon (O : C) and water-soluble organic mass (WSOM) increased with plume age: from < 0.001 to 0.2, and from 2.42 to 4.96 μg m−3, respectively, while organic mass fractions decreased slightly (~ 0.97 to ~ 0.94). High-resolution aerosol mass spectrometer (AMS) spectra show that the organic fragment m/z 43 was dominated by C2H3O+ in the small, new particle mode and by C3H7+ in the large particle mode. In the marine background aerosol, GFs for 150 nm particles at 40% RH were found to be enhanced at higher organic mass fractions: an average GF of 1.06 was observed for aerosols with an organic mass fraction of 0.53, and a GF of 1.04 for an organic mass fraction of 0.35.

scholarly journals Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests

2010 ◽  
Vol 10 (6) ◽  
pp. 2825-2845 ◽  
Author(s):  
J. G. Slowik ◽  
C. Stroud ◽  
J. W. Bottenheim ◽  
P. C. Brickell ◽  
R. Y.-W. Chang ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Cloud Condensation Nuclei ◽  
Coniferous Forest ◽  
Organic Aerosol ◽  
Chemical Mechanism ◽  
Rural Site ◽  
Chemical Transport Model ◽  
Aerosol Composition ◽  
Aerosol Mass

Abstract. Measurements of aerosol composition, volatile organic compounds, and CO are used to determine biogenic secondary organic aerosol (SOA) concentrations at a rural site 70 km north of Toronto. These biogenic SOA levels are many times higher than past observations and occur during a period of increasing temperatures and outflow from Northern Ontario and Quebec forests in early summer. A regional chemical transport model approximately predicts the event timing and accurately predicts the aerosol loading, identifying the precursors as monoterpene emissions from the coniferous forest. The agreement between the measured and modeled biogenic aerosol concentrations contrasts with model underpredictions for polluted regions. Correlations of the oxygenated organic aerosol mass with tracers such as CO support a secondary aerosol source and distinguish biogenic, pollution, and biomass burning periods during the field campaign. Using the Master Chemical Mechanism, it is shown that the levels of CO observed during the biogenic event are consistent with a photochemical source arising from monoterpene oxidation. The biogenic aerosol mass correlates with satellite measurements of regional aerosol optical depth, indicating that the event extends across the eastern Canadian forest. This regional event correlates with increased temperatures, indicating that temperature-dependent forest emissions can significantly affect climate through enhanced direct optical scattering and higher cloud condensation nuclei numbers.

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