Papers by Alejandro Salcido
InTech eBooks, May 8, 2013
in 1992. Up to 1991, Dr. Salcido was Staff Scientist (Statistical Physics and Lattice Gas Models)... more in 1992. Up to 1991, Dr. Salcido was Staff Scientist (Statistical Physics and Lattice Gas Models) and Faculty Professor (Thermodynamics, Fluid Mechanics and Electrodynamics) at the Physics Department of UNAM. Dr. Salcido has published close to a hundred scholarly articles in international journals, proceedings of conferences and book chapters, where his main research topics include micrometeorology, air pollution modeling, wind taxonomy, traffic cellular automata, and non-equilibrium thermodynamics. Recently, Dr. Salcido has edited two books on cellular automata published by In Tech.
WIT Transactions on Ecology and the Environment, 1970
Application of lattice gas techniques for the computer simulation of transport and dispersion phe... more Application of lattice gas techniques for the computer simulation of transport and dispersion phenomena of air pollutants has been proposed very recently. However, in order to be useful as a reasonable approach to air pollution modelling, the transport and diffusion properties of lattice gas models must be characterized for equilibrium and non-equilibrium situations similar to the atmospheric ones. In this work, three problems have been considered for a square two-dimensional (2D) lattice gas model with interactions up to second nearest neighbors satisfying the mass, momentum and energy conservation principles: a theoretical discussion of the equilibrium thermodynamic properties of the gas model, the characterization of its equilibrium diffusion properties, and the agreement of the gas model flow behavior with the Navier-Stokes predictions under steady and non-steady flow conditions. The possibilities of application of lattice gases to the wind field diagnostic problem over complex orography terrain are also discussed.
Results in physics, 2021
In this work, we propose a 2D lattice gas model for infection spreading, and we apply it to study... more In this work, we propose a 2D lattice gas model for infection spreading, and we apply it to study the COVID-19 pandemic in the Mexico City Metropolitan Area (MCMA). We compared the spatially averaged results of this model against the MCMA available data. With the model, we estimated the numbers of daily infected and dead persons and the epidemic's duration in the MCMA. In the simulations, we included the small-world effects and the impact of lifting/strengthen lockdown measures. We included some indicators of the goodness of fit; in particular, the Pearson correlation coefficient resulted larger than 0.9 for all the cases we considered. Our modeling approach is a research tool that can help assess the effectiveness of strategies and policies to address the pandemic phenomenon and its consequences.
A simple model to evaluate the impact of the thermal power plants emissions; Un modelo simple para evaluar el impacto de las emisiones de centrales termoelectricas
Physical Properties and Chemical Composition of Aerosols sampled in T1 site during MILAGRO Campaign
AGU Spring Meeting Abstracts, May 1, 2007
ABSTRACT Results from pollutant measurements and meteorological variables corresponding to the mo... more ABSTRACT Results from pollutant measurements and meteorological variables corresponding to the month of March of 2006 during the MILAGRO campaign at site T1 are presented (Tecamac, State of Mexico). Three 8-stage cascade impactors (MOUDI) were employed to obtain aerosol samples of different sizes. For organic species analysis, samples were collected with a PM2.5 High Volume sampler. Mass and chemical composition (inorganic and organic species) were obtained with the use of analytical techniques. Particle morphology analysis was done with a TEM-EDAX System. Physical properties of aerosols were measured with a PSAP, a nephelometer and a CPC. According with area meteorology, days with Mexico City urban influence on T1 (March 9-12) and without influence (March 14 and 15) were analyzed. The particle average concentration during the whole campaign was 20,000 particles/cm3. For the days with and without urban influence the average concentrations were 17,500 and 8,000 particles/cm3 respectively. From the MOUDI data the highest particle concentration through the campaign was during the morning in the mode d50=0.32 mum. On the other hand, the cumulative highest concentration of all the stages was observed for March 19 followed by March 9. Scattering and absorption coefficients average obtained on T1 were 5.1x10-5 m-1 and 2.54x10-5 m-1 respectively and single scattering albedo was 0.676. These values show T1 as a polluted atmosphere, just as happens with megacities. Morphology of particles captured in a MOUDI impactor was studied. Particles between d50=0.18 mum and d50=1.8 mum sampled in T1 associated with urban influence (March 9) tended to show less irregular shapes through different periods of that day. These findings suggest the presence of large numbers of secondary aerosols and aged agglomerated particles. Particles ranging from d50=0.18 mum to d50=1.8 mum sampled in T1 and associated mainly with surrounding areas influence, e.g. Tizayuca Industrial Park (March 15) showed variation in morphology with size. More irregular particles were found in the smallest size, and less irregular particles were present in the largest size. The highest concentrations of ions present in all 8 stages of the MOUDI were chlorine, sodium, calcium, and magnesium. For stages less than 1 mum, the dominant ions were sulfate, ammonium, and potassium. The nitrate ion showed an irregular behavior through the campaign. For the days with influence (March 10 to 12), the nitrate ion presented its higher concentration. During episodes without influence (March 14 and 15), potassium, chlorine, and ammonium ions showed high concentration. On average, polycyclic aromatic hydrocarbons present in PM2.5 (from acenaphthylene to benzo[ghi]perylene) had concentrations between 0.2 to 0.5 ng/m3. In particular, naphthalene had a concentration of 2.5 ng/m3. Our results show that Tecamac population is certainly exposed to high levels of pollution from Mexico megacity.
Influence of Meteorological Patterns on the 2020 COVID-19 Pandemic in the Mexico City region
Environmental advances, Dec 1, 2021
Meteorology is a critical factor affecting respiratory infectious diseases such as MERS, SARS, an... more Meteorology is a critical factor affecting respiratory infectious diseases such as MERS, SARS, and influenza, but its effect on the spread of the COVID-19 disease remains controversial. Nevertheless, since the infected people cough-jets produce plumes of droplets and aerosols that can travel for several meters in the atmosphere, the possible influence of wind circulation and atmospheric turbulence on the infectious plume's fate cannot be ignored. This paper applied cluster analysis for identifying the near surface wind circulation patterns and associated temperature and humidity distributions in the Mexico City Metropolitan Area (MCMA), then their influence on the spread of the COVID-19 disease during the 2020 pandemic was discussed. Meteorology data and daily numbers of confirmed COVID-19 infections were obtained from public sources. An intense infection activity occurred from October to December 2020, and notable spreading of the disease toward the southwest and south MCMA was observed. In the same period, temperature and humidity conditions that could favor the virus stability and replication were detected in the same sectors, besides 60% of the wind observations revealed considerable northerly components. These findings suggested the existence of correlations between both phenomena. For assessing the possible relationship, the Pearson coefficients between the daily confirmed infections and the temperature and inward flux were estimated, and values from -0.32 to -0.55 and 0.62 to 0.70 were obtained. Correlation was negligible for relative humidity. Multilinear regression for the daily infections in response to the meteorological variables produced coefficients of determination from 0.3839 to 0.6138. Because of its implications for public health, this topic deserves a more in-depth investigation.
WIT Transactions on Ecology and the Environment, Aug 16, 2001
The most recent EPA models (such as AERMOD and CALPUFF) require turbulence data to the proper sim... more The most recent EPA models (such as AERMOD and CALPUFF) require turbulence data to the proper simulation of the atmospheric dispersion of air pollutants. However, the Mexican meteorological stations are not equipped to provide the data required to calculate the turbulent parameters. This is the reason why it is necessary to determine meteorological parameterisations that allow the estimation of all the micrometeorological parameters required by the dispersion models. In this work, the effect of using turbulence data estimated from conventional meteorological parameters to simulate pollutant atmospheric dispersion with the AERMOD model in an urban tropical region where the heat island effect is present is studied. For the purposes of the study, it one meteorological campaign in the Mexico City Metropolitan Area (MCMA) was carried out in order to obtain the micrometeorological data required for the simulations. The turbulence parameters required by AERMOD were calculated directly from the ultrasonic sensor data and estimated from the conventional meteorological data. The estimation of the turbulent parameters was performed using meteorological parameterisations previously derived from statistical analysis of experimental data obtained from campaigns carried out in Minatitlan (Veracruz, Mexico), Salamanca (Guanajuato, Mexico), Salina Cruz (Oaxaca, Mexico) and Cuernavaca (Morelos, Mexico). The model estimates of the surface pollutant concentrations obtained with the calculated and estimated turbulence data were found with a reasonable good agreement.
The maximum entropy states of 1d cellular automata traffic models
international conference on Modelling and simulation, May 30, 2007
We found out the entropy function of the cellular automata traffic models in a single-lane whose ... more We found out the entropy function of the cellular automata traffic models in a single-lane whose particle interaction rules satisfy an exclusion principle, conserve the number of particles, and prevent collisions and overtaking. With it we studied the velocity distributions of the maximum entropy states of these models. As a result, although the velocity updating rules of the Nagel-Schreckenberg traffic model drive it to states far from equilibrium, we found that the velocity distributions and fundamental diagrams of the maximum-entropy states resemble strongly the steady-states of this model at low energies. We found also that entropy as a function of particle density evidences the existence of several flow regimes in these models, with a sharp transition between the free and jammed flows in the high-energy limit. Finally, on the base of the existence of entropy for these models, we conjectured an interpretation like thermodynamics of traffic flow phenomena, and the behaviors of some thermodynamic properties, such as specific heat, isothermal compressibility, and others, are presented.
Modeling pollutants dispersion in surrounding places to thermoelectric power plants
Programa Estratégico de Sustentabilidad Ambiental
Tres Iniciativas de Innovación Aplicando Modelos de Autómatas Celulares
Algunos Comentarios sobre la Propuesta de Elementos para la Construcción de una Hoja de Ruta para el INEEL
Brief Note on the Future of Cities
Intensive meteorological measurements were taken in Mexico City in May 1992. This activity was ca... more Intensive meteorological measurements were taken in Mexico City in May 1992. This activity was carried out within the framework of a joint R&D Contract awarded to IIE-Mexico and Elettronica Spa-Italy by the European Community, DG XII. Surface Layer parameters were obtained using ground level measurements. The evolution of the mixing layer depth was estimated using some well-known prognostic models (Encroachment and GryningBatchvarova models). Mixing height estimates were compared with observed ones obtained by elevated measurements. The paper presents a short description of the meteorological campaign, the meteo processing methods, the model theories and the results obtained. INTRODUCTION In order to perform environmental analysis in general, and specifically around large thermal power plants, one needs simulation models describing the atmospheric pollutant dispersion. Furthermore the optimization in termsof number and location of stations of air quality monitoring network depends o...
Application of lattice gas techniques for the computer simulation of transport and dispersion phe... more Application of lattice gas techniques for the computer simulation of transport and dispersion phenomena of air pollutants has been proposed very recently. However, in order to be useful as a reasonable approach to air pollution modelling, the transport and diffusion properties of lattice gas models must be characterized for equilibrium and non-equilibrium situations similar to the atmospheric ones. In this work, three problems have been considered for a square two-dimensional (2D) lattice gas model with interactions up to second nearest neighbors satisfying the mass, momentum and energy conservation principles: a theoretical discussion of the equilibrium thermodynamic properties of the gas model, the characterization of its equilibrium diffusion properties, and the agreement of the gas model flow behavior with the Navier-Stokes predictions under steady and non-steady flow conditions. The possibilities of application of lattice gases to the wind field diagnostic problem over complex orography terrain are also discussed.
We propose a multi-speed lattice gas model for the computer simulation of transport and dispersio... more We propose a multi-speed lattice gas model for the computer simulation of transport and dispersion phenomena of air pollutants over a complex terrain. This model uses cellular automata methods in order to define a non-reactive two-species gas mixture which evolves in a square twodimensional lattice. -The particles of the system may interact with each other up to second nearest neighbors via dispersive collisions which satisfy the mass, momentum and energy conservation principles. A gravity like external force is also included in the model. The computer simulations made with this model show that the system behaves as expected in the cases of plume rise and dispersion phenomena; in particular, our simulations show that the pollutants distribution in the flow evolves toward a Gaussian profile. Complex boundary conditions, like arbitrary fixed solid obstacles and terrain complexities, and some other effects, such as dry deposition, may be included in a very simple way in the system.
Results in Physics, 2021
In this work, we propose a 2D lattice gas model for infection spreading, and we apply it to study... more In this work, we propose a 2D lattice gas model for infection spreading, and we apply it to study the COVID-19 pandemic in the Mexico City Metropolitan Area (MCMA). We compared the spatially averaged results of this model against the MCMA available data. With the model, we estimated the numbers of daily infected and dead persons and the epidemic's duration in the MCMA. In the simulations, we included the small-world effects and the impact of lifting/strengthen lockdown measures. We included some indicators of the goodness of fit; in particular, the Pearson correlation coefficient resulted larger than 0.9 for all the cases we considered. Our modeling approach is a research tool that can help assess the effectiveness of strategies and policies to address the pandemic phenomenon and its consequences.
Study of the regional air quality south of Mexico City (Morelos state)
Science of The Total Environment, 2012
Results from the first study of the regional air quality in Morelos state (located south of Mexic... more Results from the first study of the regional air quality in Morelos state (located south of Mexico City) are presented. Criteria pollutants concentrations were measured at several sites within Morelos in February and March of 2007 and 2009; meteorological data was also collected along the state for the same time periods; additionally, a coupled meteorology-chemistry model (Mesoscale Climate Chemistry Model, MCCM) was used to gain understanding on the atmospheric processes occurring in the region. In general, concentrations of almost all the monitored pollutants (O(3), NO(x), CO, SO(2), PM) remained below the Mexican air quality standards during the campaign; however, relatively high concentrations of ozone (8-hour average concentrations above the 60 ppb level several times during the campaigns, i.e. exceeding the World Health Organization and the European Union maximum levels) were observed even at sites with very low reported local emissions. In fact, there is evidence that a large percentage of Morelos vegetation was probably exposed to unhealthy ozone levels (estimated AOT40 levels above the 3 ppm h critical limit). The MCCM qualitatively reproduced ozone daily variations in the sites with an urban component; though it consistently overestimated the ozone concentration in all the sites in Morelos. This is probably because the lack of an updated and detailed emission inventory for the state. The main wind patterns in the region corresponded to the mountain-valley system (downslope flows at night and during the first hours of the day, and upslope flows in the afternoon). At times, Morelos was affected by emissions from surrounding states (Distrito Federal or Puebla). The results are indicative of an efficient transport of ozone and its precursors at a regional level. They also suggest that the state is divided in two atmospheric basins by the Sierras de Tepoztlán, Texcal and Monte Negro.
Spatial and temporal variations in inhalable CuZnPb aerosols within the Mexico City pollution plume
Journal of Environmental Monitoring, 2008
We report on the CuPbZn content of PM10 and PM2.5 samples collected from three sites (urban T0, s... more We report on the CuPbZn content of PM10 and PM2.5 samples collected from three sites (urban T0, suburban T1 and rural T2) during the Mexico City MILAGRO campaign of March 2006. Daytime city centre concentrations of summation operator CuZnPb(PM10) were much higher (T0 > 450 ng m(-3)) than at the suburban site (T1 < 200 ng m(-3)). Rural site (T2) summation operator CuZnPb(PM10) concentrations exceeded 50 ng m(-3) when influenced by the megacity plume but dropped to 10 ng m(-3) during clean northerly winds. Nocturnal metal concentrations more than doubled at T0, as pollutants became trapped in the nightly inversion layer, but decreased at the rural site. Transient spikes in concentrations of different metals, e.g. a "copper event" at T0 (CuPM10 281 ng m(-3)) and "zinc event" at T1 (ZnPM10 1481 ng m(-3)) on the night of March 7-8, demonstrate how industrial pollution sources produce localised chemical inhomogeneities in the city atmosphere. Most metal aerosols are <2.5 microm and SEM study demonstrates the dominance of Fe, Ti, Ba, Cu, Pb and Zn (and lesser Sn, Mo, Sb, W, Ni, V, As, Bi) in metalliferous particles that have shapes including spherical condensates, efflorescent CuZnClS particles, cindery Zn, and Cu wire. Metal aerosol concentrations do not change in concert with PM10 mass, which is more influenced by wind resuspension than industrial emissions. Metalliferous particles can induce cell damage, and PM composition is probably more important than PM mass, with respect to negative health effects, so that better monitoring and control of industrial emissions would likely produce significant improvements in air quality.
A Statistical method for estimating the convective mixing height
An important parameter often required by air quality models is the so called mixing height. In da... more An important parameter often required by air quality models is the so called mixing height. In day time hours (convective situations), three over- lapped layers may be distinguished in the lowest part of the atmosphere: the superficial layer, the mixed layer and the entrainment layer. The latter is a thin atmospheric layer that reverses temperature and buffers the up- per free atmosphere. Commonly, atmospheric variables are discontinuous at the entrainment layer. In this approach this latter fact is used to develop a change point analysis for atmospheric measurements. Then, the change point considered in the statistical model is precisely the mixing height. We also discuss the a priori distributions for the parameters in our model and the techniques needed to perform the necessary calculations. Some examples are analysed using data obtained in Texcoco, Mexico.
Uploads
Papers by Alejandro Salcido