Derivation of third–order vertical velocity turbulence moment in the convective boundary layer from large eddy simulation data: an application to the dispersion modeling

AbstractA new formulation for the vertical turbulent velocity third statistical moment in a convective boundary layer is proposed. The parameterization is based directly on the definition of this higher order moment, with velocity skewness and variance being calculated from large eddy simulation data. The formulation, included in a Lagrangian stochastic dispersion model, has been tested and compared with expressions for the third moment obtained from experimental data and reported in the literature, using concentration data from field experiments. The application of a statistical evaluation shows that the proposed parameterization has one of the best overall adjustments to the data

Modern stationary phases for reversed phase high performance liquid chromatography

This review first discusses the limitations of many of the supports and stationary phases used in reversed phase high performance liquid chromatography and then describes those, developed more recently, that present better stabilities and more versatile selectivities. Emphases will be given to stationary phases that use higher purity silicas, hybrid silicas, monolithic silicas, metallic oxides and mixed oxides as supports and those that have embedded polar groups or contain phenyl or fluoro groups as the stationary phase as well as the phases used for mixed mode or hydrophilic interaction separations. These modern stationary phases facilitate the analysis of complex mixtures.15591568Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Eddy diffusivities for the convective boundary layer derived from LES spectral data

AbstractLarge Eddy Simulation (LES) spectral data and Taylor statistical diffusion theory are used to obtain Eddy diffusivities in a convective boundary layer. The derivation employs a fitting expression obtained from LES data for the vertical peak frequency. The vertical Eddy diffusivities are well behaved and show similar patterns and magnitudes as those derived from experimental spectral peak frequency data. In addition, this new vertical Eddy diffusivity was introduced into an advection diffusion equation which was solved by Generalized Integral Laplace Transform Technique (GILLT) method and validated with observed contaminant concentration data of the Copenhagen experiment. The results of this new approach are shown to agree with the measurements of Copenhagen

Proposal of a new autocorrelation function in low wind speed conditions

Abstract In this study a new mathematical expression to describe the observed meandering autocorrelation functions in low-wind speed is proposed. The analysis utilizes a large number of best fit curves to show that the proposed theoretical function well reproduces the general form and the negative lobes characterizing the experimental meandering autocorrelation function. Further, the good agreement of the measured autocorrelation curves with the proposed algebraic autocorrelation function allows to calculate the magnitudes of the meandering period and of the loop parameter. The results agree with the values presented and discussed in the literature. Therefore, the new formulation describing experimental meandering autocorrelation functions can be used to simulate the dispersion of contaminant during low wind episodes and to determine relevant meandering parameters

Identification of the major active ingredients in illegal pesticide seized by Brazilian Federal Police and quantification of metsulfuron-methyl and tebuconazole

A compilação de relatórios forenses de agrotóxicos, objetos de apreensões pela Polícia Federal no Brasil, mostrou que metsulfurom-metílico, imidacloprido, fipronil, tebuconazol, clorimurom-etílico e glifosato são os principais ingredientes ativos (IA) importados ilegalmente. Apesar destes IA não estarem entre os agrotóxicos mais comercializados no país, o alto preço das formulações correspondentes legalmente registradas pode estimular esta atividade ilegal. Com base neste estudo, amostras de agrotóxicos contrabandeados apreendidos contendo tebuconazol e metsulfurom-metílico foram analisadas quantitativamente utilizando cromatografia a gás e líquida, respectivamente. Tebuconazol, em apresentações líquidas e sólidas, apresentou concentrações concordantes com as informações dos rótulos, enquanto que a maioria das amostras de metsulfurom-metílico, rotuladas como 600 g kg-1, apresentaram concentrações mais baixas nas análises químicas (média de 337,0 g kg-1 + 2,0).The compilation of forensic reports from pesticides seized by the Federal Police in Brazil showed that metsulfuron-methyl, imidacloprid, fipronil, tebuconazole, clorimuron-ether and glyphosate were the dominant active ingredients (AI) illegally imported. Despite these AI were not among the most traded pesticides in Brazil, high prices of corresponding legal formulations may stimulate this illegal activity. Based on this study, smuggled pesticides containing tebuconazole and metsulfuron-methyl were seized and quantitatively analyzed using gas and liquid chromatography, respectively. Tebuconazole results, in liquid and solid presentations, were in accordance with the information on the label, while most metsulfuron-methyl samples, labeled as 600 g kg-1, showed lower concentrations in chemical analysis (mean of 337.0 g kg-1 + 2.0)