Desarrollo y evaluación biomecánica de plantillas de poliuretano usadas en calzado de seguridad

Este trabajo implica la evaluación de parámetros biomecánicos a plantillas de poliuretano dirigidas específicamente al calzado de seguridad y para el pie característico de los trabajadores de diversas industrias de la República Mexicana. El estudio se llevó a cabo tomando en cuenta que la mayoría de las actividades que desempeña el trabajador las realiza en forma semi-estática. La evaluación se refuerza con la valoración de la plantilla de poliuretano a partir de la medición de la absorción de energía y de su rigidez de acuerdo a estudios biomecánicos que se aplican a diversos materiales empleados en la fabricación de plantillas

Aging of dissolved copper and copper-based nanoparticles in five different soils: short-term kinetics vs long-term fate

With the growing availability and use of copper based nanomaterials (Cu-NMs), there is increasing concern regarding their release and potential impact on the environment. In this study, the short term (≤ 5 days) ageing profile and the long term (4 months) speciation of dissolved Cu, copper oxide (CuO-) and copper sulfide nanoparticles (CuS-NPs) were investigated in five different soils using X-ray absorption spectroscopy (XAS). Soil pH was found to strongly influence the short term chemistry of the Cu-NMs added at 100 mg/kg above background. Low pH soils promoted rapid dissolution of CuO-NPs that effectively aligned their behaviour to that of dissolved Cu within 3 days. In higher pH soils, CuO-NPs persisted longer due to slower dissolution in the soil and resulted in contrasting short term speciation compared to dissolved Cu, which formed copper hydroxides and carbonates that were reflective of the soil chemistry. Organic matter appeared to slow the dissolution process but in the long term, the speciation of Cu added as dissolved Cu, CuO-NPs and CuS-NPs were found to be same for each soil. The results imply that in the short term Cu-NMs may exhibit unique behaviour in alkaline soils compared to their conventional forms (e.g. in the event of an adverse leaching event), but in the long term (≥ 4 months), their fates are dictated by the soil properties and are independent of the initial Cu form, and are likely to present minimal risk of nano-specific Cu-NM impact in the soil environment for the concentration studied here

The Molecular Scale Nature of Copper (II) and Arsenate Bonding with Goethite-Humate Complexes

In soils, interactions between clay minerals and natural organic matter are known to affect the cycling of heavy metals and anions. Contaminant structures at mineral surfaces that contain adsorbed organic matter will have a significant influence on the bioavailability of the contaminant. The structure of copper(II) and arsenate complexes on goethite in the presence and absence of adsorbed humic acid were studied with extended x-ray absorption fine structure (EXAFS) spectroscopy and with x-ray absorption near edge structure (XANES) spectroscopy. The copper(II) and arsenate formed edge shared inner-sphere surface complexes with goethite. The copper(II) itself was present in a distorted octahedral configuration, and ternary complexes involving bonding with both the humic acid and the goethite (Type A complexes) or adsorbed humic acid (Type B complexes), occurred at pH 5.6. At pH 8, the copper(II) was found to display a stronger affinity for the goethite surface and the formation of ternary complexes did not occur. The EXAFS analyses demonstrated that arsenate was present in a tetrahedral configuration and was predominantly bonded to goethite surface sites. Regardless of the level of adsorbed humic acid, the arsenic coordination environment was similar and indicated that ternary complexes could not be distinguished

Diversidad funcional de la comunidad de peces en hábitats de manglar en la bahía de La Paz, B.C.S. México

impreso y digita

Diversidad funcional de la comunidad de peces en hábitats de manglar en la Bahía de La Paz, B.C.S. México

impreso y digita

Removal of arsenic from a deep well by electrocoagulation in a continuous filter press reactor

We investigated arsenic removal from groundwater by electrocoagulation (EC) using aluminum as the sacrificial anode in a continuous filter press reactor. The groundwater was collected at a depth of 200 m in the plateau region, in Central Mexico, (As 134 μg L−1, Fe 0.3 mg L−1, Cd 0.7 mg L−1, Na 58 mg L−1, pH 6.8). The influence of current density (J) and mean linear flow rate (u) on As removal was analyzed. EC revealed that u of 0.91 cm s−1 (which gives a retention time of 53.4 s) at J of 6 and 8 mA cm−2 yielded samples that met the Mexican standard for arsenic (≤25 μg L−1). EC at 10 mA cm−2 did not improve results any further owing to massive generation of gases and anode passivation. The partial EC removal of arsenic can be attributed to the mixture of HAsO2, H3AsO3 and HAsO42−. HAsO42− is more susceptible to removal by adsorption on Al(OH)3 and Al2O3 flocs. The best EC result was obtained at 6 mA cm−2 and 0.91 cm s−1, with energy consumption of 0.89 kWh m−3, which decreased arsenic from 134 to 14 μg L−1.</jats:p

Environmental drivers of fish community functional diversity in arid mangroves compared to a tropical estuary

Mangroves are important habitats for fish across latitudinal gradients, but few studies have examined fish community functional diversity in mangroves from arid environments. To address this, we assembled 11 morpho-functional traits and taxonomic diversity for 123 fish species and environmental characteristics from 3 mangrove ecosystems in the Gulf of California, where arid conditions prevail. We compared these arid mangrove fish communities to a semitropical community in an estuarine condition to analyze functionality. Arid mangrove fish communities were similar to each other, but different from semitropical estuarine fish communities (R = 0.951, P = 0.007). Mangrove fish communities had higher trait diversity than the estuarine community, but the estuary had higher redundancy. Taxonomic diversity showed a latitudinal gradient, with the southernmost site in the arid region functioning as a transition site to estuarine communities. Despite the different taxonomic composition, the functional structure remained similar in the fish communities within the arid region and had higher counts of diverse traits than the site with estuarine conditions. High salinity and evaporation deficit in the arid mangroves relaxed habitat filtering pressures relative to the estuarine conditions, where the higher tolerance to salinity changes imposes redundant morphologies. Future studies should focus on seasonal variation of environmental effects on the functional aspects of the fish community

Environmental drivers of fish community functional diversity in arid mangroves compared to a tropical estuary

Mangroves are important habitats for fish across latitudinal gradients, but few studies have examined fish community functional diversity in mangroves from arid environments. To address this, we assembled 11 morpho-functional traits and taxonomic diversity for 123 fish species and environmental characteristics from 3 mangrove ecosystems in the Gulf of California, where arid conditions prevail. We compared these arid mangrove fish communities to a semitropical community in an estuarine condition to analyze functionality. Arid mangrove fish communities were similar to each other, but different from semitropical estuarine fish communities (R = 0.951, P = 0.007). Mangrove fish communities had higher trait diversity than the estuarine community, but the estuary had higher redundancy. Taxonomic diversity showed a latitudinal gradient, with the southernmost site in the arid region functioning as a transition site to estuarine communities. Despite the different taxonomic composition, the functional structure remained similar in the fish communities within the arid region and had higher counts of diverse traits than the site with estuarine conditions. High salinity and evaporation deficit in the arid mangroves relaxed habitat filtering pressures relative to the estuarine conditions, where the higher tolerance to salinity changes imposes redundant morphologies. Future studies should focus on seasonal variation of environmental effects on the functional aspects of the fish community.</jats:p