scholarly journals An evaluation of ambient ammonia concentrations over southern Ontario simulated with different dry deposition schemes within STILT-Chem v0.8

2013 ◽  
Vol 6 (4) ◽  
pp. 6075-6115 ◽  
Author(s):  
D. Wen ◽  
L. Zhang ◽  
J. C. Lin ◽  
R. Vet ◽  
M. D. Moran
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Air Quality Model ◽  
Quality Model ◽  
Surface Exchange ◽  
Southern Ontario ◽  
Lagrangian Transport ◽  
Atmospheric Ammonia ◽  
Sensitivity Tests ◽  
Stochastic Time

Abstract. A bi-directional air-surface exchange scheme for atmospheric ammonia was incorporated into the Stochastic Time-Inverted Lagrangian Transport air quality model (STILT-Chem v0.8). STILT-Chem v0.8 was then applied to simulate atmospheric ammonia concentrations at 53 measurement sites in the province of Ontario, Canada for a six-month period from 1 June to 30 November 2006. In addition to the bi-directional scheme, two uni-directional dry deposition schemes were tested. Comparisons of modeled ammonia concentrations against observations show that all three schemes can reasonably predict observations. For sites with low observed ammonia concentrations, the bi-directional scheme clearly overestimated ammonia concentrations. Although all three schemes tend to underestimate ammonia concentrations for locations with elevated observed concentrations, the bi-directional scheme performed better due mainly to its introduction of compensation points into flux calculation parameterizations. The results of additional sensitivity tests suggest that uncertainties in the input values of emission potentials in the bi-directional scheme greatly affect the accuracy of modeled ammonia concentrations. The use of much larger emission potentials than provided in the scheme is required for accurate prediction of elevated ammonia concentrations at intensive agricultural locations.

scholarly journals An evaluation of ambient ammonia concentrations over southern Ontario simulated with different dry deposition schemes within STILT-Chem v0.8

2014 ◽  
Vol 7 (3) ◽  
pp. 1037-1050 ◽  
Author(s):  
D. Wen ◽  
L. Zhang ◽  
J. C. Lin ◽  
R. Vet ◽  
M. D. Moran
Keyword(s):  
Dry Deposition ◽  
Emission Inventory ◽  
Air Quality Model ◽  
Quality Model ◽  
Surface Exchange ◽  
Southern Ontario ◽  
Atmospheric Ammonia ◽  
Nh3 Emission ◽  
Sensitivity Tests ◽  
Stochastic Time

Abstract. A bidirectional air–surface exchange scheme for atmospheric ammonia was incorporated into the Stochastic Time-Inverted Lagrangian Transport air quality model (STILT-Chem v0.8). STILT-Chem v0.8 was then applied to simulate atmospheric ammonia concentrations at 53 measurement sites in the province of Ontario, Canada for a six-month period from 1 June to 30 November 2006. In addition to the bidirectional scheme, two unidirectional dry deposition schemes were tested. Comparisons of modeled ammonia concentrations against observations show that all three schemes can reasonably predict observations. For sites with low observed ammonia concentrations, the bidirectional scheme clearly overestimated ammonia concentrations during crop-growing season. Although all three schemes tended to underestimate ammonia concentrations after mid-October and for sites with elevated observed concentrations, mainly due to underestimated NH3 emission inventory after mid-October and/or underestimated emission potentials for those sites, the bidirectional scheme performed better because of its introduction of compensation points into the flux calculation parameterization. In addition to uncertainties in the emission inventory, the results of additional sensitivity tests suggest that uncertainties in the input values of emission potentials in the bidirectional scheme greatly affect the accuracy of modeled ammonia concentrations. The use of much larger emission potentials in the bidirectional scheme and larger anthropogenic NH3 emission after mid-October than provided in the model emissions files is needed for accurate prediction of elevated ammonia concentrations at intensive agricultural locations.

scholarly journals Modeling atmospheric ammonia and ammonium using a stochastic Lagrangian air quality model (STILT-Chem v0.7)

2013 ◽  
Vol 6 (2) ◽  
pp. 327-344 ◽  
Author(s):  
D. Wen ◽  
J. C. Lin ◽  
L. Zhang ◽  
R. Vet ◽  
M. D. Moran
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Chemical Conversion ◽  
Air Quality Model ◽  
Quality Model ◽  
Gaseous Species ◽  
Time Step ◽  
Back Trajectories ◽  
Atmospheric Ammonia ◽  
Chemistry Module

Abstract. A new chemistry module that simulates atmospheric ammonia (NH3) and ammonium (NH+4) was incorporated into a backward-in-time stochastic Lagrangian air quality model (STILT-Chem) that was originally developed to simulate the concentrations of a variety of gas-phase species at receptors. STILT-Chem simulates the transport of air parcels backward in time using ensembles of fictitious particles with stochastic motions, while accounting for emissions, deposition and chemical transformation forward in time along trajectories identified by the backward-in-time simulations. The incorporation of the new chemistry module allows the model to simulate not only gaseous species, but also multi-phase species involving NH3 and NH+4. The model was applied to simulate concentrations of NH3 and particulate NH+4 at six sites in the Canadian province of Ontario for a six-month period in 2006. The model-predicted concentrations of NH3 and particulate NH+4 were compared with observations, which show broad agreement between simulated concentrations and observations. Since the model is based on back trajectories, the influence of each major process such as emission, deposition and chemical conversion on the concentration of a modeled species at a receptor can be determined for every upstream location at each time step. This makes it possible to quantitatively investigate the upstream processes affecting receptor concentrations. The modeled results suggest that the concentrations of NH3 at those sites were significantly and frequently affected by Ohio, Iowa, Minnesota, Michigan, Wisconsin, southwestern Ontario and nearby areas. NH3 is mainly contributed by emission sources whereas particulate NH+4 is mainly contributed by the gas-to-aerosol chemical conversion of NH3. Dry deposition is the largest removal process for both NH3 and particulate NH+4. This study revealed the contrast between agricultural versus forest sites. Not only were emissions of NH3 higher, but removal mechanisms (especially chemical loss for NH3 and dry deposition for NH+4) were less efficient for agricultural sites. This combination explains the significantly higher concentrations of NH3 and particulate NH+4 observed at agricultural sites.

scholarly journals Modeling atmospheric ammonia and ammonium using a backward-in-time stochastic Lagrangian air quality model (STILT-Chem v0.7)

2012 ◽  
Vol 5 (3) ◽  
pp. 2745-2788
Author(s):  
D. Wen ◽  
J. C. Lin ◽  
L. Zhang ◽  
R. Vet ◽  
M. D. Moran
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Chemical Conversion ◽  
Air Quality Model ◽  
Quality Model ◽  
Gaseous Species ◽  
Time Step ◽  
Back Trajectories ◽  
Atmospheric Ammonia ◽  
Chemistry Module

Abstract. A new chemistry module of atmospheric ammonia (NH3) and ammonium (NH4+) was incorporated into a backward-in-time stochastic Lagrangian air quality model (STILT-Chem) that was originally developed to simulate the concentrations of a variety of gas-phase species at receptors. STILT-Chem simulates the transport of air parcels backward in time using ensembles of fictitious particles with stochastic motions, while simulating emissions, deposition and chemical transformation forward in time along trajectories identified by the backward-in-time simulations. The incorporation of the new chemistry module allows the model to simulate not only gaseous species, but also multi-phase species involving NH3 and NH4+. The model was applied to simulate concentrations of NH3 and particulate NH4+ at six sites in the Canadian province of Ontario for a six-month period in 2006. The model-predicted concentrations of NH3 and particulate NH4+ were compared with observations, which show broad agreement between simulated concentrations and observations. Since the model is based on back trajectories, the influence of each major process such as emission, deposition and chemical conversion on the concentration of a modeled species at a receptor can be determined for every upstream location at each time step. This makes it possible to quantitatively investigate the upstream processes affecting receptor concentrations. The modeled results suggest that the concentrations of NH3 at those sites were significantly and frequently affected by southwestern Ontario, northern Ohio, and nearby areas. NH3 is mainly contributed by emission sources whereas particulate NH4+ is mainly contributed by the gas-to-aerosol chemical conversion of NH3. Dry deposition is the largest removal process for both NH3 and particulate NH4+. This study revealed the contrast between agricultural versus forest sites. Not only were emissions of NH3 higher, but removal mechanisms (especially chemical loss for NH3 and dry deposition for NH4+) were less efficient for agricultural sites. This combination explains the significantly higher concentrations of NH3 and particulate NH4+ observed at agricultural sites.

scholarly journals Evaluation of a regional air-quality model with bidirectional NH<sub>3</sub> exchange coupled to an agroecosystem model

2013 ◽  
Vol 10 (3) ◽  
pp. 1635-1645 ◽  
Author(s):  
J. O. Bash ◽  
E. J. Cooter ◽  
R. L. Dennis ◽  
J. T. Walker ◽  
J. E. Pleim
Keyword(s):  
Air Quality ◽  
The United States ◽  
United States Department ◽  
Air Quality Model ◽  
Quality Model ◽  
Coupled Modeling ◽  
Surface Exchange ◽  
Agroecosystem Model ◽  
The Us ◽  
Bidirectional Exchange

Abstract. Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air–surface exchange of NH3 is bidirectional. However, the effects of bidirectional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency's (EPA) Community Multiscale Air-Quality (CMAQ) model with bidirectional NH3 exchange has been coupled with the United States Department of Agriculture's (USDA) Environmental Policy Integrated Climate (EPIC) agroecosystem model. The coupled CMAQ-EPIC model relies on EPIC fertilization timing, rate and composition while CMAQ models the soil ammonium (NH4&amp;plus;) pool by conserving the ammonium mass due to fertilization, evasion, deposition, and nitrification processes. This mechanistically coupled modeling system reduced the biases and error in NHx (NH3 &amp;plus; NH4&amp;plus;) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bidirectional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bidirectional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.

scholarly journals Sensitivity of continental United States atmospheric budgets of oxidized and reduced nitrogen to dry deposition parametrizations

2013 ◽  
Vol 368 (1621) ◽  
pp. 20130124 ◽  
Author(s):  
Robin L. Dennis ◽  
Donna B. Schwede ◽  
Jesse O. Bash ◽  
Jon E. Pleim ◽  
John T. Walker ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Aerodynamic Resistance ◽  
Grid Cell ◽  
Surface Fluxes ◽  
Air Quality Model ◽  
Quality Model ◽  
Surface Exchange ◽  
Uncertainty Estimates ◽  
Regional Air Quality ◽  
Cell Changes

Reactive nitrogen (N r ) is removed by surface fluxes (air–surface exchange) and wet deposition. The chemistry and physics of the atmosphere result in a complicated system in which competing chemical sources and sinks exist and impact that removal. Therefore, uncertainties are best examined with complete regional chemical transport models that simulate these feedbacks. We analysed several uncertainties in regional air quality model resistance analogue representations of air–surface exchange for unidirectional and bi-directional fluxes and their effect on the continental N r budget. Model sensitivity tests of key parameters in dry deposition formulations showed that uncertainty estimates of continental total nitrogen deposition are surprisingly small, 5 per cent or less, owing to feedbacks in the chemistry and rebalancing among removal pathways. The largest uncertainties (5%) occur with the change from a unidirectional to a bi-directional NH 3 formulation followed by uncertainties in bi-directional compensation points (1–4%) and unidirectional aerodynamic resistance (2%). Uncertainties have a greater effect at the local scale. Between unidirectional and bi-directional formulations, single grid cell changes can be up to 50 per cent, whereas 84 per cent of the cells have changes less than 30 per cent. For uncertainties within either formulation, single grid cell change can be up to 20 per cent, but for 90 per cent of the cells changes are less than 10 per cent.

scholarly journals Evaluation of European air quality modelled by CAMx including the volatility basis set scheme

2016 ◽  
Vol 16 (16) ◽  
pp. 10313-10332 ◽  
Author(s):  
Giancarlo Ciarelli ◽  
Sebnem Aksoyoglu ◽  
Monica Crippa ◽  
Jose-Luis Jimenez ◽  
Eriko Nemitz ◽  
...  
Keyword(s):  
Air Quality ◽  
Measurement Data ◽  
Model Performance ◽  
Monitoring And Evaluation ◽  
Basis Set ◽  
Air Quality Model ◽  
Quality Model ◽  
Aerosol Mass ◽  
Sensitivity Tests ◽  
Compensation Of Errors

Abstract. Four periods of EMEP (European Monitoring and Evaluation Programme) intensive measurement campaigns (June 2006, January 2007, September–October 2008 and February–March 2009) were modelled using the regional air quality model CAMx with VBS (volatility basis set) approach for the first time in Europe within the framework of the EURODELTA-III model intercomparison exercise. More detailed analysis and sensitivity tests were performed for the period of February–March 2009 and June 2006 to investigate the uncertainties in emissions as well as to improve the modelling of organic aerosol (OA). Model performance for selected gas phase species and PM2.5 was evaluated using the European air quality database AirBase. Sulfur dioxide (SO2) and ozone (O3) were found to be overestimated for all the four periods, with O3 having the largest mean bias during June 2006 and January–February 2007 periods (8.9 pbb and 12.3 ppb mean biases respectively). In contrast, nitrogen dioxide (NO2) and carbon monoxide (CO) were found to be underestimated for all the four periods. CAMx reproduced both total concentrations and monthly variations of PM2.5 for all the four periods with average biases ranging from −2.1 to 1.0 µg m−3. Comparisons with AMS (aerosol mass spectrometer) measurements at different sites in Europe during February–March 2009 showed that in general the model overpredicts the inorganic aerosol fraction and underpredicts the organic one, such that the good agreement for PM2.5 is partly due to compensation of errors. The effect of the choice of VBS scheme on OA was investigated as well. Two sensitivity tests with volatility distributions based on previous chamber and ambient measurements data were performed. For February–March 2009 the chamber case reduced the total OA concentrations by about 42 % on average. In contrast, a test based on ambient measurement data increased OA concentrations by about 42 % for the same period bringing model and observations into better agreement. Comparison with the AMS data at the rural Swiss site Payerne in June 2006 shows no significant improvement in modelled OA concentration. Further sensitivity tests with increased biogenic and anthropogenic emissions suggest that OA in Payerne was affected by changes in emissions from residential heating during the February–March 2009 whereas it was more sensitive to biogenic precursors in June 2006.

scholarly journals Contribution of ship emissions to the concentration and deposition of air pollutants in Europe

2016 ◽  
Vol 16 (4) ◽  
pp. 1895-1906 ◽  
Author(s):  
Sebnem Aksoyoglu ◽  
Urs Baltensperger ◽  
André S. H. Prévôt
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Nox Emissions ◽  
English Channel ◽  
Air Quality Model ◽  
Quality Model ◽  
Ship Emissions ◽  
The North ◽  
The North Sea

Abstract. Emissions from the marine transport sector are one of the least-regulated anthropogenic emission sources and contribute significantly to air pollution. Although strict limits were introduced recently for the maximum sulfur content in marine fuels in the SECAs (sulfur emission control areas) and in EU ports, sulfur emissions outside the SECAs and emissions of other components in all European maritime areas have continued to increase in the last two decades. We have used the air quality model CAMx (Comprehensive Air Quality Model with Extensions) with and without ship emissions for the year 2006 to determine the effects of international shipping on the annual as well as seasonal concentrations of ozone, primary and secondary components of PM2.5, and the dry and wet deposition of nitrogen and sulfur compounds in Europe. The largest changes in pollutant concentrations due to ship emissions were predicted for summer. Concentrations of particulate sulfate increased due to ship emissions in the Mediterranean (up to 60 %), the English Channel and the North Sea (30–35 %), while increases in particulate nitrate levels were found especially in the north, around the Benelux area (20 %), where there were high NH3 land-based emissions. Our model results showed that not only are the atmospheric concentrations of pollutants affected by ship emissions, but also depositions of nitrogen and sulfur compounds increase significantly along the shipping routes. NOx emissions from the ships, especially in the English Channel and the North Sea, cause a decrease in the dry deposition of reduced nitrogen at source regions by moving it from the gas phase to the particle phase which then contributes to an increase in the wet deposition at coastal areas with higher precipitation. In the western Mediterranean region, on the other hand, model results show an increase in the deposition of oxidized nitrogen (mostly HNO3) due to the ship traffic. Dry deposition of SO2 seems to be significant along the shipping routes, whereas sulfate wet deposition occurs mainly along the Scandinavian and Adriatic coasts. The results presented in this paper suggest that evolution of NOx emissions from ships and land-based NH3 emissions will play a significant role in future European air quality.

scholarly journals Aerosol modelling in Europe with a focus on Switzerland during summer and winter episodes

2011 ◽  
Vol 11 (14) ◽  
pp. 7355-7373 ◽  
Author(s):  
S. Aksoyoglu ◽  
J. Keller ◽  
I. Barmpadimos ◽  
D. Oderbolz ◽  
V. A. Lanz ◽  
...  
Keyword(s):  
Air Quality ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Base Case ◽  
Chemical Compositions ◽  
Aerosol Formation ◽  
Air Quality Model ◽  
Quality Model ◽  
Aerosol Composition ◽  
Sensitivity Tests

Abstract. This paper describes aerosol modelling in Europe with a focus on Switzerland during summer and winter periods. We modelled PM2.5 (particles smaller than 2.5 μm in aerodynamic diameter) for one summer and two winter periods in years 2006 and 2007 using the CAMx air quality model. The meteorological fields were obtained from MM5 simulations. The modelled wind speeds during some low-wind periods, however, had to be calibrated with measurements to use realistic input for the air quality model. The detailed AMS (aerosol mass spectrometer) measurements at specific locations were used to evaluate the model results. In addition to the base case simulations, we carried out sensitivity tests with modified aerosol precursor emissions, air temperature and deposition. Aerosol concentrations in winter 2006 were twice as high as those in winter 2007, however, the chemical compositions were similar. CAMx could reproduce the relative composition of aerosols very well both in the winter and summer periods. Absolute concentrations of aerosol species were underestimated by about 20 %. Both measurements and model results suggest that organic aerosol (30–38 %) and particulate nitrate (30–36 %) are the main aerosol components in winter. In summer, organic aerosol dominates the aerosol composition (55–57 %) and is mainly of secondary origin. The contribution of biogenic volatile organic compound (BVOC) emissions to the formation of secondary organic aerosol (SOA) was predicted to be very large (>95 %) in Switzerland. The main contributors to the modelled SOA concentrations were oxidation products of monoterpenes and sesquiterpenes as well as oligomerization of oxidized compounds. The fraction of primary organic aerosol (POA) derived from measurements was lower than the model predictions indicating the importance of volatility of POA, which has not yet been taken into account in CAMx. Sensitivity tests with reduced NOx and NH3 emissions suggest that aerosol formation is more sensitive to ammonia emissions in winter in a large part of Europe. In Switzerland however, aerosol formation is predicted to be NOx-sensitive. In summer, effects of NOx and NH3 emission reductions on aerosol concentrations are predicted to be lower mostly due to lower ammonium nitrate concentrations. In general, the sensitivity to NH3 emissions is weaker in summer due to higher NH3 emissions.

scholarly journals Evaluation of a regional air-quality model with bi-directional NH<sub>3</sub> exchange coupled to an agro-ecosystem model

2012 ◽  
Vol 9 (8) ◽  
pp. 11375-11401 ◽  
Author(s):  
J. O. Bash ◽  
E. J. Cooter ◽  
R. L. Dennis ◽  
J. T. Walker ◽  
J. E. Pleim
Keyword(s):  
Air Quality ◽  
Environmental Protection Agency ◽  
Management Practices ◽  
The United States ◽  
United States Department ◽  
Air Quality Model ◽  
Quality Model ◽  
Coupled Modeling ◽  
Surface Exchange ◽  
The Us

Abstract. Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bi-directional. However, the effects of bi-directional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency (EPA)'s Community Multiscale Air-Quality (CMAQ) model with bi-directional NH3 exchange has been coupled with the United States Department of Agriculture (USDA)'s Environmental Policy Integrated Climate (EPIC) agro-ecosystem model's nitrogen geochemistry algorithms. CMAQ with bi-directional NH3 exchange coupled to EPIC connects agricultural cropping management practices to emissions and atmospheric concentrations of reduced nitrogen and models the biogeochemical feedback on NH3 air-surface exchange. This coupled modeling system reduced the biases and error in NHx (NH3 + NH4+) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bi-directional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bi-directional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.

scholarly journals European air quality modelled by CAMx including the volatility basis set scheme

2015 ◽  
Vol 15 (24) ◽  
pp. 35645-35691 ◽  
Author(s):  
G. Ciarelli ◽  
S. Aksoyoglu ◽  
M. Crippa ◽  
J. L. Jimenez ◽  
E. Nemitz ◽  
...  
Keyword(s):  
Air Quality ◽  
Measurement Data ◽  
Model Performance ◽  
Monitoring And Evaluation ◽  
Basis Set ◽  
Air Quality Model ◽  
Quality Model ◽  
Aerosol Mass ◽  
Sensitivity Tests ◽  
Compensation Of Errors

Abstract. Four periods of EMEP (European Monitoring and Evaluation Programme) intensive measurement campaigns (June 2006, January 2007, September–October 2008 and February–March 2009) were modelled using the regional air quality model CAMx with VBS (Volatility Basis Set) approach for the first time in Europe within the framework of the EURODELTA-III model intercomparison exercise. More detailed analysis and sensitivity tests were performed for the period of February–March 2009 and June 2006 to investigate the uncertainties in emissions as well as to improve the modelling of organic aerosols (OA). Model performance for selected gas phase species and PM2.5 was evaluated using the European air quality database Airbase. Sulfur dioxide (SO2) and ozone (O3) were found to be overestimated for all the four periods with O3 having the largest mean bias during June 2006 and January–February 2007 periods (8.93 and 12.30 ppb mean biases, respectively). In contrast, nitrogen dioxide (NO2) and carbon monoxide (CO) were found to be underestimated for all the four periods. CAMx reproduced both total concentrations and monthly variations of PM2.5 very well for all the four periods with average biases ranging from −2.13 to 1.04 μg m-3. Comparisons with AMS (Aerosol Mass Spectrometer) measurements at different sites in Europe during February–March 2009, showed that in general the model over-predicts the inorganic aerosol fraction and under-predicts the organic one, such that the good agreement for PM2.5 is partly due to compensation of errors. The effect of the choice of volatility basis set scheme (VBS) on OA was investigated as well. Two sensitivity tests with volatility distributions based on previous chamber and ambient measurements data were performed. For February–March 2009 the chamber-case reduced the total OA concentrations by about 43 % on average. On the other hand, a test based on ambient measurement data increased OA concentrations by about 47 % for the same period bringing model and observations into better agreement. Comparison with the AMS data at the rural Swiss site Payerne in June 2006 shows no significant improvement in modelled OA concentration. Further sensitivity tests with increased biogenic and anthropogenic emissions suggest that OA in Payerne was largely dominated by residential heating emissions during the February–March 2009 period and by biogenic precursors in June 2006.

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