Top PDF Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign

Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign

Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign

Vertical distributions of aerosols also play an important role in the evaluation of aerosol impacts on solar radiation. Measurements from research aircrafts deployed during MI- LAGRO provide detailed spatial and temporal variation of aerosols that are not available from the surface sites. In this study, the measured nitrate, ammonium and sulfate aerosols using the PILS-IC techniques on the G-1 research aircraft are compared with the WRF-CHEM model simulations on 26 and 27 March (see Fig. 3). The model is able to cap- ture the plumes observed by the aircraft on 26 and 27 March. The model reproduces the variation of nitrate and ammo- nium aerosols, but shows some differences of the aerosol concentrations in some plumes. For sulfate aerosols, the cal- culation of the model is consistent with the measurement on March 27, but overestimates several spikes occurred on 26 March when the plumes are influenced by the Tula in- dustrial complex. The IOA for aloft nitrate, ammonium and sulfate aerosols are 0.82, 0.82, and 0.58 on 26 March, and 0.85, 0.84 and 0.88 on 27 March, respectively. Furthermore, we have compared the model results with the BC measured by the SP2 (Single Particle Soot Photometer) and the nitrate, ammonium, sulfate, and total organics components measured by the Aerodyne Time-of-Flight Mass Spectrometer (ToF- AMS) onboard C-130 on 29 March (see Fig. 4) (Molina et al., 2010). The results demonstrate that the simulated vari- ability of BC captures several measured spikes, which are resulted from the transport of city plumes. Since BC can be considered as a passive tracer during the dry season, the BC simulation suggests that the model is able to simulate the transport of city plumes during this field campaign. Although the calculated variability is similar to the observations for ni- trate, ammonium, and total organic aerosols, the calculated concentrations are generally underestimated compared to the measurements. In addition, on 29 March, the plumes formed in Mexico City move northwest in the afternoon, derived by the well organized south and northeast winds from outside of the basin (Li et al., 2011). The sulfate aerosols emitted di- rectly by the volcano occasionally influence the plumes over the city (de Foy et al., 2009). The observed spikes of sulfate aerosols from the volcano are generally well reproduced by the model.
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Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006

Chemically-resolved aerosol eddy covariance flux measurements in urban Mexico City during MILAGRO 2006

A substantial fraction of particulate pollution is produced by industry and transportation in urban areas and is recog- nized to influence regional and global atmospheric chemistry (Lawrence et al., 2007). Anthropogenic pollution problems have been intensified by the rapid urbanization and the grow- ing number of megacities (population exceeding 10 million inhabitants). Currently, about 58 % of the global population lives in urban areas, which have a population growth rate 18 times higher than in the rural areas (UN, 2010). Thus, in or- der to reliably predict future impacts on environment and hu- man health, it is essential to understand the sources, chemical nature, evolution, and fate of urban pollution. The Megacity Initiative: Local and Global Research Observations (MILA- GRO) 2006 field campaign, conducted in Mexico City dur- ing March 2006, was an international initiative designed to study these topics (Molina et al., 2010). One research focus during MILAGRO was the exchange of mass and energy be- tween the urban surface and the atmosphere. Using fast re- sponse sensors coupled with eddy covariance (EC) methods, fluxes of chemically-resolved submicron aerosols, selected volatile organic compounds (VOCs), CO 2 , and components
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Vertical distribution of aerosols in the vicinity of Mexico City during MILAGRO-2006 Campaign

Vertical distribution of aerosols in the vicinity of Mexico City during MILAGRO-2006 Campaign

On 7 March 2006, in the presence of light, northerly winds (de Foy et al., 2008; Fast et al., 2007), the University of Iowa mobile vertical lidar system performed a North-South tran- sect through the Mexico City basin. The lidar system mea- sured the vertical and horizontal distribution of the various aerosol layers. The unique topography of the basin created conditions in which the northerly winds were venting the val- ley, mostly through a narrow pass in the south of the basin. The measurements on 7 March 2006, were intended to quan- titatively capture the vertical and horizontal distribution of aerosols and observe the transition between the inside and the outside of the Mexico City basin. The exact route is il- lustrated in Fig. 2. The ground mobile lidar measurement effort was also intended to be coordinated with the airborne measurements carried out from the Veracruz airport. In retro- spect, this effort was only somewhat successful due to traffic,
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Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

Salcedo, D., Onasch, T. B., Dzepina, K., Canagaratna, M. R., Zhang, Q., Huffman, J. A., De- Carlo, P. F., Jayne, J. T., Mortimer, P., Worsnop, D. R., Kolb, C. E., Johnson, K. S., Zuberi, B., Marr, L. C., Volkamer, R., Molina, L. T., Molina, M. J., Cardenas, B., Bernab ´e, R. M., M ´arquez, C., Gaffney, J. S., Marley, N. A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T., and Jimenez, J. L.: Characterization of ambient aerosols in Mexico

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Simultaneous retrieval of aerosol and cloud properties during the MILAGRO field campaign

Simultaneous retrieval of aerosol and cloud properties during the MILAGRO field campaign

Fig. 2. The spatial context of our AAC scene is presented in this figure. The blue circle in- dicates the location of RSP observations, above a marine stratocumulus cloud on the Gulf of Mexico coast. A portion of the J-31 flight track is shown in yellow. The J-31 performed a spiral to the surface about 125 km northwest of the scene, and data collected during this descent provided information about cloud and aerosol vertical distribution. Aerosol sources include ur- ban/industrial emissions in the Mexico City Metropolitan Area (MCMA) basin, a high valley to the west, and numerous (mostly agricultural) fires indicated by the red fire icons. Fire locations were identified by the MODIS active fire product and represent fires within the previous eight days. The MODIS Terra instrument captured the underlying image.
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MAX-DOAS detection of glyoxal during ICARTT 2004

MAX-DOAS detection of glyoxal during ICARTT 2004

The strongest absorption bands of CHOCHO are located in the blue wavelength range between 420 and 460 nm (Volka- mer et al., 2005b). These bands have recently been used to measure CHOCHO for the first time directly in the open atmosphere, as part of the Mexico City Metropolitan Area (MCMA) 2003 campaign, using an active differential optical absorption spectroscopy (DOAS) device (employing a Xe- arc light source). It has further been suggested that the de- tection of CHOCHO by passive DOAS, i.e. using scattered sunlight as a light source, should be feasible from ground- or space-borne platforms (Volkamer et al., 2005a). Most re- cently measurements of CHOCHO from space have been ac- complished by three research teams using two satellite plat- forms (i.e. the Ozone Monitoring Instrument (OMI) and the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY)) (Kurosu et al., 2005; Wit- trock et al., 2006; Beirle et al., 2006). In this study we present the first comprehensive analysis of CHOCHO using passive ground-based DOAS instrumentation based on initial stud- ies by Sinreich et al. (2004). CHOCHO observations from ground-based instruments have also been reported by Wit- trock et al. (2006).
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Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

both [SOA] and [POA], during the peak time, the ensemble mean is generally lower than the observations but notably better than the reference deterministic forecast, indi- cating the possibility of improving the SOA simulation through the ensemble forecasts. As indicated in the Fig. 4a, b, there is also a best member, which fits the observations very well, including both the timing and the magnitude. Further analysis on this best

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Estimation of the mass absorption cross section of the organic carbon component of aerosols in the Mexico City Metropolitan Area (MCMA)

Estimation of the mass absorption cross section of the organic carbon component of aerosols in the Mexico City Metropolitan Area (MCMA)

B., Marr, L. C., Volkamer, R., Molina, L. T., Molina, M. J., Cardenas, B., Bernab ´e, R. M., M ´arquez, C., Gaffney, J. S., Marley, N. A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T., and Jimenez, J. L.: Characterization of ambient aerosols in Mexcico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: Results from the CENICA supersite, Atmos. Chem. Phys., 5, 925–946, 2006,

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Sources and production of organic aerosol in Mexico City: insights from the combination of a chemical transport model (PMCAMx-2008) and measurements during MILAGRO

Sources and production of organic aerosol in Mexico City: insights from the combination of a chemical transport model (PMCAMx-2008) and measurements during MILAGRO

The values of the OA concentrations at the boundaries of the domain, approximately 8 µg m −3 in the west, 11.5 µg m −3 in the east, 7 µg m −3 in the south and 5 µg m −3 in the north- ern boundary, were chosen based on results of the GISS- II’ global CTM for March (Racherla and Adams, 2006). All concentrations in this paper are under ambient pressure and temperature conditions. These levels represent the av- erage OA concentrations over the Central Mexican Plateau approximately 100 km outside Mexico City and should not be confused with the larger-scale background concentrations of Mexico (reflecting concentrations over the lower to mid- dle troposphere over the Pacific Ocean) of much less than 0.5 µg m −3 (DeCarlo et al., 2008; Fast et al., 2009). 32 % of the OA concentration at the boundaries of the domain is assumed to be 0.04–0.08 µm in size, 24 % is the 0.08– 0.16 µm range, 20 % from 0.16 to 0.31 µm, 12 % from 0.31 to 0.625 µm, 8 % from 0.625 to 1.25 µm, and 4 % in the 1.25– 2.5 µm range. Because the biomass burning emissions are not included in the current inventory, they are implicitly provided to the model as a part of the boundary conditions. These rel- atively high boundary condition values are consistent with the findings of Yokelson et al. (2007) suggesting that the fires in the mountainous forests around Mexico City (MC) could produce as much as 80–90 % of the primary fine parti- cle mass in the MC area. DeCarlo et al. (2010) reported that OA arising from open BB represents around 65 % of the OA mass in the basin and contributes similarly to OA mass in the outflow. Crounse et al. (2009) estimated that biomass burn- ing contributed two thirds of the organic aerosol to the study area in March 2006. Subsequent atmospheric oxidation of co-emitted hydrocarbons can yield low vapor pressure com- pounds that condense on the existing particulate forming sec- ondary organic aerosol. Therefore, the organic mass trans- ported into the domain is assumed to be a mixture of aged pri- mary and secondary organic aerosols, and is referred to here- after as “long range transport oxygenated OA” (LT-OOA). The model assumes that V-SOA, I-SOA and S-SOA form a pseudo-ideal solution together with the LT-OOA, which are assumed to be non-reactive and nonvolatile, and therefore, are allowed to partition into this pre-existing organic aerosol.
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Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area

Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area

POA in Mexico City is semivolatile. The average concentra- tion of the organic aerosols in Mexico City was in the range of 20 µg m −3 during the MCMA-2003 campaign (Salcedo et al., 2006). In this range of organic aerosol ambient con- centrations, the measured organic PM is approximately one third of the total emitted organic aerosols (Fig. 1a of Robin- son et al., 2007). Therefore, in order to estimate the total semivolatile organic emissions, the OA particulate inventory is multiplied by a factor of 3. Source test data for wood com- bustion, gasoline vehicles and diesel vehicles which used a sample train of quartz filters in combination with denuders and/or sorbents (Schauer et al., 1999, 2001, 2002) has shown that the mass of unmeasured IVOC vapours is between 0.25 to 2.8 times the existing primary OA emissions. In this work, the OA emissions were distributed by volatility (Table 3) us- ing the volatility distributions of Shrivastava et al. (2008). This distribution was derived by fitting gas particle partition- ing data for diesel exhaust and wood smoke assuming that the mass of unmeasured IVOC emissions is equivalent to 1.5 times the primary organic aerosol emissions. The total amount of material (POA+SVOC+IVOC) introduced in the model is 7.5 times the particle-phase POA emissions, which is identical to the factor calculated from partitioning theory
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Modeling the impacts of biomass burning on air quality in and around Mexico City

Modeling the impacts of biomass burning on air quality in and around Mexico City

beri, B., Marr, L. C., Volkamer, R., Molina, L. T., Molina, M. J., Cardenas, B., Bernab ´e, R. M., M ´arquez, C., Gaffney, J. S., Marley, N. A., Laskin, A., Shutthanandan, V., Xie, Y., Brune, W., Lesher, R., Shirley, T., and Jimenez, J. L.: Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite, Atmos. Chem. Phys., 6, 925–946, doi:10.5194/acp-6-925-2006, 2006.

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Formation of semivolatile inorganic aerosols in the mexico city metropolitan area during the milagro campaign

Formation of semivolatile inorganic aerosols in the mexico city metropolitan area during the milagro campaign

MIRAGE-Mex field campaigns respectively. However, there have been rather limited ef- forts to predict particle concentrations in Mexico City by using three-dimensional chem- ical transport models (CTMs). Tsimpidi et al. (2010, 2011) applied PMCAMx-2008 simulating the organic aerosol formation during the MCMA-2003 and MILAGRO-2006 campaigns by using the volatility basis set framework assuming that both primary and

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Impacts of HONO sources on the photochemistry in Mexico City during the MCMA-2006/MILAGO Campaign

Impacts of HONO sources on the photochemistry in Mexico City during the MCMA-2006/MILAGO Campaign

Shutthanandan, V., Zheng, J., Zhang, R., Gaffney, J., Marley, N. A., Paredes-Miranda, G., Arnott, W. P., Molina, L. T., Sosa, G., and Jimenez, J. L.: Mexico City aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 1: Fine particle composition and organic source apportionment, Atmos. Chem. Phys., 9, 6633–6653, 2009, http://www.atmos-chem-phys.net/9/6633/2009/.

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Impacts of HONO sources on the photochemistry in Mexico City during the MCMA-2006/MILAGO Campaign

Impacts of HONO sources on the photochemistry in Mexico City during the MCMA-2006/MILAGO Campaign

Additionally, a chemical model is also fully implemented into the WRF model (WRF-CHEM) (Grell et al., 2005; Tie et al., 2007). Based on the framework of the cur- rent WRF-CHEM model and the available emissions in- ventory in Mexico City (Song et al., 2010), a new flexi- ble gas phase chemical module has been developed and im- plemented into the WRF-CHEM model, which can be uti- lized with different chemical mechanisms, including CBIV, RADM2, and SAPRC. The chemistry is solved by an Eule- rian backward Gauss-Seidel iterative technique with a num- ber of iterations, inherited from NCAR-HANK (Hess et al., 1999). The short-lived species, such as OH and O ( 1 D), are assumed to be in steady state. The solution is iterated until all species are within 0.1% of their previous iterative values. For the aerosol simulations, the CMAQ/models3 (version 4.6) aerosol module developed by US EPA (Envi- ronmental Protection Agency), which is designed to be an efficient and economical depiction of aerosol dynamics in the atmosphere, has also been incorporated into the WRF- CHEM model (Binkowski and Roselle, 2003). In this aerosol component, the particle size distribution is represented as the superposition of three lognormal sub-distributions called modes. The processes of coagulation, particle growth by the addition of mass, and new particle formation are included. In addition, the wet deposition also follows the method used in the CMAQ/Models3. Surface deposition of chemical species is parameterized following Wesely (1989). The photolysis rates are calculated using the FTUV (Tie et al., 2003; Li et al., 2005). Anthropogenic emissions used in the WRF-CHEM model are constructed from the official emissions inventory for the MCMA-2006 (Song et al., 2010). Biogenic emissions are estimated using the MEGAN v2.04 model (Model of Emissions of Gases and Aerosols from Nature) developed by Guenther et al. (2006, 2007); the on-line biogenic emissions calculation is turned off. In the present study, the SAPRC 99 gas phase chemical mechanism is employed according to the available emission inventory in Mexico City.
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Aerosol plume transport and transformation in high spectral resolution lidar measurements and WRF-Flexpart simulations during the MILAGRO Field Campaign

Aerosol plume transport and transformation in high spectral resolution lidar measurements and WRF-Flexpart simulations during the MILAGRO Field Campaign

GRO field campaign, the Mexico City Metropolitan Area (MCMA) experiences particularly high aerosol loadings (de Foy et al., 2008). These contribute to high exposure lev- els on longer time scales which are an important health con- cern (Molina and Molina, 2002). These aerosols are the re- sult of emissions from very different sources including urban emissions, biomass burning smoke and wind suspended dust (Salcedo et al., 2006; Raga et al., 2001). The aerosol plumes are transported by complex wind patterns in the basin lead- ing to inhomogeneous plume dispersion (Fast and Zhong, 1998) that is strongly impacted by local convergence zones (Jazcilevich et al., 2005; de Foy et al., 2006a. Intense verti- cal mixing in the afternoon leads to rapid venting of the urban plume outside of the basin (de Foy et al., 2006c). This paper focuses on identifying aerosol plumes in the MCMA basin during the MILAGRO field campaign using High Spectral Resolution Lidar (HSRL) measurements (Hair et al., 2008) and WRF-Flexpart particle trajectory simulations of known sources (de Foy et al., 2009b).
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Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study

Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study

Here we study organic carbon in the combined gas and aerosol phases using data from the sub-urban T1 site in Mex- ico City during MILAGRO. The T1 site was located ∼30 km to the northeast of the center of Mexico City on the campus of the Technical University of Tec´amac and was chosen as part of a T0-T1-T2 series of sites to capture outflow from Mexico City to the northeast after different transport times (Doran et al., 2007; Fast et al., 2007). The Mexico City urban area extends to T1: local emissions were not insignificant and likely dominated during the night and early morning. Us- ing observed diurnal variations, the primary emissions and secondary formation of VOCs and of organic aerosol can be distinguished from each other, and the results are compared with findings obtained in the U.S. The results from multi- ple instruments are used to compare the total observed or- ganic carbon (TOOC) (Heald et al., 2008) between the morn- ing and afternoon. Finally, the influence of biomass burning on the measurements of VOCs and organic aerosol is dis- cussed using the measurements of acetonitrile. Previous es- timates of the influence of biomass burning on the emissions in and around Mexico City are highly variable (Yokelson et al., 2007; DeCarlo et al., 2008; Moffet et al., 2008; Querol et al., 2008; Stone et al., 2008).
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Long-range pollution transport during the MILAGRO-2006 campaign: a case study of a major Mexico City outflow event using free-floating altitude-controlled balloons

Long-range pollution transport during the MILAGRO-2006 campaign: a case study of a major Mexico City outflow event using free-floating altitude-controlled balloons

flow with entrainment into a cleaner westerly jet below the plateau. The C-130 aircraft intercepted the balloon-based trajectories three times on 19 March, once along each of these pathways. In all three cases, distinct peaks in the urban tracer signatures and LIDAR backscatter imagery were consistent with MCMA pollution. The coherence of the high-altitude outflow was well preserved after one day whereas that lower in the

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Thermodynamic characterization of Mexico City aerosol during MILAGRO 2006

Thermodynamic characterization of Mexico City aerosol during MILAGRO 2006

In the present work, we use ISORROPIA-II, which treats the thermodynamics of the K + -Ca 2+ -Mg 2+ -NH + 4 -Na + -SO 2− 4 -HSO − 4 -NO − 3 -Cl − -H 2 O aerosol system, to a) test the thermodynamic equilibrium assumption for the Mexico City environment during the MI- LAGRO 2006 campaign, b) gain insight on the preferred phase behavior of the aerosol (i.e. deliquescent or metastable), and, c) assess the importance of a full thermody-

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Measurements of OH and HO<sub>2</sub> concentrations during the MCMA-2006 field campaign – Part 1: Deployment of the Indiana University laser-induced fluorescence instrument

Measurements of OH and HO<sub>2</sub> concentrations during the MCMA-2006 field campaign – Part 1: Deployment of the Indiana University laser-induced fluorescence instrument

and filtered by a pulse-height discriminator that delivers TTL pulses for each detected photon. The photon counter is set with a timing gate using a delay and width for the 2 m long fiber of 130 and 260 ns after the laser pulse. These parameters were optimized to give the best signal-to-noise ratio by discriminating electronic noise and scattered laser-light against the weak OH fluorescence, and are different when the 12 m long

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Contribution of garbage burning to chloride and PM<sub>2.5</sub> in Mexico City

Contribution of garbage burning to chloride and PM<sub>2.5</sub> in Mexico City

Lelieveld, J., Crutzen, P. J., Ramanathan, V., Andreae, M. O., Brenninkmeijer, C. A. M., Campos, T., Cass, G. R., Fischer, H., de Gouw, J. A., Hansel, A., Jefferson, A., Kley, D., de Laat, A. T. J., Lal, S., Lawrence, M. G., Lobert, J. M., Mayol-Bracero, O. L., Mitra, A. P., Novakov, T., Oltman, S. J., Prather, K. A., Reiner, T., Rodhe, H., Scheeren, H. A., Sikka, D., and Williams, J.: The Indian Ocean Experiment: Widespread Air Pollution from South and Southeast Asia,

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