Evaluation of the danger of a tailings pile belonging to an active mine through its characterization and a dispersion model.

Mining is one of the principal economic activities in Mexico, which in addition to bringing benefits to the population, causes health and environmental problems. This activity produces a lot of wastes, but the main one is tailings. In Mexico, these wastes are disposed of in the open air, and there is no control over them, so the particles of these wastes are dispersed by wind currents to the surrounding population. In this research, tailings were characterized, finding in them particles smaller than 100 microns; in this way, tailings can enter into the respiratory system and hence can cause diseases. Furthermore, it is important to identify the toxic components. The present work does not have previous research in Mexico, and it shows a qualitative characterization of the tailings from an active mine using different analytical techniques. In addition to the data obtained from the characterization of the tailings, as well as the concentration of the toxic elements found, which were Pb and As, a dispersal model was generated and used to estimate the concentration of particles in the wind generated at the studied area. The air quality model used in this research is AERMOD, where it uses emission factors and available databases provided by Environmental Protection Agency (USEPA); Moreover, the model was coupled with meteorological information from the latest generation WRF model. The modeling results estimated that the dispersion of particles from the tailings dam can contribute up to 10.15 µg/m3 of PM10 to the air quality of the site, which, according to the characterization of the samples obtained, could be dangerous for human health and can be estimated up to a concentration of 0.04 µg/m3 of Pb and 10.90 ng/m3 of As. It is very important to make this kind of research to know the risk which people around this disposal sites are exposed to.

Fate of mercury in a terrestial biological lab process using Polypogon monspeliensis and Cyperus odoratus.

Mercury has been extracted in Queretaro, Mexico since the 1960s. The mining wastes were open-air disposal and these mercury wastes have polluted the zone. The aim of this research was to evaluate mercury's fate in lab scale terrestrial reactors considering the following mercury species: soluble, interchangeable, strongly bound, organic, and residual ones. Soils were sampled in two former mines of Pinal de Amoles, Queretaro, Mexico (N 20° 58' to 21° 21' and West 99° 26' to 99° 43') with initial mercury concentrations were 424 ± 29 and 433 ± 12 mg kg-1 for "La Lorena" and "San Jose" former mines, respectively. Two vegetal species Polypogon monspeliensis and Cyperus odoratus were used and 20 reactors were constructed for the lab process. Total mercury was removed to 49-79% from both soils. Mercury elemental, exchangeable, and organic species had the most removal or exchange in the process. Metal uptake, by the plants, was of 5-6% for P. monspeliensis and 5-15% for C. odoratus. Also, mercury fate was estimated to the atmosphere to be 3.3-4.5 mg m-2 h-1 for both soils.

Slaughterhouse wastewater treatment in a full-scale system with constructed wetlands.

This work evaluated the performance of a full-scale system with wetlands for slaughterhouse (abattoir) effluent treatment in the State of Hidalgo, México. The treatment system consisted of a primary sedimentation tank, an anaerobic lagoon, and a constructed subsurface-flow wetland, in series. The wetland accounted for almost 30% of the removal of organic matter. In general, the treatment system achieved satisfactory pollutant removals, but the final effluent could not meet the Mexican environmental regulations for fecal coliform counts, five-day biochemical oxygen demand (BOD5), and total suspended solids (TSS). Overall, removal levels were 91%, 89%, and 85% for BOD5, chemical oxygen demand, and TSS, respectively. However, BOD5 in the final effluent (137 mg/L) was higher than the maximum level of 30 mg/L allowed by the regulatory agency. Although organic nitrogen removal levels were approximately 80%, the nitrogen persisted in oxidation state -3 as ammonia-nitrogen, the removal of which was only 9% in the wetland stage. On average, phosphorus removal was null, and, on occasion, the phosphorus concentration in the treated effluent was higher than that of the influent. Coliform reductions in the overall system were high (on the order of 5 logs on average), whereas the coliform removal in the wetland was between 2 to 3.5 logs. The treatment system was also effective at removing pathogens (Vibrio cholerae, Salmonella, and Shigella). Further laboratory tests with the wetland effluent suggest that post treatment in a sand filter stage followed by disinfection with sodium hypochlorite (NaOCl) could help meet the Mexican discharge regulations, particularly the criteria for coliforms and total BOD5.

Tecnologías de tratamiento para la descontaminación de suelos / Treatment technologies for polluted soil

Existe una gran variedad de sustancias que contaminan los suelos, cuya presencia se debe a la disposición de materiales peligrosos que se desechan de diversos procesos industriales o bien por derrames accidentales de compuestos químicos. En el presente trabajo se mencionan las principales sustancias químicas tóxicas presentes en los suelos y se describen algunos de los métodos de tratamiento que se han desarrollado en los últimos 10 años, los cuales permiten la recuperación de estas sustancias y la regeneración del suelo contaminado. Estas técnicas se clasifican en los siguientes grupos dependiendo del tipo de proceso: - Ténica de inyección directa - Técnicas de extracción por solventes - Técnicas mediante microorganismos para degradación de contaminantes orgánicos. También se plantea la situación actual en México, ya que en el país no se ha dado la debida importancia al problema de contaminación, ni se han estudiado las posibles técnicas de tratamiento. La actividad petrolera se considera una de las pricnipales fuentes de contaminación de suelos en el país. Así como los patios de algunas industrias y los sitios clandestinos donde se acumulan residuos tóxicos. También representan un problema importante los tiraderos municipales donde se mezclan residuos industriales con desechos domésticos, lo que implica un riesgo a la salud. Por último, se presenta la legislación vigente en México contenida básicamente en las normas ecológicas expedidas por la Secretaría de Desarrollo Social (SEDESOL). (AU)

Tecnologías de tratamiento para la descontaminación de suelos / Treatment technologies for polluted soil

Existe una gran variedad de sustancias que contaminan los suelos, cuya presencia se debe a la disposición de materiales peligrosos que se desechan de diversos procesos industriales o bien por derrames accidentales de compuestos químicos. En el presente trabajo se mencionan las principales sustancias químicas tóxicas presentes en los suelos y se describen algunos de los métodos de tratamiento que se han desarrollado en los últimos 10 años, los cuales permiten la recuperación de estas sustancias y la regeneración del suelo contaminado. Estas técnicas se clasifican en los siguientes grupos dependiendo del tipo de proceso: - Ténica de inyección directa - Técnicas de extracción por solventes - Técnicas mediante microorganismos para degradación de contaminantes orgánicos. También se plantea la situación actual en México, ya que en el país no se ha dado la debida importancia al problema de contaminación, ni se han estudiado las posibles técnicas de tratamiento. La actividad petrolera se considera una de las pricnipales fuentes de contaminación de suelos en el país. Así como los patios de algunas industrias y los sitios clandestinos donde se acumulan residuos tóxicos. También representan un problema importante los tiraderos municipales donde se mezclan residuos industriales con desechos domésticos, lo que implica un riesgo a la salud. Por último, se presenta la legislación vigente en México contenida básicamente en las normas ecológicas expedidas por la Secretaría de Desarrollo Social (SEDESOL).