Secondary Organic Aerosol Study - Look Rock (SOAS-LR) in Great Smoky Mountains National Park

Field Methods:
We propose to make measurements of fine particle composition using FTIR, XRF, and AMS techniques as part of the SOAS campaign. The instruments are housed in a 20’x8’ trailer with 3 m isokinetic inlet. The Russell group will collect fine particle mass on Teflon filters for quantification of organic functional group concentrations by FTIR spectroscopy and elemental concentrations by X-ray fluorescence (XRF). These techniques allowed not only for quantitative characterization of the organic composition of fine aerosol, but also identification of source categories and quantitative source contributions through the use of elemental tracers and positive matrix factorization (PMF). The sample collection will be conducted alongside simultaneous aerosol mass spectrometer (AMS) measurements, allowing for comparison of total organic mass and providing complementary information on organic composition (mass spectral fragments as opposed to chemical functional groups). 

Fine particle mass will be collected on Teflon filters for with both PM1 (4-6 hr) and PM2.5 (24 hr) cyclones. All filters will be analyzed by FTIR to quantify organic functional group concentrations, and selected filters will be analyzed by XRF to compare and validate ongoing IMPROVE sampling protocols. We will also collect samples for scanning transmission X-ray microscopy (STXM) near-edge X-ray absorption fine structure (NEXAFS) for selected periods. While limited in sample number, the unique single-particle organic functional group and morphology measurements provided by STXM-NEXAFS provides one-of-a-kind insight into the composition and structure of individual aerosol particles. We will collect approximately 10 samples for this analysis at the Look Rock site and archive an additional 40 samples for analysis if resources permit at a later date. The Ziemann group will also use spectrophotometric methods to analyze functional groups in a subset of aerosol filter samples (due to higher method detection limits and the need for larger samples) collected by the Russell group at Centerville, AL, and Look Rock, TN. In addition, we plan to exchange samples with the Surratt group (also located at Look Rock, TN) to augment inter-comparison of their tracer-compound methods with our functional group based methods, for both atmospheric and chamber sampling. 

The Russell group will also measure aerosol size-resolved chemical composition with high time resolution using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and black carbon components of the aerosol using a single particle soot photometer (SP2), which provide distinctive characteristics to quantify the contributions of biogenic and anthropogenic sources. Measurements of inorganic and organic fine particle composition and size distributions (near 100% transmissions for 60-600 nm, and partial transmission extending to ~30 nm and ~1.5 µm) will be conducted using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). This operation scheme will provide high time resolution measurements of inorganic and organic composition (5 min), mass fragments (5 min), elemental composition (10 min), single particles (2 hr), and mass fragment size distributions (1-4 hr).

Tags: aphn, appalachian-highlands-network, great-smoky-mountains-national-park, grsm, origin-external, ser, southeast-region, studyid-grsm-01133
Organization: Department of the Interior