Several urban and industrial areas in Southern Europe are not capable of meeting the implemented EU standards for particulate matter. Efficient air quality management is required in order to ensure that the legal limits are not exceeded and that the consequences of poor air quality are controlled and minimized.
Of special relevance for Southern Europe is the problem of resuspended mineral matter. The origin of mineral matter is diverse and difficult to be quantified. The sources of mineral dust include brake and road pavement abrasion, construction/demolition, fugitive industrial and harbor emissions, agricultural resuspension, regional soil resuspension and African dust outbreaks. Furthermore, the scarce precipitation favors accumulation (and availability for resuspension) of the deposited dust material. Conversely, in other regions of Europe, the frequent washout caused by rain diminishes this problem. This is why the high contribution of mineral dust in PM10 and PM2.5 (atmospheric particulate matter with diameter less than 10 and 2.5 microns respectively) of most urban sites of Southern Europe (around 30 and 12%, in front to 10 to <5% in central Europe) may cause exceedances of the air quality standards.
Another key issue in air quality is the contribution to urban ambient PM levels from biomass burning. Thus, whereas in central and northern Europe the contribution from wood stoves and other domestic biomass burning reach important contributions, in Southern Europe this is still not demonstrated. The scenario may be in this region very different. Firstly, domestic biomass burning is not a relevant source for the high density population Mediterranean cities, secondly the cold period is short and thirdly other sources of biomass burning, such as agricultural fires and forest fires prevail.
The application of mitigation measures and the development of appropriate air pollution abatement national strategies require the precise identification of emission sources. This is a difficult task for exposure levels of PM. Of specific interest is the quantification of the different sources, both of anthropogenic and natural origin.
The EU official guidelines suggest that models are the scientifically relevant tools to be used also for source apportionment (2008/50/EU). A wide range of modeling methodologies has been proposed and applied for source apportionment purposes, including receptor-based models. Receptor models have been previously used to develop emission reduction strategies for attaining PM10, PM2.5 and ozone standards, decreasing human exposures to toxic substances, and improving visibility. As part of these reductions many of the chemical markers for major sources, such as lead in gasoline engine exhaust and trace elements in primary industrial emissions, have been reduced or eliminated. Receptor models used for source apportionment have to be optimized and harmonised prior to their use for regulatory purposes.
Among many source apportionment methods, PMF (Positive Matrix Factorization) has been shown to be a powerful alternative to traditional multivariate receptor modeling like CMB (Chemical Mass Balance) and PCA (Principal Component Analysis). A newly developed algorithm namely ME-2 (Multilinear Engine) is the most recent advance in source apportionment modelling. To maximize the information resulting by PMF and/or ME-2 a number of operational parameters should be optimized and new data interpretation techniques should be initiated.
The improvement of the source apportionment will consist of the next steps:
– The number of the explanatory variables will be extended by including organic markers (e.g levoglucosan as a marker for biomass burning)
– The data derived by off-line measurements (traditional chemical analysis) and on-line instrumentation (size distribution measurements) will be combined in order to calculate the contribution of emission sources with a high time resolution
– Meteorological data and back trajectory analysis will be merged with the models outputs to elucidate the origin of the emission sources
– State of the art instrumentation such as the AMS (Aerosol Mass Spectrometry) will be adapted to distinguish primary and secondary emissions
Once the source apportionment tool is mastered, the causes of the reported PM exceedances can be assessed. This will allow the implementation of the appropriate abatement methods. The efficiency of the applied mitigation measures could then be tested by means of source apportionment to investigate temporal changes in the source contribution.
In general, vehicle emissions are believed to be the most important pollution source in urban areas. For this reason various mitigation strategies that focus on traffic emissions have been initiated earlier. However for the high amount of resuspended mineral matter more work should be conducted concerning the mitigation strategies. For the reduction of resuspended road dust the available mitigation measures include street washing and the use of dust suppressants. Regarding the industrial fugitive dust various types of dust control equipment is used including scrubbers, baghouses, cyclones, electrostatic precipitators and water nozzles. The minimization of construction dust is mainly achieved by the use of water spraying and the placement of mesh screening. Within the framework of the proposed project the efficiency of these measures will be tested.
The specific objectives of the project will be:
• To optimize/improve source apportionment methods
• To prioritize the source categories for evolving cost-effective air pollution mitigation strategies.
• To assess the impact of sources on ambient air quality under different mitigation measures.
• Develop, demonstrate and adapt measures that considered appropriate and cost effective to ensure better air quality in urban areas.