Overview
The International State of the Science Workshop on Organic Speciation in Atmospheric Aerosol Research (April 5-7, 2004 in Las Vegas, Nevada at the Desert Research Institute) is being developed to bring together diverse members of the research community in hopes of evaluating the state of the science and identifying information gaps with regard to characterization of organic aerosols. The workshop is a step in working to achieve the goals of the Atmospheric Particulate Exchange (APACE) series of symposia. Particular emphasis is placed on identifying the needs of air pollution researchers in complementary disciplines, such as ambient air modeling (particularly source-receptor), health hazard research, visibility, and climate. Workshop discussions will emphasize the following general questions:

1. How do we define semi-volatile and particle-associated organic compounds?
2. What are the conventional and emerging methods for collecting and analyzing organic carbonaceous aerosols, and how do we assess those methods for their ability to fulfill the needs of public health, climate, and modeling?
3. How do we assess accuracy and precision, and what criteria should be met for regulatory or other purposes?

This workshop aspires to summarize current knowledge, articulate needs for further research, and document where the greatest capacity for advancement exists. One goal is to characterize the state of the science and needs across disciplines through a combination of lectures, open-forum discussions, and focus groups.

The workshop findings and recommendations on the state of the science will be summarized in a peer-reviewed article to be prepared by pre-selected participants. Findings and recommendations will also be disseminated to non-workshop participants on the email list with a request for input in order to further develop an account of the state of the science that accurately reflects current research reality and future potential. The results will be disseminated to interested and affected research and sponsor communities.

Reaching out to key experts and sponsoring organizations through a non-competitive, cooperative dialogue to identify new capacities in organic aerosols speciation research is a primary purpose of this third workshop in an on-going series of yearly workshops. The workshops are planned and conducted by a network of researchers, sponsors, support organizations, and individuals referred to as the Atmospheric PArticulate Carbon Exchange (APACE).

Statement of Problem
Organic carbon comprises a large fraction of the PM10 and PM2.5 ambient aerosol mass. In many areas, organic carbon is predominant over elemental carbon and other inorganic constituents. The health effect of fine PM has been postulated to be associated with the organic fraction of PM. Yet, the composition of organic aerosol is still not well-defined. Many uncertainties remain concerning the presence of specific compounds, especially the composition of more polar, water soluble and bioorganic fractions, which is not known. There is a need for defining the current state of knowledge and what are the remaining gaps that need to be addressed.

Workshop Goals
A. Clarification of Organic Aerosol Terminology
Uncertainty exists in defining commonly used terminology, such as semi-volatile organic compounds (SVOC), volatile organic compounds (VOC), particle-associated organic compounds.

Objective 1: Document agreement, where it is possible, among leading researchers in the field of organic aerosols on the definition of these terms. In addition, new terms may be derived to more explicitly characterize the molecular structure and/or classes of organic aerosol species present in the atmosphere.

B. Identify and Explore Limitations of Current Organic Aerosol Sampling Technologies
Due to the numerous types of chemical species comprising organic aerosols, with their inherently different physical properties, accurate sampling of organic aerosols is a very challenging task. First, traditional organic sampling approaches are prone to artifacts, leading to ambiguous operational definitions of either particle bound or vapor phase semi-volatile organic compounds. Other artifacts may exist because of the presence of organic material in the background of sample collection devices or sample processing procedures. Sampling techniques must take into consideration the sensitivity of the end analysis, and often the amount of material required for analysis or trace components is a limiting factor.

Objective 2: Address sampling difficulties such as the condensability (i.e., positive artifacts) and volatility of organic species (i.e., negative artifacts), and identify current sampling techniques (including emerging techniques) and needs for specific types of organic aerosols depending on their physical and chemical attributes.

C. Identify and Explore Limitations of Current Technology for Analyzing Organic Aerosols
A difficult problem in the study of organic aerosols is the lack of reliable chemical analysis methods to distinguish the hundreds of compounds that exist in air. Two important components of the analysis are: 1) how is the sample processed or introduced to an analyzer, and: 2) what is the analysis technique and how is it calibrated? Conventional organic analysis relies on solvent extraction or thermal desorption of material collected on filters or sorbents, and analysis by gas-liquid or liquid chromatography interfaced to a mass spectrometer or other detection device. Current analysis techniques are only able to account for a small fraction of the individual organic species that make-up the bulk of organic material. Of the compounds that have been identified and characterized, there are few criteria for evaluating the accuracy and precision among different techniques and laboratories.

Objective 3: Assess our current knowledge of sample introduction and analysis techniques, with emphasis on current state of the science and knowledge gaps, particularly with respect to challenges associated with compounds in different chemical classes.

Objective 4: Assess promising techniques for measuring the unidentified component of organic carbon. Do macromolecular analysis techniques help fill in the knowledge gap? What macromolecular analysis techniques, or other techniques aimed at sorting out the composition of total organic material exist?

Goal 5. Define criteria and needs for assessing and improving accuracy of organic analysis techniques, with consideration of both research and regulatory communities.

D. Identify and Explore Organic Aerosol Speciation Needs of Related Disciplines (i.e. Modeling, Public Health, Outdoor and Indoor Air, Climate)

Arguably, the major portion of the push to analyze several classes of different organic compounds and compound classes in air has been driven by the needs of the source apportionment community to develop chemical signatures that allow accurate attribution of carbonaceous sources. Other communities, such as health hazard and to some extent climate researchers, have benefited from this increased knowledge in the composition of ambient air and sources. It is currently unclear if the needs of any of those communities have been met or exceeded, and while communication between the analytical chemistry community and these communities has improved, there has not been a summary of research needs of these communities assembled in a large interdisciplinary forum.

Objective 6: Review and define the organic speciation needs of the modeling, health and climate communities.

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