A Three-Dimensional Model Study of the Impact of AVOC and BVOC Emissions on Ozone in an Urban Area of the Eastern Spain

This study concentrated on the effects of Biogenic Volatile Organic Compounds (BVOC) emissions on ozone (O₃) in an area of the Eastern Spain on June 12, 1997, a day characterised by sea breeze. Simulation of meteorology was performed with the three-dimensional model ADREA-I. Comparisons of the model results with observations have revealed overall a good agreement in temperature and wind velocity. Two runs were performed with UAM-IV for the photochemical calculations. The first simulated the effects of the anthropogenic emissions only (run A) and the second the combined effects of anthropogenic and biogenic emissions, (run B). Comparisons of the model O₃ concentrations with measurements showed a general agreement with the experimental data. Discrepancies between the calculated results and the observations during the early morning hours could be attributed to inaccuracies in nitrogen oxides (NO_x) from the anthropogenic emissions inventory. Comparisons between runs A and B yielded differences up to 30% in the morning, over inland areas. It was deduced that the inclusion of BVOC in total emissions could result in an increase or decrease of tropospheric O₃, depending on the available amounts of anthropogenic emissions.     

A new methodology development for the regulatory forecasting of PM10. Application in the Greater Athens Area,Greece

The paper introduces a new methodology for the prediction of daily PM10 concentrations, in line with the regulatory framework introduced through the EU Directive 2008/50/EC. The proposed approach is based on the efficient utilisation of the data collected over short time intervals (hourly) rather than the daily values used to derive the daily regulatory threshold. It is sufficiently simple and easily applicable in operational forecasting systems with the ability to accept as inputs both historical data and exogenous paraeters, such as meteorological variables. The application of the proposed methodology is demonstrated using data from five monitoring stations of air pollutants located in Athens, over a five year period (2000–2004) as well as compatible meteorological data from the NCEP (National Centers for Environmental Protection). A set of different models have been tested at the same time to reveal the effectiveness of the proposed approach, both univariate and multivariate, and linear and non-linear models. The analysis of all examined datasets has shown conclusive evidence that the introduction of the newly developed procedure which utilises data collected over a shorter horizon can significantly increase the forecasting ability of any developed model using daily historic PM10 data, under all examined metrics.     

Modelling of Flow and Pollution Dispersion in a Two Dimensional Urban Street Canyon

The wind-driven flow patterns and the dispersion of vehicle exhaust pollutants released at street level has been simulated with the three-dimensional (3-D) dispersion model ADREA-HF (Andronopoulos et al., 1993), for idealised two-dimensional urban fetches occupied by buildings with slanted roofs. The simulation used oncoming atmospheric boundary layer characteristics corresponding to realistic above-town wind characteristics, as measured in reference wind tunnel experiments (Rafailidis, 1997). At that stage, analysis was limited to neutral stability conditions only. Firstly, the quality assurance of the numerical model was investigated in terms of the sensitivity to different grid allocations. The modelling results were corroborated by comparison with wind tunnel measurements in a similar two-dimensional domain (Pavageau et al., 1997). The numerical modelling replicated well the high degree of non-uniformity in the dispersion field in the test street, and the results agreed satisfactorily with the experimental measurements. The reasons for the differences observed have been investigated. With the model thus validated, three different exhaust release scenarios have been tested, keeping the same overall emission rate but different spatial patterns of street-release. The effect of the different street-release scenarios was found to be only marginal, with the dispersion patterns on the sidewalls affected only locally, close to the street level.     

Studies on Pollutant Dispersion from Moving Vehicles

Remote sensing instruments may be used to make measurements of emission levels from individual vehicles under realdriving conditions. In designing such an instrument, that will identify the gross polluters, the CFD modelling approach has been used to study the effects of the parameters involved on the characteristics of the exhaust gas plume. The analysis was performed using the ADREA-HF code in open space, street canyon and tunnel environments, with sensitivity parameters the car speed and meteorological conditions. The calculations have been performed in a moving coordinate system, with the car and site geometry being fully resolved. A discussion is given on the effects of the various parameters affecting the design of the instrument.