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Diagnostic Evaluation: Investigation of the Carbonaceous Fine Particle System
Research Programs
Routine measurements of speciated PM2.5 (e.g., IMPROVE, STN) are insufficient to diagnose the causes of model errors relative to organic carbon concentrations because they do cannot separate out the origin of organic carbon between primary vs. secondary, anthropogenic vs. biogenic, or mobile sources vs. area sources. Through identification of the sources and processes contributing the the organic carbon, the necessary improvements in the modeled processes or emission inputs can be identified. Current diagnostic evaluation work is listed below that will support better understanding of the carbonaceous aerosol system:
Estimating how much organic carbon (OC) observed is secondary: Routine measurements of EC & OC can be used in conjunction with model predictions of elemental carbon and primary organic carbon to estimate concentrations of secondary OC, as demonstrated by Yu et al., 2004. These estimates can be used as a preliminary assessment of model performance for secondary OC.
Model Evaluation
Diagnostic Evaluation:
Indicator Metrics & Instrumented CMAQ Investiguations for Inorganic Fine Particle System
Primary organic carbon predictions from different sources: Measurements of individual organic compounds that are specific to certain primary emission sources may be used to evaluate model predictions of primary OC on a source-by-source basis. Measurements of this type at the SEARCH monitoring sites are being used to evaluate model results during the Summer 1999 period in the Southeastern U.S. (Bhave et al., 2004).
Fossil-fuel versus Modern Carbon predictions: Measurements of radiocarbon allow one to distinguish fossil-fuel carbon (e.g., motor vehicle exhaust, coal and oil combustion) from modern carbon (e.g., biomass combustion, biogenic SOA). Measurements of this type at Nashville in Summer 1999 will be used to evaluate model predictions of these two types of carbon.
Source-specific primary OC, biogenic secondary OC, and anthropogenic secondary OC: The combination of primary organic compound speciation with radiocarbon data allow for a potentially accurate estimate of source-specific primary OC, biogenic secondary OC, and anthropogenic secondary OC. This combination of data is being generated from filter samples collected at Tampa Bay in May 2002 and will be used for model evaluation.
Tracers of anthropogenic and biogenic Secondary Organic Aerosols (SOA): Novel analytical techniques for quantifying individual organic compounds that are unique tracers of anthropogenic and biogenic SOA have been developed by scientists in the HEASD. These compounds have been measured at an RTP site throughout the 2003 calendar year and will be used to evaluate the current version of CMAQ as well as a future improved version of the CMAQ SOA module.
Many of these exploratory projects are in collaboration with scientists in the USEPA NERL Human Exposure and Atmospheric Sciences Division (HEASD).