The aim of this present study was to evaluate the interaction between the ozone and the pipe material used for transporting it, usually of polymeric material, to then determine ozone loss during the process. For this purpose, a mixture of ozone-oxygen was transported through two types of pipes, PVC and silicone, from the ozone generator to the point of collection. The ozone concentration in the gas mixture and volumetric flow of the gas stream were varied for each experiment. The ozone mass flow was measured at the point of collection, applying the iodometric method by indirect titration. Ozone loss was observed in both pipes. These losses are associated with the chemical reaction between ozone and the pipe material, as well as to the ozone self-decomposition.

El objetivo del presente estudio fue evaluar la interacción entre el ozono y el material de la tubería usada para su transporte, usualmente polimérica, a fin de determinar las pérdidas de ozono durante el proceso. Para este propósito, una mezcla gaseosa de ozono-oxígeno se hizo fluir a través de dos tipos de tubería, PVC y silicona, desde el generador de ozono hasta el punto de recolección. La concentración de ozono en la mezcla gaseosa y el flujo volumétrico de la corriente gaseosa fueron variadas para cada experimento. El flujo másico de ozono fue medido en el punto de recolección, aplicando el método yodométrico por titulación indirecta. La pérdida de ozono fue observada en ambas tuberías. Estas pérdidas están asociadas a la reacción química entre el ozono y el material de la tubería, como también a la auto descomposición del ozono.

The degradation of air quality in great urban centers is noted by frequent critical episodes of air pollution and public health issues, and vehicles are a great source of pollutant emissions, mainly derived from combustion processes. A database is needed to direct mitigation of emissions. The main objective of this work is to present it as an emissions inventory. The results show that vehicular sources of CO, HC and NOx represent over 75% of total emissions in the MRC. Besides, the proposed methodology presented results consistent with the literature

This paper proposes a methodology to predict benzene uptake rate in ambient air, using passive samplers with Tenax TA. Variations in the uptake rate were found to occur as a function of the sampling time; and were greater at the beginning of sampling. An empirical model was obtained and values for uptake rate agree with literature. Concentration prediction errors can be minimized by using sampling times of 4 to 14 days, thus avoiding the influence of excessive uptake rates in the initial days and the influence of back diffusion at the end of the sampling period.

Este trabalho apresenta um modelo Fluidodinâmico Computacional tridimensional para simular a dispersão de substâncias solúveis em rios. O modelo pode predizer o impacto causado pela ocorrência de múltiplos pontos de emissão no trecho estudado. O código numérico para o modelo matemático foi desenvolvido em linguagem Fortran. Os resultados mostram que a metodologia proposta é uma boa ferramenta para a avaliação do impacto ambiental causado pela emissão de efluentes em rios. O software é bastante rápido, especialmente quando comparado com outros pacotes de CFD disponíveis comercialmente. Foram feitas comparações entre os resultados numéricos e dados experimentais coletados no rio Atibaia. Os resultados numéricos apresentaram uma boa concordância com os dados coletados experimentalmente.

This work presents a three-dimensional model for the dispersion of effluents in rivers using Computational Fluid Dynamics (CFD) techniques. There are several models in the literature, some of which even analyze complex flows. They are however restricted to small river sections. The main contribution of this work is that it proposes a new software capable of predicting the dispersion of effluents in very large open channels. The model is very fast, an unusual feature of CFD models. Due to this, it is possible to predict the dispersion of substances in long sections of rivers with some kilometers in extension. Moreover, multiple emissions can be analyzed by the model, allowing its use as a predictive tool to analyze and guide management decisions on future industrial installations near rivers. Results for the dispersion of an inert emission in a river near Campinas (Brazil) were used to validate the model.

In order to characterize the composition of the main urban air organic compounds in the megacity of Sao Paulo, analysis of samples collected during the winter of 2003 downtown was carried out. The samplings were performed on the roof of a building in the commercial center of São Paulo. Hydrocarbons and carbonyls compounds were collected on August 4, 5 and 6. Comparing to previous data, the concentration of hydrocarbons presented no decrease in the concentration, except for the aldehydes, which decreased when compared to previous data. Among the HCs species analyzed, the highest concentrations observed were those of toluene (7.5 ± 3.4 ppbv), n-decane (3.2 ± 2.0 ppbv), benzene (2.7 ± 1.4 ppbv) and 1,3,5-trimethylbenzene (2.2 ± 1.5 ppbv).