Source apportionment to support air quality management practices

This guide is the latest update of the report “Source apportionment to support air quality management practices – A fitness for purpose guide (V 3.1)” (Thunis et al. 2020) by the Joint Research Centre (JRC). It summarizes the current FAIRMODE1 knowledge on best practices in source apportionment modelling. Compared to the previous version, this document clarifies aspects related to the formulation, properties and assumptions of source apportionment approaches. It extends its scope to NO2 and includes a new section dedicated to receptor modelling. Air pollution is one of the main causes of damages to human health in Europe, with an estimate of about 310 000 premature deaths per year in the EU27, as the result of exposure to fine particulate matter (PM2.5) alone (EEA, 2021). One of the main challenges in improving this situation is to understand the origins of the pollution in order to ensure that air quality plans target the appropriate sources at the right scales to give effective results. Source apportionment is a technique used to meet this challenge. Source apportionment can be applied to different pollutants. In the context of this guide, we address the most critical ones: particulate matter and nitrogen dioxide, although the primary focus is on particulate matter. This document aims to support organisations in charge of air quality management in the context of the EU Ambient Air Quality Directives (AAQD). In particular, it provides information on the different source apportionment approaches that are currently in common use, describes their main characteristics and discusses their fitness-for-purpose. Finally, it also aims to support the interpretation of source apportionment results. We first review the main source apportionment methodologies and related concepts, before addressing their fitness-for-purpose. Finally, some remaining open questions are discussed.