2013 Progress Report: BC and Other Light-Absorbing Impurities in North American Great Plains Snow: Sources, Impacts, and a Comparison with North China Snow

EPA Grant Number: R835038
Title: BC and Other Light-Absorbing Impurities in North American Great Plains Snow: Sources, Impacts, and a Comparison with North China Snow
Investigators: Doherty, Sarah , Fu, Qiang , Hegg, Dean A. , Warren, Stephen
Institution: University of Washington
EPA Project Officer: Chung, Serena
Project Period: July 1, 2011 through June 30, 2014 (Extended to June 30, 2015)
Project Period Covered by this Report: July 1, 2012 through June 30,2013
Project Amount: $825,483
RFA: Black Carbon's Role In Global To Local Scale Climate And Air Quality (2010) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Climate Change , Air


  1. Investigate the concentrations, sources and regional climate impacts of black carbon (BC) and other light-absorbing aerosol (LAA) in snow in the North American Great Plains.
  2. Compare the concentrations, sources and regional climate impacts of LAA in snow for the North American Great Plains vs. the steppes of North Asia.
  3. Improve our understanding of (a) the deposition rates of BC to snow, which affects both atmospheric and snowpack BC concentrations, and (b) consolidation of BC and other LAA at the snowpack surface during melting, a potentially strong positive feedback mechanism.
  4. Test and improve our ability to measure BC and other LAA in snow by conducting a comparison of three methods for measuring BC: our ISSW Spectrophotometer, the Single Particle Soot Photometer, and the thermo-optical method.
  5. Use snow BC concentrations extending from the northern United States to the North Pole to make a first-order estimate of the contribution by North American sources to BC in Arctic snow.

Progress Summary:

  1. We carried out our first field season, 28 Jan - 21 Mar 2013, gathering 527 samples from 67 sites across the northwest United States and the U.S. and Canadian Great Plains regions. Our northern-most site was Churchill, Manitoba on Hudson Bay. Filter samples from the 2013 field campaign were measured with the ISSW Spectrophotometer and the results are in the process of being interpreted.
  2. The snow samples to accompany each filter sample have been analyzed for anions with ion-exchange chromatography and for selected carbohydrates with liquid chromatography- mass spectroscopy. Samples are in the process of being analyzed for various elements via triple quadrupole (with collision cell) inductively coupled plasma - mass spectroscopy.
  3. We have been working on chemically extracting organic absorbers from the sample filters as a test of our optical partitioning of light absorption to BC and non-BC absorbers.  Two samples were collected at most of the 67 sites in our 2013 field season for this serial extraction process.  To date, we have extracted these samples with methanol, hexane and di-chloro methane. Several artifacts have made the results difficult to interpret so far.
  4. A subset of 18 parallel samples were gathered at sites we expect to cover a range of concentrations and absorbing particulate types (e.g., carbonaceous aerosol, dust) and were shipped, frozen, to our colleagues at NOAA. These will be analyzed in the upcoming year with an SP2, for comparison to parallel samples we will analyze with our ISSW Spectrophotometer.
  5. The instrument we use to measure BC and other light-absorbing particles in snow, the ISSW Spectrophotometer, was modified for improved performance, and a new set of calibration standards was generated using fullerene, a synthetic black carbon. Fullerene is used as a calibration material for the SP2, so this will make our estimates of BC concentrations more directly comparable to SP2 measurements.

Future Activities:

Year 3 of this project will focus on preparation and execution of the January-March 2014 North American field campaign, meta-analysis of the optical and chemical data from the 2013 field campaign, and analysis of the samples from the 2014 campaign.  We will continue to investigate whether our serial extraction of organics from the 2013 samples can provide insights to the contributions of specific groups of organics to snow particulate light absorption. PMF analysis will be used to apportion sources of particulate light absorption in the snow based on correlations between light absorption and chemical tracers of specific source types (e.g., biomass burning, fossil fuel combustion, soil, mineral dust).  These results will be compared with the concentrations and sources of light-absorbers at the sample sites as represented in a global and regional model, in a collaborative effort with our colleagues at Department of Energy's Pacific Northwest National Laboratory (DOE-PNNL).  We also will compare our estimates of snow black carbon concentrations with those from parallel samples sent to NOAA for measurement with an SP2.  No delays to the project schedule are foreseen.

Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 10 publications 10 publications in selected types All 10 journal articles
Type Citation Project Document Sources
Journal Article Doherty SJ, Grenfell TC, Forsstrom S, Hegg DL, Brandt RE, Warren SG. Observed vertical redistribution of black carbon and other insoluble light-absorbing particles in melting snow. Journal of Geophysical Research–Atmospheres 2013;118(11):5553-5569. R835038 (2012)
R835038 (2013)
R835038 (Final)
  • Full-text: AGU-Full Text PDF
  • Abstract: AGU-Abstract
  • Journal Article Schwarz JP, Doherty SJ, Li F, Ruggiero ST, Tanner CE, Perring AE, Gao RS, Fahey DW. Assessing single particle soot photometer and integrating sphere/integrating sandwich spectrophotometer measurement techniques for quantifying black carbon concentration in snow. Atmospheric Measurement Techniques 2012;5(11):2581-2592. R835038 (2012)
    R835038 (2013)
    R835038 (Final)
  • Full-text: AMT-Full Text PDF
  • Abstract: AMT-Abstract
  • Journal Article Wang X, Doherty SJ, Huang J. Black carbon and other light-absorbing impurities in snow across Northern China. Journal of Geophysical Research–Atmospheres 2013;118(3):1471-1492. R835038 (2012)
    R835038 (2013)
    R835038 (Final)
  • Full-text: Wiley-Full Text PDF
  • Abstract: Wiley-Abstract
  • Journal Article Zhang R, Hegg DA, Huang J, Fu Q. Source attribution of insoluble light-absorbing particles in seasonal snow across Northern China. Atmospheric Chemistry and Physics 2013;13(12):6091-6099. R835038 (2013)
    R835038 (Final)
  • Full-text: ACP-Full Text PDF
  • Abstract: ACP-Abstract
  • Supplemental Keywords:

    black carbon, climate, cryosphere, radiative forcing

    Relevant Websites:

    Soot In Arctic Snow Exit
    Sarah J. Doherty Exit

    Progress and Final Reports:

    Original Abstract
  • 2012 Progress Report
  • 2014 Progress Report
  • Final Report