1. Sub Group 2 – Contribution of natural sources and source apportionment FAIRMODE Sub Group 2 – Contribution of natural sources and source apportionment John Douros Aristotle University of Thessaloniki, LHTEE

2. Modelling for source apportionment in the AQD Source apportionment studies include assessing the contribution from local sources as well as from natural sources, neighbouring countries and the contribution from resuspended road sand and salt. AQD: possibility to discount natural sources and long- range transport of pollution and resuspension attributable to winter sanding-salting of roads when assessing compliance against limit values. Although not explicitly mentioned in the AQD, modelling is necessary for this purpose as monitoring of these contributions everywhere in a zone or agglomeration would be unrealistic.

3. SG2 of FAIRMODE (WG2) The working sub-group (SG) on the “Contribution of natural sources and source apportionment” has been formed within the frame of WG2 on the quality assurance of models SG2 focuses on source apportionment (SA) and the contribution of natural sources on pollutant concentrations and aims to:  provide useful guidance and suggest best modelling practices and quality assurance procedures for member countries.  promote harmonised model use for SA in the EU

4. SG2 – 4 Phases  Phase 1: Review of the current status of modelling practices used for source attribution and quantification of contributions by member states to identify gaps and problems.  Phase 2: Review of current practices for the evaluation of models used for SA to identify limitations and needs regarding assessment of uncertainties.  Phase 3: Model/methodology Intercomparison  Phase 4: Compile a guidance document for model use for SA (to be finally integrated with the GD of WG1)

5. Expression of interest for SG2 ALASTUEY, A.KALLOS, G. AQUILINA, N.KARPPINEN, A. BAKLANOV, A.KRAJCOVICOVA, J. BALDASANO, J. M.KUKKONEN, J. BARTZIS, J.MARTIN, F. BATCHVAROVA, E.MONKS, P. BELIS, C.OLESEN, H. BESSAGNET, B.PAPADOPOULOS, C. DOGAN, E.PIROVANO, G. DOUROS, J.QUEROL, X. FINZI, G.SAN JOSE, R. FRAGKOU, E.SYRAKOS, A. FRITZEL, A.UDINA SISTACH, M. GOODDARD, C.VAN DEN HOUT, D. HARRISON, R.VINCENT, K. HIRTL, M.VLCEK, O. KAISER, A.ZANINI, G.

6. Modelling SA for regulation: Control & Contribution Assessments Address relative efficacy of source/pollutant emissions reductions – Response Surface Modelling (among others) A statistical “reduced-form” model of a complex air quality model Address source/pollutant “contribution” to non attainment – Sector Zero-Out Modelling Model simulation with “zero-out” of single or all pollutants from sector/sources of interest – Advanced SA Modelling Allows estimation of contributions from different source areas / categories within a single run

7. Receptor models are commonly used for SA Receptor models mass balance equations Receptor models complement source models by independently identifying sources and quantifying their contributions using ambient measurements of different observables at different times and locations. SA is accomplished by solution of the mass balance equations that express concentrations at several measured pollutants as a linear sum of products of pollutant abundances in source emissions and source contributions. These equations can be solved by several methods, such as PMF. However, the solution does not guarantee physical reality, so internal and external validation measures must be evaluated. Receptor models are best used in conjunction with source models to create a “weight of evidence” for justifying emission reduction measures on different source types. (Watson and Chow; 2005)

8. Dispersion and Receptor Models The dispersion model uses source emissions as inputs and calculates ambient concentrations. The receptor model uses ambient concentrations as inputs and calculates source contributions. (Adapted from Watson, 1979.) DISPERSION MODEL RECEPTOR MODEL DISPERSION MODEL RECEPTOR MODEL

9. Modelling for source apportionment Most commonly used methods PCA Principal Component Analysis (PCA) PMF Positive Matrix Factorization (PMF) CMB Chemical Mass Balance (CMB) Viana et al, 2008

10. Models for SA used by different EU countries for the time extension reports

12. Conclusions so far… SG2 Phase 1 review confirms the increased use of modelling tools for SA by member states and modellers/researchers However, a large part of SA is carried out mostly with receptor modelling and only limited use of dispersion modelling The analysis of the time extension reports revealed (as expected!) the lack of a uniform methodology for SA

13. Conclusions so far… A standardised methodological framework and guidance would be useful, putting emphasis on issues of QA and uncertainty estimation Still many limitations regarding:  certain compounds not adequately quantified (e.g. biogenic secondary organics, nitrate components etc.)  specific anthropogenic emission sources not sufficiently discriminated in many SA studies (e.g. shipping emissions)  the identification of biomass combustion sources

14. The need for QA in all model applications Uncertainties in input data and model processes (e.g. Emissions, secondary organics, nitrate partitioning, meteo variability etc.) Models have to be assessed to ensure that they meet certain quality objectives recommended for regulatory use. Lack of appropriate uncertainty estimates is a clear limitation when applying models for SA Missing uncertainty data may result in restriction of the potential of the models to resolve the sources.

15. Future activities (1) Phase 2 review of currently used methods for the evaluation of models used for SA applications by member states. Provide assistance to member states regarding the use of models for NO 2 SA, in view of the preparation of time extension reports for NO 2.  …through the NO 2 guidance document and the discussion forum now in operation in the FAIRMODE website

16. Future activities (2) Update of the MDS system will take place to account for SA model applications, and thus to include SA in its structured search for appropriate models. Continue investigating options for synergy with other projects and activities (JRC initiative, MEGAPOLI, PASODOBLE, MACC etc.) in regard to Phase 3 (intercomparison exercise). A Guidance document on SA with emphasis on QA (Phase 4) that will be finally be integrated with the model Guidance Document.