3 research outputs found
Application of Time-of-Flight Aerosol Mass Spectrometry for the Online Measurement of Gaseous Molecular Iodine
Here we present a new application of a time-of-flight
aerosol mass
spectrometer (TOF-AMS) for the measurement of atmospheric trace gases
in real-time. Usually, TOF-AMS instruments are not sensitive to gas-phase
species due to the aerodynamic particle focusing inlet system which
reduces the gas phase species by a factor of about 10<sup>7</sup> relative
to the particle phase. This efficient removal of the gas phase and
the resulting high relative enrichment of particles is one reason
for the very high sensitivity of TOF-AMS instruments for particle
phase compounds (detection limits in the sub-Ī¼g/m<sup>3</sup>-range for online measurements with 1 min integration time), which
allows application of the instruments even under clean atmospheric
conditions. Here we use artificially generated particles as sampling
probes to transfer selected atmospheric trace gases into the particle
phase before entering the AMS (gaseous compound trapping in artificially
generated particles-AMS, GTRAP-AMS). The sampling probe particles
are mixed with the gaseous analytes upstream of the TOF-AMS in a 0.5
L flow tube. As an exemplary application of the method, the measurement
of trace levels of gaseous molecular iodine is demonstrated. Ī±-Cyclodextrin
(Ī±-CD/NH<sub>4</sub>Br) particles are used as selective sampling
probes to transfer molecular iodine into the AMS. A detection limit
in the subparts-per-billion (sub-ppb) range was achieved. The method
was compared to a recently developed off-line method that combines
denuder sampling of gaseous I<sub>2</sub> and gas chromatography/mass
spectrometry (GC/MS) analysis. To demonstrate the usability of the
method, temporally resolved I<sub>2</sub> emission profiles from a
brown algae species (<i>Laminaria saccharina</i>) under
exposure of ambient ozone levels were investigated. Total I<sub>2</sub> release rates of 36.5 pmol min<sup>ā1</sup> grams fresh weight
(gFW)<sup>ā1</sup> at 100 pbb O<sub>3</sub> and 33.4 pmol min<sup>ā1</sup> gFW<sup>ā1</sup> at 50 ppb O<sub>3</sub> were
obtained within the first hour of ozone exposure
Characterization of Primary Organic Aerosol from Domestic Wood, Peat, and Coal Burning in Ireland
An
aerosol chemical speciation monitor (ACSM) was deployed to study
the primary nonrefractory submicron particulate matter emissions from
the burning of commercially available solid fuels (peat, coal, and
wood) typically used in European domestic fuel stoves. Organic mass
spectra (MS) from burning wood, peat, and coal were characterized
and intercompared for factor analysis against ambient data. The reference
profiles characterized in this study were used to estimate the contribution
of solid fuel sources, along with oil combustion, to ambient pollution
in Galway, Ireland using the multilinear engine (ME-2). During periods
influenced by marine air masses, local source contribution had dominant
impact and nonsea-spray primary organic emissions comprised 88% of
total organic aerosol mass, with peat burning found to be the greatest
contributor (39%), followed by oil (21%), coal (17%), and wood (11%).
In contrast, the resolved oxygenated organic aerosol (OOA) dominated
the aerosol composition in continental air masses, with contributions
of 50%, compared to 12% in marine air masses. The source apportionment
results suggest that the use of domestic solid fuels (peat, wood,
and coal) for home heating is the major source of evening and night-time
particulate pollution events despite their small use
Radiocarbon-Based Source Apportionment of Carbonaceous Aerosols at a Regional Background Site on Hainan Island, South China
To assign fossil
and nonfossil contributions to carbonaceous particles,
radiocarbon (<sup>14</sup>C) measurements were performed on organic
carbon (OC), elemental carbon (EC), and water-insoluble OC (WINSOC)
of aerosol samples from a regional background site in South China
under different seasonal conditions. The average contributions of
fossil sources to EC, OC and WINSOC were 38 Ā± 11%, 19 Ā±
10%, and 17 Ā± 10%, respectively, indicating generally a dominance
of nonfossil emissions. A higher contribution from fossil sources
to EC (ā¼51%) and OC (ā¼30%) was observed for air-masses
transported from Southeast China in fall, associated with large fossil-fuel
combustion and vehicle emissions in highly urbanized regions of China.
In contrast, an increase of the nonfossil contribution by 5ā10%
was observed during the periods with enhanced open biomass-burning
activities in Southeast Asia or Southeast China. A modified EC tracer
method was used to estimate the secondary organic carbon from fossil
emissions by determining <sup>14</sup>C-derived fossil WINSOC and
fossil EC. This approach indicates a dominating secondary component
(70 Ā± 7%) of fossil OC. Furthermore, contributions of biogenic
and biomass-burning emissions to contemporary OC were estimated to
be 56 Ā± 16% and 44 Ā± 14%, respectively