Single‐particle measurements of midlatitude black carbon and light‐scattering aerosols from the boundary layer to the lower stratosphere

Abstract

[1] A single-particle soot photometer (SP2) was flown on a NASA WB-57F high-altitude research aircraft in November 2004 from Houston, Texas. The SP2 uses laser-induced incandescence to detect individual black carbon (BC) particles in an air sample in the mass range of $3-300 fg ($0.15-0.7 mm volume equivalent diameter). Scattered light is used to size the remaining non-BC aerosols in the range of $0.17-0.7 mm diameter. We present profiles of both aerosol types from the boundary layer to the lower stratosphere from two midlatitude flights. Results for total aerosol amounts in the size range detected by the SP2 are in good agreement with typical particle spectrometer measurements in the same region. All ambient incandescing particles were identified as BC because their incandescence properties matched those of laboratory-generated BC aerosol. Approximately 40% of these BC particles showed evidence of internal mixing (e.g., coating). Throughout profiles between 5 and 18.7 km, BC particles were less than a few percent of total aerosol number, and black carbon aerosol (BCA) mass mixing ratio showed a constant gradient with altitude above 5 km. SP2 data was compared to results from the ECHAM4/MADE and LmDzT-INCA global aerosol models. The comparison will help resolve the important systematic differences in model aerosol processes that determine BCA loadings. Further intercomparisons of models and measurements as presented here will improve the accuracy of the radiative forcing contribution from BCA.Citation: Schwarz, J. P., et al. (2006), Single-particle measurements of midlatitude black carbon and light-scattering aerosols from the boundary layer to the lower stratosphere,

Are Emissions of Black Carbon from Gasoline Vehicles Underestimated? Insights from Near and On-Road Measurements

“…An additional uncertainty may also arise from the incandescence of metallic species present in exhaust, resulting in an overestimation of BC mass. However, the ratio of broadband to narrowband detector signals (as a measure of sublimation temperature 30 ) in close proximity to the highway is qualitatively similar to that of the BC calibration material (Supporting Information), indicating that such an interference was unlikely.…”

“…29 The effective density was found to be 0.72 ± 0.06 g cm −3 which was utilized in subsequent mass calculations. Variations in the effective density or organic coating thickness of ambient particles does not affect ambient BC mass determination for the SP2 30,31 or HS-LII. The SP2 is able to detect single particles with effective diameter greater than about 90 nm with approximately 100% transmission efficiency.…”

“…30 Potential uncertainties during the current study are primarily associated with the BC response linearity as determined by the mass calibration (± ∼15%), and the ability to measure the effective density of the calibration material (± ∼8%). An additional uncertainty may also arise from the incandescence of metallic species present in exhaust, resulting in an overestimation of BC mass.…”

An evaluation of real‐time air quality forecasts and their urban emissions over eastern Texas during the summer of 2006 Second Texas Air Quality Study field study

“…Ethylene is measured at 10-s resolution with the photoacoustic laser spectroscopy technique described by Kuster et al [2005]. Elemental carbon is determined by single particle soot photometer measurements [Schwarz et al, 2006[Schwarz et al, , 2008. Size (and volume) distribution measurements of aerosol were made aboard the NOAA P-3 at 1-s time resolution by laser optical particle counters, similar to the measurements made during the ICARTT/NEAQS-2004 field project [Brock et al, 2008].…”

Variation of secondary coatings associated with elemental carbon by single particle analysis

“…Advances in on-line instrumentation have provided a direct measurement of sizeresolved mixing state, and thus this could help to track the evolution of chemical compositions and their influence on the optical properties of aerosols with high time resolution. Volatility Tandem Differential Mobility Analyzer (VTDMA) and Single Particle Soot Photometer (SP2) can obtain the information on mixing state of refractory black carbon (rBC), in addition to mass quantification (Schwarz et al, 2006). Through the application of VTDMA, Cheng et al (2009) observed significantly enhanced light scattering and absorption capacity of rBC due to the secondary processing of rBC in a polluted region of China.…”