Bivariate Analysis of Pollutants Monthly Maxima in Mexico City Using Extreme Value Distributions and Copula

In the present work, we are interested in studying the joint distributions of pairs of the monthly maxima of the pollutants used by the environmental authorities in Mexico City to classify the air quality in the metropolitan area. In order to obtain the joint distributions a copula will be considered. Since we are analyzing the monthly maxima, the extreme value distributions of Weibull and Fréchet are taken into account. Using these two distributions as marginal distributions in the copula a Bayesian inference was made in order to estimate the parameters of both distributions and also the association parameters appearing in the copula model. The pollutants taken into account are ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter with diameters smaller than 10 and 2.5 microns obtained from the Mexico City monitoring network. The estimation was performed by taking samples of the parameters generated through a Markov chain Monte Carlo algorithm implemented using the software OpenBugs. Once the algorithm is implemented it is applied to the pairs of pollutants where one of the coordinates of the pair is ozone and the other varies on the set of the remaining pollutants. Depending on the pollutant and the region where they were collected, different results were obtained. Hence, in some cases we have that the best model is that where we have a Fréchet distribution as the marginal distribution for the measurements of both pollutants and in others the most suitable model is the one assuming a Fréchet for ozone and a Weibull for the other pollutant. Results show that, in the present case, the estimated association parameter is a good representation to the correlation parameters between the pair of pollutants analyzed. Additionally, it is a straightforward task to obtain these correlation parameters from the corresponding association parameters.

Air Quality Estimation Using Nonhomogeneous Markov Chains: A Case Study Comparing Two Rules Applied to Mexico City Data

A nonhomogeneous Markov chain is applied to the study of the air quality classification in Mexico City when the so-called criterion pollutants are used. We consider the indices associated with air quality using two regulations where different ways of classification are taken into account. Parameters of the model are the initial and transition probabilities of the chain. They are estimated under the Bayesian point of view through samples generated directly from the corresponding posterior distributions. Using the estimated parameters, the probability of having an air quality index in a given hour of the day is obtained.

Knowledge and preventive measures practiced by junior high school students from Mexico City regarding influenza A (H1N1)

Background: Influenza A (H1N1) is the most recent pandemic disease that has affected the human population. Objective: To evaluate knowledge and preventive measures related with this disease one year after the epidemic of Mexico- that took place in 2009. Material and methods: An epidemiologic survey regarding influenza A (H1N1) was conducted in June 2010 among 2541 students from the second grade of all public high schools in a borough in Mexico City. The questionnaire included items on the knowledge of the disease and practice of preventive measures. Results: Most students obtained the information from television, half of them from parents and only one fifth from teachers;72% of the participants had a favorable knowledge about the disease and the measures to avoid being infected. However, only 37% practiced such preventive measures. Conclusion: Knowledge has a positive influence on practices towards health. Parents and teachers have an important role in health education, thus efforts should be directed to involve them more intensely in health education.

Culture Mixed-Sex and Monosex of Tilapia in Ponds in Mexico City

In this study, the growth of Oreochromis niloticus both mixed sex and males sexually reversed were analyzed in concrete ponds in the FES Zaragoza, UNAM, under the environmental conditions of the Mexico City. The experiment was carried from May to November 2013, in two concrete ponds of 50 m2. Similar feeding regime and stocking density of fish were maintained for the culture systems. Different growth parameters like body weight, length, daily weight gain (DWG), specific growth rate (SGR), feed conversion rate (FCR), Fulton’s condition index (K) and survival were analyzed during six months culture period. It was found that culture with monosex males tilapias yielded the highest weight, length, DWG and SGR compared to mixed sex populations tilapias. Water quality was monitored along the experiment. Based on the results, there were statistically significant differences in size (W = 20942.5, p 5 mg/L), warm water (>20°C), productive (3) and slightly basic (pH > 8). Acceptable growth of fish and a yield of 3 ton/ha/6 months were obtained in both two ponds;therefore, the culture of tilapia under conditions of Mexico City was recommended.

Comparing the Adequacy of Some Non-Homogeneous Poisson Models to Estimate Ozone Exceedances in Mexico City

We consider some non-homogeneous Poisson models to estimate the mean number of times that a given environmental threshold of interest is surpassed by a given pollutant. Seven different rate functions for the Poisson processes describing the models are taken into account. The rate functions considered are the Weibull, exponentiated-Weibull, and their generalisation the Beta-Weibull rate function. We also use the Musa-Okumoto, the Goel-Okumoto, a generalised Goel- Okumoto and the Weibull-geometric rate functions. Whenever thought justifiable, the model allowing the presence of change-points is also going to be considered. The different models are applied to the daily maximum ozone measurements data provided by the monitoring network of the Metropolitan Area of Mexico City. The aim is to compare the adjustment of different rate functions to the data. Even though, some of the rate functions have been considered before, now we are applying them to the same data set. In previous works they were used in different data sets and therefore a comparison of the adequacy of those models were not possible. The measurements considered here were obtained after a series of environmental measures were implemented in Mexico City. Hence, the data present a different behaviour from that of earlier studies.

An Integrative Collaborative Project Approach to Climate-Change Resilience and Urban/Regional Sustainability for the Mexico-Lerma-Cutzamala Hydrological Region

In a rapidly urbanizing world, the social, economic, and ecological complexities of cities require conceptual and operational innovations to enhance climate resilience and sustainability. We describe our Integrative Collaborative Project (ICP) approach to co-create climate resilience in the Mexico-Lerma-Cutzamala Hydrological Region (MLCHR). In recent years, it has suffered from frequent natural disasters, and under climate change scenarios, the intensity and frequency of extreme events, including severe floods, droughts, heat waves and landslides are expected to increase. ICPs are framed as socio-technical capacity building enterprises, with networks operating at multiple scales. The approach differs from other integrative efforts, which tend to be top-down with scant civil society co-ownership, and focus on limited aspects like indicators/assessment, or institutional capacity building. We reimagine all operational stages, from creative thinking, through ethos and concept, assessment, planning, project design, implementation and management, and monitoring and evaluation. The design of ICPs is informed by six integrative domains: 1) project ethos, concept, and framing;2) sectors, topics, and issues;3) spatial and temporal scales;4) stakeholder interests, relationships and capacities;5) knowledge types, models and methods;and 6) socio-technical capacities and networks. Empirically, the approach is based on participatory development practices, pilot project work tackling sustainable water and sanitation in Mexico, and a synthesis of rich experiential knowledge spanning 20 years. The theoretical basis considers a pragmatic knowledge frame, socio-technical transitions literature, and education for social transformation. We describe forward-looking operational details of the Pilot ICP for the Mexico-Lerma-Cutzamala Hydrological Region, with our three-university partnership as catalyst, and a new breed of socio-technical enterprise organization as a key partner, engaging stakeholders at municipal and regional scales.

Stochastic seismic response of multi-layered soil with random layer heights

This paper deals with the effect of layer height randomness on the seismic response of a layered soil. These parameters are assumed to be lognormal random variables. The analysis is carried out via Monte Carlo simulations coupled with the stiffness matrix method. A parametric study is conducted to derive the stochastic behavior of the peak ground acceleration and its response spectrum,the transfer function and the amplification factors. The input soil characteristics correspond to a site in Mexico City and the input seismic accelerations correspond to the Loma Prieta earthquake. It is found that the layer height heterogeneity causes a widening of the frequency content and a slight increase in the fundamental frequency of the soil profile,indicating that the resonance phenomenon is a concern for a large number of structures. Variation of the layer height randomness acts as a variation of the incident angle,i.e.,a decrease of the amplitude and a shift of the resonant frequencies.

Airborne bacteria associated with particulate matter from a highly urbanised metropolis:A potential risk to the population’s health

Bacteria in the air present patterns in space and time produced by different sources and environmental factors.Few studies have focused on the link between airborne pathogenic bacteria in densely populated cities,and the risk to the population’s health.Bacteria associated with particulate matter(PM)were monitored from the air of Mexico City(Mexico).We employed a metagenomic approach to characterise bacteria using the 16S rRNA gene.Airborne bacteria sampling was carried out in the north,centre,and south of Mexico City,with different urbanisation rates,during 2017.Bacteria added to the particles were sampled using high-volume PM_(10) samplers.To ascertain significant differences in bacterial diversity between zones and seasons,the Kruskal-Wallis,Wilcoxon tests were done on alpha diversity parameters.Sixty-three air samples were collected,and DNA was sequenced using next-generation sequencing.The results indicated that the bacterial phyla in the north and south of the city were Firmicutes,Cyanobacteria,Proteobacteria,and Actinobacteria,while in the central zone there were more Actinobacteria.There were no differences in the alpha diversity indices between the sampled areas.According to the OTUs,the richness of bacteria was higher in the central zone.Alpha diversity was higher in the rainy season than in the dry season;the Shannon index and the OTUs observed were higher in the central zone in the dry season.Pathogenic bacteria such as Kocuria,Paracoccus,and Micrococcus predominated in both seasonal times,while Staphylococcus,Corynebacterium,and Nocardioides were found during the rainy season,with a presence in the central zone.