Extracción secuencial de plomo y vanadio en sedimentos del río Catatumbo utilizando FAAS, ETAAS e ICP-AES

Se presenta la evaluación del procedimiento de extracción secuencial aprobado por la BCR (BCR, por sus siglas en inglés, Community Bureau of Reference) para determinar metales en muestras de sedimentos del río Catatumbo, Venezuela. Las fracciones consistieron en 4 etapas: en la primera, llamada intercambiable, se extrajo utilizando ácido acético; la segunda, o reducible, con hidroxicloruro de amonio; la tercera, u oxidable, con peróxido de hidrógeno y acetato de amonio y la residual, que es la etapa remanente, se digirió con agua regia. El análisis se realizó por espectrometría de absorción atómica con llama (FAAS), horno de grafito (ETAAS) y espectrometría de emisión atómica con plasma inductivamente acoplado (ICP-AES). Los metales determinados fueron Pb y V. Las determinaciones por FAAS, ETAAS e ICP-AES indicaron que no hubo diferencias estadísticamente significativas (p < 0,05) cuando se compararon los resultados de 24 muestras de sedimentos del río Catatumbo realizadas por triplicado. La exactitud encontrada sumando las cuatro etapas de la BCR para Pb y V fueron comparables a los resultados obtenidos por digestión ácida, lo cual indica que el procedimiento es adecuado para la cuantificación de los metales estudiados. El Pb y V se encontró mayormente (55-97 %) en la etapa residual lo que los hace no disponibles. Palabras clave: digestión ácida, extracción BCR, sedimento, plomo, vanadio  Abstract: The aim of the present work is the evaluation of the procedure of sequential extraction approved by the BCR and used to determine metals in samples of sediments from Catatumbo River in Venezuela. The fractions consisted in four (4) stages: the first one or interchangeable was extracted using acetic acid, the second one or reducible with ammonia hydroxi-chloride, the third one or oxidable with hydrogen peroxide and ammonium acetate and the residual which is the remnant stage was digested with aqua regia. The analysis was made by Flame Atomic Absorption Spectrometry (FAAS), Electrothermal Atomisation Atomic Absorption Spectrometry (ETA-AAS) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The metals evaluated were Pb and V. The evaluations for FAAS, ETA-AS and ICP-AES indicated that there were not statistically significant differences (p <0.05) when the results of 24 samples of sediments from the Catatumbo River carried out in triplicate were compared. The exact result found by adding the four stages of the BCR for Pb and V were comparable to the results obtained by acid digestion. The Pb and V were found mainly (55-97 %) in the residual stage which makes them not available and these results are comparable to other studies published. Key words: Acid Digestion, Extraction of BCR, sediment, Pb, V&nbsp

CUANTIFICACIÓN DE CADMIO Y PLOMO EN GRANOS DE SOJA (Glycine max) COMERCIALIZADOS EN EL CANTÓN QUEVEDO, ECUADOR.

La contaminación por cadmio y plomo en cultivos agrícolas representa uno de los problemas ambientales más graves, debido a su naturaleza no biodegradable. Las altas concentraciones de cadmio y plomo son un riesgo para la salud de las personas por el consumo de alimentos contaminados. La soja se destaca por tener una alta tolerancia a los metales tóxicos. El objetivo de la presente investigación fue cuantificar los niveles de cadmio y plomo en granos de soja (Glycine max) comercializados en el cantón Quevedo, Ecuador. Para el análisis de las muestras recolectadas aleatoriamente por triplicado, se pesaron aproximadamente dos (2) g de soja que fueron introducidos en la mufla (600°C) durante dos (2) horas. Las muestras una vez calcinadas, se disolvieron en cinco (5) mL de una disolución de HNO3 al 1%. La cuantificación de cadmio y plomo se realizó por espectrometría de absorción atómica con llama. Las concentraciones mínimas y máximas de plomo encontradas en granos de soja fueron 0,61 y 2,06 mg. Kg-1, respectivamente, superando los niveles máximos y los límites máximos permisibles establecidos por el Codex Alimentarius y la Unión Europea. En el caso del cadmio también se encontraron concentraciones significativas (0,02-0,07 mg.kg-1), pero, en este caso, los valores se encuentran dentro de los intervalos establecidos. Considerando estos resultados es necesario llevar a cabo una revisión y modificación de los criterios establecidos sobre la calidad de los suelos agrícolas y el uso excesivo de agroquímicos, fortaleciendo el diseño de estrategias que conduzcan a la prevención de la contaminación de los mismos

Avaliação de fatores organizacionais na implementação de projetos integradores de saberes no segundo nível da Carreira de Engenharia Química

In the academic period of October 2017 to February 2018, integrated knowledge projects were carried out for the first time in the second level of the Chemical Engineering career at the Universidad Técnica de Manabí (UTM). At the end of this academic period, 66% of the students did not reach the minimum qualification necessary to consider the integrating knowledge projects as approved. This research aimed to evaluate if the organizational factors to be taken into account when implementing learning strategies based on problem-solving were considered during the mentioned academic period, such as integrating knowledge projects. This study was conducted by implementing two instruments designed to collect information, one for the teaching staff and the other one for the students. Among the evaluated aspects are the number of students per workgroup and per course, criteria for group formation, the definition of the topic of the integrating knowledge projects, identification of the problem to be solved, support through tutorials, cooperative learning, teachers trained in integrating knowledge projects, among others are highlighted. When the collected information was compared with other studies carried out in this matter, it was found that several of the aspects evaluated in this study were not established in correspondence with learning through integrating knowledge projects. Among the obtained results stands out the need for the UTM to have a normative framework for implementing the integrating knowledge projects in which the evaluated aspects are adapted to teaching based on problem-solving, and prior training is considered mandatory for both teachers and students in this learning strategy.En el periodo académico octubre 2017-febrero 2018 se realizaron, por primera vez, proyectos integradores de saberes (PIS) en el segundo nivel de la carrera de Ingeniería Química de la Universidad Técnica de Manabí (UTM). Al finalizar este periodo académico, el 66% del estudiantado no alcanzó la calificación mínima necesaria para considerar como aprobado los PIS. El objetivo de esta investigación fue evaluar, si durante el periodo académico antes mencionado, fueron considerados los factores organizacionales que se deben tomar en cuenta al implementar estrategias de aprendizaje basadas en la solución de problemas, como los PIS. Para la realización de este estudio se diseñaron dos instrumentos para la recolección de la información, uno para el profesorado y otro para el estudiantado. Entre los aspectos evaluados destacan el número de estudiantes por grupo de trabajo y por curso, criterios para la conformación de grupo, definición de la temática de los PIS, identificación del problema a resolver, acompañamiento mediante tutorías, aprendizaje cooperativo, capacitación del profesorado en PIS, entre otros aspectos. Al comparar la información recabada con otros estudios realizados en esta materia se encontró que varios de los aspectos evaluados en este estudio no han sido establecidos en correspondencia con un aprendizaje mediante PIS. Entre los resultados obtenidos, destaca la necesidad, por parte de la UTM, de contar con un marco normativo para la implementación de los PIS, en las que se adapten los aspectos evaluados a una enseñanza basada en la solución de problemas, en la que se considere la capacitación previa obligatoria tanto del profesorado y como del alumnado en esta estrategia de aprendizaje.No período letivo de outubro de 2017 a fevereiro de 2018, foram realizados, pela primeira vez, projetos de integração de conhecimento (PIC) no segundo nível da carreira de Engenharia Química da Universidade Técnica de Manabí (UTM). Ao final desse período letivo, 66% de estudantes não alcançavam a qualificação mínima necessária para considerar aprovado o PIC. O objetivo desta pesquisa foi avaliar, durante o referido período letivo, os fatores organizacionais que devem ser levados em consideração na implementação de estratégias de aprendizagem baseadas na resolução de problemas, como o PIC. Para a realização deste estudo, foram elaborados dois instrumentos de coleta de informações, um para o corpo docente e outro para estudantes. Dentre os aspectos avaliados, destacam-se o número de estudantes por grupo de trabalho e por curso, critérios para formação do grupo, definição do tema do PIC, identificação do problema a ser resolvido, apoio através de tutoriais, aprendizagem cooperativa, formação de professores no PIC, entre outros aspectos. Ao comparar as informações coletadas com outros estudos realizados nesta matéria, constatou-se que vários dos aspectos avaliados neste estudo não foram estabelecidos em correspondência com a aprendizagem pelo PIC. Dentre os resultados obtidos, destaca-se a necessidade do UTM ter um princípio normativo para implantação do PIC, no qual os aspectos avaliados sejam adaptados ao ensino com base na resolução de problemas, na que seja considerada a formação prévia obrigatória de professores e alunos nesta estratégia de aprendizagem

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030