Revista Internacional de Contaminación Ambiental
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Prediction, modeling, and optimization studies of eco-friendly gold extraction using alpha-cyclodextrin and the RSM and CCD methods
Get PDFIn the Democratic Republic of the Congo, gold extraction from ore in South Kivu utilized alpha-cyclodextrin (α-CD) as an eco-friendly method to replace harmful methods. Analysis of variance and response surface methodology were employed for prediction, modeling, and optimization studies. Atomic absorption spectroscopy revealed a 0.06% gold content in a randomly taken ore sample. Leaching with modified aqua regia was optimized with the following parameters: 7.27 h, 50 g/L HBr concentration, pH 1, and 200 rpm stirring speed, resulting in 98.5% removal. Neutralization tests with potassium hydroxide (KOH) followed leaching to prepare the solution medium with appropriate pH for extraction test, by varying parameters such as time, KOH concentration, and pH. Following neutralization, extraction tests with α-CD were carried out and optimized with the following parameters: 40 min, α-CD concentration of 11.6166 g/L, and a pH of 5, resulting in a percent removal of 98.9%. α-CD’s eco-friendly nature, cost-effectiveness, and high percent removal make it a promising and sustainable alternative for gold recovery, appealing to the mining industry.In the Democratic Republic of the Congo, gold extraction from ore in South Kivu utilized alpha-cyclodextrin (α-CD) as an eco-friendly method to replace harmful methods. Analysis of variance and response surface methodology were employed for prediction, modeling, and optimization studies. Atomic absorption spectroscopy revealed a 0.06% gold content in a randomly taken ore sample. Leaching with modified aqua regia was optimized with the following parameters: 7.27 h, 50 g/L HBr concentration, pH 1, and 200 rpm stirring speed, resulting in 98.5% removal. Neutralization tests with potassium hydroxide (KOH) followed leaching to prepare the solution medium with appropriate pH for extraction test, by varying parameters such as time, KOH concentration, and pH. Following neutralization, extraction tests with α-CD were carried out and optimized with the following parameters: 40 min, α-CD concentration of 11.6166 g/L, and a pH of 5, resulting in a percent removal of 98.9%. α-CD’s eco-friendly nature, cost-effectiveness, and high percent removal make it a promising and sustainable alternative for gold recovery, appealing to the mining industry
Tratamiento electroquímico mejorado para la remoción de metales de suelos contaminados por pasivos ambientales mineros
Get PDFMining environmental liabilities (MEL) are metal-intensive wastes that have the potential to contaminate the surrounding soil, adversely affecting water and air quality, degrading ecosystems, and causing toxic effects on human health. This study used electrochemical treatment as a remediation technique to decontaminate soil affected by MEL. Through a mixed factorial design, the effects of the improvement solutions, acetic acid, and nitric acid, and three distances from the soil with respect to the anode, on the residual concentration and one-dimensional spatial distribution of Pb, Cd, and Zn were investigated. The tests were carried out in triplicate, in acrylic cells, for five days, submitted to 30 V of power, and with nitric acid as cathode fluid. The results showed that nitric acid reduces 4.0, 11.5, and 11.3 times the content of Pb, Cd, and Zn compared to acetic acid, that is, the highest removal percentages of Pb, Zn, and Cd were 40, 34, and 23 %, respectively, when using nitric acid. Moreover, the one-dimensional spatial distribution of metals in the post-treatment soil was not an increasing concentration gradient from the anode region to the cathodic region, but was rather a homogeneous trend. Therefore, using nitric acid as the enhancement fluid confirmed the viability of the electrochemical treatment, although it should be enhanced under other experimental conditions to achieve higher remediation rates.Los pasivos ambientales mineros (PAM) son residuos con alta carga de metales que tienen el potencial de contaminar el suelo circundante, afectar negativamente la calidad del agua y aire, degradar los ecosistemas y provocar efectos tóxicos en la salud humana. Este estudio utilizó el tratamiento electroquímico como técnica de remediación para descontaminar un suelo afectado por PAM. A través de un diseño factorial mixto se investigó los efectos de las soluciones de mejora, ácido acético y ácido nítrico, y tres distancias del suelo respecto al ánodo, sobre la concentración residual y distribución espacial unidimensional de Pb, Cd y Zn. Los ensayos se realizaron por triplicado, en celdas de acrílico, durante cinco días, sometidos a 30 V de potencia y con ácido nítrico como fluido catódico. Los resultados demostraron que el ácido nítrico reduce 4.0, 11.5 y 11.3 veces el contenido de Pb, Cd y Zn en comparación con el ácido acético, es decir, que los mayores porcentajes de remoción del Pb, Zn y Cd fueron 40, 34 y 23 % respectivamente, al emplear ácido nítrico. Asimismo, la distribución espacial unidimensional de los metales en el suelo después del tratamiento, no fue un gradiente de concentración creciente desde la región anódica hacia la región catódica, sino una tendencia homogénea. Por tanto, emplear ácido nítrico como fluido de mejora confirmó la viabilidad del tratamiento electroquímico, aunque se debería potenciar en otras condiciones experimentales para alcanzar mayores tasas de remediación
Regulaciones para la descarga de aguas residuales de México: comparación con otros países y su cumplimiento en plantas de tratamiento seleccionadas
No full textThe purpose of this study was: i) to describe and compare the 1996 and 2021 official mexican standards for wastewater discharge (actual standard-NA and new standard-NN, as per the abbreviation in Spanish); ii) to compare the two official mexican standards for wastewater discharge with the regulations of Brazil, the United States, Canada and the European Union (UE), as well as to determine the environmental permissiveness index of basic pollutants and the subset of heavy metals and cyanides (also called ‘other pollutants’); and iii) to analyze the compliance with the Mexican NN and NA of 25 municipal wastewater treatment plants that operate in a metropolitan area of Mexico. The results suggest that the new NOM 2021 is very close to the previous 1996 norm in terms of permissiveness, and in turn both are much more permissive compared to those of the developed countries of the United States-Mexico-Canada Agreement (USMCA) and the UE. The high permissible maximum levels of most pollutants in both Mexican standards could cause negative impacts on water bodies and national assets. The updating and expansion of NOM 002 and 003 is recommended, and eventually the revision of NOM 001 2021 itself is also recommended to eliminate or reduce the risk to health and the environment of water contaminants and upgrade the quality of the water resource in the context of the member countries of the USMCA.El propósito de este estudio fue: i) describir y comparar las normas oficiales mexicanas de descarga de aguas residuales 1996 y 2021 (norma antigua, NA y norma nueva NN, respectivamente); ii) comparar las dos normas oficiales mexicanas para la descarga de aguas residuales con las regulaciones de Brasil, Estados Unidos, Canadá y la Unión Europea (UE); así como determinar el índice de permisividad de los contaminantes básicos y del subconjunto de los metales pesados y los cianuros, también llamados “otros contaminantes”; y iii) analizar el cumplimiento de las NN y NA mexicanas con una muestra de resultados analíticos de los efluentes de 25 plantas de tratamiento de aguas residuales municipales que operan en un área metropolitana de México. Los resultados de esta investigación sugieren que la nueva NOM 2021 es muy cercana a la norma previa 1996 en términos de permisividad, y a su vez ambas son muchísimo más permisivas comparadas con las de los países desarrollados del Tratado entre México, Estados Unidos y Canadá (T-MEC) y de la UE. Los altos límites máximos permisibles de la mayoría de los contaminantes en ambas normas mexicanas podrían causar impactos negativos en los cuerpos de agua y en los bienes nacionales. Se recomienda la actualización y expansión de las NOM-002 y 003, y eventualmente la revisión de la propia NOM-001-2021 para eliminar o reducir el riesgo para la salud y el ambiente de los contaminantes del agua y homologar la calidad del recurso agua en el contexto de los países integrantes del T-MEC
Seasonal variation in the concentration of potentially toxic elements in fish from El Tunal river, Durango, Mexico: Possible implications for human health
Get PDFEnvironmental pollution is a major problem worldwide. One of the major health issues is the consumption of potentially toxic elements through fish intake, particularly in urban areas. Therefore, it is necessary to assess the human health risks of fish consumers. This study aims to determine concentrations of As, Cd, Cr, Cu, Hg, Pb, and Zn in the liver and muscle of freshwater carp (Cyprinus carpio) caught in El Tunal River, Durango, Mexico. Carps were collected in dry (n = 7) and rainy (n = 10) seasons. The highest concentrations of all elements were found in the liver, where As and Zn (4.83 and 6.51 µg/g w/w, respectively) were predominant. Meanwhile, As, Cr, and Zn (1.00, 1.12, and 1.09 µg/g w/w, respectively) were predominant in muscle. The concentrations of As, Cd, Cr, Pb, and Zn had significant differences between seasons (p < 0.05), showing that during the rainy season the concentration of elements in the river, and hence in fish tissues, was reduced. Elements in edible tissue were below the levels allowed in Mexico and by international agencies. The mean and total target hazard quotients were below 1, indicating a minor risk to human health. Based on this study, fish consumption does not represent a risk to human health; however, it is necessary to continue monitoring pollutants since their accumulation can increase over time.Environmental pollution is a major problem worldwide. One of the major health issues is the consumption of potentially toxic elements through fish intake, particularly in urban areas. Therefore, it is necessary to assess the human health risks of fish consumers. This study aims to determine concentrations of As, Cd, Cr, Cu, Hg, Pb, and Zn in the liver and muscle of freshwater carp (Cyprinus carpio) caught in El Tunal River, Durango, Mexico. Carps were collected in dry (n = 7) and rainy (n = 10) seasons. The highest concentrations of all elements were found in the liver, where As and Zn (4.83 and 6.51 µg/g w/w, respectively) were predominant. Meanwhile, As, Cr, and Zn (1.00, 1.12, and 1.09 µg/g w/w, respectively) were predominant in muscle. The concentrations of As, Cd, Cr, Pb, and Zn had significant differences between seasons (p < 0.05), showing that during the rainy season the concentration of elements in the river, and hence in fish tissues, was reduced. Elements in edible tissue were below the levels allowed in Mexico and by international agencies. The mean and total target hazard quotients were below 1, indicating a minor risk to human health. Based on this study, fish consumption does not represent a risk to human health; however, it is necessary to continue monitoring pollutants since their accumulation can increase over time
The hydromorphological quality of the basin of Mexico: A proposal of its indicator value of the ecological state in the riparian ecosystem
Get PDFThe characterization of hydromorphological quality is the evaluation of the physical structure and the flow regime associated with fluvial ecosystems. Its value indicates the state of ecosystem conservation, as well as the anthropogenic pressures that disturb it. The present study proposes an hydromorphological quality (HYQI) index that aims to establish reference conditions in the preserved rivers and springs in the Basin of Mexico, through: (i) the basin quality associated with the riparian zone’s state, including the vegetation’s naturalness, level of erosion, and land use in 13 sub-basins (63 sites); (ii) hydrology, related to natural or disturbance conditions in the channel; (iii) anthropogenic alterations in the riparian zone, and (iv) the characterization of the trophic level. The final evaluation is divided into five classes: high (> 100), good (76-99), moderate (51-75), bad (26-50), and poor (< 25). The HQYI evaluation showed that 44 sites have a high rating (120 to 100 points), where potential reference conditions for the Mexico Basin can be recognized. The remaining 19 sites have good to poor quality conditions. The vegetation cover was represented by 70% of native species in one of three types of forest: Pinus, Abies, and mixed forest dominated by Quercus. Modifications in the canal structure, extraction and retention of water, and introduced plant species were the causes that confirmed the moderate quality value in the middle and lower portions. The HQYI value was found to be significantly correlated with nutrient water enrichments with soluble reactive phosphorus and dissolved inorganic nitrogen. Therefore, this index is recommended for monitoring the Basin of Mexico and registering multiple environmental stressors.The characterization of hydromorphological quality is the evaluation of the physical structure and the flow regime associated with fluvial ecosystems. Its value indicates the state of ecosystem conservation, as well as the anthropogenic pressures that disturb it. The present study proposes an hydromorphological quality (HYQI) index that aims to establish reference conditions in the preserved rivers and springs in the Basin of Mexico, through: (i) the basin quality associated with the riparian zone’s state, including the vegetation’s naturalness, level of erosion, and land use in 13 sub-basins (63 sites); (ii) hydrology, related to natural or disturbance conditions in the channel; (iii) anthropogenic alterations in the riparian zone, and (iv) the characterization of the trophic level. The final evaluation is divided into five classes: high (> 100), good (76-99), moderate (51-75), bad (26-50), and poor (< 25). The HQYI evaluation showed that 44 sites have a high rating (120 to 100 points), where potential reference conditions for the Mexico Basin can be recognized. The remaining 19 sites have good to poor quality conditions. The vegetation cover was represented by 70% of native species in one of three types of forest: Pinus, Abies, and mixed forest dominated by Quercus. Modifications in the canal structure, extraction and retention of water, and introduced plant species were the causes that confirmed the moderate quality value in the middle and lower portions. The HQYI value was found to be significantly correlated with nutrient water enrichments with soluble reactive phosphorus and dissolved inorganic nitrogen. Therefore, this index is recommended for monitoring the Basin of Mexico and registering multiple environmental stressors
La percepción de estudiantes de agronomía sobre la contaminación por agroquímicos
Get PDFThis research involves an interdisciplinary study on the perception of agrochemical pollution in students from six Mexican universities enrolled in agronomic science engineering programs and related areas, such as agroecology, agroforestry engineering, and innovation for sustainable agriculture. The research method is mixed with an exploratory approach; data were collected in an online questionnaire, measuring attitudes, values, and actions related to the use of agrochemicals, as well as a self-assessment knowledge test about pesticides, fertilizers, and their effects on the environment and human health. The theoretical approach emerges from environmental psychology, agroecology, and environmental education. A theoretical model is proposed to explore the formation of mental models and beliefs about sustainable agricultural systems, and recommendations are made for optimizing agronomic science engineering programs with a focus on sustainability. The results show a high level of environmental awareness in students, a low perception of social norms for environmental conservation, and the perception of agrochemicals as essential for production, representing a cognitive barrier to implementing sustainable agricultural strategies.Esta investigación involucra un estudio interdisciplinario sobre la percepción de la contaminación por agroquímicos en estudiantes de seis universidades mexicanas que cursan programas de ingeniería en agronomía y áreas afines, como agroecología, ingeniería agroforestal e innovación agrícola sustentable. El método de investigación es mixto con corte exploratorio, se recolectaron datos en un cuestionario en línea, sobre las actitudes, valores y acciones relacionadas al uso de agroquímicos, además de una autoevaluación de conocimientos sobre plaguicidas, fertilizantes y sus efectos en el ambiente y la salud humana. El enfoque teórico surge de la psicología ambiental, así como de la agroecología y de la educación ambiental. Se propone un modelo teórico para explorar la formación de modelos mentales y creencias sobre sistemas agrícolas sustentables y se plantean recomendaciones para la optimización de programas académicos de ingenierías en agronomía con enfoque hacia la sustentabilidad. Los resultados demuestran un alto nivel de consciencia ambiental en los estudiantes, una baja percepción de normas sociales para la conservación ambiental y la percepción de los agroquímicos como indispensables para la producción, lo que representa una barrera cognitiva para la implementación de estrategias agrícolas sustentables
Distribución espacial del plomo en el suelo urbano de Callao, Perú
Get PDFHeavy metal contamination in urban soils is a major problem due to the serious consequences it generates on human health. The objective of this study was to quantify the concentration and spatial distribution of lead in the urban soil of the Mi Perú district in the Constitutional Province of Callao, Peru. Forty-four sampling points in an area of 50 ha were evaluated, and the total concentration of lead was analyzed by atomic absorption spectroscopy. Two sampling points were identified that exceeded 140 mg/kg of lead in the soil (Peruvian Environmental Quality Standard for urban soil) and it was concluded that the study area does not present generalized lead contamination, but it does present local contamination. Since the data density was insufficient to run a directed variogram, it was impossible to determine if the spatial distribution of Pb was dominated by the direction of the wind. It is recommended to carry out complementary analyses to continue with the detailed evaluation of this environmental problem, such as analysis of the precipitates, redox potential, detail sampling, lead speciation, lead bioaccessibility, health risk assessments, and environmental risk assessments.La contaminación por metales pesados en suelos urbanos constituye una gran problemática debido a las graves consecuencias que genera en la salud humana. El objetivo de este estudio fue cuantificar la concentración y distribución espacial del plomo (Pb) en suelo urbano del distrito Mi Perú, en la Provincia Constitucional del Callao, Perú. Se evaluaron 44 puntos de muestreo en un área de 50 ha y se analizó la concentración total de Pb por espectroscopia de absorción atómica. Se identificaron dos puntos de muestreo que excedieron los 140 mg/kg de Pb en suelo (Estándar de Calidad Ambiental peruano para suelos de uso urbano) y se concluyó que el área de estudio no presenta contaminación generalizada por Pb, pero sí contaminación local. No se pudo determinar si la distribución espacial del Pb fue dominada por la dirección del viento, ya que la densidad de datos fue insuficiente para ejecutar una variograma direccional. Se recomienda realizar análisis complementarios para continuar con la evaluación detallada de esta problemática ambiental, como análisis de los precipitados, potencial redox, muestreo de detalle, especiación del Pb, bioaccesibilidad del Pb, evaluaciones de riesgo a la salud y evaluaciones de riesgo ambiental
Heavy metals phytoextraction potential of Medicago sativa L. irrigated with waste and groundwater
Get PDFWastewater is generally used for crop irrigation purposes it since provides nutrients and organic matter to the soil. However, it can also add contaminants such as heavy metals. The objective of the present study was to evaluate the absorption and accumulation of lead and copper in the aerial and root parts of alfalfa (Medicago sativa L.) irrigated with raw wastewater, treated wastewater, and groundwater using the bioconcentration (BCF) and translocation (TF) factors. Three treatments (raw wastewater, treated wastewater, and groundwater) were tested in a randomized block design with four replicates. The results showed significant differences between treatments. The highest concentrations of lead and copper occurred in the aerial part of the alfalfa irrigated with raw wastewater. The TF factor for lead and copper was higher than one in all treatments; something similar was observed for the BCF, except in the groundwater treatment, indicating that alfalfa has the potential for phytoextraction.Wastewater is generally used for crop irrigation purposes it since provides nutrients and organic matter to the soil. However, it can also add contaminants such as heavy metals. The objective of the present study was to evaluate the absorption and accumulation of lead and copper in the aerial and root parts of alfalfa (Medicago sativa L.) irrigated with raw wastewater, treated wastewater, and groundwater using the bioconcentration (BCF) and translocation (TF) factors. Three treatments (raw wastewater, treated wastewater, and groundwater) were tested in a randomized block design with four replicates. The results showed significant differences between treatments. The highest concentrations of lead and copper occurred in the aerial part of the alfalfa irrigated with raw wastewater. The TF factor for lead and copper was higher than one in all treatments; something similar was observed for the BCF, except in the groundwater treatment, indicating that alfalfa has the potential for phytoextraction
Caracterización de lixiviados y análisis del índice de potencial de contaminación en dos rellenos sanitarios peruanos
Get PDFLandfill disposal is the predominant strategy in developing countries. Leachate generation is one of the most significant environmental impacts of these sites. This study aimed to characterize the leachate from El Zapallal and Portillo Grande sanitary landfills in Lima, Peru. For this purpose, leachate sample results were analyzed, and the Leachate Pollution Index (LPI) was applied. The samples showed elevated electrical conductivity, an alkaline pH, and significant levels of content of total dissolved solids. The high organic load (expressed in DQO and DBO5) and the high ammonium concentration reflect active degradation processes of organic matter. The LPI indicates a highly toxic and poorly stabilized leachate. Leachate recirculation increases its toxicity and could lead to a higher concentration of heavy metals in the waste platforms. However, under desert climatic conditions, with an adequate landfill liner system and management of leachate collection and storage, this strategy is shaped as an alternative that does not pose a high environmental risk and is economically viable. Nevertheless, the two landfills studied show signs of leachate migration and infiltration due to inadequate operating conditions. These results are expected to contribute to understanding the composition of leachate, its pollutant potential, and the implications of leachate recirculation in the studied landfills.En los países en desarrollo la disposición final de residuos en rellenos sanitarios es la estrategia predominante. La generación de lixiviados genera uno de los impactos ambientales más significativos en estos sitios. El objetivo de este estudio fue analizar la caracterización de los lixiviados de los rellenos sanitarios El Zapallal y Portillo Grande de Lima, Perú. Para ello, se examinaron los resultados de las muestras de lixiviados y se aplicó el índice de potencial de contaminación de lixiviados (LPI, por su sigla en inglés). Las muestras presentaron una elevada conductividad eléctrica, un pH alcalino y alto contenido de sólidos totales disueltos. La elevada carga orgánica (expresada en DQO y DBO5) y la alta concentración de amonio reflejan procesos activos de descomposición de la materia orgánica. El LPI indica que el lixiviado es altamente tóxico y está poco estabilizado. La recirculación de lixiviados aumenta su toxicidad y podría elevar la concentración de metales pesados en las plataformas de residuos. A pesar de ello, en condiciones climáticas desérticas, con una adecuada impermeabilización de la plataforma y manejo de la recolección y almacenamiento del lixiviado, esta estrategia se perfila como una alternativa que no representa un alto riesgo ambiental y es económicamente viable. Sin embargo, en los dos rellenos sanitarios de estudio las condiciones inadecuadas de operación muestran indicios de desplazamiento e infiltración de lixiviados. Con estos resultados se espera contribuir al conocimiento de la composición de los lixiviados, su potencial contaminante y las implicaciones de la recirculación de lixiviados en los rellenos sanitarios de estudio
Impacto del uso de suelo y la fragmentación del paisaje sobre la calidad del agua del río Teaone en Ecuador
Get PDFWater quality in watersheds depends on several factors and in Ecuador many rivers are polluted by anthropogenic impact. This study evaluated the influence of different land uses and landscape fragmentation on the physical and chemical characteristics of the Teaone river, Ecuador. Eight sampling points were located by land use (livestock, agroforestry systems, forests, and urban areas) where temperature, turbidity, total dissolved solids (TDS), pH, electrical conductivity, dissolved oxygen (DO), salinity, vegetation type, flow width, substrate, and water depth were measured. Digital circular plots were created to calculate indicators of landscape structure and fragmentation (edge index, dominance, and fragmentation index), and spectral indicators through vegetation indices such as the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and near infrared (NIR), red, and blue bands. Several physical and chemical parameters were within allowable limits (turbidity = –38.7 UNT, pH = 8.1, electrical conductivity = 365 μS/cm, temperature = 26.0 ºC, salinity = 0.15 UPS). However, OD and SDT were outside the limits in all land uses (OD = 4.04, SDT = 186.1 mg/L). Grassland had the highest number of fragments (12.1), followed by settlements (9.4). For NIR, EVI and NDVI high values were observed in native forest, agroforestry, and livestock and lowest values in the urban area. The parameters show that agroforestry systems and native forests maintain good water quality, while in livestock and urban areas water quality decreases.La calidad del agua en las cuencas hídricas depende de varios factores y en Ecuador muchos ríos se encuentran contaminados por impacto antrópico. Este estudio evaluó la influencia de diferentes usos de suelo y la fragmentación del paisaje sobre las características físicas y químicas del río Teaone, Ecuador. Se ubicaron ocho puntos de muestreo por uso de suelo (ganadería, sistemas agroforestales, bosques y zonas urbanas) donde se midieron temperatura, turbiedad, sólidos disueltos totales (SDT), pH, conductividad eléctrica, oxígeno disuelto (OD) y salinidad. Se registró el tipo de vegetación, ancho del caudal, sustrato y profundidad del agua. Se crearon parcelas circulares digitales para calcular indicadores de la estructura y fragmentación del paisaje (índice de bordes, dominancia e índice de fragmentación), e indicadores espectrales a través de índices de vegetación como el índice de vegetación de diferencia normalizada (NDVI, por su sigla en inglés), el índice de vegetación mejorado (EVI), y bandas del infrarrojo cercano (NIR), del rojo y azul. Varios parámetros físicos y químicos estuvieron dentro de los límites permisibles (turbidez = –38.7 UNT, pH = 8.1, conductividad eléctrica = 365 μS/cm, temperatura = 26.0 ºC, salinidad = 0.15 UPS). Sin embargo, el OD y los SDT quedaron fuera de los límites en todos los usos de suelo (OD = 4.04, SDT = 186.1 mg/L). El pastizal tuvo mayor número de fragmentos (12.1), seguido de los poblados (9.4). Para el NIR, el EVI y el NDVI se observaron valores altos en bosque nativo, agroforestal y ganadería y el menor valor en la zona urbana. Los parámetros demuestran que los sistemas agroforestales y bosques nativos mantienen una buena calidad de agua, mientras que en la zona ganadera y urbana la calidad decrece