Measurement of particle-bound organic carbon (OC) may
be complicated by sampling artifacts such as adsorption
of gas-phase species onto particles or filters or evaporation
of semivolatile compounds off the particles. A denuderbased
integrated organic gas and particle sampler (IOGAPS),
specifically designed to minimize sampling artifacts, has
been developed to sample atmospheric carbonaceous
aerosols. IOGAPS is designed to first remove gas-phase
chemicals via sorption to the XAD-coated denuder,
and subsequently particles are trapped on a quartz filter.
A backup sorbent system consisting of sorbent- (XAD-4 resin)
impregnated filters (SIFs) was used to capture the
semivolatile OC that evaporates from the particles accumulated
on the upstream quartz filter. A traditional filter
pack (FP) air sampler, which uses a single quartz filter
to collect the particles, was employed for comparison in
this study. Elemental and organic carbon were determined
from filter punches by a thermal optical transmittance
aerosol carbon analyzer. Field measurements show that
there was no significant difference between the elemental
carbon concentrations determined by the FP and IOGAPS,
indicating that particle loss during the transit through
the denuder tube was negligible. Compared with the OC
determined by FP (3.9-12.6 µg of C/m3
), the lower OC observed
on the quartz filter in the IOGAPS (2.2-6.0 µg of C/m3
)
was expected because of the removal of gas-phase organics
by the denuder. Higher semivolatile organic carbon
(SVOC) on the backup SIFs during the night (1.24-8.43 µg
of C/m3
) suggests that more SVOC, emitted from primary
sources or formed as secondary organic compounds,
partitions onto the particles during the night because of
the decreased ambient temperature. These data illustrate
the utility of an IOGAPS system to more accurately
determine the particle-bound OC in comparison to FPbased
systems.