scholarly journals Interannual variability of ammonia concentrations over the United States: sources and implications

2016 ◽  
Vol 16 (18) ◽  
pp. 12305-12328 ◽  
Author(s):  
Luke D. Schiferl ◽  
Colette L. Heald ◽  
Martin Van Damme ◽  
Lieven Clarisse ◽  
Cathy Clerbaux ◽  
...  
Keyword(s):  
United States ◽  
Interannual Variability ◽  
Model Comparison ◽  
Transport Model ◽  
The United States ◽  
Ammonia Concentration ◽  
Phase Changes ◽  
Spatial And Temporal Variability ◽  
Ammonia Emissions ◽  
Chemical Transport Model

Abstract. The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008–2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26 % at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations.

scholarly journals Interannual Variability of Ammonia Concentrations over the United States: Sources and Implications

2016 ◽  
Author(s):  
Luke D. Schiferl ◽  
Colette L. Heald ◽  
Martin Van Damme ◽  
Lieven Clarisse ◽  
Cathy Clerbaux ◽  
...  
Keyword(s):  
United States ◽  
Interannual Variability ◽  
Model Comparison ◽  
Transport Model ◽  
The United States ◽  
Ammonia Concentration ◽  
Phase Changes ◽  
Spatial And Temporal Variability ◽  
Ammonia Emissions ◽  
Chemical Transport Model

Abstract. The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008–2012). We find that the model generally underrepresents the ammonia concentration near large source regions and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64 %) as compared to reductions in SO2 and NOx emissions imposed by regulation (32 %) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. Further, this work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations.

scholarly journals Global modeling of organic aerosol: the importance of reactive nitrogen

2010 ◽  
Vol 10 (9) ◽  
pp. 21259-21301 ◽  
Author(s):  
H. O. T. Pye ◽  
A. W. H. Chan ◽  
M. P. Barkley ◽  
J. H. Seinfeld
Keyword(s):  
United States ◽  
Transport Model ◽  
Organic Aerosol ◽  
The United States ◽  
Oxidation Products ◽  
Reactive Nitrogen ◽  
Nitrate Radical ◽  
Chemical Transport Model ◽  
Radical Oxidation ◽  
High Volatility

Abstract. Reactive nitrogen compounds, specifically NOx and NO3, likely influence global organic aerosol levels. To assess these interactions, GEOS-Chem, a chemical transport model, is updated to include improved biogenic emissions (following MEGAN v2.1/2.04), a new organic aerosol tracer lumping scheme, aerosol from nitrate radical (NO3) oxidation of isoprene, and NOx-dependent terpene aerosol yields. As a result of significant nighttime terpene emissions, fast reaction of monoterpenes with the nitrate radical, and relatively high aerosol yields from NO3 oxidation, biogenic hydrocarbon-NO3 reactions are expected to be a major contributor to surface level aerosol concentrations in anthropogenically influenced areas such as the United States. By including aerosol from nitrate radical oxidation in GEOS-Chem, terpene aerosol approximately doubles and isoprene aerosol is enhanced by 30 to 40% in the Southeast United States. In terms of the global budget of organic aerosol, however, aerosol from nitrate radical oxidation is somewhat minor (slightly more than 3 Tg/yr) due to the relatively high volatility of organic-NO3 oxidation products. Globally, 69 to 88 Tg/yr of organic aerosol is predicted to be produced annually, of which 14–15 Tg/yr is from oxidation of monoterpenes and sesquiterpenes and 8–9 Tg/yr from isoprene.

scholarly journals Trends and spatial shifts in lightning fires and smoke concentrations in response to 21st century climate over the forests of the Western United States

2020 ◽  
Author(s):  
Yang Li ◽  
Loretta J. Mickley ◽  
Pengfei Liu ◽  
Jed O. Kaplan
Keyword(s):  
Climate Change ◽  
United States ◽  
21St Century ◽  
Transport Model ◽  
Fine Particulate Matter ◽  
The United States ◽  
Western United States ◽  
Fire Season ◽  
Future Climate Change ◽  
Chemical Transport Model

Abstract. Almost US$ 3bn per year is appropriated for wildfire management on public land in the United States. Recent studies have suggested that ongoing climate change will lead to warmer and drier conditions in the Western United States with a consequent increase in the number and size of wildfires, yet large uncertainty exists in these projections. To assess the influence of future changes in climate and land cover on lightning-caused wildfires in National Forests and Parks of the Western United States and the consequences of these fires on air quality, we link a dynamic vegetation model that includes a process-based representation of fire (LPJ-LMfire) to a global chemical transport model (GEOS-Chem). Under a scenario of moderate future climate change (RCP4.5), increasing lightning-caused wildfire enhances the burden of smoke fine particulate matter (PM), with mass concentration increases of ~ 53 % by the late-21st century during the fire season. In a high-emissions scenario (RCP8.5), smoke PM concentrations double by 2100. RCP8.5 also shows large, northward shifts in dry matter burned, leading to enhanced lightning-caused fire activity especially over forests in the northern states.

scholarly journals Trends and spatial shifts in lightning fires and smoke concentrations in response to 21st century climate over the national forests and parks of the western United States

2020 ◽  
Vol 20 (14) ◽  
pp. 8827-8838
Author(s):  
Yang Li ◽  
Loretta J. Mickley ◽  
Pengfei Liu ◽  
Jed O. Kaplan
Keyword(s):  
Climate Change ◽  
United States ◽  
21St Century ◽  
Transport Model ◽  
The United States ◽  
Western United States ◽  
Fire Season ◽  
Future Climate Change ◽  
National Forests ◽  
Chemical Transport Model

Abstract. Almost USD 3 billion per year is appropriated for wildfire management on public land in the United States. Recent studies have suggested that ongoing climate change will lead to warmer and drier conditions in the western United States, with a consequent increase in the number and size of wildfires, yet large uncertainty exists in these projections. To assess the influence of future changes in climate and land cover on lightning-caused wildfires in the national forests and parks of the western United States and the consequences of these fires on air quality, we link a dynamic vegetation model that includes a process-based representation of fire (LPJ-LMfire) to a global chemical transport model (GEOS-Chem). Under a scenario of moderate future climate change (RCP4.5), increasing lightning-caused wildfire enhances the burden of smoke fine particulate matter (PM), with mass concentration increases of ∼53 % by the late 21st century during the fire season in the national forests and parks of the western United States. In a high-emissions scenario (RCP8.5), smoke PM concentrations double by 2100. RCP8.5 also shows enhanced lightning-caused fire activity, especially over forests in the northern states.

scholarly journals Global modeling of organic aerosol: the importance of reactive nitrogen (NO<sub>x</sub> and NO<sub>3</sub>)

2010 ◽  
Vol 10 (22) ◽  
pp. 11261-11276 ◽  
Author(s):  
H. O. T. Pye ◽  
A. W. H. Chan ◽  
M. P. Barkley ◽  
J. H. Seinfeld
Keyword(s):  
United States ◽  
Transport Model ◽  
Organic Aerosol ◽  
The United States ◽  
Oxidation Products ◽  
Reactive Nitrogen ◽  
Nitrate Radical ◽  
Chemical Transport Model ◽  
Radical Oxidation ◽  
High Volatility

Abstract. Reactive nitrogen compounds, specifically NOx and NO3, likely influence global organic aerosol levels. To assess these interactions, GEOS-Chem, a chemical transport model, is updated to include improved biogenic emissions (following MEGAN v2.1/2.04), a new organic aerosol tracer lumping scheme, aerosol from nitrate radical (NO3) oxidation of isoprene, and NOx-dependent monoterpene and sesquiterpene aerosol yields. As a result of significant nighttime terpene emissions, fast reaction of monoterpenes with the nitrate radical, and relatively high aerosol yields from NO3 oxidation, biogenic hydrocarbon-NO3 reactions are expected to be a major contributor to surface level aerosol concentrations in anthropogenically influenced areas such as the United States. By including aerosol from nitrate radical oxidation in GEOS-Chem, terpene (monoterpene + sesquiterpene) aerosol approximately doubles and isoprene aerosol is enhanced by 30 to 40% in the Southeast United States. In terms of the global budget of organic aerosol, however, aerosol from nitrate radical oxidation is somewhat minor (slightly more than 3 Tg/yr) due to the relatively high volatility of organic-NO3 oxidation products in the yield parameterization. Globally, 69 to 88 Tg/yr of organic aerosol is predicted to be produced annually, of which 14–15 Tg/yr is from oxidation of monoterpenes and sesquiterpenes and 8–9 Tg/yr from isoprene.

scholarly journals Estimates of mercury flux into the United States from non-local and global sources: results from a 3-D CTM simulation

2008 ◽  
Vol 8 (6) ◽  
pp. 19861-19890 ◽  
Author(s):  
B. A. Drewniak ◽  
V. R. Kotamarthi ◽  
D. Streets ◽  
M. Kim ◽  
K. Crist
Keyword(s):  
United States ◽  
Transport Model ◽  
Source Region ◽  
The United States ◽  
Chemical Transport Model ◽  
Wet And Dry Deposition ◽  
Chemical Tracers ◽  
Non Local ◽  
Global Chemical Transport Model ◽  
No Emissions

Abstract. The sensitivity of Hg concentration and deposition in the United States to emissions in China was investigated by using a global chemical transport model: Model for Ozone and Related Chemical Tracers (MOZART). Two forms of gaseous Hg were included in the model: elemental Hg (HG(0) and oxidized or reactive Hg (HGO). We simulated three different emission scenarios to evaluate the model's sensitivity. One scenario included no emissions from China, while the others were based on different estimates of Hg emissions in China. The results indicated, in general, that when Hg emissions were included, HG(0) concentrations increased both locally and globally. Increases in Hg concentrations in the United States were greatest during spring and summer, by as much as 7%. Ratios of calculated concentrations of Hg and CO near the source region in eastern Asia agreed well with ratios based on measurements. Increases similar to those observed for HG(0) were also calculated for deposition of HGO. Calculated increases in wet and dry deposition in the United States were 5–7% and 5–9%, respectively. The results indicate that long-range transcontinental transport of Hg has a non-negligible impact on Hg deposition levels in the United States.

scholarly journals Significant contrasts in aerosol acidity between China and the Unites States

2020 ◽  
Author(s):  
Bingqing Zhang ◽  
Huizhong Shen ◽  
Pengfei Liu ◽  
Hongyu Guo ◽  
Yongtao Hu ◽  
...  
Keyword(s):  
United States ◽  
Transport Model ◽  
Ground Level ◽  
The United States ◽  
Formation Mechanisms ◽  
Aerosol Formation ◽  
Chemical Transport Model ◽  
Aerosol Composition ◽  
Aerosol Acidity ◽  
Acidic Component

Abstract. Aerosol acidity governs several key processes in aerosol physics and chemistry, thus affecting aerosol mass and composition, and ultimately the climate and human health. Previous studies have reported the aerosol pH separately in China and the United States, implying a different aerosol acidity between these two countries. However, underlying mechanisms responsible for the pH difference are not fully understood, limited by the scarcity of simultaneous measurements of aerosol composition and gas species, especially in China. Here we conduct a comprehensive assessment of the aerosol acidity in China and the United States, using extended ground-level measurements and regional chemical transport model simulations. We show aerosol in China is significantly less acidic than that in the United States, with pH values 1–2 units higher. Based on a multivariable Taylor Series method and a series of sensitivity tests, we identify several major factors leading to the pH difference. Compared to the United States, aerosols in China are generally in total ammonia (TNH3 = NH4+ + NH3) rich conditions where particle phase ammonium (NH4+) concentrations are adequate enough to nearly neutralize major acidic inorganic anions such as sulfate, nitrate, and chloride, leading to a higher aerosol pH. Higher relative availability of the stronger acidic component, sulfate, compared with the weaker acidic component, total nitrate (TNO3 = NO3− + HNO3), also contributes to the lower aerosol pH in the United States. As a response to higher aerosol pH, the higher nitrate to sulfate molar ratios in China indicates a nitrate-rich condition, further leading to higher aerosol water uptake which will continually promote nitrate aerosol formation. Considering the historical emissions trends, the difference in aerosol acidity between these two countries is expected to continue as SO2 and NOx emissions are further controlled. The differences in aerosol acidity highlight in the present study imply potential differences in formation mechanisms, physicochemical properties, and toxicity of aerosol particles between China and the United States.

scholarly journals Simulation of nitrate, sulfate, and ammonium aerosols over the United States

2012 ◽  
Vol 12 (8) ◽  
pp. 19499-19527 ◽  
Author(s):  
J. M. Walker ◽  
J. H. Seinfeld ◽  
L. Clarisse ◽  
P.-F. Coheur ◽  
C. Clerbaux ◽  
...  
Keyword(s):  
United States ◽  
Emission Inventory ◽  
Transport Model ◽  
The United States ◽  
Ammonia Emission ◽  
Chemical Transport Model ◽  
Emissions Inventory ◽  
Nh3 Emission ◽  
The Us ◽  
Nitrate Aerosol

Abstract. Atmospheric concentrations of inorganic gases and aerosols (nitrate, sulfate, and ammonium) are simulated for 2009 over the United States using the chemical transport model GEOS-Chem. This work is motivated, in part, by the inability of previous modeling studies to reproduce observed high nitrate aerosol concentrations in California. Nitrate aerosol concentrations over most of the US are over-predicted relative to Interagency Monitoring of Protected Visual Environments (IMPROVE) and Clean Air Status and Trends Network (CASTNET) data. In California, on the other hand, nitrate and ammonium are under-predicted as compared to California Air Resources Board (CARB) measurements. Over-prediction of nitrate in the East and Midwest is consistent with results of recent studies, which have suggested that nighttime nitric acid formation by heterogeneous hydrolysis of N2O5 is over-predicted with current values of the N2O5 uptake coefficient, γ, onto aerosols. Accordingly, the value of γ is reduced here by a factor of 10. Despite this, predicted nitrate levels in the US Midwest remain higher than those measured and over-prediction of nitrate in this region remains to be explained. Data from the Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp-A satellite indicate the presence of a strong ammonia maximum in central and southern California that is not present in the simulations, which are based on the EPA National Emissions Inventory (NEI) NH3 emission inventory. In order to predict ammonia columns similar to the satellite measurements in the San Joaquin Valley, CA and Riverside, CA, the current ammonia emission inventory in California would need to be increased substantially. Based on the sensitivity of ammonium nitrate formation to the availability of ammonia, the present results suggest that under-prediction of ammonia emissions is likely the main cause for the under-prediction of nitrate aerosol in California.

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