Electronic waste is a widespread environmental problem. From all waste streams, e-waste is registering one of the largest growing rates (between 3% and 5%). In Mexico, the e-waste recovery system comprises a mix of formal and informal sectors not well known to date. The goal of this article was to analyze electronic waste in Mexico through the active actors in the recovery chain. This article presents the evolution of studies on electronic waste in Mexico. The legal regulations and public policies were analyzed, as were the existing practices of electronic waste handling, and some challenges facing this country for waste flow management. A management model is proposed which highlights components that must be considered in the model and the opportunities and challenges to transition from an unbundled handling, which still has practices that lack environmental and technical support, to sustainable management.

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RESUMENLos eventos climáticos extremos pueden tener consecuencias graves en la población y el medio ambiente, por lo que en este artículo para la ciudad de Mexicali, México, con una serie de tiempo de 1950 a 2010, se analizan las tendencias anuales de temperaturas extremas; asimismo, se estiman los periodos de retorno de 5 a 100 años mediante la modelación de la temperatura máxima estival y la temperatura mínima invernal. Para determinar las tendencias temporales se aplicaron la prueba no paramétrica tau de Kendall y el estimador de pendiente de Sen. También se aplicaron la distribución generalizada de valores extremos (GVE) a la aproximación de máximo por bloques, y la distribución generalizada de Pareto (DGP) a valores sobre un umbral determinado previamente. Debido a las características no estacionarias de la serie de valores de temperatura, se incluyó la tendencia temporal como covariable en el parámetro de ubicación, observándose mejoras sustanciales, sobre todo respecto a la temperatura mínima extrema en comparación con lo obtenido con la distribución GVE sin covariable y con la DGP. Se encontró una tendencia positiva estadísticamente significativa para ambas temperaturas extremas: máxima estival y mínima invernal. Hacia finales del siglo XXI la temperatura máxima extrema podría ser de 2 a 3 ºC más alta que la actual, y el invierno podría ser menos severo, ya que el modelo probabilístico sugiere incrementos de 7 a 9 ºC en la temperatura mínima extrema respecto del periodo de base estudiado. Se analizan las posibles consecuencias de lo anterior en la ciudad de Mexicali. ABSTRACTExtreme weather events can have severe consequences for the population and the environment. Therefore, in this study a temporal trend of annual temperatures was built with a time series from 1950 to 2010 for Mexicali, Mexico, and estimates of 5-to 100-year return periods are provided by modeling of summer maximum and winter minimum temperatures. A non-parametric Kendall's tau test and the Sen's slope estimator were used to compute trends. The generalized extreme value (GEV) distribution was applied to the approximation of block maxima and the generalized Pareto distribution (GPD) to values over a predetermined threshold. Due to the non-stationary characteristic of the series of temperature values, the temporal trend was included as a covariable in the location parameter and substantial improvements were observed, particularly with the extreme minimum temperature, compared to that obtained with the GEV with no covariable and with the GPD. A positive and significant statistically trend in both summer maximum temperature and winter minimum temperature was found. By the end of 21st century the extreme maximum temperature could be 2 to 3 ºC higher than current, and the winter could be less severe, as the probabilistic model suggests increases of 7 to 9 ºC in the extreme minimum temperature with respect to the base period. The foreseeable consequences on Mexicali city are discussed.

This paper presents a hypothetical and comparative performance of a 5 ton air conditioner (AC) operating in two zones in different urban microclimates for 25 days. One site represents a type of homogeneous planned urbanism and the other is a traditional heterogeneous zone. Air temperature data was collected and then processed using a linear regression model included in the operating manual of the AC in order to obtain their energy consumption. Results indicate that for an area with 500 homes, a traditional urban complex requires 12,350 kWh of electrical energy more than a planned zone (1.89%). This extra energy amounts up to $1180 and adds 9191 kg of CO2 to the atmosphere. The increased energy consumption has implications that increase the cost and environmental aspects of two urban microclimates, so that urbanization without planning is less friendly to the environment. In this sense, this study highlights the effects of urban microclimates on domestic electricity consumption from air conditioning. In addition, for a city with an arid desert climate, the variation in electricity consumption is associated with changes in the urban mosaic. The results found represent scientific evidence that can be used as a reference to establish public policies that could be incorporated into the local construction regulations, oriented to reduce the energy consumption associated with the use of air conditioning equipment.

RESUMEN mosférica (K 0) y la emisividad atmosférica (ε atm asfalto, concreto, poliestireno con pintura elastomérica blanca (PPEB), arcilla y césped. Se encontró que para un ciclo de 24 h de medición, el mayor valor promedio de radiación neta fue para el asfalto (146.1 Wm-2), y el menor valor promedio para el PPEB (33.6 Wm-2). Los valores estimados de albedo varían de acuerdo K 0 y ε atm dependen de las condiciones atmosféricas prevalentes. A partir de las mediciones se propusieron modelos estadísticos preliminares de la radiación neta en función de la determinación superiores a 0.97. Se analizan las probables implicaciones de los resultados encontrados en el medio urbanizado. ABSTRACT paper attempts to quantify this balance over different surface types in an arid city of northwest Mexico over several days in August 2011. The albedo of each surface type, as well as local atmospheric properties such as the atmospheric clearness index (K 0) and atmospheric emissivity (ε atm), were estimated. The surfaces on which measurements were performed were asphalt, concrete, polystyrene painted with white elastomeric paint (PWEP), clay, and grass. It was found that, for a 24-h cycle of measurement, the highest average value of net radiation was for asphalt (146.1 Wm-2), and the lowest average value was for PWEP (33.6 Wm-2). Estimates of albedo values vary depending on the surface, whereas K 0 and ε atm are dependent on prevailing atmospheric conditions. From these measurements, preliminary statistical models of net radiation as a function determination were higher than 0.97. We discuss the likely implications of the results found for the urban planning of the city.

Net radiation is an essential forcing of climate in the lower layers of Earth's atmosphere. In this paper, radiation balance is measured in clay soil and green grass, and is compared with three urban materials. These materials: asphalt, concrete and white painted elastomeric polystyrene roofing sheet are widely used in Mexicali, Baja California, México. This study was carried out during August of 2011, the hottest time of the year. The 24-hour average values of net radiation found were: 137.2 W·m −2 for asphalt, 119.1 for concrete, 104.6 for clay soil, 152 for green grass and 29.2 for the polystyrene insulation. The latter two types of materials are likely to be the most effective in reducing urban heat island effects. This variation in the radiation balance has widespread implications for human living conditions, as land cover change tends to be towards surfaces that have higher levels of net radiation.

RESUMENLa radiación solar es una de las fuentes de energía más importantes de nuestro planeta. El interés por su uso como energía renovable y limpia para mitigar los efectos de los gases de efecto invernadero (GEI) se ha incrementado de manera significativa. Este artículo presenta una evaluación de las mediciones de radiación solar y la estimación del potencial energético, así como una comparación de ambas, como ejemplo del esfuerzo para reducir los GEI. Las mediciones fueron realizadas con piranómetros instalados en la ciudad de Mexicali, Baja California, localizada en el noroeste de México, y en la ciudad de Yuma, Arizona, en el suroeste de EUA, que están separadas por una distancia de 96 km. Ambas ciudades muestran un desarrollo sostenido y características climáticas similares con numerosos días soleados, elevadas temperaturas extremas y escasa precipitación. Los resultados muestran diferencias tanto en su comportamiento como en las mediciones de radiación solar global, especialmente durante las estaciones críticas primavera y verano, con valores 15.73% (0.042 KW/m 2 ) superiores en Mexicali con respecto a Yuma a pesar a pesar de su cercanía. Esto indica que los flujos de mesoescala parecen dominar los sistemas sinópticos prevalentes en la región. Se estima el potencial energético, y se analiza con algunas variables como radiación solar global, precipitación, temperatura del aire, humedad relativa y climatología de los días claros, parcialmente nublados y nublados. Con esto se estima la energía proyectada para Mexicali en caso de que se utilizara el recurso solar, y se calcula que se evitarían 291 ton de GEI. Los valores de energía potencial obtenidos en Mexicali son mayores que los registrados en Yuma, por lo que este estudio comparativo de radiación solar y energía contribuye al desarrollo de estas tecnologías en México. Los resultados de las mediciones en la región demuestran la importancia de la estrategia propuesta para mitigar el cambio climático. ABSTRACT Solar radiation is one of the most important energy resources of our planet. The interest in its use as a renewable and clean energy to mitigate the greenhouse gases (GHG) effects has increased significantly. This paper evaluates the measurements of global solar radiation and its energy potential and presents a comparison between both of them, as an example of the effort to reduce GHG emissions. The measurements were made with pyranometers installed in the city of Mexicali, Baja California, located in northwestern Mexico, and the city of Yuma, Arizona, located in the southwestern United States. Separated by a distance of 96 km, both cities have a sustained development and are climatically similar, since they present numerous sunny days, extreme hot temperatures and little precipitation. The results presented show differences in their behavior and in the solar radiation measurement values, especially for the critical spring and summer seasons, with values 15.73% (0.042 kW/m 2 ) higher in Mexicali with respect to Yuma. Energy power is estimated, and it ...