There is a lack of objective and scientifically-based information on the contributions of complex and multiple sources of air pollution – especially for the particulate matter (PM) pollution. PM is the pollutant of most concern and linked to adverse health effects, and in urban areas alone accounts for approximately 800,000 premature deaths worldwide each year.
What is Source Apportionment of Air Pollution?
Building an effective air quality management system (AQMS) requires a process of continual improvement in knowing where the pollution is coming from and how much each of the sources are contributing to the ambient air quality. The source apportionment techniques are now well developed to develop this information and help informed decision making.There are two ways in apportioning pollution - (a) A top-down approach starting with monitoring of pollution and (b) A bottom-up approach starting with the activity data (like fuel consumption). Both the methods are well studied and documented.
The figure to the right presents an overview of the steps involved in conducting a top-down study.The process is time consuming and technically intense, but the results are scientifically robust. Three major steps involved are (a) sampling (b) chemical analysis (c) receptor modeling and the each step can be performed in multiple ways. Notes on each of the steps are explained in detail as part of the SIM-air working paper series (listed below).
A number of cities in the developing and developed countries where the combination of rapid growth, dirty fuels, and old and polluting technologies are overwhelming the capacities to control air pollution, these source apportionment techniques are already in practice. The figure to the left presents a summary of source apportionment results from cities across the world. For these cities, an application of source apportionment offers policymakers practical tools for identifying and quantifying the different sources of air pollution, and thereby increasing the ability to put in place effective policy measures to reduce air pollution to acceptable levels.
In March, 2011, a handbook was published under the ESMAP program (The World Bank) with details on when and how these studies were performed, "Tools for Improving Air Quality Management - A Review of Top-down Source Apportionment Techniques". Co-authored by Johnson TM, Guttikunda SK, Watson J, Russell AG, West J, Bond T, and Artaxo P.
The literature available on top-down and bottom-up approaches to successfully conduct a source apportionment study is immense. In September, 2011, for the readers, we simplified the explanations, methods available, frequently asked questions, myths, expected results, and on how to consolidate the results from the two studies, into a graphic document, as part of the SIM-comic book series. Please click on the image (to the right) to access the document.
SIM-air Working papers on "what is source apportionment", "how to perform source apportionment", and "sample results from applications of source apportionment studies from Asia, Africa, and Latin America" are presented in
SIM 10-2008: What is Particulate Matter: Composition & Science
SIM 16-2009: Urban Particulate Pollution Source Apportionment (Part 1) Methodology & Resources
SIM 17-2009: Ten Frequently Asked Questions About Particulate Matter
SIM-23-2009: Urban Particulate Pollution Source Apportionment (Part 2): Applications & Policy Implications