The input–output balance methodology has been applied to characterize the energy balance of agricultural systems. This study proposes to extend this methodology with the inclusion of multivariate analysis to reveal particular patterns in the energy use of a system. The objective was to demonstrate the usefulness of multivariate exploratory techniques to analyze the variability found in a farming system and, establish efficiency categories that can be used to improve the energy balance of the system. To this purpose an input–output analysis was applied to the major greenhouse tomato production area in Colombia. Individual energy profiles were built and the k-means clustering method was applied to the production factors. On average, the production system in the study zone consumes 141.8 GJ ha−1 to produce 96.4 GJ ha−1, resulting in an energy efficiency of 0.68. With the k-means clustering analysis, three clusters of farmers were identified with energy efficiencies of 0.54, 0.67 and 0.78. The most energy efficient cluster grouped 56.3% of the farmers. It is possible to optimize the production system by improving the management practices of those with the lowest energy use efficiencies. Multivariate analysis techniques demonstrated to be a complementary pathway to improve the energy efficiency of a system.

PALABRAS CLAVE: Energy use, Regional analysis, Greenhouse tomato, k-means clustering, Colombia

REVISTA: Energy  Vol. 47 Páginas 465-470

ISSN: 0360-5442

The input–output balance methodology has been applied to characterize the energy balance of agricultural systems. This study proposes to extend this methodology with the inclusion of multivariate analysis to reveal particular patterns in the energy use of a system. The objective was to demonstrate the usefulness of multivariate exploratory techniques to analyze the variability found in a farming system and, establish efficiency categories that can be used to improve the energy balance of the system. To this purpose an input–output analysis was applied to the major greenhouse tomato production area in Colombia. Individual energy profiles were built and the k-means clustering method was applied to the production factors. On average, the production system in the study zone consumes 141.8 GJ ha−1 to produce 96.4 GJ ha−1, resulting in an energy efficiency of 0.68. With the k-means clustering analysis, three clusters of farmers were identified with energy efficiencies of 0.54, 0.67 and 0.78. The most energy efficient cluster grouped 56.3% of the farmers. It is possible to optimize the production system by improving the management practices of those with the lowest energy use efficiencies. Multivariate analysis techniques demonstrated to be a complementary pathway to improve the energy efficiency of a system.

PALABRAS CLAVE: Energy use, Regional analysis, Greenhouse tomato, k-means clustering, Colombia

REVISTA: Energy  Vol. 47 Páginas 465-470

ISSN: 0360-5442

The presence of 17 pesticide residues was determined in just-picked tomatoes coming from open field and greenhouse farms in Colombia. Pesticide residues were quantified through a multiresidue method using ultra performance liquid chromatograph coupled to mass spectrometer. The results give no clear indication about which farming system is producing the most contaminated tomatoes. While the share of open field samples violating the maximum residue limits (MRLs) was higher, the presence of more than one pesticide per sample was detected in a higher number of greenhouse samples. Results showed that all positive samples for acephate exceeded the recommended MRL, indicating indiscriminate use of this insecticide. In both farming systems, the pre-harvest intervals are not respected due to the management practices applied and the continuous ripening of the fruit, once the harvest starts. The results of the present study confirm the need for a monitoring program, actually inexistent, focused in the food commodities consumed locally.

PALABRAS CLAVE: Colombia, Tomato, Pesticide residues, Faming systems

REVISTA: Food Control  Vol.30 Páginas 400-403

ISSN: 0956-7135

This work presents the validation results of a simple, fast and low-cost sample preparation method for the determination of pesticide residues in soil by ultrafast liquid chromatography coupled to electrospray ionization mass spectrometry. The method uses acetonitrile ultrasound-assisted extraction, centrifugation and evaporation step, without further cleanup. Recovery studies were performed for two soil blanks, presenting results in the range of 70-110% with relative standard deviation lower than 20%. The correlation coefficients for analytical calibration curves were higher than 0.99. Pesticide residues were detected in soils in the range of 1-62 ng g-1, depending on the compound. The uncertainty of the method was estimated from different addition-recovery experiments and calculations from certificates. The extraction process was identified as the main source of uncertainty, and the expanded uncertainties for each pesticide, using a coverage factor of two, were between 8.4 and 33%. The proposed method was applied to the determination of pesticides in real samples.

PALABRAS CLAVE: pesticide, mass spectrometry, liquid chromatography, soil

REVISTA: Journal of the Brazilian Chemical Society

ISSN: 0103-5053

Worldwide, the presence of pesticide residues in vegetables has been extensively characterized. In Colombia, tomato is among the most consumed horticultural commodities; however, the presence of pesticide residues in tomato has not been determined. Through an extensive sampling in Bogota, we assessed the presence of 24 pesticides in fresh tomatoes. Only one sample containing carbendazim exceeded the Maximum Residue Limit. At least one pesticide was detected in 70.5% of the samples and the most detected were pyrimethanil, carbendazim, dimethomorph and acephate. The results showed that tomato consumption in Bogota does not represent a risk to human health. Nevertheless, a monitoring program must be established to control the contamination of staple foods, such as tomato.

PALABRAS CLAVE: Pesticide residues, Maximum residue limit, Risk

REVISTA: Food Control Vol. 35 Páginas 213-217

ISSN: 0956-7135

A comparative study on acid and hydrothermal methods as ways to reduce interlamellar charge has been carried out on a vermiculite. This study showed that the application of the hydrothermal treatment as a previous step to pillaring the vermiculites, reported here for the first time, is a new route to obtain the porous material with a particular interest as heterogeneous catalysts, starting from mineral clays with a high density of charge. Modified clays have been characterized by atomic absorption, emission spectrograph, X-ray diffraction, cation-exchange capacity, total acidity, infrared spectroscopy (DRIFT), and nitrogen adsorption. The results have shown that all solids have been structurally modified. However, acid and hydrothermal methods showed different behavior. For the vermiculite, the hydrothermal treatment did not produce major differences in terms of the crystalline structure, whereas the acid method caused severe structural damage. The catalytic properties have been tested over Pt-impregnated samples (1%) using the hydroisomerization of heptane. Important catalytic activity was established for all solids with high selectivity regarding the isomer products.

REVISTA: Journal of Physical Chemistry. B Vol. 109(40) Páginas 19026-19033

ISSN: 1520-6106

A series of vermiculites pillared with mixed precursors of Al–Zr, Al–Hf and Al–Ce were obtained from natural vermiculite subjected to a process of negative harge reduction through hydrothermal treatment. The catalytic activity of the solids evaluated in the decane hydroconversion, was superior to that of recognized pillared clays and comparable to those of very active catalysts such as zeolites USY. The distributions of profiles of the reaction products suggest that the porosity/pore architecture of the pillared vermiculites should be similar to that of ultrastable Y zeolites.

PALABRAS CLAVE: Vermiculite, Pillared vermiculite, Decane hydroconversion.

REVISTA: Applied Catalysis A: Gen  Vol. 345 Páginas112-118

ISSN: 0926-860X

A natural mineral from Santa Marta-Colombia used as the starting material in the synthesis of pillared clays has been characterized by several techniques, including X-ray diffraction, X-ray fluorescence, electronic paramagnetic resonance, aluminum nuclear magnetic resonance and scanning electron microscopy. The information revealed that the mineral corresponds to trioctahedral vermiculite. The identification of this mineral is valuable in the control of reduction charge and pillaring processes on these materials to obtain more complex solids like the ones required to specific catalytic applications.

PALABRAS CLAVE: Vermiculita; fórmula estructura; capa de carga.

REVISTA: Earth Sciences Research Journal Vol. 13 Páginas 108-118

ISSN: 1794-6190

Vermiculites have the potential to serve as effective catalysts if pillared with Al, but their high charge presents an obstacle to the pillaring process. The purpose of this studywas to submit natural vermiculite to thermal treatments in the presence of water vapor in order to effect a reduction in the global negative charge and therebyto enhance its susceptibilityto pillaring. The process of charge reduction in vermiculite under the conditions selected involved the extraction of 25% of IVAl accompanied bythe extraction of structural Mg and charge-compensating cations (Ca2+, Na+, and K+). The results indicate a reduction of 35% in the lobal negative charge in vermiculite bythe end of the treatment. Some of the VIAl content was not removed during acid washing, and probablyremained in the solid in structural positions in the octahedral sheet.

REVISTA: Clays and Clay Miner Vol. 58 Páginas  97-109

ISSN:  0009-8604

El proceso industrial utilizado para la producción de furfural es la deshidratación de pentosas, la cual se lleva a cabo por medio de ácidos minerales, altamente corrosivos y contaminantes como catalizadores. Debido a los efectos ecológicos y toxicológicos asociados a este proceso, y a la dificultad en la separación del producto, el desarrollo de nuevos catalizadores sólidos ácidos ha tenido una significativa expansión en los últimos años. El presente trabajo de investigación se enfocó en la producción de furfural a partir de D-xilosa empleando como catalizadores sólidos ácidos, arcillas pilarizadas con aluminio y hafnio. Después de 4 h de reacción a temperaturas entre 140 y 170 °C, los resultados evidenciaron una conversión entre el 50 y el 80%, mientras que los niveles de selectividad alcanzados estuvieron entre el 40 y el 65%. Finalmente, la estabilidad de los catalizadores fue evaluada por medio de un tratamiento térmico, antes de usarlo de nuevo.
En cuatro reacciones consecutivas no fue observada una disminución significativa en la selectividad. En conclusión, las arcillas pilarizadas
evidencian ser catalizadores activos, selectivos y estables para la deshidratación de pentosas.

PALABRAS CLAVE: xilosa, deshidratación de pentosas, arcilla pilarizada, furfural.

REVISTA: DYNA Vol. 180 Páginas 105-112.

ISSN: 0012-7353