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.
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.
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.
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