A33A-01
Preliminary Estimations of the Photostationary Parameter and Peroxy Radicals for the Atmosphere of São Paulo
The Metropolitan Area of São Paulo (MASP) is a megacity with more than 17 million inhabitants and presents severe problems of the air quality, affecting the people health. In order to evaluate air quality of MASP, ozone was analyzed and the photostationary state (PSS) parameter and peroxy radicals concentrations were calculated using environmental measurements of ozone and nitrogen oxides. They were estimated from 09:00 to 18:00 h, local time. This preliminary analysis was first performed for four days at Ibirapuera Park, which has an official air quality monitoring station. Three of the chosen days, in spite of being cloudless, presented ozone values much higher than the standard air quality value (160 mg/m3). The fourth was a cloudless day, but was observed lower ozone concentration. The days with high ozone levels presented the PSS parameter higher than the unity almost all day long; sometimes it was higher than three times. These maximum values were observed from noon up to two in the afternoon and indicated the presence of other oxidants besides ozone at São Paulo. The day with low ozone levels presented PSS parameter values around the unity without maximum values, probably due to small amount of oxidants. The peroxy radicals oscillated between 5 and 701 pptv for the analyzed days and can be an indication of the high oxidant power in the troposphere of São Paulo.
A33A-02
Remote Measurements of Carbon Monoxide over North America and Europe during Summer- Fall 2004 and Southern Hemisphere 2006
The MicroMAPS instrument is a nadir-viewing, gas filter-correlated radiometer which operating in the 4.67 micrometer fundamental band of carbon monoxide. Originally designed and built for a space mission, this CO remote sensor is being flown in support of satellite validation and science instrument demonstrations for potential UAV applications. The MicroMAPS instrument system was integrated and tested at NASA LaRC, in partnership with Scaled Composites and Virginia Space Grant Consortium (VSGC). Full system integration and flight testing was performed at Scaled Composites, in Mojave, in June 2004. Its successful performance enabled participation in four international science missions on Proteus: in 2004, INTEX -NA over eastern North America in July, ADRIEX over the Mediterranean region and EAQUATE over the United Kingdom region in September,and TWP-ICE over Darwin, Australia and the surrounding oceans in Jan-Feb 2006. These flights resulted in nearly 300 hours of data. In parallel with the engineering developments, theoretical radiative transfer models were developed specifically for the MicroMAPS instrument system at the University of Virginia, Mechanical Engineering Department by a combined undergraduate and graduate student team. With technical support from Resonance Ltd. in June 2005, the MicroMAPS instrument was calibrated for the conditions under which the Summer-Fall 2004 flights occurred. The analyses of the calibration data, combined with the theoretical radiative transfer models, provide the first data reduction for the science flights reported here. The influence on widespread fires in Alaska and Canada, coupled with the influence of stratospheric intrusions over the eastern portion of North America during Summer 2004, provides the opportunity to examine the evolution of the tropospheric column and to examine how the transport histories of the air resulted in the CO columns sampled from the Proteus aircraft. These early results and comparisons with profile data from the NASA DC-8, the coincident AIRS CO retrievals, and selected measurements from the MOZAIC program and RAQMS model runs will be presented. Preliminary retrievals for the TWP-ICE transit flights and comparison with the coincident AIRS CO retrievals will also be presented.
A33A-03
Variability in Tropospheric Ozone Observed through Ozone Soundings from Mexico City
As part of the INTEX Ozonesonde Network 2006 Study (IONS-06) thirty ozonesondes were launched from the Central de Ciencias de la Atmósfera (CCA) at the Universidad Nacional Autónoma de México, in the southwest sector of Mexico City, in August and September of 2006. Vertical profiles of ozone, temperature and relative humidity were measured up to altitudes that usually exceeded 30 km. These measurements are complementary to those that were made during the same period at 22 other locations in the United States and Canada. The analysis compares the profiles of ozone made in the tropical latitude of Mexico City (19°N, 99°W) with those made at mid and high latitudes. The evaluation includes day to day variability, altitudes of peak ozone and the number of distinct layers. Special emphasis will be given the unique features of the tropical ozone profiles in relationship to previous measurements that were made earlier in 2006 during the MILAGRO field project and how the observed differences are related to local and larger scale meteorology.
A33A-04
Optical Remote Sensing Measurements of Air Pollution in Mexico City During MCMA- 2006
During March 2006 the Optical Remote sensing group at Chalmers University of Technology participated in the MCMA-2006 field campaign in Mexico City, performing measurements of air pollution using a set of different optical remote sensing instruments. This poster gives an overview of the techniques applied and results obtained. The techniques applied were:
A33A-05
Measurements of Methylglyoxal and Aromatic Hydrocarbons during 06 MILAGRO Campaign
Methylglyoxal (CH3COCHO) is produced in the atmosphere from photochemical oxidation of volatile organic compounds (VOCs). Oxidation of anthropogenic aromatics (toluene, xylenes, or trimethylbenzenes) and biogenic isoprene leads to a significant production of methylglyoxal in the urban and regional atmospheres. For example, the molar molecular yield of methylglyoxal is about 0.9 from 1,3,5-trimethylbenzene oxidation and 0.4 to 0.16 for toluene oxidation. In the gas-phase, photolysis or reaction with the OH radical has been identified as the major loss process for methylglyoxal, with the lifetimes of about 1-3 h during the daytime. Recently, it has been suggested that aerosol-phase reactions of methylglyoxal contribute to secondary organic aerosol (SOA) formation, by forming low-vapor pressure oligomers in the aerosols. Measurements of methylglyoxal and aromatic hydrocarbons using proton transfer-reaction mass spectrometer (PTR-MS) during the MILAGRO field campaign will be presented. The implications of the results on SOA formation will be discussed.
A33A-06
The Ecological Monitoring Of Atmosphere Pollution In A City With Microwave
The ecological problem is a problem of mutual relation of a society and nature preservation of an environment. The development of industry results in increasing of the atmosphere pollution. This paper presents the measurements of degree of pollution zone on several links with length di each. The amount of links depends on city dimension and on presence of enterprises with emission into atmosphere of harmful substances. It is known, that by the emissions in an atmosphere of harmful substances (CO, CO2 , NO etc) the environment refraction coefficient nAV (average value) is changed. So, the phase progression of microwave kd identifies the properties of an environment, where k - microwave propagation constant. In a paper (I. B. Shirokov, M. V. Ivashina, Amplitude and Phase Progression Measurements on Microwave Line-of- Sight Links, IEEE Conf. Proc. IGARSS'01, Sydney, Australia) it was shown the possibility of phase progression measurement on microwave. In this paper it is suggested to abandon the synchronization of the microwave oscillations by low frequency oscillations and to use the origin microwave oscillations as heterodyne ones with the same initial phase and a frequency shift. The length of measurement link can reach several kilometers, so the phase stability of link in low frequency band was enough for phase measurement on microwave band with high accuracy, because of length of testing link is much less than low frequency wavelength. So, presented method let us measure phase difference, which is proportional to phase progression of microwave on line-of-sight link. Taking into account that phase progression of microwave depends on refraction coefficient of medium n, we have possibility to carry out the ecological monitoring of region, where the testing link is placed. However, the phase measurements are uncertain principally. In a paper it is presented the possibility of elimination of these disadvantages by the changing of the frequency f of microwave. According to known data and the diagrams, represented in a paper, the limiting content of dangerous gases in atmosphere is not high. So, the changing of refraction coefficient of atmosphere not exceeds tens ppm (hundreds max) in relation of changing of pollution. However, taking into account the lengths of testing links in kilometers, or hundred of thousands of microwave length, there is an opportunity of registration and control of volumes of emissions of harmful substances in an atmosphere by the microwave phase measurements with high accuracy. Thus, it is possible to study the influence of the environment properties both on the microwave propagation losses that is well investigated today and the insertion phase shift of the microwave. There is every reason to assume that the idea put forward in the paper will allow to expand our knowledge about the microwave propagation mechanisms and also to help solving the inverse problem — determine the of influence of emissions of harmful substances on properties of environment. Furthermore, it is possible to obviate difficulties, associated with the establishment of automatic control of the environmental atmosphere surface layer. This method doesn't need in numerous manpower, travel facilities, complicated and expensive equipment. The process becomes easy and less time-consuming. It can carry out permanent ecology control. Measurement accuracy is determined with the radiation wavelength and doesn't depend on instrumental errors of measurements. Suggested method of measurements permits to solve not only the tasks of ecology. It will be find the application in chemistry and other branches of industry.
A33A-07
Development and Evaluation of a Gas and PM Emissions Inventory for Mexico City
One of the main goals of MCMA-2006/MILAGRO Campaign (http:www.mce2.org) is to study the emissions of primary pollutants, the atmospheric processes leading to the formation of secondary aerosols from precursor gases, as well as to understand the transport and transformation of these gases and aerosols on local, regional, and global scales. Evaluation of these processes using chemical transport models requires an emissions inventory with detailed information of emitted gaseous and particulate matter (PM) pollutants. We have developed an emissions inventory for the Mexico City Metropolitan Area (MCMA) that includes both speciated gas and partitioned PM emissions. Emissions from point, area (biogenic and anthropogenic) and mobile sources are spatially and temporally resolved by using a bottom-up approach with a Geographic Information System. The emissions of gaseous species are based on the SAPRC99 chemical mechanism. The PM is partitioned in its primary organic, primary elemental carbon, and primary inorganic components (sulfates, nitrates and ammonium). Crustal species and aerosol water content are also considered in the partitioning. The estimated emissions inventory is implemented in the PMCAMx and the CMAQ/Models3 regional chemical transport models. The simulated aerosol composition from these models is compared with measurements from the MCMA- 2006/MILAGRO Campaign.
A33A-08
Mobile Emission Trends in the MCMA: Effects on Photochemistry
Emissions from mobile sources have a strong influence on the photochemical levels and other pollutants of an urban area. Mobile emissions in the Mexico City Metropolitan Area (MCMA) have been studied for the period 1991- 2006 with several measurement techniques that include remote sensing, dynamometer and tunnel studies and - more recently- with the chasing technique. During the same time period, several factors that directly affect the emission characteristics of the vehicle fleet have occurred. These factors include the implementation of more stringent emission standards, emission control technologies and changes in fuel composition, among others. Along with these changes, concurrent non-linear changes in photochemical levels as well as in toxic and criteria pollutants have been observed. In this study we compare the historical trends of CO, NOx and VOCs from mobile emission sources in the MCMA from 1991 to 2006 with pollutant trends of hourly data of CO, NOX, and the CO/NOX ratio during peak traffic. Using the historical trends comparison and the on-road emission data obtained with the Aerodyne Research Inc. (ARI) Mobile Laboratory during the 2002/2003-MCMA and the MCMA-2006/MILAGRO field campaigns (see http:www.mce2.org), we derive historical changes on the VOC/NOX ratio from mobile sources. The inferred trend is in turn compared with observed trends of O3 to quantify the induced changes on photochemical levels in the MCMA by mobile sources. Finally, the effect of the perturbed VOC/NOX ratio on simulated historical ozone levels is investigated in a companion modeling study.
A33A-09
Risk Assessment for Criteria Pollutants and Air Toxics in two Sites of Mexico City During 2003 Field Campaign
An environmental risk assessment for criteria pollutants and air toxics in Mexico City is presented. The data used in the study were collected by FTIR and DOAS systems during the Mexico City Metropolitan Area field campaign on April 2003 (MCMA2003). The systems were deployed in two different sites: One in downtown (Merced) and the other in the south east (CENICA). Concentrations of criteria pollutants and air toxics were obtained every 5 min and were used to obtain hourly average concentrations and the month average for April. The concentration values were used to estimate the risks of acute and chronic exposure to ambient concentrations using risk measures like hazard index, life cancer probability, life lost expectancy and maximum individual cancer risk. Results revealed that both sites have similar risk values. For acute exposure, criteria pollutants have larger risks than air toxics, but air toxics have larger risks for chronic exposure. Ambient concentrations of benzene showed the largest carcinogenic risk of the measured air toxics.
A33A-10
IMP Supersite vs Pico de Tres Padres: The first few hours of mixing and oxidation during the MCMA-2006/MILAGRO Campaign
The Aerodyne Research, Inc. (ARI) mobile laboratory was deployed in the Mexico City Metropolitan Area (MCMA) for the full month of March 2006 to support the MCMA-2006/MAX-Mex/MILAGRO research project activities, in collaboration with other MCMA-2006 research groups (see information on MCMA-2006/MILAGRO posted at http:www.mce2.org). The ratios of various volatile organic compounds (VOCs) to combustion tracer species such as CO and CO2 are compared at one of the supersites (T0) and Pico de Tres Padres. T0 (located at the Mexican Petroleum Institute, IMP) is heavily influenced by various emission sources in the local area, predominantly roadway traffic. Pico de Tres Padres is an isolated, privately owned mountain located within the Mexico City Metropolitan Area (MCMA). It rises 1000 m above the MCMA basin floor and is located about halfway between T0 and T1. The airmasses analyzed at Pico de Tres Padres seem to be mixed urban emissions absent of high frequency spikes of CO, NO or CO2. Relationships between VOCs, and combustion tracers will be used to gain a crude understanding of the initial photochemical processing of the urban emissions. How the initial photochemical processing of Mexico City's air may relate to secondary aerosol production is also explored.
A33A-11
Formaldehyde Surface Distributions and Variability in the Mexico City Basin
Formaldehyde ambient air mole fractions were measured throughout the dry season in March at three different locations in the Mexico City basin. The continuously running instruments were operated at Tenago del Aire, a site located in the Chalco valley in the southern venting area of the basin, at the Intituto Mexicano del Petroleo (IMP) in the northern part of the city and about 30 km north of the city at the campus of the Universidad Tecnològica de Tecamac (UTTEC). The technique used is the Hantzsch technology with a time resolution of 2 minutes and a detection limit of 100 ppt. Daily maxima peaked at 35 ppb formaldehyde in the city and about 15 to 20 ppb at the other sites. During night formaldehyde levels dropped to about 5 ppb or less. It is evident that the observed spatial and temporal variability in near surface formaldehyde distributions is strongly affected by local and regional advection processes.
A33A-12
MTBE as a Tracer for Asian and Mexican Megacity Emissions
Methyl tertiary butyl ether (MTBE) is an oxygenated volatile organic compound (OVOC) added to gasoline to either increase the oxygenated content and/or to increase the octane rating. MTBE is currently added to fuels in Asia and Mexico in the range of 2-7%. Only small quantities of MTBE are found in fuels in the United States because of extensive regulatory action restricting its use. MTBE is short lived in the atmosphere with a lifetime of approximately 3.5 days. Losses are primarily due to reaction with the OH radical. It is an exclusive indicator of tailpipe and evaporative emissions and unlike ethyne is not emitted from biomass burning. We used MTBE measured during the MIRAGE and INTEX-B airborne studies and during the CLIVAR P16N oceanographic cruise that coincidently traversed the Pacific Ocean to differentiate and quantify important VOC emission sources from Asia and Mexico.
A33A-13
Trace gas measurements at the Altzomoni site (4000 masl) near Mexico City
The Altzomoni site is located on a mountain pass 60 km southeast of Mexico City and more than 1700 m above the basin. This high altitude station is well above the boundary layer and thus gives the possibility to observe long range transport of pollutants primarily between the Puebla and the MCMA basins. Situated inside the Izta-Popo National Park, with close to 20000 hectares, the site has no significant anthropogenic emissions. Trace gas measurements were done using an open-path FTIR spectrometer during November 2005 and March of 2006. The bistatic telescope system was placed on top of two hills separated by 367 m. Spectra in the region 600 - 4000 cm-1 were averaged and recorded at 0.5 cm-1 spectral resolution every 5 min and the concentrations of CO, CO2, CH4, N2O, O3, HCHO and other trace gases were retrieved using an NL-CLS algorithm. Comparisons with point samplers were made during the November campaign. Afternoon peaks and high correlations of co-located PAN, PPN and VOC measurements indicate a growth of the boundary layer enough to submerge over the observation site and thus giving place to pollution transport in the regional scale. The evolution of the mixing layer height was also followed with a LIDAR system located downhill 22 km west of Altzomoni.
A33A-14
Optical remote sensing of the SO2 plume from Popocatepetl volcano (Mexico): 2D visualization and flux estimations
Popocatepetl volcano (19.023N, 98.622W, 5452 masl) is a passively degassing eruptive volcano with a current average emission of 5 kt/d of sulfur dioxide, which is located in the central front of the Mexican Transvolcanic Belt . It is approx. 60 km SE of Mexico City and 45 km NW from Puebla City. SO2 emissions from the volcano are known to interact with urban pollution playing a role in the atmospheric chemistry and the formation of particles. Optical remote sensing techniques were deployed during March 2006 to study the dispersion of the volcanic plume and to quantify the SO2 fluxes. A Scanning Infrared Gas Imaging System (SIGIS) was used to acquire passive IR spectra at 4 cm-1 resolution in a two-dimensional array, from which a false-color image was produced representing the degree of correlation of a specific gaseous pollutant. A real-life animation of the SO2- distribution from the volcanic plume allows understanding dispersion phenomena in various atmospheric conditions. Passive DOAS instruments installed both on ground and from an ultra-light aircraft, allowed for discrete SO2 column measurements below the plume. Flux estimations were done using wind profiles from balloons launched periodically
A33A-15
Evaluation of a dispersion model in Tula's industrial complex in Mexico by optical remote sensing methods
Tula's Industrial complex (20.05°N, 99.28°W, 2100 masl), located 70 km NNW of Mexico City, is an important SO2 emitter in the region due to the high sulphur content in the fuels burnt primarily by a power plant and an oil refinery. In this study, optical remote sensing techniques have been deployed during October 2005 and June 2006 in order to evaluate the performance of the gaussean dispersion model AERMOD used to estimate surface concentrations in the region. Traversals around the industrial complex with a zenith-sky DOAS instrument served to estimate the total emissions used to feed the model and to know the instantaneous spatial distribution of the plume. A Scanning Imaging Gas Infrared System (SIGIS), based on the spectral analysis of passive IR radiation of the plume, was used to visualize the plume´s dispersion in 2D and thus determine its vertical distribution. The results from various comparisons between observations and model outputs are presented.
A33A-16
Peroxy Radical Behavior During MIRAGE and INTEX-B as Measured Aboard the NSF/NCAR C- 130
We report measurements of HO2 and HO2+RO2 made onboard the NSF/NCAR C-130 using our Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) during the MIRAGE-Mex and INTEX-B field campaigns in the spring of 2006. Separation of HO2 and HO2+RO2 was achieved by varying the [NO]/[O2] ratio in the PeRCIMS inlet. At small ratios, most RO2 radicals are measured efficiently, while at larger ratios the measurement efficiency of most RO2 radicals is reduced to less than 0.15 of the HO2 measurement. The O2 concentration is changed by diluting the air sample containing the radicals by half with either O2 or N2. Likewise, the reagent gas concentrations are varied by a factor of 10. Comparisons between observations and box model calculations show relatively good agreement for NO mixing ratios below 1 ppb. As NO mixing ratios increase, the box model predicts decreases for both hydroperoxy and organic peroxy radicals, with values nearing zero in air masses where NO exceeds 5 ppbV while our measurements show little change compared to those at lower NO values. We also present comparisons of the ratios of HO2 to HO2+RO2 in urban air masses, air masses heavily influenced by fires, and air masses in the marine boundary layers of the Pacific Ocean and the Gulf of Mexico. We compare these ratios with ratios predicted from box models.
A33A-17
Evaluation of Volatile Organic Compounds in Mexico City Metropolitan Area 2005- 2006
One of the main air quality problems in the Mexico City Metropolitan Area (MCMA) are the high ozone levels, resulting from the photochemical reactions among precursors such as nitrogen oxides and volatile organic compounds. The MCMA air quality monitoring network includes 19 NOx and 19 O3 monitoring sites. However, no routine VOC monitoring is carried out. This work presents results of a field campaign done from September 2005 to September 2006 in the MCMA. 24 hours integrated samples were obtained every six days in five different sites, considered representative of the northwest, northeast, southeast, southwest, and center of the MCMA. Samples were obtained in stainless steel canisters adapted with a programmable flow controller. Analyses were done using a GC-FID to identify 57 VOCs following USEPA-TO-14A. A total of 354 samples were obtained corresponding to 62 sampling days. On the average, highest concentrations were found in the center, whereas lowest concentrations were found at the southwest. However, the overall maximum concentration (741 ppbV) was determined at the northeast site, and the overall minimum concentration (27 ppbV) was determined at the southwest site. At all sites, propane, butane, acetylene and toluene were the compounds found at highest concentrations. The main source for propane and butane is LPG, whereas for acetylene and toluene are combustion and evaporation of gasoline. It was found that southwest site is significantively different from the rest of all sites. A short field campaign was also done during 5 days in November-December 2005 with 3 periods of 3hrs integrated samples.
A33A-18
Vertical profiles of ozone, VOCs and meteorological parameters in within and outside of Mexico City during the MILAGRO field Campaign
High ozone levels with maxima over 250 ppb have been an air quality problem in Mexico City for more than a decade. This ozone is produced in the daytime by photochemical reactions, initiated by its precursors, nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of solar ultraviolet radiation. The objective of this work is to contribute to the understanding of the evolution of these air pollutants at different heights of the boundary layer by means of vertical profile measurements. Ozone, VOCs and meteorological vertical profiles were determined in Northern Mexico City (T0 site) using a tethered balloon for 10 days during the MILAGRO field Campaign 2006, between 4 AM and 4 PM. Measurements were done up to 1000 meter above ground (ozone and meteorological parameters) and up to 200 m above ground for VOCs. VOCs samples were collected during 4 minutes in canisters and analyzed with GC-FID to identify 13 species (ethane, propane, propylene, butane, acetylene, pentane, hexane, heptane, benzene, octane, toluene, nonane and o-xylene). For 4 of the days, VOC integrated samples were also taken using personal pumps and absorbent cartridges at height between 200 and 1000 m. Sample cartridges were analyzed by GC-MS for volatile organic compounds (n-butane, i-pentane, n- pentane, benzene, toluene, ethyl-benzene, o-xylene, m&p-xylene, 1,2,4-tri-methyl-benzene and C3-benzenes). Ozone vertical profiles, frequently presented high concentrations above 400 m in the early morning. During the daytime, more homogeneous profiles indicate an increased vertical mixing. VOCs profiles show similar concentrations for all heights at dawn. In the morning, highest concentrations were determined at a height of about 100 meter, whereas at noon and in the afternoon concentrations decreased with height. Comparing VOC concentrations during the course of a day, highest values are measured in the morning. The highest VOC concentrations were propane, butane, and toluene. For some days, VOC concentrations at T0 were compared with measurements done at surface levels in the southeast of Mexico City. Vertical profiles measured in the city at T0 were also compared with VOC and ozone concentrations measured at heights up to 700m using a tethered balloon system deployed at the T1 site north of Mexico City.
A33A-19
Airborne measurements of acetonitrile and other organic tracers during MIRAGE- MEX
Biomass burning (BB) plumes are known to impact air quality throughout the globe and can be important sources of pollution in megacities. A number of chemical tracers for BB have been used in the recent past with acetonitrile, a long-lived (~6 months) organic trace gas, among them. However, the atmospheric budget of acetonitrile is not well-known. It has been accepted in the recent literature that the primary source for acetonitrile is from BB, but a recent study points to an oceanic source. Loss is believed to be by reaction with OH and oceanic uptake. Earlier studies indicated that acetonitrile may be produced in emissions from automobile exhaust but a study done in the late 1990s appeared to discredit this. We use measurements from the Trace Organic Gas Analyzer (TOGA) onboard the NCAR C-130 aircraft to investigate the sources and sinks of acetonitrile in and around the Mexico City Metropolitan Area, investigate its utility as a tracer of emissions, and present data on emissions characterization based on measurements of acetonitrile and other co-measured VOCs.
A33A-20
Observations of the Valley of Mexico Basin Ventilation Through the Tenango del Aire- Amecameca Geographical Gap
Past air quality modeling exercises have suggested the existence of basin drainage flows which may transport Mexico City Metropolitan Area's air pollution plume outside the Valley of Mexico Basin. The MCMA-2006 field campaign offered the opportunity to study the basin ventilation through a geographical gap in the southeast mountains of the basin. A mobile monitoring lab was placed at the Tenango del Aire town, a unique site located in this gap for measuring the pass of air masses from (and towards) the MCMA to (and from) the Cuautla Valley. O3, CO, NOx, NOy, CH2O global and UV radiation and MLH were measured continuously during MILAGRO from March 2 until April 6, together with other chemical species. Complementary backward and forward trajectories were constructed for the site using MCCM in prognostic mode during MILAGRO. An exploratory analysis of the air pollution roses measured at Tenango showed a sharp dominance of two flow patterns: one from the north well associated with relatively higher levels of primary pollutants and ozone levels; and another one from the south typically associated with lower levels primary pollutants but not so low of secondary ones as ozone. On the other hand, measured CO data at Tenango were compared with CO data measured at one local monitoring station in the town of Ocuituco in the State of Morelos. Ocuituco is located to the south of Tenango towards the Cuautla Valley. The preliminary results suggest that the back and forth pass of air masses through the Tenango del Aire - Amecameca area can be an important process in the regional transport of air pollution between two valleys and their metropolitan areas within the Central Mexico region.