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.