Air pollutant concentrations

About: Air pollutant concentrations is a research topic. Over the lifetime, 1652 publications have been published within this topic receiving 36138 citations.

CFD Modeling of Near-Roadway Air Pollution

Abstract: Currently, there is an increasing interest in modeling the dispersion of atmospheric pollutants using computational fluid dynamics (CFD), to characterize the influence of the traffic-generated emissions on the temporal and spatial variability in air pollutant concentrations in the near-roadway environment. To advance in this task, we modeled the dispersion of total suspended particles (TSP), over a flat terrain, within a neutrally stratified and fully developed atmospheric boundary layer. We included the effect of turbulence and deposition on particle size distribution downstream. We found that TSP concentration downwind exhibits a single profile when expressed in terms of three dimensionless numbers: normalized concentration, normalized distance, and emission speed ratio. Using this generic character of the results, we determined the average short- and long-term TSP concentration, modeling successive short-term intervals in which it could be assumed a pseudo-steady-state behavior. Results exhibited correlation levels of R2 > 0.85 for daily and R2 > 0.94 for monthly averages when compared with measured TSP concentrations downwind two unpaved roadways. Results also showed that the implemented CFD model resolved the two main issues with Gaussian models (currently the most used air quality model): over-prediction of pollutant concentrations near the roadway and problems dealing with wind speeds < 1 ms−1.

Analysis of measurement errors of cvs method used for tests of pollutant emissions from light-duty vehicles

Abstract: The test procedure for the pollutant emissions from light-duty vehicles is currently under verification carried out at the international level. For this purpose, GRPE (Groupe des rapporteurs sur la pollution et energie) – the body developing UNECE regulations proposals has set up a task group WLTP (Worldwide harmonized Light vehicles Test Procedure) which is supposed to prepare a new GTR (Global Technical Regulation) relating to this procedure. The development of light-duty vehicles, leading to the reduction of pollutants emissions, caused the increase of the requirements for their test procedure. A large number of factors associated, inter alia, with the test equipment affects its accuracy, repeatability and reproducibility. In the ongoing analysis attention is paid even to factors, which affect test results in a relatively small way, and which have been overlooked yet. One of the problems to which attention is paid is the impact of pollutant concentration in the dilution air in the CVS (constant volume sampler) system on test results. The CVS principle is accepted as the standard method to determine light-duty vehicle exhaust emissions on chassis dynamometer test cells worldwide. It was introduced in the early 1970s. One of its drawbacks is that it introduces an error resulting from the fact that the contractual DF dilution factor, rather than the actual dilution ratio DR, is used for the correction of concentration measurement results. The article discusses this error for different type of engines used in light-duty vehicles and different pollutants subject to measurements.