Jose A. Souto

Synoptic patterns and air mass transport during ozone episodes in northwestern Iberia

High levels of ozone are frequently measured at the Galicia (NW Iberian Peninsula) air quality monitoring stations from March to October. However, there have been very few studies on surface ozone in the northwestern Iberian Peninsula, most likely because the climate of this region is not favourable to photochemical ozone generation. The occurrence of these episodes may be related to either local-scale photochemical pollution or regional-scale transport from other polluted regions. In addition, high ozone episodes usually are developed under specific synoptic conditions. The main purposes of this study are to characterise the atmospheric conditions that lead to the ozone episodes in this region and to identify possible advection paths of ozone and precursors. A surface hourly ozone dataset (2002-2007) measured at rural sites in Galicia was analysed to identify high ozone episodes together with their associated synoptic patterns using a subjective classification with 23 different synoptic types. The synoptic weather patterns revealed that most of the episodes occur with high surface pressures centred over the British Isles and/or Central Europe while a high-altitude anticyclonic ridge crosses the Peninsula from North Africa, causing easterly or southeasterly winds. This analysis was completed with 3-day backward air mass trajectories obtained with HYSPLIT to assess the contribution of long-range transport, resulting in the following main routes: Mediterranean-Peninsular, South Atlantic-Portuguese, local and French-Cantabric.

Modeling the Odor Generation in WWTP: An Integrated Approach Review

Nuisance odors generation from waste and wastewater treatment plants are a cause of public discomfort and complaints. This situation impairs the air quality and represents a growing social and public health problem, especially in developing countries. Several modeling approaches have been developed and successfully implemented in the frame of a wastewater treatment plant for both the biological treatment and physicochemical processes. The mathematical modeling of the odor generation process is still considered a quite complex issue, mainly due to the fact that olfactory nuisance can be caused by many different chemical compounds and the perception of odors is influenced by subjective thresholds. Moreover, the impact of odor sources on air quality is highly conditioned by complex atmospheric dispersion processes. This review presents a critical state-of-art and assessment where information related to odor emissions impact studies as well as modeling applications are compiled and discussed.

The role of transboundary air pollution over Galicia and North Portugal area

In summer, high levels of ozone (O3) are frequently measured at both Galicia and Northern Portugal air quality monitoring stations, even exceeding the limit values imposed by legislation. This work aims to investigate the origin of these high O3 concentrations by the application of a chemical transport modelling system over the northwestern area of the Iberian Peninsula. The WRF–CHIMERE modelling system was applied with high resolution to simulate the selected air pollution episodes that occurred simultaneously in Galicia and North Portugal and in order to study both the contribution of local emission sources and the influence of transboundary pollution. Emission inputs have been prepared based on the development of the Portuguese and Galician emission inventories. The obtained results for O3 have been evaluated and validated against observations. Modelling results show possible contribution of the transboundary transport over the border of two neighbour regions/countries, indicating that the O3 episode starts over the urban and industrialised area of North coast of Portugal, reaching the maximum peaks over this region; at the same time, O3 levels increased over Galicia region, where lower concentrations, but still high, were observed. These results pointed out that air quality management should not be driven by political boundaries and highlight the importance of joining efforts between neighbouring countries.

Development of a Limited-Area Model for Operational Weather Forecasting around a Power Plant: The Need for Specialized Forecasts

A hydrostatic meteorological model, ‘‘PMETEO,’’ was developed for short-range forecasts for a high-resolution limited area located in the northwest region of Spain. Initial and lateral boundary conditions are externally provided by a coarse-mesh model that has much poorer horizontal and vertical resolution than the fine PMETEO grid. Limitations of limited-area models due to lateral boundary conditions are widely known, given that they can have a large impact on the evolution of the predicted fields through the propagation of errors into the interior of the domain. The guidelines to minimize this problem depend on the particular circumstances of the model application. In this case, a specific treatment of the initial and time-dependent boundary conditions is presented that obtains the best accuracy in the model results, because PMETEO is run operationally to predict air quality levels around a power plant.

Application Of Short And 24 Hours Air PollutionForecasting Around A Power Plant

A model-based system for real-time simulation and prediction of SĈ concentration around a Power Plant has been applied. The real-time simulation is done for 5 minutes average-time periods, from the measurements of nine meteorological towers and one Remtech sodar. A meteorological prediction model has been developed for providing a one-day forecast (for 30 minutes average-time periods), as input in time for the adaptive plume model. This system allows the prediction of SC>2 concentration around a power plant for different emission levels, along the following 24 hours. Both systems run continously on an area around As Pontes Power Plant, since November 1994. Their ground level concentration (glc) results are compared to the measurements from 17 glc remote stations, 30 km around the Power Plant. This one provides a database for the validation of the real-time and forecasting systems, and both are applied to the control of the SC>2 emissions at the surrounding of As Pontes 1400 MW Coal-Fired Power Plant.

SAGA: a decision support system for air pollution management around a coal-fired power plant

Air quality models are currently feasible approaches to prevent air pollution episodes. From one of the first source-oriented modelling approaches for air pollution forecasting (Souto et al., 1994, 1996, 1998), a new decision support system for air quality management, SAGA, was developed to provide support to As Pontes Power Plant (APPP) staff. SAGA can provide air pollution forecasts and manage meteorological and air quality measurements. Power plant decisions are supported by the results of a non-hydrostatic meteorological model (ARPS, Xue et al., 2001) to produce Meteorological Forecasts (MFs), and to be coupled to different Lagrangian dispersion models.

The effect of the limited availability of H2O2 in the competitive deposition of sulfur and oxidized nitrogen.

To understand the influence of the reduction of SO2 emissions from a single source in the S and N deposition around its local environment, the application of the Sulphur Transport Eulerian Model 2 (STEM-II) was introduced in this paper. Observed local deposition patterns were analysed and explained in terms of the main processes involved in the pollutants deposition. It was necessary to take into account the limited availability of H2O2 because of its influence on both S(IV) and oxidized nitrogen deposition. In order to estimate the quantitative relationship between the SO2 emissions reduction and the observed S and N deposition patterns, these processes were simulated for different meteorological conditions. Simulation results were in agreement with both observed deposition patterns and limited availability of H2O2, specially if significant changes in the S deposition patterns were considered. Both observed and estimated S deposition patterns changed their top value location from the Southwest (1990) to the Northwest (1997) of the domain, because of the reduction of dry deposition. The global reduction of total S depositions, estimated and observed, were in good agreement too. Model simulations could explain the higher S dry deposition reduction, considering the emissions reduction strategy applied.

A comparison of Lagrangian dispersion models coupled to a meteorological model for high stack air pollution forecast

Since 1994, operational air pollution forecast is routinely applied at the As Pontes coal-fired power plant, with a 350-m stack, in order to prevent local fiunigation episodes. Over the last ten years, several improvements in the numerical models were done, to obtain more accurate air pollution forecasts on a daily basis. In this work, a comparison of the results obtained for different periods, using two different lagrangian dispersion models, Adaptive Puff Model 2 (APM2) and Lagrangian Particle Model (LPM), is presented, Both models, in different ways, were coupled to the same non-hydrostatic meteorological prediction model, Advanced Regional Prediction System (ARPS) adapted to this environment. From the results obtained, it can be seen that both models can reproduce the location of the main plume impacts measured in the area. However, LPM impacts are usually farther and shorter in time than APM2 impacts, in agreement with field data.

Simulation of plume dispersion using different stack configurations and meteorological inputs

The application of CALMET/CALPUFF modelling system is well known, and several validation tests were performed until now; however, most of them were based on experiments with a large compilation of surface and aloft meteorological measurements, not always available. Also, the use of an operational large smokestack as tracer source is not so usual. In this work, CALPUFF model is applied to simulate the local dispersion of SO 2 (as a tracer) from the large smokestack (with four parallel liners) of a coal-fired power plant emitting SO 2 (as a tracer), considering both different stack configurations (one single point source vs. one point source per liner) and meteorological inputs (WRF model output vs. measurements). Comparison of CALPUFF results against glc measurements along three different periods shows that the best model performance was obtained by using WRF model output; better results, but not so significant, are obtained considering one point source per liner.

Coupling WRF and CALMET Models: Validation During Primary Pollutants glc Episodes in an Atlantic Coastal Region

The application of Lagrangian dispersion models, as CALPUFF, at local scales requires as input accurate and very high resolution meteorological fields. In these high resolution applications, the computational cost of numerical weather forecast models, as WRF, recommends the steady-state nesting of a diagnostic model, as CALMET, in order to properly consider the influence of land use and terrain topography over complex terrain domains.