Revista Internacional de Contaminación Ambiental
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RESIDUOS DE PLAGUICIDAS EN SUELOS DE USO AGRÍCOLA Y RIESGO DE EXPOSICIÓN EN LA MICROCUENCA LOS ZARZALES, MUNICIPIO RIVAS DÁVILA, ESTADO MÉRIDA, VENEZUELA
Get PDFThere is a growing concern about the presence of pesticide residues in agricultural land because they constitute an environmental risk and a source of human exposure. In this work, the presence of these residues and the risk of exposure was determined in the micro-watershed of Los Zarzales, Rivas Dávila municipality, Mérida, Venezuela. Soil samples were taken in the initial, middle and final stages of short cycle crops, and the active ingredients were extracted and analyzed by HPLC. The risk of exposure was estimated by calculating the dose of pesticides through non-dietary intake of contaminated soil and dust, according to the US-EPA criteria. The highest concentration and variety of compounds was recorded during the middle stage: 26 ± 7 mg/kg of total residues and 100% detection frequency, standing out among them paraquat (15 ± 7 mg/kg), carbendazim (8 ± 2 mg/kg), mancozeb (3.7 ± 0.7 mg/kg) and carbofuran (1.2 ± 0.5 mg/kg). Based on these values, the calculated daily doses were 1.5, 0.8, 0.37 and 0.12 μg/day, respectively, all of which were below the admissible daily intake established by FAO/WHO, which is used as reference. Despite of this, the total dose reached 2.8 μg/day, which is considered as a risk of exposure.La preocupación sobre la presencia de residuos de plaguicidas en suelos de uso agrícola es cada vez mayor debido a que constituyen un riesgo ambiental y una fuente de exposición humana. En este trabajo se determinó la presencia de estos residuos y el riesgo de exposición en la microcuenca Los Zarzales, municipio Rivas Dávila, Mérida, Venezuela. Se tomaron muestras de suelos en la etapa inicial, media y final de cultivos de ciclo corto, se extrajeron los principios activos y analizaron por cromatografía líquida de alta resolución. El riesgo de exposición se estimó calculando la dosis de plaguicidas a través de la ingesta no dietética de suelo y polvo contaminado, según los criterios de la US-EPA. La mayor concentración y variedad de compuestos se registró durante la etapa media: 26 ± 7 mg/kg de residuos totales y 100 % de frecuencia de detección, destacando entre ellos paraquat (15 ± 7 mg/kg), carbendazim (8 ± 2 mg/kg), mancozeb (3.7 ± 0.7 mg/kg) y carbofurano (1.2 ± 0.5 mg/kg). Con base en estos valores, las dosis diarias calculadas fueron: 1.5, 0.8, 0.37 y 0.12 µg/día, respectivamente, todas las cuales resultaron estar por debajo de la ingesta diaria admisible establecida por la Organización de las Naciones Unidas para la Agricultura y la Alimentación y la Organización Mundial de la Salud, que es utilizada como referencia. A pesar de ello, la dosis total alcanzó los 2.8 µg/día, lo cual se considera que puede constituir un riesgo de exposición
MÉTODO OPTIMIZADO PARA LA DETERMINACIÓN DE HIDROCARBUROS AROMÁTICOS POLICÍCLICOS ASOCIADOS A PARTÍCULAS ATMOSFÉRICAS
Get PDFPolycyclic aromatic hydrocarbons are ubiquitous air pollutants, derived from the incomplete combustion of organic matter. Due to its physical and chemical characteristics, its association with the particulate matter is favored, and therefore its permanence in the atmosphere. In recent decades, the monitoring of polycyclic aromatic hydrocarbons in urban atmospheres has become a priority due to the high number of exposed individuals. In the present work, modifications of a standard methodology for the extraction, detection and quantification of polycyclic aromatic hydrocarbons were evaluated. These modifications resulted in reductions both in the extraction and quantification time, as well as in processing costs, which implies a substantial improvement in sample processing time, without reducing the sensitivity. In addition, the considerable reduction in the amount of solvent employed resulted in an environmentally friendly methodology.Los hidrocarburos aromáticos policíclicos son contaminantes ambientales ubicuos en el aire, derivados de la combustión incompleta de materia orgánica. Por sus características físicas y químicas, es frecuente encontrarlos asociados a partículas, favoreciendo su permanencia en la atmósfera. En las últimas décadas, el monitoreo de hidrocarburos aromáticos policíclicos en ambientes urbanos se ha convertido en una prioridad debido a la gran cantidad de individuos expuestos. En este trabajo se evaluaron modificaciones de una metodología estándar para la extracción, detección y cuantificación de hidrocarburos aromáticos policíclicos adsorbidos en partículas de 2.5 µm de diámetro aerodinámico. Estas variaciones permitieron reducir considerablemente los tiempos y costos de procesamiento, la detección y cuantificación, sin disminuir la sensibilidad para la detección de estos compuestos. Por otro lado, la reducción considerable en la cantidad de disolvente utilizado resulta en una metodología más amigable con el ambiente
REMOCIÓN DE Pb2+ Y Cd2+ EN SOLUCIÓN ACUOSA USANDO LA MACRÓFITA ACUÁTICA Typha latifolia INERTE
Get PDFThe use of inert biomass to remove dissolved metals from water is an alternative to the conventional technologies of wastewater treatments. In the present paper the capacity of the inert macrophyte Typha latifolia as a biosorbent for Pb2+ and Cd2+ from aqueous solutions was investigated. Batch experiments were conducted suspending 0.075 g of biomass in 15 mL of metal solution. After 60 min, more than 90 % of lead and more than 80 % of cadmium were removed for the biomass at pH 6. The maximum sorption capacity was 38.61 mg/g for lead and 7.20 mg/g for cadmium. Both processes were carried out by a chemical interaction where the carboxylic group of the biomass surface could be especially active. Dynamic experiments were carried out in fixed-bed biomass columns of 1.5 cm in height. A flow-through of 0.053 mL/min was used. Sorption capacity of the bed was 40.67 mg/g for lead and 12.60 mg/g for cadmium. The useful lifetime was 378 h for lead sorption and 130 h for cadmium. Typha latifolia proved to be efficient in the removal of Pb2+ and Cd2+ from aqueous solutions. With the data obtained it is possible to extend the process to a greater scale. El uso de biomasa inerte con la capacidad de retener metales disueltos en un medio acuoso constituye una alternativa para el tratamiento de agua contaminada. El objetivo de este estudio fue evaluar el desempeño de la macrófita Typha latifolia inerte como bioadsorbente de Pb2+ y Cd2+. Se realizaron dos tipos de experimentos: estáticos en lote y dinámicos en columnas. Para los experimentos estáticos se pusieron en contacto 0.075 g del bioadsorbente con 15 mL de solución de un metal. Las concentraciones iniciales de los metales fueron de 10, 20, 30, 40 y 50 mg/L. Después de 60 min, más del 90 % de plomo y más del 80 % de cadmio fueron removidos por la biomasa a pH de 6. De acuerdo con la isoterma de Langmuir la capacidad máxima de adsorción de plomo fue de 38.61 mg/g y la de cadmio de 7.20 mg/g. El proceso de adsorción se da en la superficie del bioadsorbente, donde se forma una monocapa en la que el grupo carboxílico, presente en el bioadsorbente, puede ser especialmente activo. Para los experimentos dinámicos se prepararon columnas de lecho fijo a una altura de 1.5 cm del bioadsorbente, a través de las cuales se pasó un flujo ascendente de 0.053 mL/min. Las concentraciones iniciales de los metales fueron de 10, 30 y 50 mg/L. La capacidad de adsorción del lecho fue de 40.67 mg/g de plomo y de 12.60 mg/g de cadmio. El tiempo de vida útil del bioadsorbente fue de 378 h cuando se removió Pb2+ y de 130 h cuando se removió Cd2+. La Typha latifolia demostró ser eficiente para remover Pb2+ y Cd2+ de soluciones acuosas. Con los datos obtenidos es posible reproducir el proceso a una mayor escala
A CFD MODEL BASED ON WET DEPOSITION OF LARGE-SCALE NATURAL DRAFT COOLING TOWER
Get PDFTraditional research on environmental impacts of natural draft cooling tower in nuclear power plant is mainly based on Gaussian diffusion model or wind tunnel experiments. With the development of modern mainframe computers and turbulence models, CFD method is possible to use for simulating plume drift. CFD software, as it owns powerful computing ability, can simulate and display the plume drift more accurately. In this paper, data from the 1977 Chalk Point Dye Tracer prove CFD simulation to be effective. Also, this paper provides case study on Taohuajiang and Pengze inland nuclear power plants in China. In conclusion, CFD result conforms with the data from the Chalk Point experiment. Compared with SACTI model. As down-wind distance increases, SACTI results decreases faster than CFD. This paper provides a solution that in the lack of field data, CFD will be a powerful tool for assessing environment impacts.Traditional research on environmental impacts of natural draft cooling tower in nuclear power plant is mainly based on Gaussian diffusion model or wind tunnel experiments. With the development of modern mainframe computers and turbulence models, CFD method is possible to use for simulating plume drift. CFD software, as it owns powerful computing ability, can simulate and display the plume drift more accurately. In this paper, data from the 1977 Chalk Point Dye Tracer prove CFD simulation to be effective. Also, this paper provides case study on Taohuajiang and Pengze inland nuclear power plants in China. In conclusion, CFD result conforms with the data from the Chalk Point experiment. Compared with SACTI model. As down-wind distance increases, SACTI results decreases faster than CFD. This paper provides a solution that in the lack of field data, CFD will be a powerful tool for assessing environment impacts
A MORRIS-SOBOL TWO-LAYER PROGRESSIVE MODEL FOR SENSITIVITY ANALYSIS OF PARAMETERS IN RAINFALL THRESHOLD CALCULATION OF FLASH FLOOD
Get PDFAs one of the most hazardous natural events, flash flood is frequently responsible for loss of life and severe damage to infrastructure and public health. The Rainfall Threshold (RT) is the main warning index of flash flood that is used in China. However, the amount of parameters in RT calculation is significantly large, and the determination of some parameter values is affected by subjective factors substantially. In this paper, a Morris-Sobol Two-layer Progressive Model (M-STPM) is established to identify sensitive parameters in RT calculation. Firstly, the Morris screening method is applied to qualitatively analyse the sensitivity of parameters, while the insensitive parameters are filtered. Then the Sobol method is employed to quantify the sensitivity. The sensitivity of parameters in RT calculation is determined through a case study in Duli Village of Anyang County in Henan Province. The results indicate that mean of 1-h annual maximum point rainfall is the most influential parameter. It is found that the parameters in water level-discharge relation calculation have a large influence on the RT, which shows that the proposed model can provide a reference for determining the value of parameters and can lay a theoretical foundation for further error analysis in RT calculation.As one of the most hazardous natural events, flash flood is frequently responsible for loss of life and severe damage to infrastructure and public health. The Rainfall Threshold (RT) is the main warning index of flash flood that is used in China. However, the amount of parameters in RT calculation is significantly large, and the determination of some parameter values is affected by subjective factors substantially. In this paper, a Morris-Sobol Two-layer Progressive Model (M-STPM) is established to identify sensitive parameters in RT calculation. Firstly, the Morris screening method is applied to qualitatively analyse the sensitivity of parameters, while the insensitive parameters are filtered. Then the Sobol method is employed to quantify the sensitivity. The sensitivity of parameters in RT calculation is determined through a case study in Duli Village of Anyang County in Henan Province. The results indicate that mean of 1-h annual maximum point rainfall is the most influential parameter. It is found that the parameters in water level-discharge relation calculation have a large influence on the RT, which shows that the proposed model can provide a reference for determining the value of parameters and can lay a theoretical foundation for further error analysis in RT calculation
ASSESSMENT OF FOREST ECOSYSTEM HEALTH BASED ON FUZZY EVALUATION METHOD-A CASE STUDY OF FOREST ECOSYSTEM IN LIANGSHUI NATURAL RESERVE
Get PDFBased on the establishment of health assessment index system of forest ecosystem in Liangshui Natural Reserve, the weight of each index was determined by using analytic hierarchy process (AHP) and questionnaire method, and then the model of forest ecosystem fuzzy evaluation was established to assess the health of Liangshui Natural Reserve from 2007 to 2013. The results indicated that certain changes have taken place to the health of forest ecosystem in Liangshui Natural Reserve from 2007 to 2013, which showed a declining trend, while the trend of the change is also consistent with the changes of internal and external environments of the forest ecosystem in Liangshui Natural Reserve.Based on the establishment of health assessment index system of forest ecosystem in Liangshui Natural Reserve, the weight of each index was determined by using analytic hierarchy process (AHP) and questionnaire method, and then the model of forest ecosystem fuzzy evaluation was established to assess the health of Liangshui Natural Reserve from 2007 to 2013. The results indicated that certain changes have taken place to the health of forest ecosystem in Liangshui Natural Reserve from 2007 to 2013, which showed a declining trend, while the trend of the change is also consistent with the changes of internal and external environments of the forest ecosystem in Liangshui Natural Reserve
EVALUATION OF CONFINEMENT CONDITIONS AND CONTENT OF LIGNOCELLULOSIC COMPOUNDS ON URBAN SOLID WASTE BIODEGRADATION RATES
Get PDFThe organic fraction (OF) is the main component of urban solid wastes (USW) generated in Mexico and other developing countries. The increasing generation of USW in combination with the long periods required for OF stabilization at confinement sites has exceeded the management capacity of environmental authorities. OF biodegradation has commonly been estimated using theoretical approaches and by characterizing fresh USW, while confinement scenarios have been ignored. This study evaluated the effects of composition, biodegradability and confined conditions on biodegradation of USW in a characteristic dumpsite. Biodegradability was evaluated by the characterization of lignocellulosic compounds, biodegradation by volatile solids (VS) and the confinement conditions by temperature, pH and humidity measurements. On average, the OF represented 56.1 % of the confined USW, and was primarily derived from vegetable wastes (~78 %). The results indicate heterogeneity in the confined USW composition and different degradation stages. Measurement of temperature, pH, moisture and VS suggests that confinement conditions do not promote the establishment of a microbial consortia that degrades the OF. Lignin (LI) and cellulose + hemicellulose (CE + HE) contents suggest low biodegradability of the USW, which was confirmed by inverse correlations between lignocellulosic content and VS. The common use of soil as cover material in dumpsites allows considerable variations in crucial physical and chemical parameters that, when combined with the high percentages of lignocellulosic compounds in the USW, lead to low biodegradation rates.The organic fraction (OF) is the main component of urban solid wastes (USW) generated in Mexico and other developing countries. The increasing generation of USW in combination with the long periods required for OF stabilization at confinement sites has exceeded the management capacity of environmental authorities. OF biodegradation has commonly been estimated using theoretical approaches and by characterizing fresh USW, while confinement scenarios have been ignored. This study evaluated the effects of composition, biodegradability and confined conditions on biodegradation of USW in a characteristic dumpsite. Biodegradability was evaluated by the characterization of lignocellulosic compounds, biodegradation by volatile solids (VS) and the confinement conditions by temperature, pH and humidity measurements. On average, the OF represented 56.1 % of the confined USW, and was primarily derived from vegetable wastes (~78 %). The results indicate heterogeneity in the confined USW composition and different degradation stages. Measurement of temperature, pH, moisture and VS suggests that confinement conditions do not promote the establishment of a microbial consortia that degrades the OF. Lignin (LI) and cellulose + hemicellulose (CE + HE) contents suggest low biodegradability of the USW, which was confirmed by inverse correlations between lignocellulosic content and VS. The common use of soil as cover material in dumpsites allows considerable variations in crucial physical and chemical parameters that, when combined with the high percentages of lignocellulosic compounds in the USW, lead to low biodegradation rates
HERBICIDE GENOTOXICITY REVEALED WITH THE SOMATIC WING SPOT ASSAY OF Drosophila melanogaster
Get PDFThe genotoxicity of the herbicides clomazone, linuron and simazine was detected using the somatic wing spot assay of Drosophila melanogaster. For the evaluation of the mutagenic and recombinogenic activities induced by the herbicides two crosses were used: the standard cross (ST) which expresses basal levels of cytochrome P450 enzymes and the high bioactivation cross (HB) with overexpression of P450 genes conferring increased sensitivity to promutagens and procarcinogens. Third-instar larvae were exposed by chronic feeding (48 h) to three different concentrations of each herbicide. The frequencies of spots per individual in the treated series were compared to the negative concurrent control series (water or 5 % ethanol solution depending on the herbicide). Clomazone showed positive results for small and total spots in both the ST and the HB crosses. Linuron was positive at all concentrations tested for small and total spots in the ST cross while only positive for small and total spots at the highest concentration assayed in the HB cross. Simazine did not produce positive results in the ST cross while it was positive in the HB cross. The bifunctional cross-linking agent mitomycin C (MMC – 0.15 mM) was used as positive control and produced as expected a significant increase of all types of spots in both crosses. In conclusion, the positive results were due to induced mutations and not by recombinogenic activity, furthermore the significant increase in the frequency of total spots was mainly due to the induction of small single spots.The genotoxicity of the herbicides clomazone, linuron and simazine was detected using the somatic wing spot assay of Drosophila melanogaster. For the evaluation of the mutagenic and recombinogenic activities induced by the herbicides two crosses were used: the standard cross (ST) which expresses basal levels of cytochrome P450 enzymes and the high bioactivation cross (HB) with overexpression of P450 genes conferring increased sensitivity to promutagens and procarcinogens. Third-instar larvae were exposed by chronic feeding (48 h) to three different concentrations of each herbicide. The frequencies of spots per individual in the treated series were compared to the negative concurrent control series (water or 5 % ethanol solution depending on the herbicide). Clomazone showed positive results for small and total spots in both the ST and the HB crosses. Linuron was positive at all concentrations tested for small and total spots in the ST cross while only positive for small and total spots at the highest concentration assayed in the HB cross. Simazine did not produce positive results in the ST cross while it was positive in the HB cross. The bifunctional cross-linking agent mitomycin C (MMC – 0.15 mM) was used as positive control and produced as expected a significant increase of all types of spots in both crosses. In conclusion, the positive results were due to induced mutations and not by recombinogenic activity, furthermore the significant increase in the frequency of total spots was mainly due to the induction of small single spots
MODELOS DE CALIBRACIÓN PARA LA CUANTIFICACIÓN ESPECTROFOTOMÉTRICA DE HIDROCARBUROS TOTALES DEL PETRÓLEO EN SUELO
Get PDFCalibration models used in analytical chemistry must be previously validated to achieve their aim. Generally, this is achieved by means of regression analysis. This study proposes strategies of internal and external validation of simple linear calibration models (LCM) to determine total petroleum hydrocarbons (TPH) by means of ultraviolet visible spectrometry (UV-Vis). In the crossed validation, the model is used to estimate one by one the reference concentrations with which it was constructed/calibrated, whereas in the external validation the model estimates reference concentrations that were not used in its calibration, which demonstrates its robustness. Four models were constructed and validated, demonstrating in all cases the linearity and robustness of the MCLS in the studied range. All the models were adequate for the spectrometric quantification of TPH in soils or in water extracted by different solvents, in quantities that comply with the maximum permissible limits established by Mexican regulations. In the calibrated models, the matrix effect was identified due to the type of solvent used to dilute the hydrocarbons and the type of hydrocarbon, which is influenced by the limits of detection and quantification.Los modelos de calibración usados en química analítica deben ser previamente validados para cumplir con su objetivo, lo que generalmente se hace mediante análisis de regresión. En el presente estudio se proponen estrategias de validación interna y externa de modelos de calibración lineal simple (MCLS) para determinar hidrocarburos totales del petróleo (HTP) mediante espectrometría ultravioleta-visible (UV-Vis). En la validación cruzada, el modelo se emplea para estimar una a una las concentraciones de referencia con las que fue construido/calibrado, mientras que en la validación externa estima concentraciones de referencias que no fueron utilizadas en la calibración, con lo cual se demuestra su robustez. Se construyeron y validaron cuatro modelos, demostrando en todos los casos la linealidad y robustez de los MCLS en el rango estudiado. Los cuatro MCLS son adecuados para su aplicación en la cuantificación espectrofotométrica de HTP en suelos o en agua extraídos con diferentes disolventes, en cantidades que se encuentran dentro de los límites máximos permitidos en la normativa mexicana. En los modelos calibrados se identificó el efecto matricial debido al tipo de disolvente usado para diluir los hidrocarburos y por el tipo de hidrocarburo, lo cual influyó en los límites de detección y cuantificación