FY 2003

Sampling methods used for the collection of particle-phase organic and elemental carbon during ACE-Asia

Mader, B.T., J.J. Schauer, J.H. Seinfeld, R.C. Flagan, J.Z. Yu, H. Yang, H.-J. Lim, B.J. Turpin, J.T. Deminter, G. Heidemann, M.S. Bae, P. Quinn, T. Bates, D.J. Eatough, B.J. Huebert, T. Bertram, and S. Howell

Atmos. Environ., 37(11), 1435–1449, doi: 10.1016/S1352-2310(02)01061-0 (2003)

The semi-volatile nature of carbonaceous aerosols complicates their collection, and for this reason special air sampling configurations must be utilized. ACE-Asia provided a unique opportunity to compare different sampling techniques for collecting carbonaceous aerosols. In this paper detailed comparisons between filter-based carbonaceous aerosol sampling methods are made. The majority of organic carbon (OC) present on a backup quartz fiber filter (QFF) in an undenuded-filter sampler resulted from the adsorption of native gaseous OC rather than OC evaporated from collected particles. The level of OC on a backup QFF placed behind a QFF was lower than the level present on a backup QFF placed behind a Teflon membrane filter (TMF) indicating that gas/filter equilibrium may not be achieved in some QFF front and backup filter pairs. Gas adsorption artifacts can result in a 20–100% overestimation of the ambient particle-phase OC concentration. The gas collection efficiency of XAD-coated and carbon-impregnated filter-lined denuders were not always 100%, but, nonetheless, such denuders minimize gas adsorption artifacts. The median fraction of particle-phase OC that is estimated to evaporate from particles collected by denuder-filter samplers ranged from 0 to 0.2; this value depends on the sampler configuration, chemical composition of the OC, and sampling conditions. After properly correcting for sampling artifacts, the measured OC concentration may differ by 10% between undenuded- and denuder-filter samplers. Uncorrected, such differences can be as large as a factor two, illustrating the importance of sampling configurations in which gas adsorption or evaporation artifacts are reduced or can be corrected.