scholarly journals Impact of model grid spacing on regional- and urban-scale air quality predictions of organic aerosol

2010 ◽  
Vol 10 (12) ◽  
pp. 30347-30379 ◽  
Author(s):  
C. A. Stroud ◽  
P. A. Makar ◽  
M. D. Moran ◽  
W. Gong ◽  
S. Gong ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Secondary Organic Aerosol ◽  
Chemical Transport ◽  
Organic Aerosol ◽  
Great Lakes Region ◽  
Grid Spacing ◽  
Aerosol Composition ◽  
Resolution Model ◽  
Bear Creek

Abstract. Regional-scale chemical transport model predictions of urban organic aerosol to date tend to be biased low relative to observations, a limitation with important implications for applying such models to human exposure health studies. We used a nested version of Environment Canada's AURAMS model (42-to-15-to-2.5 km nested grid spacing) to predict organic aerosol concentrations for a temporal and spatial domain corresponding to the Border Air Quality and Meteorology Study (BAQS-Met), an air-quality field study that took place in the southern Great Lakes region in the summer of 2007. The use of three different horizontal grid spacings allowed the influence of this parameter to be examined. A domain-wide average for the 2.5 km domain and a matching 15 km subdomain yielded very similar organic aerosol averages (4.8 vs. 4.3 μg m−3, respectively). On regional scales, secondary organic aerosol dominated the organic aerosol composition and was adequately resolved by the 15 km model simulation. However, the shape of the organic aerosol concentration histogram for the Windsor urban station improved for the 2.5 km simulation relative to those from the 42 and 15 km simulations. The model histograms for the Bear Creek and Harrow rural stations were also improved in the high concentration "tail" region. As well the highest-resolution model results captured the midday 4 July organic-aerosol plume at Bear Creek with very good temporal correlation. These results suggest that accurate simulation of urban and large industrial plumes in the Great Lakes region requires the use of a high-resolution model in order to represent urban primary organic aerosol emissions, urban VOC emissions, and the secondary organic aerosol production rates properly. The positive feedback between the secondary organic aerosol production rate and existing organic mass concentration is also represented more accurately with the highest-resolution model. Not being able to capture these finer-scale features may partly explain the consistent negative bias reported in the literature when urban-scale organic aerosol evaluations are made using coarser-scale chemical transport models.

scholarly journals Impact of model grid spacing on regional- and urban- scale air quality predictions of organic aerosol

2011 ◽  
Vol 11 (7) ◽  
pp. 3107-3118 ◽  
Author(s):  
C. A. Stroud ◽  
P. A. Makar ◽  
M. D. Moran ◽  
W. Gong ◽  
S. Gong ◽  
...  
Keyword(s):  
Air Quality ◽  
Great Lakes ◽  
Secondary Organic Aerosol ◽  
Chemical Transport ◽  
Organic Aerosol ◽  
Great Lakes Region ◽  
Grid Spacing ◽  
Aerosol Composition ◽  
Resolution Model ◽  
Bear Creek

Abstract. Regional-scale chemical transport model predictions of urban organic aerosol to date tend to be biased low relative to observations, a limitation with important implications for applying such models to human exposure health studies. We used a nested version of Environment Canada's AURAMS model (42- to- 15- to- 2.5-km nested grid spacing) to predict organic aerosol concentrations for a temporal and spatial domain corresponding to the Border Air Quality and Meteorology Study (BAQS-Met), an air-quality field study that took place in the southern Great Lakes region in the summer of 2007. The use of three different horizontal grid spacings allowed the influence of this parameter to be examined. A domain-wide average for the 2.5-km domain and a matching 15-km subdomain yielded very similar organic aerosol averages (4.8 vs. 4.3 μg m−3, respectively). On regional scales, secondary organic aerosol dominated the organic aerosol composition and was adequately resolved by the 15-km model simulation. However, the shape of the organic aerosol concentration histogram for the Windsor urban station improved for the 2.5-km simulation relative to those from the 42- and 15-km simulations. The model histograms for the Bear Creek and Harrow rural stations were also improved in the high concentration "tail" region. As well the highest-resolution model results captured the midday 4 July organic-aerosol plume at Bear Creek with very good temporal correlation. These results suggest that accurate simulation of urban and large industrial plumes in the Great Lakes region requires the use of a high-resolution model in order to represent urban primary organic aerosol emissions, urban VOC emissions, and the secondary organic aerosol production rates properly. The positive feedback between the secondary organic aerosol production rate and existing organic mass concentration is also represented more accurately with the highest-resolution model. Not being able to capture these finer-scale features may partly explain the consistent negative bias reported in the literature when urban-scale organic aerosol evaluations are made using coarser-scale chemical transport models.

scholarly journals Ubiquitous Influence of Wildfire Emissions and Secondary Organic Aerosol on Summertime Atmospheric Aerosol in the Forested Great Lakes Region

2017 ◽  
Author(s):  
Matthew J. Gunsch ◽  
Nathaniel W. May ◽  
Miao Wen ◽  
Courtney L. H. Bottenus ◽  
Daniel J. Gardner ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Great Lakes ◽  
Long Range ◽  
Mass Spectrometer ◽  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Great Lakes Region ◽  
Aerosol Mass ◽  
Biomass Burning Particles

Abstract. Long-range aerosol transport affects locations hundreds of kilometers from the point of emission, leading to distant particle sources influencing rural environments that have few major local sources. Source apportionment was conducted using real-time aerosol chemistry measurements made in July 2014 at the forested University of Michigan Biological Station near Pellston, Michigan, a site representative of the remote forested Great Lakes region. Size-resolved chemical composition of individual 0.5–2.0 μm particles was measured using an aerosol time-of-flight mass spectrometer (ATOFMS), and non-refractory aerosol mass less than 1 μm (PM1) was measured by a high resolution aerosol mass spectrometer (HR-AMS). The field site was also influenced by air masses transporting Canadian wildfire emissions and urban pollution from Milwaukee and Chicago. During wildfire influenced periods, 0.5–2.0 μm particles were primarily aged biomass burning particles (88 % by number). These particles were heavily coated with secondary organic aerosol (SOA) formed during transport, with organics (average O/C ratio of 0.8) contributing 89 % of the PM1 mass. During urban-influenced periods, organic carbon, elemental carbon/organic carbon, and aged biomass burning particles were identified, with inorganic secondary species (ammonium, sulfate, and nitrate) contributing 41 % of the PM1 mass, indicative of atmospheric processing. With current models under-predicting organic carbon (OC) in this region and biomass burning being the largest combustion contributor to SOA by mass, these results highlight the importance for regional chemical transport models to accurately predict the impact of long-range transported particles on air quality in the upper Midwest United States, particularly considering increasing intensity and frequency of Canadian wildfires.

scholarly journals Ubiquitous influence of wildfire emissions and secondary organic aerosol on summertime atmospheric aerosol in the forested Great Lakes region

2018 ◽  
Vol 18 (5) ◽  
pp. 3701-3715 ◽  
Author(s):  
Matthew J. Gunsch ◽  
Nathaniel W. May ◽  
Miao Wen ◽  
Courtney L. H. Bottenus ◽  
Daniel J. Gardner ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Great Lakes ◽  
Long Range ◽  
Mass Spectrometer ◽  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Great Lakes Region ◽  
Aerosol Mass ◽  
Biomass Burning Particles

Abstract. Long-range aerosol transport affects locations hundreds of kilometers from the point of emission, leading to distant particle sources influencing rural environments that have few major local sources. Source apportionment was conducted using real-time aerosol chemistry measurements made in July 2014 at the forested University of Michigan Biological Station near Pellston, Michigan, a site representative of the remote forested Great Lakes region. Size-resolved chemical composition of individual 0.5–2.0 µm particles was measured using an aerosol time-of-flight mass spectrometer (ATOFMS), and non-refractory aerosol mass less than 1 µm (PM1) was measured with a high-resolution aerosol mass spectrometer (HR-AMS). The field site was influenced by air masses transporting Canadian wildfire emissions and urban pollution from Milwaukee and Chicago. During wildfire-influenced periods, 0.5–2.0 µm particles were primarily aged biomass burning particles (88 % by number). These particles were heavily coated with secondary organic aerosol (SOA) formed during transport, with organics (average O∕C ratio of 0.8) contributing 89 % of the PM1 mass. During urban-influenced periods, organic carbon, elemental carbon–organic carbon, and aged biomass burning particles were identified, with inorganic secondary species (ammonium, sulfate, and nitrate) contributing 41 % of the PM1 mass, indicative of atmospheric processing. With current models underpredicting organic carbon in this region and biomass burning being the largest combustion contributor to SOA by mass, these results highlight the importance for regional chemical transport models to accurately predict the impact of long-range transported particles on air quality in the upper Midwest, United States, particularly considering increasing intensity and frequency of Canadian wildfires.

scholarly journals Modeling the effect of reduced traffic due to COVID-19 measures on air quality using a chemical transport model: impacts on the Po Valley and the Swiss Plateau regions

2021 ◽  
Author(s):  
Giancarlo Ciarelli ◽  
Jianhui Jiang ◽  
Imad El Haddad ◽  
Alessandro Bigi ◽  
Sebnem Aksoyoglu ◽  
...  
Keyword(s):  
Air Quality ◽  
Nitrogen Dioxide ◽  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Chemical Transport ◽  
Organic Aerosol ◽  
Chemical Transport Model ◽  
Po Valley ◽  
Swiss Plateau

Our results indicate that lockdown measures induced a mild increase in secondary organic aerosol (SOA) concentrations in areas with substantial reductions in nitrogen dioxide (NO2) concentrations, i.e. the “Greater Milan” area.

scholarly journals Current State of Atmospheric Aerosol Thermodynamics and Mass Transfer Modeling: A Review

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 156 ◽  
Author(s):  
Kirill Semeniuk ◽  
Ashu Dastoor
Keyword(s):  
Mass Transfer ◽  
Air Quality ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Aerosol Composition ◽  
Quality Models ◽  
Secondary Aerosol ◽  
Size Limit ◽  
The Past ◽  
Hygroscopic Properties

A useful aerosol model must be able to adequately resolve the chemical complexity and phase state of the wide particle size range arising from the many different secondary aerosol growth processes to assess their environmental and health impacts. Over the past two decades, significant advances in understanding of gas-aerosol partitioning have occurred, particularly with respect to the role of organic compounds, yet aerosol representations have changed little in air quality and climate models since the late 1990s and early 2000s. The gas-aerosol partitioning models which are still commonly used in air quality models are separate inorganics-only thermodynamics and secondary organic aerosol (SOA) formation based on absorptive partitioning theory with an assumption of well-mixed liquid-like particles that continuously maintain equilibrium with the gas phase. These widely used approaches in air quality models for secondary aerosol composition and growth based on separated inorganic and organic processes are inadequate. This review summarizes some of the important developments during the past two decades in understanding of gas aerosol mass transfer processes. Substantial increases in computer performance in the last decade justify increasing the process detail in aerosol models. Organics play a central role during post-nucleation growth into the accumulation mode and change the hygroscopic properties of sulfate aerosol. At present, combined inorganic-organic aerosol thermodynamics models are too computationally expensive to be used online in 3-D simulations without high levels of aggregation of organics into a small number of functional surrogates. However, there has been progress in simplified modeling of liquid-liquid phase separation (LLPS) and distinct chemical regimes within organic-rich and inorganic-rich phases. Additional limitations of commonly used thermodynamics models are related to lack of surface tension data for various aerosol compositions in the small size limit, and lack of a comprehensive representation of surface interaction terms such as disjoining pressure in the Gibbs free energy which become significant in the small size limit and which affect both chemical composition and particle growth. As a result, there are significant errors in modeling of hygroscopic growth and phase transitions for particles in the nucleation and Aitken modes. There is also increasing evidence of reduced bulk diffusivity in viscous organic particles and, therefore, traditional secondary organic aerosol models, which are typically based on the assumption of instantaneous equilibrium gas-particle partitioning and neglect the kinetic effects, are no longer tenable.

scholarly journals Oligomer formation in the troposphere: from experimental knowledge to 3-D modeling

2016 ◽  
Vol 9 (4) ◽  
pp. 1361-1382 ◽  
Author(s):  
Vincent Lemaire ◽  
Isabelle Coll ◽  
Florian Couvidat ◽  
Camille Mouchel-Vallon ◽  
Christian Seigneur ◽  
...  
Keyword(s):  
Air Quality ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Kinetic Process ◽  
Critical Element ◽  
Order Kinetic ◽  
Continental Scale ◽  
Oligomer Formation ◽  
Modeling Approach ◽  
Ph Dependent

Abstract. The organic fraction of atmospheric aerosols has proven to be a critical element of air quality and climate issues. However, its composition and the aging processes it undergoes remain insufficiently understood. This work builds on laboratory knowledge to simulate the formation of oligomers from biogenic secondary organic aerosol (BSOA) in the troposphere at the continental scale. We compare the results of two different modeling approaches, a first-order kinetic process and a pH-dependent parameterization, both implemented in the CHIMERE air quality model (AQM) (www.lmd.polytechnique.fr/chimere), to simulate the spatial and temporal distribution of oligomerized secondary organic aerosol (SOA) over western Europe. We also included a comparison of organic carbon (OC) concentrations at two EMEP (European Monitoring and Evaluation Programme) stations. Our results show that there is a strong dependence of the results on the selected modeling approach: while the irreversible kinetic process leads to the oligomerization of about 50 % of the total BSOA mass, the pH-dependent approach shows a broader range of impacts, with a strong dependency on environmental parameters (pH and nature of aerosol) and the possibility for the process to be reversible. In parallel, we investigated the sensitivity of each modeling approach to the representation of SOA precursor solubility (Henry's law constant values). Finally, the pros and cons of each approach for the representation of SOA aging are discussed and recommendations are provided to improve current representations of oligomer formation in AQMs.

scholarly journals Mixing times of organic molecules within secondary organic aerosol particles: a global planetary boundary layer perspective

2017 ◽  
Author(s):  
Adrian M. Maclean ◽  
Christopher L. Butenhoff ◽  
James W. Grayson ◽  
Kelley Barsanti ◽  
Jose L. Jimenez ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Laboratory Data ◽  
Chemical Transport ◽  
Organic Aerosol ◽  
Mixing Times ◽  
Chemical Transport Model ◽  
Transport Models ◽  
Lack Of Information

Abstract. When simulating the formation and life cycle of secondary organic aerosol (SOA) with chemical transport models, it is often assumed that organic molecules are well mixed within SOA particles on the time scale of 1 h. While this assumption has been debated vigorously in the literature, the issue remains unresolved in part due to a lack of information on the mixing times within SOA particles as a function of both temperature and relative humidity. Using laboratory data, meteorological fields and a chemical transport model, we determine how often mixing times are

Gas-phase kinetics modifies the CCN activity of a biogenic SOA

2018 ◽  
Vol 20 (9) ◽  
pp. 6591-6597
Author(s):  
A. E. Vizenor ◽  
A. A. Asa-Awuku
Keyword(s):  
Particle Size ◽  
Thermodynamic Properties ◽  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Cloud Condensation Nuclei ◽  
Organic Aerosol ◽  
Aerosol Composition ◽  
Phase Partitioning ◽  
Gas Phase Kinetics ◽  
Ccn Activity

Cloud condensation nuclei (CCN) activity and the hygroscopicity of secondary organic aerosol (SOA) depends on the particle size and composition, explicitly, the thermodynamic properties of the aerosol solute and subsequent interactions with water. The gas-to-aerosol phase partitioning is critical for aerosol composition and thus gas-phase vapors and kinetics can play an important role in the CCN activity of SOA.

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