American Association for Aerosol Research - Abstract Submission

AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA

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Investigating Missing Sulfur Sources at Fairbanks, Alaska

KABINDRA M. SHAKYA, Richard E. Peltier, University of Massachusetts, Amherst

Abstract Number: 268
Working Group: Remote and Regional Atmospheric Aerosols

Abstract
Series of intensive field measurement studies of fine particle chemical components at Fairbanks, Alaska has revealed unusual aerosol climatology where, at times, significantly more elemental sulfur was observed from X-ray Fluorescence (XRF) compared to sulfate as measured by chromatographic (IC) separation. Sulfur and organic carbon are the largest fraction of aerosol mass in Fairbanks, a subarctic small city characterized by exceptionally polluted wintertime conditions, and relatively clean conditions during the summer. We observed large inconsistencies when comparing these two sulfur measurements at the single EPA monitoring site at Fairbanks after analysis all of all available chemical measurements by XRF and IC from 2005 until 2012. We analyzed data where the ratio of sulfur by XRF to sulfur by IC was significantly different from unity after propagating reported instrument uncertainties. We observed a significant deviation in 28% of total measurements since 2005 where elemental sulfur (by XRF) exceeding the inorganic sulfur (by IC) indicating the presence of apparently unmeasured sulfur compounds. The largest discrepancies between elemental sulfur and sulfate were most frequently observed in the summer, though discrepancies were observed year round. An analysis of all available AQS data suggest that this recurring phenomena is linked to seasons, and total carbon, nitrate, and zinc sources (for colder temperatures) and ozone (for warmer temperatures). This suggests that it is more than a simple systematic bias indicating the missing sulfur sources and unmeasured sulfur species at Fairbanks, a finding that has important implications for interpretation of data from the larger speciation trends network.