Author: Leonel Hernández Mena

Ionic composition in aqueous extracts from PM2.5 in ambient air at the City od Cuernavaca, Mexico

Hugo Albeiro Saldarriaga Noreña Leonel Hernández Mena ENRIQUE SANCHEZ SALINAS Fernando Ramos Quintana Ma. Laura Ortiz Hernández RODRIGO MORALES CUETO ADRIANA VANESA ALARCON GONZALEZ SANDRA IGNACIA RAMIREZ JIMENEZ (2014)

"The present study was carried out between May and June 2012 in the city of Cuernavaca, Mexico. During this time the average ambient temperatures were about 25˚C, suggesting the formation of secondary aerosols, consisting mainly of ammonium and sulfate. The average PM2.5 concentration was 37 μg·m−3 for the entire urban area and there were only two days which exceeded the limit established by the official standards for periods of 24 h. The most abundant ionic species associated with PM2.5 were sulfates (3634.82 ng·m−3, average) and ammonium (1709.53 ng·m−3, average). The ratio estimated between total anions and total cations indicated that the concentration of total anions was 1.94 times total cations. The contribution percentage of the ionic species associated with PM2.5 revealed that 76% of the PM2.5 is sulfates and ammonium. The ion balance made for the urban area of Cuernavaca indicated that during the study period, the aerosols showed alkaline characteristics; that is to say the concentration of anions was not sufficient to neutralize the cations, specifically ammonia (m = 0.060). Finally, wind fields showed that during the study the winds came in 50% from the south west, followed by 25% from east and 12.5% of the south east, which in part allowed transport of contaminants into the portion of the city, where the AUSM campus site was located."

Article

BIOLOGÍA Y QUÍMICA BIOLOGÍA Y QUÍMICA

Competitive kinetics versus stopped flow method for determining the degradation rate constants of steroids by ozonation.

ALBERTO LOPEZ LOPEZ VALENTIN FLORES PAYAN ELIZABETH LEON BECERRIL LEONEL HERNANDEZ MENA RAMIRO VALLEJO RODRIGUEZ (2016)

"Steroids are classified as endocrine disrupting chemicals; they are persistent with low

biodegradability and are hardly degraded by conventional methods. Ozonation process

has been effective for steroids degradation and the determination of the kinetics

is a fundamental aspect for the design and operation of the reactor. This study assessed

two methods: competitive kinetics and stopped flow, for determining the degradation

kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water.

Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger

of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference

compound. For the stopped flow, the experiments were performed in a BioLogic SFM-

3000/S equipment. For both methods, the second order rate constants were in the

order of 106 and 105 M−1 s−1 for E2 and EE2 respectively. The competitive kinetics can

be applied with assurance and reliability but needing an additional analysis method

to measure the residual concentrations. Stopped flow method allows the evaluation

of the degradation kinetics in milliseconds and avoids the use of additional analytical

methodologies; this method allows determining the reaction times on line. The methods

are applicable for degradation of other emerging contaminants or other steroids

and could be applied in water treatment at industrial level. Finally, it is important to

consider the resources available to implement the most appropriate method, either

competitive kinetics or the stopped-flow method".

Article

Steroids, Competitive kinetics, Stopped flow, Second order constant INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS INGENIERÍA Y TECNOLOGÍA DEL MEDIO AMBIENTE OTRAS

Atmospheric Distribution of PAHs and Quinones in the Gas and PM1 Phases in the Guadalajara Metropolitan Area, Mexico: Sources and Health Risk

VALERIA OJEDA CASTILLO ALBERTO LOPEZ LOPEZ Leonel Hernández Mena MARIO ALFONSO MURILLO TOVAR José de Jesús Díaz Torres IVAN YASSMANY HERNANDEZ PANIAGUA Jorge del Real Olvera Elizabeth León Becerril (2018)

"Polycyclic aromatic hydrocarbons (PAHs) and quinones in the gas phase and as submicron particles raise concerns due to their potentially carcinogenic and mutagenic properties. The majority of existing studies have investigated the formation of quinones, but it is also important to consider both the primary and secondary sources to estimate their contributions. The objectives of this study were to characterize PAHs and quinones in the gas and particulate matter (PM1) phases in order to identify phase distributions, sources, and cancer risk at two urban monitoring sites in the Guadalajara Metropolitan Area (GMA) in Mexico. The simultaneous gas and PM1 phases samples were analyzed

using a gas chromatography–mass spectrometer. The lifetime lung cancer risk (LCR) due to PAH exposure was calculated to be 1.7 10􀀀3, higher than the recommended risk value of 10􀀀6, indicating a potential health hazard. Correlations between parent PAHs, criteria pollutants, and meteorological parameters suggest that primary sources are the main contributors to the S8 Quinones concentrations in PM1, while the secondary formation of 5,12-naphthacenequinone and 9,10-anthraquinone may contribute less to the observed concentration of quinones. Additionally, naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene in PM1, suggest photochemical degradation into unidentified

species. Further research is needed to determine how these compounds are formed."

Article

MEDICINA Y CIENCIAS DE LA SALUD MEDICINA Y CIENCIAS DE LA SALUD

Optimization of analytical conditions to determine steroids and pharmaceuticals drugs in water sample using solid phase-extraction and HPLC

ALBERTO LOPEZ LOPEZ LEONEL HERNANDEZ MENA RAMIRO VALLEJO RODRIGUEZ MARIO ALFONSO MURILLO TOVAR (2011)

Two reliable methods were optimized to determine two steroids (17-Estradiol and 17-Ethinylestradiol) and two pharmaceutical drugs (ibuprofen and naproxen) using Solid-Phase Extraction (SPE) for sample preparation and High Performance Liquid Chromatography (HPLC) for analysis. SPE (C18) conditions were evaluated varying elution solvent volume, pH conditions and sample mass in the cartridge and reduction techniques of the extract. The efficiency of the analytical methods was evaluated by spiking ultrapure water samples with compounds at three and four levels of concentration for steroids and pharmaceutical drugs, re- spectively. The recoveries were independent (P > 0.05) of added mass of target analytes with a repeatability lower than 6.5% for steroids and 12.1% for pharmaceutical compounds. The recovery factor (coefficient of variation, CV) was higher than 83% for steroids (CV < 3.8%) and >93% for pharmaceuticals (CV < 5.2%). The optimized analytical method was applied for the evaluation of a steroid degradation test using ozone, finding that the estimated limit of detection is sufficient to determine the residual mass (μg·L–1) of 17β-Estradiol after the experiment.

Article

Steroids, Pharmaceuticals Drugs, Solid-Phase Extraction, HPLC-DAD INGENIERÍA Y TECNOLOGÍA

COMPARATIVE STUDY OF COMPETITIVE KINETICS AND STOPPED FLOW METHODS ON THE DETERMINATION OF RATE CONSTANTS OF STEROIDS DEGRADATION USING OZONE

RAMIRO VALLEJO RODRIGUEZ ALBERTO LOPEZ LOPEZ LEONEL HERNANDEZ MENA ELIZABETH LEON BECERRIL VALENTIN FLORES PAYAN (2016)

Steroids are classified as endocrine disrupting chemicals; they are persistent with low

biodegradability and are hardly degraded by conventional methods. Ozonation process

has been effective for steroids degradation and the determination of the kinetics

is a fundamental aspect for the design and operation of the reactor. This study assessed

two methods: competitive kinetics and stopped flow, for determining the degradation

kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water.

Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger

of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference

compound. For the stopped flow, the experiments were performed in a BioLogic SFM-

3000/S equipment. For both methods, the second order rate constants were in the

order of 106 and 105 M−1 s−1 for E2 and EE2 respectively. The competitive kinetics can

be applied with assurance and reliability but needing an additional analysis method

to measure the residual concentrations. Stopped flow method allows the evaluation

of the degradation kinetics in milliseconds and avoids the use of additional analytical

methodologies; this method allows determining the reaction times on line. The methods

are applicable for degradation of other emerging contaminants or other steroids

and could be applied in water treatment at industrial level. Finally, it is important to

consider the resources available to implement the most appropriate method, either

competitive kinetics or the stopped-flow method.

Article

Steroids, Competitive kinetics, Stopped flow, Second order constant INGENIERÍA Y TECNOLOGÍA

Evaluación de la calidad del agua ante la enfermedad renal crónica en la Zona Oriente de Michoacán, México

María de Guadalupe Panduro Rivera Leonel Hernández Mena Alberto López López Mario Alfonso Murillo Tovar José de Jesús Díaz Torres Jorge Del Real Olvera (2014)

Actualmente en la población de la región oriente de Michoacán existe una alta incidencia y prevalencia de la Enfermedad Renal Crónica (ERC), problema de salud grave que se presenta en individuos jóvenes sin diabetes mellitus o hipertensión arterial (causas comunes de la ERC), sugiriéndose así un posible origen ambiental.

Currently in the population of the eastern region of Michoacan there is a high incidence and prevalence of Chronic Kidney Disease (CKD), a serious health problem that occurs in individuals without diabetes mellitus or hypertension (common causes of CKD), suggesting This is a possible environmental origin.

Article

Agua Enfermedad renal crónica BIOLOGÍA Y QUÍMICA QUÍMICA