scholarly journals A case study of ozone production, nitrogen oxides, and the radical budget in Mexico City

2009 ◽  
Vol 9 (7) ◽  
pp. 2499-2516 ◽  
Author(s):  
E. C. Wood ◽  
S. C. Herndon ◽  
T. B. Onasch ◽  
J. H. Kroll ◽  
M. R. Canagaratna ◽  
...  
Keyword(s):  
Mexico City ◽  
Production Efficiency ◽  
Formation Rate ◽  
Oxidation Products ◽  
Ozone Production ◽  
Air Mass ◽  
Time Period ◽  
Ambient Nh3 ◽  
Coarse Aerosol

Abstract. Observations at a mountain-top site within the Mexico City basin are used to characterize ozone production and destruction, nitrogen oxide speciation and chemistry, and the radical budget, with an emphasis on a stagnant air mass observed on one afternoon. The observations compare well with the results of recent photochemical models. An ozone production rate of ~50 ppbv/h was observed in a stagnant air mass during the afternoon of 12 March 2006, which is among the highest observed anywhere in the world. Approximately half of the ozone destruction was due to the oxidation of NO2. During this time period ozone production was VOC-limited, deduced by a comparison of the radical production rates and the formation rate of NOx oxidation products (NOz). For [NOx]/[NOy] values between 0.2 and 0.8, gas-phase HNO3 typically accounted for less than 10% of NOz and accumulation-mode particulate nitrate (NO3(PM1)−) accounted for 20%–70% of NOz, consistent with high ambient NH3 concentrations. The fraction of NOz accounted for by the sum of HNO3(g) and NO3(PM1)− decreased with photochemical processing. This decrease is apparent even when dry deposition of HNO3 is accounted for, and indicates that HNO3 formation decreased relative to other NOx "sink" processes during the first 12 h of photochemistry and/or a significant fraction of the nitrate was associated with the coarse aerosol size mode. The ozone production efficiency of NOx on 11 and 12 March 2006 was approximately 7 on a time scale of one day. A new metric for ozone production efficiency that relates the dilution-adjusted ozone mixing ratio to cumulative OH exposure is proposed.

scholarly journals Ozone production, nitrogen oxides, and radical budgets in Mexico City: observations from Pico de Tres Padres

2008 ◽  
Vol 8 (4) ◽  
pp. 15739-15789 ◽  
Author(s):  
E. C. Wood ◽  
S. C. Herndon ◽  
T. B. Onasch ◽  
J. H. Kroll ◽  
M. R. Canagaratna ◽  
...  
Keyword(s):  
Mexico City ◽  
Production Efficiency ◽  
Formation Rate ◽  
Oxidation Products ◽  
Ozone Production ◽  
Time Period ◽  
Ambient Nh3 ◽  
Photochemical Processing ◽  
Coarse Aerosol ◽  
Size Mode

Abstract. Observations at a mountain-top site within the Mexico City basin are used to characterize ozone production and destruction, the nitrogen oxide budget, and the radical budget during the MILAGRO campaign. An ozone production rate of ~50 ppbv/h was observed in a stagnant air mass during the afternoon of 12 March 2006, which is among the highest observed anywhere in the world. Approximately half of the ozone destruction was due to the oxidation of NO2. During this time period ozone production was VOC-limited, deduced by a comparison of the radical production rates and the formation rate of NOx oxidation products (NOz) For [NOx]/[NOy] values between 0.2 and 0.8, gas-phase HNO3 typically accounted for less than 10% of NOz and accumulation-mode particulate nitrate (NO3−(PM)) accounted for 20%–70% of NOz, consistent with high ambient NH3 concentrations. The fraction of NOz accounted for by the sum of HNO3(g) and NO3−(PM) decreased with photochemical processing. This decrease is apparent even when dry deposition of HNO3 is accounted for, and indicates that HNO3 formation decreased relative to other NOx "sink" processes during the first 12 h of photochemistry and/or a significant fraction of the nitrate was associated with the coarse aerosol size mode. The ozone production efficiency of NOx on 11 and 12 March 2006 was approximately 7 on a time scale of one day. A new metric for ozone production efficiency that relates the dilution-adjusted ozone mixing ratio to cumulative OH exposure is proposed.

scholarly journals Investigation of the correlation between odd oxygen and secondary organic aerosol in Mexico City and Houston

2010 ◽  
Vol 10 (2) ◽  
pp. 3547-3604 ◽  
Author(s):  
E. C. Wood ◽  
M. R. Canagaratna ◽  
S. C. Herndon ◽  
J. H. Kroll ◽  
T. B. Onasch ◽  
...  
Keyword(s):  
Mexico City ◽  
Secondary Organic Aerosol ◽  
Formation Rate ◽  
Organic Aerosol ◽  
Ozone Production ◽  
Volatile Components ◽  
Petrochemical Plant ◽  
Plant Emissions ◽  
Photochemical Aging ◽  
Odd Oxygen

Abstract. Many recent models underpredict secondary organic aerosol (SOA) particulate matter (PM) concentrations in polluted regions, indicating serious deficiencies in the models' chemical mechanisms and/or missing SOA precursors. Since tropospheric photochemical ozone production is much better understood, we investigate the correlation of odd-oxygen ([Ox]≡[O3]+[NO2]) and the oxygenated component of organic aerosol (OOA), which is interpreted as a surrogate for SOA. OOA and Ox measured in Mexico City in 2006 and Houston in 2000 were well correlated in air masses where both species were formed on similar timescales (less than 8 h) and not well correlated when their formation timescales or location differed greatly. When correlated, the ratio of these two species ranged from 30 μg m−3 ppm−1 (STP) in Houston during time periods affected by large petrochemical plant emissions to as high as 160 μg m−3 ppm−1 in Mexico City, where typical values were near 120 μg m−3 ppm−1. On several days in Mexico City, the [OOA]/[Ox] ratio decreased by a factor of ~2 between 08:00 and 13:00 LT. This decrease is only partially attributable to evaporation of the least oxidized and most volatile components of OOA; differences in the diurnal emission trends and timescales for photochemical processing of SOA precursors compared to ozone precursors also likely contribute to the observed decrease. The extent of OOA oxidation increased with photochemical aging. Calculations of the ratio of the SOA formation rate to the Ox production rate using ambient VOC measurements and traditional laboratory SOA yields are lower than the observed [OOA]/[Ox] ratios by factors of 5 to 15, consistent with several other models' underestimates of SOA. Calculations of this ratio using emission factors for organic compounds from gasoline and diesel exhaust do not reproduce the observed ratio. Although not succesful in reproducing the atmospheric observations presented, modeling P(SOA)/P(Ox) can serve as a useful test of photochemical models using improved formulation mechanisms for SOA.

scholarly journals Characteristics of the NO-NO<sub>2</sub>-O<sub>3</sub> system in different chemical regimes during the MIRAGE-Mex field campaign

2008 ◽  
Vol 8 (1) ◽  
pp. 2275-2309 ◽  
Author(s):  
Z.-H. Shon ◽  
S. Madronich ◽  
S.-K. Song ◽  
F. M. Flocke ◽  
D. J. Knapp ◽  
...  
Keyword(s):  
Production Efficiency ◽  
Tropospheric Chemistry ◽  
Ozone Production ◽  
Industrial Complex ◽  
Peroxy Radicals ◽  
Air Mass ◽  
Field Campaign ◽  
Air Masses ◽  
Photostationary State ◽  
Mass Dependent

Abstract. The NO-NO2 system was analyzed in different chemical regimes/air masses based on observations of reactive nitrogen species and peroxy radicals made during the intensive field campaign MIRAGE-Mex (4 to 29 March 2006). In general, NO2/NO ratios, which can be used as an indicator to test current understanding of tropospheric chemistry mechanism, are near photostationary state. The air masses were categorized into 5 groups: boundary layer (labeled as "BL"), free troposphere (continental, "FTCO" and marine, "FTMA"), biomass burning ("BB"), and Tula industrial complex ("TIC"). The time- and air mass-dependent NO2/NO ratios ranged from 2.35 (TIC) to 5.18 (BB), while the NOx/NOy ratios varied from 0.17 (FTCO) to 0.54 (BL). The ozone production efficiency for the 5 air mass categories ranged from 5.0 (TIC) to 10.2 (BL), indicating photochemically young and reactive air masses.

scholarly journals Impact of Mexico City emissions on regional air quality from MOZART-4 simulations

2010 ◽  
Vol 10 (2) ◽  
pp. 3457-3498 ◽  
Author(s):  
L. K. Emmons ◽  
E. C. Apel ◽  
J.-F. Lamarque ◽  
P. G. Hess ◽  
M. Avery ◽  
...  
Keyword(s):  
Air Quality ◽  
Mexico City ◽  
Production Efficiency ◽  
Transport Model ◽  
Ozone Production ◽  
Atmospheric Composition ◽  
Chemical Transport Model ◽  
Model Calculations ◽  
Fire Emissions ◽  
Regional Air Quality

Abstract. An extensive set of measurements was made in and around Mexico City as part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) experiments in March 2006. Simulations with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4), a global chemical transport model, have been used to provide a regional context for these observations and assist in their interpretation. These MOZART-4 simulations reproduce the aircraft observations generally well, but some differences in the modeled volatile organic compounds (VOCs) from the observations result from incorrect VOC speciation assumed for the emission inventories. The different types of CO sources represented in the model have been "tagged" to quantify the contributions of regions outside Mexico, as well as the various emissions sectors within Mexico, to the regional air quality of Mexico. This analysis indicates open fires have some, but not a dominant, impact on the atmospheric composition in the region around Mexico City, when averaged over the month. However, considerable variation in the fire contribution (2–15% of total CO) is seen during the month. The transport and photochemical aging of Mexico City emissions were studied using tags of CO emissions for each day, showing that typically the air near Mexico City was a combination of many ages. Ozone production in MOZART-4 is shown to agree well with the net production rates from box model calculations constrained by the MILAGRO aircraft measurements. Ozone production efficiency derived from the ratio of Ox to NOz is higher in MOZART-4 than in the observations for moderately polluted air. OH reactivity determined from the MOZART-4 results shows the same increase in relative importance of oxygenated VOCs downwind of Mexico City as the reactivity inferred from the observations. The amount of ozone produced by emissions from Mexico City and surrounding areas has been quantified in the model by tracking NO emissions, showing little influence beyond Mexico's borders, and also relatively minor influence from fire emissions on the monthly average tropospheric ozone column.

scholarly journals Ozone production efficiency of a ship-plume: ITCT 2K2 case study

Chemosphere ◽  
2016 ◽  
Vol 143 ◽  
pp. 17-23 ◽  
Author(s):  
Hyun S. Kim ◽  
Yong H. Kim ◽  
Kyung M. Han ◽  
Jhoon Kim ◽  
Chul H. Song
Keyword(s):  
Production Efficiency ◽  
Ozone Production

scholarly journals Global tropospheric effects of aromatic chemistry with the SAPRC-11 mechanism implemented in GEOS-Chem

2018 ◽  
Author(s):  
Yingying Yan ◽  
David Cabrera-Perez ◽  
Jintai Lin ◽  
Andrea Pozzer ◽  
Lu Hu ◽  
...  
Keyword(s):  
Production Efficiency ◽  
Chemical Species ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Peroxy Radicals ◽  
Mixing Ratios ◽  
Regional Effects ◽  
Source Regions ◽  
Remote Troposphere

Abstract. The GEOS-Chem model has been updated with the SAPRC-11 aromatics chemical mechanism, with the purpose of evaluating global and regional effects of the most abundant aromatics (benzene, toluene, xylenes) on the chemical species important for tropospheric oxidation capacity. The model evaluation based on surface and aircraft observations indicates good agreement for aromatics and ozone. A comparison between scenarios in GEOS-Chem with simplified aromatic chemistry (as in the standard setup, with no ozone formation from related peroxy radicals or recycling of NOx) and with the SAPRC-11 scheme reveals relatively slight changes in ozone, hydroxyl radical, and nitrogen oxides on a global mean basis (1–4 %), although remarkable regional differences (5–20 %) exist near the source regions. NOx decreases over the source regions and increases in the remote troposphere, due mainly to more efficient transport of peroxyacetyl nitrate (PAN), which is increased with the SAPRC aromatic chemistry. Model ozone mixing ratios with the updated aromatic chemistry increase by up to 5 ppb (more than 10 %), especially in industrially polluted regions. The ozone change is partly due to the direct influence of aromatic oxidation products on ozone production rates, and in part to the altered spatial distribution of NOx that enhances the tropospheric ozone production efficiency. Improved representation of aromatics is important to simulate the tropospheric oxidation.

scholarly journals Global tropospheric effects of aromatic chemistry with the SAPRC-11 mechanism implemented in GEOS-Chem version 9-02

2019 ◽  
Vol 12 (1) ◽  
pp. 111-130 ◽  
Author(s):  
Yingying Yan ◽  
David Cabrera-Perez ◽  
Jintai Lin ◽  
Andrea Pozzer ◽  
Lu Hu ◽  
...  
Keyword(s):  
Production Efficiency ◽  
Chemical Species ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Peroxy Radicals ◽  
Mixing Ratios ◽  
Earth Observing System ◽  
Source Regions ◽  
Remote Troposphere

Abstract. The Goddard Earth Observing System with chemistry (GEOS-Chem) model has been updated with the State-wide Air Pollution Research Center version 11 (SAPRC-11) aromatics chemical mechanism, with the purpose of evaluating global and regional effects of the most abundant aromatics (benzene, toluene, xylenes) on the chemical species important for tropospheric oxidation capacity. The model evaluation based on surface and aircraft observations indicates good agreement for aromatics and ozone. A comparison between scenarios in GEOS-Chem with simplified aromatic chemistry (as in the standard setup, with no ozone formation from related peroxy radicals or recycling of NOx) and with the SAPRC-11 scheme reveals relatively slight changes in ozone, the hydroxyl radical, and nitrogen oxides on a global mean basis (1 %–4 %), although remarkable regional differences (5 %–20 %) exist near the source regions. NOx decreases over the source regions and increases in the remote troposphere, due mainly to more efficient transport of peroxyacetyl nitrate (PAN), which is increased with the SAPRC aromatic chemistry. Model ozone mixing ratios with the updated aromatic chemistry increase by up to 5 ppb (more than 10 %), especially in industrially polluted regions. The ozone change is partly due to the direct influence of aromatic oxidation products on ozone production rates, and in part to the altered spatial distribution of NOx that enhances the tropospheric ozone production efficiency. Improved representation of aromatics is important to simulate the tropospheric oxidation.

scholarly journals Characterizing ozone production in the Mexico City Metropolitan Area: a case study using a chemical transport model

2006 ◽  
Vol 6 (4) ◽  
pp. 7959-8009
Author(s):  
W. Lei ◽  
B. de Foy ◽  
M. Zavala ◽  
R. Volkamer ◽  
L. T. Molina
Keyword(s):  
Mexico City ◽  
Metropolitan Area ◽  
Production Efficiency ◽  
Transport Model ◽  
Ozone Production ◽  
Urban Region ◽  
Air Quality Model ◽  
Chemical Transport Model ◽  
Quality Model ◽  
Photochemical Production

Abstract. An episodic simulation is conducted to characterize ozone (O3) photochemical production and investigate its sensitivity to emission changes of ozone precursors in the Mexico City Metropolitan Area (MCMA) using the Comprehensive Air Quality Model with extensions (CAMx). High Ox (O3+NO2) photochemical production rates of 10–80 ppb/h are predicted due to the high reactivity of volatile organic compounds (VOCs) in which alkanes, alkenes, and aromatics exert comparable contributions. The predicted ozone production efficiency is between 4–10 O3 molecules per NOx molecule oxidized, and increases with VOC-to-NO2 reactivity ratio. Process apportionment analyses indicate significant outflow of pollutants such as O3 and peroxyacetyl nitrate (PAN) from the urban area to the surrounding regional environment. PAN is not in chemical-thermal equilibrium during the photochemically active periods. Sensitivity studies of O3 production suggest that O3 formation in the MCMA urban region with less chemical aging (NOz/NOy<0.3) is VOC-limited. Both the simulated behavior of O3 production and its sensitivities to precursors suggest that midday O3 formation during this episode is VOC sensitive in the urban region on the basis of the current emissions inventory. More episodic studies are needed to construct a comprehensive and representative picture of the O3 production characteristics and its response to emission controls.

scholarly journals Why do models overestimate surface ozone in the Southeast United States?

2016 ◽  
Vol 16 (21) ◽  
pp. 13561-13577 ◽  
Author(s):  
Katherine R. Travis ◽  
Daniel J. Jacob ◽  
Jenny A. Fisher ◽  
Patrick S. Kim ◽  
Eloise A. Marais ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Production Efficiency ◽  
Surface Ozone ◽  
Satellite Observations ◽  
Oxidation Products ◽  
Ozone Production ◽  
Large Contribution ◽  
Nox Emissions ◽  
Tropospheric No2 ◽  
Southeast Us

Abstract. Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx  ≡  NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25°  ×  0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30–60 %, dependent on the assumption of the contribution by soil NOx emissions. Upper-tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 6 ± 14 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer.

scholarly journals Impact of Mexico City emissions on regional air quality from MOZART-4 simulations

2010 ◽  
Vol 10 (13) ◽  
pp. 6195-6212 ◽  
Author(s):  
L. K. Emmons ◽  
E. C. Apel ◽  
J.-F. Lamarque ◽  
P. G. Hess ◽  
M. Avery ◽  
...  
Keyword(s):  
Air Quality ◽  
Mexico City ◽  
Production Efficiency ◽  
Transport Model ◽  
Ozone Production ◽  
Atmospheric Composition ◽  
Chemical Transport Model ◽  
Model Calculations ◽  
Fire Emissions ◽  
Regional Air Quality

Abstract. An extensive set of measurements was made in and around Mexico City as part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) experiments in March 2006. Simulations with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4), a global chemical transport model, have been used to provide a regional context for these observations and assist in their interpretation. These MOZART-4 simulations reproduce the aircraft observations generally well, but some differences in the modeled volatile organic compounds (VOCs) from the observations result from incorrect VOC speciation assumed for the emission inventories. The different types of CO sources represented in the model have been "tagged" to quantify the contributions of regions outside Mexico, as well as the various emissions sectors within Mexico, to the regional air quality of Mexico. This analysis indicates open fires have some, but not a dominant, impact on the atmospheric composition in the region around Mexico City when averaged over the month. However, considerable variation in the fire contribution (2–15% of total CO) is seen during the month. The transport and photochemical aging of Mexico City emissions were studied using tags of CO emissions for each day, showing that typically the air downwind of Mexico City was a combination of many ages. Ozone production in MOZART-4 is shown to agree well with the net production rates from box model calculations constrained by the MILAGRO aircraft measurements. Ozone production efficiency derived from the ratio of Ox to NOz is higher in MOZART-4 than in the observations for moderately polluted air. OH reactivity determined from the MOZART-4 results shows the same increase in relative importance of oxygenated VOCs downwind of Mexico City as the reactivity inferred from the observations. The amount of ozone produced by emissions from Mexico City and surrounding areas has been quantified in the model by tracking NO emissions, showing little influence beyond Mexico's borders, and also relatively minor influence from fire emissions on the monthly average tropospheric ozone column.

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