Santiago Saavedra

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.

Trends of Rural Tropospheric Ozone at the Northwest of the Iberian Peninsula

Tropospheric ozone levels around urban and suburban areas at Europe and North America had increased during 80s–90s, until the application of NOx reduction strategies. However, as it was expected, this ozone depletion was not proportional to the emissions reduction. On the other hand, rural ozone levels show different trends, with peaks reduction and average increments; this different evolution could be explained by either emission changes or climate variability in a region. In this work, trends of tropospheric ozone episodes at rural sites in the northwest of the Iberian Peninsula were analyzed and compared to others observed in different regions of the Atlantic European coast. Special interest was focused on the air quality sites characterization, in order to guarantee their rural character in terms of air quality. Both episodic local meteorological and air quality measurements along five years were considered, in order to study possible meteorological influences in ozone levels, different to other European Atlantic regions.

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.

Edaphic heterogeneity related to below-canopy water and solute fluxes in a Canarian laurel forest

AimTo study the differences in the edaphic properties between stemflow infiltration areas around different tree species and between these and other areas of the forest.MethodsSoil samples were collected in stemflow infiltration areas and other areas only exposed to throughfall. pH, soluble salt concentration, soil organic carbon and nitrogen, exchangeable bases and Al3+, soluble and available phosphorus and phosphate retention were measured in the soil samples. The inputs of water and H+, Na+, K+, Ca2+, Mg2+, TOC, Fe, NO3−, SO42−, PO43−, and Cl− that reached these areas were calculated.ResultsComparison of the soil properties measured in the throughfall and stemflow infiltration areas corresponding to each species revealed significant differences (p < 0.05), except for exchangeable Mg2+ and Al3+. Differences were observed between i) the stemflow infiltration areas around Morella faya and around each of the other species, and ii) the throughfall infiltration area and the stemflow infiltration area around each of the different species. pH, electric conductivity and available phosphorus of sampled soils were correlated with the corresponding stemflow inputs.ConclusionsThe edaphic properties varied in different below-canopy infiltration areas (mainly between the stemflow infiltration area around M. faya and other parts of the forest soil).

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.

PRESAXIO regional air quality modelling system: validation and applications

Different operational air quality forecasts (ESSEM Cost Action 0602) are currently available in Europe. However, most of them are not suitable for regional application and, also, their coarse outputs do not fit well with air quality management needs. In this work, PRESAXIO regional air quality modelling system is validated and applied over Galicia (NW of Spain), including WRF and CHIMERE models. WRF validation is done by comparison with surface meteorological measurements; CHIMERE validation applies DELTA tool with AirBase data. PRESAXIO applications include an operational air quality forecast, design of a regional air quality monitoring network, and impact assessment of EMEP emissions changes in regional O 3 peaks.

Evaluating the Influence of Regional Gridded Emissions Distribution on Air Quality Simulation

The aim of this work is the assessment of changes in modelled regional air quality, by the comparison of the EMEP inventory vs. the application of a regional inventory based in a mixed top-down and bottom-up methodology over the NW of the Iberian Peninsula. Air quality simulations were carried out with the CHIMERE model for an ozone episode in 2008. Comparison against measurements using the Delta Tool show better scores for the regional inventory daily maxima 8 and 1 h ozone simulation results.

Modelling the Impact of Best Available Techniques for Industrial Emissions Control in Air Quality

The strategies for industrial emissions control depend on, amongst other variables, the best available techniques, their economical feasibility, and their positive impact over air quality; i.e., advances in power generation technology are making older coal and fuel oil power plants to be replaced by natural gas combined cycles. In ITM 2007, the estimation of the impact of the application of best available techniques (BATs) in industrial emissions control in Galicia (NW Spain) was presented [Rodriguez R et al (2008) Modelling the impact of best available techniques for industrial emissions control in air quality: setting up inventories and establishing projections. In: Air pollution modeling and its application XIX. Springer, Dordrecht, pp 677–678]. In this work, the effect of these changes over the tropospheric ozone levels in this region is simulated using the CAMx model, for three different ozone episodes previously characterised.

Comparison of EMEP Emissions Inventory and Limited Area Bottom-Up Inventory in the Simulation of Air Quality by Means of CHIMERE

The purpose of this work was to assess the influence of emission data on CHIMERE, by means of the study of episodic ozone levels in 2007 at Galicia (NW of Spain). As input data to the simulations both EMEP emissions inventory data and a detailed bottom-up inventory for the EMEP (51,14) grid cell were applied, in order to compare their impact in the air quality results.