Pioneer plant species and fungal root endophytes in metal-polluted tailings deposited near human populations and agricultural areas in Northern Mexico.

As a consequence of industrial mining activity, high volumes of tailings are scattered around Mexico. Frequently, tailings contain heavy metals (HM) which entail threats against all organisms. The aim of this research was to identify plants and root fungal endophytes in polymetallic polluted tailings with the potential to be used in strategies of bioremediation. Four deposits of mine wastes, situated in a semi-arid region near urban and semi-urban populations, and agricultural areas, were studied. The physical and chemical characteristics of substrates, accumulation of HM in plant tissues, root colonization between arbuscular mycorrizal (AMF) and dark septate endophyte (DSE) fungi, and the identification of DSE fungi isolated from the roots of two plant species were studied. Substrates from all four sites exhibited extreme conditions: high levels in sand; low water retention; poor levels in available phosphorus and nitrogen content; and potentially toxic levels of lead (Pb), cadmium (Cd), and zinc (Zn). The native plants Lupinus campestris, Tagetes lunulata, and Cerdia congestiflora, as well as the exotic Cortaderia selloana and Asphodelus fistulosus, demonstrated a relevant potential role in the phytostabilization and/or phytoextraction of Pb, Cd, and Zn, according to the accumulation of metal in roots and translocation to shoots. Roots of eleven analyzed plant species were differentially co-colonized between AMF and DSE fungi; the presence of arbuscules and microsclerotia suggested an active physiological interaction. Fourteen DSE fungi were isolated from the inner area of roots of T. lunulata and Pennisetum villosum; molecular identification revealed the predominance of Alternaria and other Pleosporales. The use of native DSE fungi could reinforce the establishment of plants for biological reclamation of mine waste in semi-arid climate. Efforts are needed in order to accelerate a vegetation practice of mine wastes under study, which can reduce, in turn, their potential ecotoxicological impact on organisms, human populations, and agricultural areas.

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NH4SCN) or ammonium thiosulfate [(NH4)2S2O3]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg-1 of either NH4SCN or (NH4)2S2O3, respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH4)2S2O3 or NH4SCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH4)2S2O3+Aspergillus, or NH4SCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH4)2S2O3 or (NH4)2S2O3+Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NH4SCN + Aspergillus, and (NH4)2S2O3 enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NH4SCN+ Aspergillus, and (NH4)2S2O3+ Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NH4SCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NH4SCN+ Aspergillus, or (NH4)2S2O3+ Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NH4SCN or (NH4)2S2O3 (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg-1 of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg-1) by applying either NH4SCN or (NH4)2S2O3 + A. niger.

Design of an explosive detection system using Monte Carlo method.

Regardless the motivation terrorism is the most important risk for the national security in many countries. Attacks with explosives are the most common method used by terrorists. Therefore several procedures to detect explosives are utilized; among these methods are the use of neutrons and photons. In this study the Monte Carlo method an explosive detection system using a 241AmBe neutron source was designed. In the design light water, paraffin, polyethylene, and graphite were used as moderators. In the work the explosive RDX was used and the induced gamma rays due to neutron capture in the explosive was estimated using NaI(Tl) and HPGe detectors. When light water is used as moderator and HPGe as the detector the system has the best performance allowing distinguishing between the explosive and urea. For the final design the Ambient dose equivalent for neutrons and photons were estimated along the radial and axial axis.

Dosis y Factores Gamma de una paciente con 131I / Doses and Gamma factors in a patient with 131I

Mediante métodos Monte Carlo se calcularon las dosis en los órganos internos de una mujer, con tres meses de embarazo, debidas al radioiodo captado por su tiroides, así como a 1 metro de la glándula. Se utilizó un modelo tridimensional del cuerpo de la mujer y mediante Monte Carlo, los fotones de radioiodo se transportaron isotrópicamente desde la tiroides hacia todo el cuerpo y se calculó la dosis absorbida por sus órganos internos. También se determinó el Kerma en aire (K) y la dosis equivalente ambiental (H*(10)) a 1 m de la glándula. Se determinaron dos factores de actividad a dosis, también llamados Factores Gamma, que permiten estimar la dosis que la paciente produce a personas a su alrededor. De la radiación gamma que emite el 131I en la tiroides se encontró que el timo recibe la mayor dosis mientras que el útero es el órgano que menor dosis recibe. Los factores gamma determinados fueron: ΓKAire = 52.06 μGy-m2-h-1-GBq-1, y ΓH*(10) = 67.72 μSv-m2-h-1-GBq-1. La distribución de la dosis absorbida por los órganos internos se atribuye a la distancia relativa entre la tiroides y los otros órganos, al blindaje inter-órganos, su tamaño y a su composición elemental. Los factores ΓKAire y ΓH*(10) permiten estimar la exposición que la paciente produce sobre el personal a su alrededor. Con esto, el médico nuclear, el físico médico o el responsable de la seguridad radiológica en el hospital pueden dar indicaciones mas precisas sobre el comportamiento de las personas en torno al paciente.

[Lead levels in high-risk populations and the surrounding environment in San Ignacio, Fresnillo, Zacatecas, México]. / Niveles de plomo en la población de alto riesgo y su entorno en San Ignacio, Fresnillo, Zacatecas, México.

OBJECTIVE: To determine the lead concentration in the blood of children and nursing or pregnant women from San Ignacio, Fresnillo, in Zacatecas, Mexico as well as in soil, plants, ash and lead-glazed pottery, in order to determine exposure due to a metal-recycling facility. MATERIAL AND METHODS: The study was carried out from December 2004 to April 2005. Lead in blood was measured with anodic stripping voltammetry, while dispersive energy X-ray fluorescence was used in the other matrices. RESULTS: Based upon the criteria outlined in the Official Mexican Standards, 90% of the children was identified as category 1, 5% as category II and another 5% as category III. The soil in the land near the facility contained from 73 to 84,238 microg/g, with an average of 4940 microg/g. Larger lead concentrations were found on sites located closer to the facility. San Ignacio's soil contained, on average, 109 microg/g. High lead levels were found in glazed pottery and the concentration in agricultural crops was greater than 300 microg/g. CONCLUSIONS: Although the majority of children in San Ignacio have blood lead concentrations considered to be acceptable according to the Official Mexican Standards, several studies indicate that deleterious effects on children's health exist even at low concentrations. The land around the metal recycling facility is contaminated with lead, and to that extent, the crops that are produced there, once ingested, are a source of contamination, which is compounded by the use of glazed pottery.

Niveles de plomo en la población de alto riesgo y su entorno en San Ignacio, Fresnillo, Zacatecas, México / Lead levels in high-risk populations and the surrounding environment in San Ignacio, Fresnillo, Zacatecas, México

OBJETIVO: Determinar la concentración de plomo en la sangre de niños y mujeres, en periodo de lactancia o embarazadas, de la comunidad de San Ignacio, Fresnillo, en Zacatecas, así como en matrices de suelo, plantas, ceniza y barro vidriado, para determinar la exposición que genera una empresa recicladora de metales. MATERIAL Y MÉTODOS: El estudio se realizó de diciembre de 2004 al mes de abril de 2005. El Pb en sangre se midió por voltamperometría de redisolución anódica, mientras que se utilizó energía dispersa de fluorescencia por rayos X para las otras matrices. RESULTADOS: Con base en los criterios de la Norma Oficial Mexicana (NOM) se encontró que 90 por ciento de los menores está en la categoría I, 5 por ciento se encuentra en la categoría II y el otro 5 por ciento se ubica en la categoría III. El suelo de los terrenos aledaños a la recicladora tiene en promedio 4 940 µg/g, en un intervalo de 73 a 84 238 µg/g. Las mayores concentraciones se localizan en los puntos más cercanos a la empresa. El suelo de San Ignacio tiene en promedio 109 µg/g. Se encontraron valores altos en el barro vidriado y la concentración del Pb en las plantas es superior a los 300 µg/g. CONCLUSIONES: A pesar de que la mayoría de los niños analizados presenta niveles de plomo en sangre que la Norma Mexicana señala como aceptables, varios estudios indican que existen efectos nocivos aun a concentraciones bajas. Los terrenos aledaños a la empresa están contaminados, y en esa medida los alimentos que ahí se producen, al ser consumidos, son una fuente de contaminación, que se agudiza con el uso de barro vidriado.