Various crystallite size estimation methods were used to analyze X-ray diffractograms of spherical cerium dioxide and titanium dioxide anatase nanoparticles aiming to evaluate their reliability and limitations. The microstructural parameters were estimated from several integral breadth methods such as Scherrer, Monshi, Williamson–Hall, and their variants: (i) uniform deformation model, (ii) uniform strain deformation model, and (iii) uniform deformation energy density model. We also employed the size–strain plot and Halder–Wagner method. For this purpose, an instrumental resolution function of an Al₂O₃ standard was used to subtract the instrumental broadening to estimate the crystallite sizes and strain, and the linear regression analysis was used to compare all the models based on the coefficient of determination. The Rietveld whole powder pattern decomposition method was introduced for comparison purposes, being the best candidate to fit the X-ray diffraction data of metal-oxide nanoparticles. Refined microstructural parameters were obtained using the anisotropic spherical harmonic size approach and correlated with the above estimation methods and transmission electron microscopy images. In addition, μ-Raman spectra were recorded for each material, estimating the mean crystallite size for comparison by means of a phonon confinement model.

The purpose of this study was to determine PM_2.5 mass concentration and the contents of trace elements and water-soluble ions in samples collected inside the Metropolitan area of Huancayo. Four monitoring stations were installed at three urban areas (UNCP, HYO, and CHI) and one rural (IGP). The sampling campaign was carried out from March 2017 to November 2017. The PM_2.5 content was determined by gravimetric method, and fifteen trace elements (TE) and seven water-soluble ions were detected by inductively coupled plasma mass spectrometry (ICP–MS), and ion chromatography (IC), respectively. Datasets were assessed by one ANOVA test to detect significant differences among monitoring station. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were applied for source identification. The mean annual concentration of PM_2.5 mass concentrations has ranged (average) from 3.4 to 36.8 µg/m³ (16.6 ± 6.8 µg/m³) for the monitoring stations under study. The annual World Health Organization thresholds and national air quality standards were exceeded. Significant differences (p < 0.05) were observed between most trace elements at urban and rural areas. PCA and HCA illustrated that the most important sources of traces element originated of natural origin (soil re-suspension) and vehicular sources (fuel combustion, abrasion of vehicles tires, wear car components).

Zeolites 5A were obtained by ion exchange of a zeolite 4A, previously synthesized by the hydrothermal method from precursor kaolin, with the aim of removal As(V) from drinking water and Pb(II) from irrigation surface water. Zeolite 5A was characterized before and after adsorption by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. To find the adsorption mechanisms of both As and Pb in real waters, experiments on adsorption kinetics, optimum pH, adsorbent dose, and adsorption isotherms were developed. Adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was made using the residual sum of squares (RSS) and Bayesian information criterion (BIC). As a result, removal adsorption of As(V) and Pb(II) was higher than 95% in 9 and 12 h, respectively. The estimated maximum adsorption capacities for As and Pb were 36.35 mg g⁻¹ and 46.67 mg g⁻¹, respectively. Zeolite 5A is a low-cost adsorbent, through which a concentration of less than 0.01 mg L⁻¹ of As and Pb was obtained in drinking and irrigation water, which is below the permissible limit established by the World Health Organization (WHO).

The adsorption characteristics of titanium dioxide nanoparticles (nano-TiO₂) for the removal of Pb(II) from irrigation water were investigated in this work. To accomplish this, several adsorption factors, such as contact time and pH, were tested to assess adsorption efficiencies and mechanisms. Before and after the adsorption experiments, commercial nano-TiO₂ was studied using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The outcomes showed that anatase nano-TiO₂ was remarkably efficient in cleaning Pb(II) from water, with a removal efficiency of more than 99% after only one hour of contact time at a pH of 6.5. Adsorption isotherms and kinetic adsorption data matched the Langmuir and Sips models quite well, showing that the adsorption process occurred at homogenous sites on the surface of nano-TiO₂ by forming a Pb(II) adsorbate monolayer. The XRD and TEM analysis of nano-TiO₂ following the adsorption procedure revealed a non-affected single phase (anatase) with crystallite sizes of 9.9 nm and particle sizes of 22.46 nm, respectively. According to the XPS data and analyzed adsorption data, Pb ions accumulated on the surface of nano-TiO₂ through a three-step mechanism involving ion exchange and hydrogen bonding mechanisms. Overall, the findings indicate that nano-TiO₂ has the potential to be used as an effective and long-lasting mesoporous adsorbent in the treatment and cleaning of Pb(II) from water bodies.

El presente estudio realizo la dispersión de PM2.5 emitidos por pollerías en Huancayo Metropolitano. Se utilizaron datos topográficos de 30 metros de resolución, datos meteorológicos superficiales y verticales de enero a diciembre del 2017 y características de la fuente como concentraciones de emisión de PM2.5 de pollerías. Para la determinar la eficiencia del modelo AERMOD en la dispersión de PM2.5 se instalaron estaciones de monitoreo de calidad de aire en tres áreas urbanas de Huancayo Metropolitano (UNCP, HYO y CHI), la campaña de muestreo se llevó a cabo de marzo a noviembre del 2017. Los resultados, identificaron la asociación de la dirección y velocidad del viento con la dispersión de PM2.5 y que las concentraciones obtenidas por el modelo AERMOD subestimaron con las obtenidas de las estaciones de monitoreo de calidad de aire, esto debido a que se modelo solo pollerías y no de otras aportaciones de fuentes de emisión. AERMOD provee buenas opciones para modelar dispersión de contaminantes del aire en regiones de montaña para gestión de la calidad del aire.

Este estudio informa por primera vez el contenido de elementos traza y partículas absorbentes de luz (PAL) en muestras de nieve colectadas de un glaciar peruano (glaciar Huaytapallana). La campaña de muestreo se realizó mensualmente desde noviembre de 2015 hasta marzo de 2019. El contenido de elementos traza se cuantificó mediante espectrometría de masa de plasma acoplado inductivamente, mientras que las PAL se analizaron utilizando un método de calentamiento por absorción de luz. El conjunto de datos de los elementos químicos se sometió a pruebas estadísticas para evaluar cambios entre las épocas seca y húmeda. Además, se emplearon análisis de agrupamiento jerárquico (AAJ), el factor de enriquecimiento (FE) y trayectorias inversas calculadas con el modelo HYSPLIT para identificar posibles fuentes de emisión. Se utilizó el modelo de transferencia radiativa SNICAR para estimar el efecto de los PAL sobre el albedo de nieve y el forzamiento radiativo (FR). De acuerdo con el análisis del FE y el AAJ, los elementos Al, Ti, Si, Co, Ce, Sr, Mn, Mg, Ba y Na están influenciados por fuentes naturales, en tanto que el K, Ca, Fe, Cu, Pb y As sugieren una mezcla de origen de fuentes naturales y antrópicas, y el Zn presenta una fuente significativamente antrópica. Por otro lado, según el modelo SNICAR, la presencia de las PAL redujo el albedo de la nieve hasta un 4.5 % en la estación seca con valores de FR de hasta 33 W/m². Por lo tanto, concluimos que la presencia de estas partículas provenientes de fuentes antrópicas aumenta sustancialmente las tasas de fusión o sublimación de los glaciares peruanos.