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Drum samplers (Davis Rotating-drum Universal-size-cut Monitor)
hold promise for reducing operator effort while collecting more
highly time- and size-resolved particle data than is possible with
filters. The drum sampler operates continuously for up to
six weeks (or longer if not on a continuous schedule) and collects
3 or 8 different size fractions of PM from 2.5 um to 0.09 um on
impaction strips. These separate size fractions can be analyzed
for elemental composition, mass, and optical absorption at multiple
wavelengths. A mass-spectroscopy analysis can also be conducted
to determine concentrations of organic species. The time resolution
of all of these measurements is typically 3 to 6 hours. And,
best of all (?), once the monitor is set up, it requires no attention
until the end of the 6 week period, when the entire unit is shipped
to the lab for analysis.
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Here's a view of our sampler running at the Allen Park site in
Michigan (suburb of Detroit) . It gets my vote for the cutest
monitor. You can see that it is quite compact and requires
only a source of electrical power (there's a battery-run version
as well). The Michigan Department of Environmental Quality
(special thanks to Ann Chevalier) operated the drum sampler from
the beginning of March 2002 to mid-April 2002, which coincided with
the end of the Detroit Toxics Pilot Project (part of EPA's toxics
trends pilot), so there were plenty of collocated measurements to
help put the data in perspective. Tom Cahill of the Delta
Group at UC-Davis provided LADCO with the analytical data; view
his presentation and summary of his findings by clicking
here.
Hilary Hafner and Steve Brown of Sonoma Technology have conducted
a preliminary source apportionment of the data; click here.
Notice the spiky characteristic of many of these
components; pm in this small size fraction seems to be influenced
by short-duration plumes of complex aerosols. Phil Hopke and
Eugene Kim of Clarkson University are continuing analysis of this
interesting dataset--more revelations are expected by fall 2004.
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