Research Project Summary Information
A Method to Extract and Interpret Additional Aerosol Organic Carbon Fractions from Thermal Optical Analysis of Filter-Based and Continuous Data(ST10605)
Research Foundation of SUNY
The carbonaceous fraction (both elemental carbon and organic carbon) represents a large component of fine particulate matter (PM2.5) in New York State, approximately 40%. The sources and chemical reactions of precursors of this fraction, as well as the specific compounds comprising this fraction are largely unknown. The Speciation Trends Network (STN) and Improve Network, part of EPA’s national monitoring system for urban and rural locations, collect ambient PM samples for analysis of elemental carbon (EC) and organic carbon (OC). The method of analysis is non-specific and uses “thermal fractions”, or measurements of gases desorbed at certain temperature levels that are maintained for a period of time during analysis before ramping up to the next plateau.
Three tasks were identified to improve the methods for extracting and identifying the carbonaceous components of PM. Thermal optical measurement methods were used to characterize a suite of known primary and secondary carbonaceous aerosol compounds that were generated in the laboratory. The methods were then applied to a select group of organic compounds incorporated into mixed aerosols samples that contained ammonium sulfate, ammonium nitrate and soot, to evaluate matrix effects on the thermal evolution of the organic species. Results from the first two tasks were used to re-analyze existing data sets to obtain additional information about aerosol carbon fractions and their interpretation with respect to source contribution and atmospheric processes.
This project was an opportunity to extract new, more specific information from existing data sets of continuous- and filter-based measurements of carbonaceous aerosols in NYS. It also offered a possibility of optimizing the thermal optical analysis method to improve the identification of primary and secondary organic species, useful for studying chemical processes, performing source apportionment, and addressing policy-relevant questions.
A suite of organic and inorganic carbonaceous aerosols were generated in the laboratory. The resultant thermograms were measured using four different well-defined measurement protocols. A series of experiments were conducted using the Combustion Aerosol Standard (CAST) system. This controlled combustion system was used to vary combustion conditions, while measuring detailed thermograms using one or more temperature protocols. By combining the CAST system and an aerosol minimizer, detailed thermograms were measured for mixed organic and inorganic aerosols. Time series of the reported carbon fractions from the filter speciation data from the seven EPA network protocol sites in New York State were examined. That examination yielded a pictorial display of the changing volatility classes of the aerosols at the different sites as a function of location and season. The policy relevance of this work is related to the need of meeting the requirements of air quality regulations for PM and the important contribution of carbonaceous compounds to the PM. Carbonaceous PM comes from many sources of combustion activity, including an important contribution from fossil fuels burned in the process of electricity generation. A complete understanding of the sources of this carbon, its chemical properties and the atmospheric processes involved in transport and deposition, are needed to achieve and maintain ambient air quality standards.
Research Foundation of SUNY
Office of Sponsored Programs Attn: Anne DePietri
Stony Brook, NY 11794
SUNY Atmospheric Science Research Ctr
Environmental Monitoring & Research
NYSERDA Contact Information
R&D - Environment & Energy Res