HR: 08:45h
AN: A51H-03    [Abstracts]
TI: SPLAT II: An Ultra-Sensitive, High Precision Instrument for the In-Situ Characterization of the Size, Composition, Density, Shape, Hygroscopicity, and Fractal Dimension of Fine and Ultrafine Particle
AU: * Zelenyuk, A
EM: alla.zelenyuk@pnl.gov
AF: Pacific Northwest National laboratory, 3335 Q Avenue K8-88, Richland, WA 99354, United States
AU: Yang, J
EM: juan.yang@pnl.gov
AF: Pacific Northwest National laboratory, 3335 Q Avenue K8-88, Richland, WA 99354, United States
AU: Imre, D
EM: imreconsulting@charter.net
AF: Imre Consulting, 181 McIntosh Ct, Richland, WA 99352,
AB: Single particle mass spectrometers (SPMS) have been developed and deployed to characterize, in real-time the size and chemical compositions of individual ambient particles. SPMS have undeniably proven to be extremely valuable, improving our understanding of the properties and evolution of atmospheric aerosols. At the same time these instruments have also persistently been subject to criticism on a number of fronts. Recently we have completed the construction of our second generation single particle mass spectrometer - SPLAT II, in which we have made significant improvements that directly address the shortcomings that are often associated with SPMS. We will present the results of instrument characterization experiments demonstrating that considerable improvements in instrument performance have been accomplished. SPLAT II offers significantly improved detection sensitivity of small particles, such that 30% of all 100 nm particles that enter the instrument are detected and characterized. This represents an improvement of nearly 2 orders of magnitude over the previous instrument. The efficiency of detection of particles larger than 150 nm is 100%. SPLAT II can measure and record the vacuum aerodynamic diameters of up to 300 particles per second and record 100 individual particle mass spectra per second - an increase of a factor of 10 in temporal resolution over the previous instrument. SPLAT II uses an IR laser to evaporate the semivolatile fraction of the particle and a time delayed UV laser to generate ions. The IR and UV lasers are configured to assure that the individual particle mass spectra represent the complete composition of each particle. The semivolatile fraction is ionized in the gas phase, while the nonvolatile fraction is concurrently ablated. This approach yields extremely reproducible, high quality mass spectral signatures while providing complete particle characterization. The two step – IR/UV - approach is particularly suitable for the characterization of organic molecules in fine and ultrafine particles. SPLAT II uses a data acquisition system with a 14 bit dynamic range- an increase of a factor of 128 in dynamic range over the previous instrument. This allows the instrument to record mass spectra of internally mixed particles that contain a range of substances with very different ionization probabilities. SPLAT II offers ultra-sensitive detection capabilities, making it possible to combine it with a DMA or a tandem DMA. The SPLAT II/DMA can simultaneously measure, in-situ individual particle size, composition, density, effective density, dynamic shape factor, fractal dimension, and hygroscopicity at a rate that yields statistically robust data. The SPLAT II/DMA system can also provide quantitative individual particle composition. To take a full advantage of the vast amounts of detailed data produced by SPLAT II we have developed two software packages: SpectraMiner and ClusterSculptor. SpectraMiner is a statistical analysis and data mining and visualization program that offers the user a wide range of visually driven controls to explore the data. ClusterSculptor is a software package that is coupled to SpectraMiner and is designed to overcome the limitation of statistics by offering the user the ability to insert his/hers scientific knowledge into the data organization phase.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting