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PATTERNS IN FINE PARTICULATE MATTER
Project No. A-57
Leaders: A. M. Dunker
R. S. MacArthur
Scope and Objective
The objective of this research is to analyze
time series of particle-phase pollutant concentrations to determine if weekly
cycles are present in the data. Both particulate nitrate and black carbon (BC)
were studied, using 10-minute time-resolved measurements made over full annual
cycles.
Current Status and Future
Program
A time and frequency-domain analysis of
particulate nitrate and BC concentrations, with a specific goal of testing for
the presence of weekly cycles in the data, was proposed. Unlike past studies
that relied mostly on results of filter-based sampling, online measurements of
nitrate and BC were used. Data analysis relied on recent (January 2000 and
later) nitrate measurements made in four cities: Claremont, Fresno, Pittsburgh,
and St. Louis. At these locations, yearlong measurements of nitrate
concentrations were conducted at 10-minute time resolutions. The data analysis
for Claremont used continuous size-resolved measurements of fine particle
nitrate in three size ranges: <0.45
mm,
0.45-1.0 mm,
and 1.0-2.5 mm.
Nitrate measurements at the other sites included only total nitrate mass,
without any size distribution information. Continuous BC concentrations were
measured at these sites using aethalometers. Time and frequency-domain analyses
of the nitrate data (all 4 sites) and BC data (Fresno plus at least 1 other
site) were conducted to characterize weekly cycles and diurnal patterns. Of
special interest was the response of ambient nitrate and BC concentrations to a
70-80% decrease in HD diesel truck traffic on weekends.
This project was conducted over a period of 18
months by a team of Dr. Rob Harley of the University of California at Berkeley
and Dr. Susanne Hering of Aerosol Dynamics. The research task breakdown was:
Task 1 (data acquisition and quality assurance), Task 2 (time domain analyses),
Task 3 (frequency domain analyses), and Task 4 (reporting). The committee
reviewed the draft Final Report and elected to extend the analysis and prepare a
journal article using unspent funds from the project. A weekly cycle was
observed for BC at Fresno and St. Louis with lowest readings on Sundays. A
weekly cycle was observed in PM nitrate at Fresno, St. Louis, and Claremont (but
not in Pittsburgh) with the lowest levels on Mondays. The revised Final Report
was updated to include additional discussion on the relationship between BC and
PM nitrate, and the Final Report was released in November 2006 and is posted on
the CRC website. A draft journal article has also been submitted for
publication to Atmospheric Environment.
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