Improvements of air quality simulations of particulate matter in the Iberian peninsula with road dust resuspension and dust emission modules

The Mediterranean Basin is one of the most sensitive zones in the planet to air pollution. Besides anthropogenic emissions, the Iberian Peninsula is affected by natural particule matter (PM) sources. Dry weather conditions allow road dust to be resuspended by vehicle-induced turbulence. These emissions may be as important as those directly emitted by vehicles (combustion and from road abrasion and tyre and break wear processes). In addition, it is widely documented that crustal particles transported from the Saharan Desert may contribute significantly to ambient PM concentration in Madrid. This poster summarizes the methodology and results of the implementation of a module to account for these sources -not included in current emission inventories- into the Eulerian air quality model CMAQ. Comparison of predicted PM concentrations with ambient air quality measurements and satellite observation point out that this module clearly improves the performance of the standard CMAQ version

Comparison and Assessment of Two Emission inventories for the Madrid Region

Emission inventories are databases that aim to describe the polluting activities that occur across a certain geographic domain. According to the spatial scale, the availability of information will vary as well as the applied assumptions, which will strongly influence its quality, accuracy and representativeness. This study compared and contrasted two emission inventories describing the Greater Madrid Region (GMR) under an air quality simulation approach. The chosen inventories were the National Emissions Inventory (NEI) and the Regional Emissions Inventory of the Greater Madrid Region (REI). Both of them were used to feed air quality simulations with the CMAQ modelling system, and the results were compared with observations from the air quality monitoring network in the modelled domain. Through the application of statistical tools, the analysis of emissions at cell level and cell – expansion procedures, it was observed that the National Inventory showed better results for describing on – road traffic activities and agriculture, SNAP07 and SNAP10. The accurate description of activities, the good characterization of the vehicle fleet and the correct use of traffic emission factors were the main causes of such a good correlation. On the other hand, the Regional Inventory showed better descriptions for non – industrial combustion (SNAP02) and industrial activities (SNAP03). It incorporated realistic emission factors, a reasonable fuel mix and it drew upon local information sources to describe these activities, while NEI relied on surrogation and national datasets which leaded to a poorer representation. Off – road transportation (SNAP08) was similarly described by both inventories, while the rest of the SNAP activities showed a marginal contribution to the overall emissions

Modelling reactive pollutants dispersion in an urban hot-spot in summer conditions using a CFD model coupled with meteorological mesoscale and chemistry-transport models

Air quality assessment requires detailed studies about urban air pollution. In a city, the interaction between atmosphere and urban morphology induces complex flow pattern which leads to irregular spatial distributions of pollutants in the streets. In addition, the influence of chemical reactions and the variability of air temperature and wind make difficult to reproduce the pollutants dispersion at microscale during long periods, especially in summer conditions. The aim of this work is to simulate reactive pollutants dispersion in summer conditions in an urban hot-spot using a computational fluid dynamics (CFD) model. In summer, the high solar radiation and the high levels of O3 concentration requires introducing a chemical system in the CFD modelling. Focusing on studying the NO2 dispersion, the photostationary state is implemented in the CFD simulation. The detailed boundary conditions are obtained from the outputs of other microscale and mesoscale models. The vertical profiles of wind speed, turbulence and temperature are derived from a meteorological mesoscale simulation (WRF) and the background concentration of pollutants is obtained from a chemistry-transport (CMAQ) simulation. Additionally, the emissions of traffic-related pollutants are implemented into the CFD simulation based on the results of a microscale traffic model. Finally, the time evolution of meteorological variables and pollutants concentration resulting from the CFD simulation are thoroughly evaluated with measurements registered at several points from an experimental campaign carried out in the research area (in the framework of TECNAIRE project (S2013/MAE-2972)). Regarding the air quality assessment, the deviation of NO2 concentration including chemical reactions in the CFD simulation is quantified in comparison with a non-reactive pollutant. Likewise, the differences of assuming neutral atmospheric conditions instead of using profiles from mesoscale model for this period are analyzed through the time average concentration map at pedestrian level. In this way, the improvements included in the CFD modelling and the conclusions obtained from this analysis provide information on how to simulate reactive pollutant dispersion in an urban hot-spot in summer conditions

Analysis of Contributions to NO2 Ambient Air Quality Levels in Madrid City (Spain) through Modeling. Implications for the Development of Policies and Air Quality Monitoring

As environmental standards become more stringent (e.g. European Directive 2008/50/EC), more reliable and sophisticated modeling tools are needed to simulate measures and plans that may effectively tackle air quality exceedances, common in large cities across Europe, particularly for NO2. Modeling air quality in urban areas is rather complex since observed concentration values are a consequence of the interaction of multiple sources and processes that involve a wide range of spatial and temporal scales. Besides a consistent and robust multi-scale modeling system, comprehensive and flexible emission inventories are needed. This paper discusses the application of the WRF-SMOKE-CMAQ system to the Madrid city (Spain) to assess the contribution of the main emitting sectors in the region. A detailed emission inventory was compiled for this purpose. This inventory relies on bottom-up methods for the most important sources. It is coupled with the regional traffic model and it makes use of an extensive database of industrial, commercial and residential combustion plants. Less relevant sources are downscaled from national or regional inventories. This paper reports the methodology and main results of the source apportionment study performed to understand the origin of pollution (main sectors and geographical areas) and define clear targets for the abatement strategy. Finally the structure of the air quality monitoring is analyzed and discussed to identify options to improve the monitoring strategy not only in the Madrid city but the whole metropolitan area

Implementation of a module for risk of ozone impacts assessment to vegetation in the integrated assessment modelling system for the Iberian peninsula. Evaluation for wheat and holm oak

A module to estimate risks of ozone damage to vegetation has been implemented in the Integrated Assessment Modelling system for the Iberian Peninsula. It was applied to compute three different indexes for wheat and Holm oak; daylight AOT40 (cumulative ozone concentration over 40 ppb), cumulative ozone exposure index according to the Directive 2008/50/EC (AOT40-D) and PODY (Phytotoxic Ozone Dose over a given threshold of Y nmol m−2 s−1). The use of these indexes led to remarkable differences in spatial patterns of relative ozone risks on vegetation. Ozone critical levels were exceeded in most of the modelling domain and soil moisture content was found to have a significant impact on the results. According to the outputs of the model, daylight AOT40 constitutes a more conservative index than the AOT40-D. Additionally, flux-based estimations indicate high risk areas in Portugal for both wheat and Holm oak that are not identified by AOT-based methods

Comparasion of road traffic emission models in Madrid (Spain)

Many cities in Europe have difficulties to meet the air quality standards set by the European legislation, most particularly the annual mean Limit Value for NO2. Road transport is often the main source of air pollution in urban areas and therefore, there is an increasing need to estimate current and future traffic emissions as accurately as possible. As a consequence, a number of specific emission models and emission factors databases have been developed recently. They present important methodological differences and may result in largely diverging emission figures and thus may lead to alternative policy recommendations. This study compares two approaches to estimate road traffic emissions in Madrid (Spain): the COmputer Programme to calculate Emissions from Road Transport (COPERT4 v.8.1) and the Handbook Emission Factors for Road Transport (HBEFA v.3.1), representative of the ‘average-speed’ and ‘traffic situation’ model types respectively. The input information (e.g. fleet composition, vehicle kilometres travelled, traffic intensity, road type, etc.) was provided by the traffic model developed by the Madrid City Council along with observations from field campaigns. Hourly emissions were computed for nearly 15 000 road segments distributed in 9 management areas covering the Madrid city and surroundings. Total annual NOX emissions predicted by HBEFA were a 21% higher than those of COPERT. The discrepancies for NO2 were lower (13%) since resulting average NO2/NOX ratios are lower for HBEFA. The larger differences are related to diesel vehicle emissions under “stop & go” traffic conditions, very common in distributor/secondary roads of the Madrid metropolitan area. In order to understand the representativeness of these results, the resulting emissions were integrated in an urban scale inventory used to drive mesoscale air quality simulations with the Community Multiscale Air Quality (CMAQ) modelling system (1 km2 resolution). Modelled NO2 concentrations were compared with observations through a series of statistics. Although there are no remarkable differences between both model runs, the results suggest that HBEFA may overestimate traffic emissions. However, the results are strongly influenced by methodological issues and limitations of the traffic model. This study was useful to provide a first alternative estimate to the official emission inventory in Madrid and to identify the main features of the traffic model that should be improved to support the application of an emission system based on “real world” emission factors

High resolution emission estimation in hot-spots of Madrid (Spain)

This work aims at obtaining high resolution NOx and PM10 emissions from road traffic at hot-spots in Madrid (Spain). For that, 12 1-hour representative scenarios are simulated with the traffic microsimulation model VISSIM. Measured traffic data (fluxes and fleet composition) are used as input for the model to obtain speed-time profiles for each vehicle. These profiles are used to predict representative emission factors for different vehicle classes in the VERSIT+micro model through the ENVIVER interface. Emission factors are compared with the ones of COPERT 4, a widely used average-speed model, as a preliminary model assessment. The results are strongly influenced by low average speeds due to saturated traffic situations

Development of urban air quality plans and measures in Madrid (Spain) under a multi-scale air quality modeling approach

Poor urban air quality is one of the main environmental concerns worldwide. According to WHO (WHO, 2014) outdoor air pollution caused 3.7 million premature deaths in 2012, most of them in urban areas where both, emission sources and population concentrate. Even in Europe, despite of significant efforts, exceedances of air quality standards are common in large urban areas, particularly for NO2 (EEA, 2014). Therefore, tackling urban air quality constitutes a pressing priority from the social and political point of view. However, air pollution dynamics in urban environments is extremely complex and the design and assessment of effective emission abatement plans and measures posses a major scientific challenge. Emissions of different pollutants from a variety of sources interact through intertwined atmospheric transport processes and chemical transformations involving several spatial and temporal scales. In this context, air quality modelling constitutes an essential research tool for understanding and simulating the potential effect of emission abatement measures as well as to identify the best course of action to improve air quality in cities. This contribution reflects on the inherent complexities of urban air pollution and the development of air quality plans for the Madrid city as a representative case study

Assessment of urban parameterizations in the WRF model for air quality modelling purposes in Madrid (Spain)

This study aims to assess the performance or multi-layer canopy parameterizations implemented in the mesoscale WRF model in order to understand their potential contribution to improve the description of energy fluxes and wind fields in the Madrid city. It was found that the Building Energy Model (BEP+BEM) parameterization yielded better results than the bulk standard scheme implemented in the Noah LSM, but very close to those of the Building Energy Parameterization (BEP). The later was deemed as the best option since data requirements and CPU time were smaller. Two annual runs were made to feed the CMAQ chemical-transport model to assess the impact of this feature in routinely air quality modelling activities

Implementation of road dust resuspension in air quality simulations of particulate matter in Madrid (Spain)

An evaluation of the concentration levels of Particulate Matter (PM) was carried out in Madrid (Spain) by introducing the emissions from road dust resuspension. Road dust resuspension emission factors (EF) for different types of vehicles were calculated from EPA-AP42, a global resuspension factor of 0.097 g veh−1km−1 as described in Amato et al. (2010) and a rain-dependent correction factor. With these resuspension EFs, a simulation at street canyon level was performed with the OSPM model without rainfall. Subsequently, a simulation using the CMAQ model was implemented adding resuspension emissions affected by the rain. These data were compared with monitored data obtained from air quality stations. OSPM model simulations with resuspension EFs but without the effect of rainfall improve the PM estimates in about 20gm−3μ compared to the simulation with default EFs. Total emissions were calculated by adding the emissions estimated with resuspension EFs to the default PM emissions to be used by CMAQ. For the study in the Madrid Area, resuspension emissions are approximately of the same order of magnitude as inventoried emissions. On a monthly scale, rain effects are negligible for resuspension emissions due to the dry weather conditions of Spain. With the exception of April and May, the decrease in resuspension emissions is not >3%. The predicted PM10 concentration increases up to 9μ gm−3 on annual average for each station compared to the same scenario without resuspension. However, in both cases, PM 10 estimates with resuspension are still underestimating observations. It should be noted that although that accounting for resuspension improves the quality of model predictions, other PM sources (e.g., Saharan dust) were not considered in this study