Instrument
Descriptions For NASA TRACE-P
R.
Weber
Georgia Institute of Technology
Two instrument packages
will be deployed for TRACE-P. Separate
descriptions are given of each
Instrument A: Measurements of aerosol particle chemical composition.
A schematic of this
instrument is shown in Figure 1. This
is an automated instrument that continually collects particles
into a liquid and quantitatively measures, in real time, the soluble
ionic mass concentration via a dual channel ion chromatograph. The
instrument is capable of measuring the anions; chloride, nitrate,
methanesulfonate (MS), and sulfate, and cations, sodium, ammonium,
potassium, magnesium, and calcium with a sensitivity of ~30 ng m‑3 (~5 pptv)
over a sample integration interval and duty cycle of roughly 4
minutes. This is a
newly developed technique, for further details see Weber et al.
2000.
Instrument B: Measurement of newly
formed 3-4 nm particles
This involves measurements
of 3-10 nm particle spectra and total ultrafine particle concentrations
(all particles larger than 3 nm diameter) for studies of new particle
formation and growth. This
instrument is a modified ultrafine condensation particles counter
(UCPC) (TSI 3025) equipped with white light optics to enable pulse
height analysis. This
provides two types of information on ambient particle number concentrations. First,
measurements of total ultrafine particle concentrations are measured
at a rate of 1 Hz. Simultaneously,
pulse height analysis provides a measurement of size resolved number
concentrations of particles between 3 and nominally 10 nm diameter
and at sampling rate of 30 s. This
approach has high sensitivity for measuring nanoparticle concentrations. For
example, the relative uncertainty associated with a concentration
of 0.1 cm-3, for particles between 3-4 nm is roughly 50%. Further
details can be found in Weber et al. 1995, 1998
Weber,
R.J., D. Orsini, Y. Daun, Y.-N. Lee, P. Klotz, F. Brechtel, and
K. Okuyama, A new particle-in-liquid collector for rapid measurements
of aerosol chemical composition, J.
Aerosol Sci., in press,
2000.
Weber,
R.J., M. Stolzenburg, S. Pandis, and P.H. McMurry, Inversion of
UCNC pulse height distributions to obtain ultrafine (~3 to 10 nm)
particle size distributions, J.
Aerosol Sci., 29, 601-615, 1998
Weber,
R.J., P.H. McMurry, F.L. Eisele, and D.J. Tanner, Measurement of
expected nucleation precursor species and 3 to 500 nm diameter
particles at Mauna Loa Observatory, Hawaii, J.
Atmos. Sci., 52,
2242-2257, 1995.
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