Influence of Green Roofs on Early Morning Mixing Layer Depths in Mexico City

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Williams Vázquez Morales ◽  
Arón Jazcilevich ◽  
Agustín García Reynoso ◽  
Ernesto Caetano ◽  
Gabriela Gómez ◽  
...  
Keyword(s):  
Mexico City ◽  
Mixing Layer ◽  
Green Roofs ◽  
Early Morning ◽  
Urban Morphology ◽  
Box Model ◽  
World Health ◽  
Building Energy Efficiency ◽  
Mixing Depth ◽  
Synoptic Forcing

An urbanized version of MM5 (uMM5) was used at a 500 m horizontal grid-resolution to study effects on morning urban mixing depths and near roof-top stability from use of extensive green roofs in Mexico City, which is characterized by large Bowen ratios and high building storages. The model uses urban-morphology data, while building hydrothermal uMM5 input parameters were obtained from measurements over green and nearby conventional roofs. Evaluation of uMM5 predicted values against rooftop and planetary boundary layer (PBL) observations from extensive field measurement campaigns showed that the model performed reasonably well. Additional simulations were carried assuming that the roofs in entire urban neighborhoods were greened. Predicted mixing depths from these simulations, along with observed air pollution concentrations, were then used in a simple box model to evaluate potential green roof impacts on concentration. Results showed that green roofs produced an early morning (7–10 LST) cooling of up to 1.2 °C at rooftop levels, which reduced mixing depths during that period. Effects were greater on a day with weak synoptic forcing that on one 48 h later with strong synoptic forcing. The mixing-depth decreases produced increased box-model pollutant concentrations. While the green roofs did not elevate the observed concentrations of CO, SO2, and NO2 above World Health Organization (WHO) health standards, they did increase PM10, values (which were already above its standard) by as much as 8% from 7 to 9 LST, when local populations are normally exposed to peak concentrations. This study has applications in the analyses of building energy efficiency.

scholarly journals Nocturnal Boundary Layer Evolution and Its Impacts on the Vertical Distributions of Pollutant Particulate Matter

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 610
Author(s):  
Yu Shi ◽  
Lei Liu ◽  
Fei Hu ◽  
Guangqiang Fan ◽  
Juntao Huo
Keyword(s):  
Boundary Layer ◽  
Nitrate Concentration ◽  
Inversion Layer ◽  
Mixing Layer ◽  
Early Morning ◽  
Nocturnal Boundary Layer ◽  
Atmospheric Environment ◽  
Considerable Proportion ◽  
Surface Inversion ◽  
Vertical Distributions

To investigate the evolution of the nocturnal boundary layer (NBL) and its impacts on the vertical distributions of pollutant particulates, a combination of in situ observations from a large tethered balloon, remote sensing instruments (aerosol lidar and Doppler wind lidar) and an atmospheric environment-monitoring vehicle were utilized. The observation site was approximately 100 km southwest of Beijing, the capital of China. Results show that a considerable proportion of pollutant particulates were still suspended in the residual layer (RL) (e.g., the nitrate concentration reached 30 μg m−3) after sunset. The NBL height calculated by the aerosol lidar was closer to the top of the RL before midnight because of the pollutants stored aloft in the RL and the shallow surface inversion layer; after midnight, the NBL height was more consistent with the top of the surface inversion layer. As the convective mixing layer gradually became established after sunrise the following day, the pollutants stored in the nocturnal RL of the preceding night were entrained downward into the mixing layer. The early morning PM2.5 concentration near 700 m in the RL on 20 December decreased by 83% compared with the concentration at 13:34 on 20 December at the same height. The nitrate concentration also decreased significantly in the RL, and the mixing down of nitrate from the RL could contribute about 37% to the nitrate in the mixing layer. Turbulence activities still existed in the RL with the bulk Richardson number (Rb) below the threshold value. The corresponding increase in PM2.5 was likely to be correlated with the weak turbulence in the RL in the early morning.

scholarly journals Public Health Considerations for PM10 in a High-Pollution Megacity: Influences of Atmospheric Condition and Land Coverage

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 118
Author(s):  
Carlos Zafra ◽  
Joaquín Suárez ◽  
Jorge E. Pachón
Keyword(s):  
Public Health ◽  
Mixing Layer ◽  
Atmospheric Condition ◽  
World Health ◽  
Measuring Devices ◽  
Reference Limits ◽  
High Pollution ◽  
Health Organization ◽  
Daily Pm10 ◽  
Research Period

This paper analyzes the PM10 concentrations and influences of atmospheric condition (AC) and land coverage (LC) on a high-pollution megacity (Bogota, Colombia) from a public health viewpoint. Information of monitoring stations equipped with measuring devices for PM10/temperature/solar-radiation/wind-speed were used. The research period lasted eight years (2007–2014). AC and LC were determined after comparing daily PM10 concentrations (DPM10) to reference limits published by the World Health Organization (WHO). ARIMA models for DPM10 were also developed. The results indicated that urban sectors with lower atmospheric instability (AI) had a 2.85% increase in daily mortality (DM) in relation to sectors with greater AI. In these sectors of lower AI, impervious LC predominated, instead of vegetated LC. An ARIMA analysis revealed that a greater extent of impervious LC around a station led to a greater effect on previous days’ DPM10 concentrations. Extreme PM10 episodes persisted for up to two days. Extreme pollution episodes were probably also preceded by low mixing-layer heights (between 722–1085 m). The findings showed a 13.0% increase in WHO standard excesses (PE) for each 10 µg/m3 increase in DPM10, and a 0.313% increase in DM for each 10% increase in PE. The observed average reduction of 14.8% in DPM10 (−0.79% in DM) was probably due to 40% restriction of the traffic at peak hours.

Pious Delinquents: Anticlericalism and Crime in Postrevolutionary Mexico

2016 ◽  
Vol 73 (2) ◽  
pp. 185-210
Author(s):  
Robert Weis
Keyword(s):  
Mexico City ◽  
Police Officers ◽  
Early Morning ◽  
Apartment Building ◽  
Religious Expression ◽  
Virgin Of Guadalupe

As Agent 15 of the Mexico City judicial police made his way home for lunch on a day early in December 1926, he saw a balloon floating in the breeze. He rushed to the rooftop observatorio of his apartment building, where he spotted a girl around 14 years old, wearing a lilac-colored dress, standing on a nearby roof and holding a string. Certain that the balloon had been released from this location, he ran down the stairs, and, while crossing the street, looked up to see yet another balloon. Balloons had been drifting through the sky since early morning, so many and from so many directions that police struggled to find where they were coming from. When the balloons popped, flyers came tumbling down, urging Catholics to engage in peaceful protest against government anticlericalism by adorning their houses with yellow and white stripes in honor of the Virgin of Guadalupe on her upcoming feast day, December 12. Accompanied by a beat policeman, Agent 15 approached two men in the building where he had seen the girl with the string, surmising that they had aided the launch. Although a search yielded nothing more incriminating than a stick with four strings, he arrested the men. He and other balloon-chasing police officers were obeying specific orders in hunting down the perpetrators that day, but in a broader sense they had become enforcers of laws introduced in the 1917 constitution that sharply restricted the scope of religious expression and observation in public.

scholarly journals The daytime mixing layer observed by radiosonde, profiler, and lidar during MILAGRO

2007 ◽  
Vol 7 (5) ◽  
pp. 15025-15065 ◽  
Author(s):  
W. J. Shaw ◽  
M. S. Pekour ◽  
R. L. Coulter ◽  
T. J. Martin ◽  
J. T. Walters
Keyword(s):  
Boundary Layer ◽  
Mexico City ◽  
Deep Convection ◽  
National Laboratory ◽  
Mixing Layer ◽  
Argonne National Laboratory ◽  
Pacific Northwest National Laboratory ◽  
Layer Growth ◽  
Hygroscopic Growth ◽  
Layer Depth

Abstract. During the MILAGRO campaign centered in the Mexico City area, Pacific Northwest National Laboratory (PNNL) and Argonne National Laboratory (ANL) operated atmospheric profiling systems at Veracruz and at two locations on the Central Mexican Plateau in the region around Mexico City. These systems included radiosondes, wind profilers, a sodar, and an aerosol backscatter lidar. An additional wind profiler was operated by the University of Alabama in Huntsville (UAH) at the Mexican Petroleum Institue (IMP) near the center of Mexico City. Because of the opportunity afforded by collocation of profilers, radiosondes, and a lidar, and because of the importance of boundary layer depth for aerosol properties, we have carried out a comparison of mixing layer depth as determined independently from these three types of measurement systems during the campaign. We have then used results of this comparison and additional measurements to develop a detailed description of the daily structure and evolution of the boundary layer on the Central Mexican Plateau during MILAGRO. Our analysis indicates that the profilers were more consistently successful in establishing the mixing layer depth during the daytime. The boundary layer growth was similar at the three locations, although the mixing layer tended to be slightly deeper in the afternoon in central Mexico City. The sodar showed that convection began about an hour after sunrise. Maximum daily mixing layer depths always reached 2000 m a.g.l. and frequently extended to 4000 m. The rate and variability of mixing layer growth was essentially the same as that observed during the IMADA-AVER campaign in the same season in 1997. This growth did not seem to be related to whether deep convection was reported on a given day. Wind speeds within the boundary layer exhibited a daily low-altitude maximum in the late afternoon with lighter winds aloft, consistent with previous reports of diurnal regional circulations. Norte events, which produced high winds at Veracruz, did not appreciably modulate the winds on the plateau. Finally, despite the typically dry conditions at the surface, radiosonde profiles showed that relative humidity often exceeded 50% in the early morning and in the upper part of the boundary layer. This suggests that aerosol particles would have experienced hygroscopic growth within the boundary layer on many days.

scholarly journals Prevalence of Antibiotics Prescription and Assessment of Prescribed Daily Dose in Outpatients from Mexico City

Antibiotics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 38 ◽  
Author(s):  
Ramiro Sánchez-Huesca ◽  
Abel Lerma ◽  
Rebeca M.E Guzmán-Saldaña ◽  
Claudia Lerma
Keyword(s):  
Mexico City ◽  
Drug Dose ◽  
High Rate ◽  
World Health ◽  
Defined Daily Dose ◽  
Duration Of Treatment ◽  
Dose Frequency ◽  
Antibiotic Drug ◽  
Daily Dose ◽  
Health Organization

Pharmacoepidemiological research about antibiotics is supported by the World Health Organization (WHO), but data regarding antibiotic prevalence based on actual prescriptions and dosing patterns are insufficient. The aims were: (i) To estimate the prevalence and prescribed daily dose (PDD) of antibiotics in outpatients from Mexico City and (ii) to compare the PDD against the defined daily dose (DDD), as established by the WHO. The study included 685 prescriptions of antibiotics selected randomly from five geographical zones of Mexico City. Drug, dose, frequency, and duration of treatment were obtained from each prescription. PDD values of each antibiotic drug were calculated as the average of the daily doses. Sub-use and overuse were determined by the ratio PDD/DDD for each prescription. The most prescribed antibiotics to outpatients from Mexico City included six pharmacological groups: quinolones (28%), penicillins (23%), cephalosporins (17%), macrolides (10%), lincosamides (9%), and sulfonamides (4%). Both overuse and sub-use were high (55% and 63%, respectively). In conclusion, most of the antibiotics with a high prevalence of prescription also had a high rate of either sub-use or overuse, with prescribed doses that significantly differ with their corresponding DDD. The dosing variation has important clinical implications since it denotes low prescription control.

Presence of organochlorine contaminants in bottled drinking water from Mexico City

2012 ◽  
Vol 12 (4) ◽  
pp. 470-479 ◽  
Author(s):  
Rey Gutiérrez ◽  
Salvador Vega ◽  
Rutilio Ortiz ◽  
Beatriz Schettino
Keyword(s):  
Drinking Water ◽  
Organochlorine Pesticides ◽  
Mexico City ◽  
Organic Contaminants ◽  
Monitoring Program ◽  
World Health ◽  
Drinking Water Standards ◽  
Toxicological Effects ◽  
Bottled Drinking Water ◽  
Organochlorine Contaminants

Concentrations of organic contaminants (organochlorine pesticides and biphenyls) were studied in bottled drinking water (BDW) from Mexico City where consumption is high and considered a healthy alternative to the potable water network. The results of 36 samples (1.5 L and 19 L presentations, 18 samples of each) showed the presence of seven pesticides (HCH-hexachlorocyclohexane isomers, heptachlor, aldrin and p,p'-DDE'-dichlorodiphenyldichloroethylene) and some polychlorinated biphenyls-PCBs (28, 58 and 101). The concentrations were compared with the drinking water standards set by NOM-127-SSA1–1994, USEPA (United States Environment Protection Agency) and the World Health Organization (WHO) for pesticides and NOM-127-SSA1–1994 for biphenyls. The concentrations of the majority of organochlorine pesticides were within drinking water standards (0.01 μg L−1) except for β-HCH in BDW samples 3, 5 and 6 with values of 0.121, 0.136 and 0.192 μg L−1, respectively. The total PCBs concentration in BDW did not represent any hazard to human health, according to Mexican regulations, which establish a maximum permissible level of 0.50 μg L−1. A BDW quality monitoring program is recommended and further research on ways of reducing the presence of organochlorine contaminants to prevent bioaccumulation and toxicological effects over population with emphasis in those that with constant consumption.

scholarly journals Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume

2011 ◽  
Vol 11 (24) ◽  
pp. 13219-13241 ◽  
Author(s):  
J. Lee-Taylor ◽  
S. Madronich ◽  
B. Aumont ◽  
A. Baker ◽  
M. Camredon ◽  
...  
Keyword(s):  
Mexico City ◽  
Organic Aerosols ◽  
Early Morning ◽  
Particulate Emissions ◽  
Vapor Pressures ◽  
Reaction Products ◽  
Large N ◽  
Radiative Impacts ◽  
Organic Hydroperoxides ◽  
Oxidation Chemistry

Abstract. The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15–20 μg m−3, and SOA peaking at 10–15 μg m−3 during mid-day. The majority (≥75%) of the model SOA stems from reaction products of the large n-alkanes, used here as surrogates for all emitted hydrocarbons of similar volatility, with the remaining SOA originating mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by δ-hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.

scholarly journals The Development of Air Pollution in Mexico City

SAGE Open ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 215824402093107
Author(s):  
Natalia Soto-Coloballes
Keyword(s):  
Air Pollution ◽  
Mexico City ◽  
Dust Storms ◽  
World Health ◽  
Dust Particles ◽  
Automotive Emissions ◽  
Industrialized Nations ◽  
Suspended Dust ◽  
The 1960S ◽  
Health Organization

The present essay documents changes to both objects of inquiry and the meaning of the epistemological concept of air pollution and it explains the processes that produced them. Smog as a result of production processes and the use of the automobile was not a concern for researchers and government managers in Mexico City, who were used to the dust storms resulting from the desiccation of the great Texcoco Lake during much of the 20th century, until the most industrialized nations of the West and the World Health Organization (WHO), alongside other international bodies such as the Organization for European Economic Cooperation (OEEC), reframed what was understood as air pollution, between the end of the 1960s and the beginning of the 1970s. Concerns about dust storms were displaced by concerns about factory and automotive emissions that contained new dangers—invisible hazards, just then being estimated, which altered what was understood or considered air pollution and gave rise to the quantification of particulate matter (which was then known as suspended dust particles) and new practices such as atmospheric monitoring. This essay concludes that what is understood as air pollution is situated; its meaning is not finite but simply evolves with time and with the rise of new global risks and concerns.

scholarly journals Determination of particulate lead using aerosol mass spectrometry: MILAGRO/MCMA-2006 observations

2010 ◽  
Vol 10 (12) ◽  
pp. 5371-5389 ◽  
Author(s):  
D. Salcedo ◽  
T. B. Onasch ◽  
A. C. Aiken ◽  
L. R. Williams ◽  
B. de Foy ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mexico City ◽  
Mass Spectrometer ◽  
Metropolitan Area ◽  
Inductively Coupled Plasma ◽  
Early Morning ◽  
Back Trajectory ◽  
Slow Evaporation ◽  
Aerosol Mass ◽  
Icp Ms

Abstract. We report the first measurements of particulate lead (Pb) from Aerodyne Aerosol Mass Spectrometers, which were deployed in and around Mexico City during the Megacity Initiative: Local and Global Research Observations (MILAGRO)/Mexico City Metropolitan Area 2006 (MCMA-2006) field campaigns. The high resolution mass spectrometer of one of the AMS instruments (HR-AMS) and the measured isotopic ratios unequivocally prove the detection of Pb in ambient particles. A substantial fraction of the lead evaporated slowly from the vaporizer of the instruments, which is indicative of species with low volatility at 600 °C. A model was developed in order to estimate the ambient particulate Pb entering the AMS from the signals in the "open" and the "closed" (or "background") mass spectrum modes of the AMS. The model suggests the presence of at least two lead fractions with ~25% of the Pb signal exhibiting rapid evaporation (1/e decay constant, τ<0.1 s) and ~75% exhibiting slow evaporation (τ~2.4 min) at the T0 urban supersite and a different fraction (70% prompt and 30% slow evaporation) at a site northwest from the metropolitan area (PEMEX site). From laboratory experiments with pure Pb(NO3)2 particles, we estimated that the Pb ionization efficiency relative to nitrate (RIEPb) is 0.5. Comparison of time series of AMS Pb with other measurements carried out at the T0 supersite during MILAGRO (using Proton Induced X-ray Emission (PIXE), Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) and single-particle counts from an Aerosol Time-of-Fight Mass Spectrometer (ATOFMS)) shows similar levels (for PIXE and ICP-MS) and substantial correlation. During part of the campaign, sampling at T0 was alternated every 10 min with an Aerosol Concentrator, which enabled the detection of signals for PbCl+ and PbS+ ions. PbS+ displays the signature of a slowly evaporating species, while PbCl+ appears to arise only from fast evaporation, which is likely due to the higher vapor pressure of the compounds generating PbCl+. This is consistent with the evaporation model results. Levels of particulate Pb measured at T0 were similar to previous studies in Mexico City. Pb shows a diurnal cycle with a maximum in the early morning, which is typical of primary urban pollutants. Pb shows correlation with Zn, consistent with previous studies, while the sources of Pb appear to be at least partially disjoint from those of particulate chloride. Back trajectory analysis of the T0 Pb data suggests the presence of sources inside the urban area SSW and N of T0, with different chemical forms of Pb being associated with different source locations. High signals due to particulate lead were also detected in the PEMEX site; again, no correlation between Pb and chloride plumes was observed, suggesting mostly different sources for both species.

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