CONCEPTUAL MODEL OF ORGANIC PM FORMATION

Project No. A-60

Leaders:     J. C. Ball
                  R. S. MacArthur

Scope and Objective

This project (1) developed a conceptual model of atmospheric organic PM formation based on data from comprehensive measurement programs (supersites and others), (2) related this conceptual model to our understanding of organic PM based on laboratory and theoretical analyses (i.e., results from A-59), and (3) identified the major processes missing in current models that are of atmospheric importance in the United States.

Current Status and Future Program 

Under Project A-59, Atmospheric and Environmental Research (AER) assessed the current state-of-the-science for secondary organic aerosol (SOA) formation.  The literature review results suggest that many pathways for SOA formation are currently missing or crudely represented in current models of atmospheric PM.  Project A-59 further investigated those new SOA formation pathways and assessed their potential atmospheric importance with some preliminary modeling.  On the ambient measurement side, a large body of information on atmospheric organic PM became available via the supersite program and other special studies and the data were analyzed.  However, there was a need to integrate the current knowledge gained from laboratory and theoretical studies of SOA formation and advanced measurement programs of organic PM (both primary and secondary), and to use the resulting information to improve current PM models.

The project resulted in completion of the following tasks: (1) review relevant data from supersites and other special studies using results of previous data analyses to the extent possible, (2) develop a conceptual model of organic PM formation (e.g., diurnal profiles; dependence on meteorological variables such as solar radiation, relative humidity and temperature; chemical characteristics; correlations with other variables such as other pollutant concentrations), (3) provide a scientific basis for this conceptual model based on current knowledge of organic PM, (4) identify the major deficiencies in terms of scientific formulation in current PM, and (5) develop a set of recommendations to remediate those deficiencies.

This project was a new start in late 2006 and was conducted by AER as a follow-on study.  A draft journal article covering Phase 1 and Phase 2 work from the project was approved by the committee for submission to Environmental Science & Technology (ES&T).  This article was released for publication by ES&T in August 2008. 

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