RESEARCH

 

Current Project Abstracts

 

Characterization of Terra Nove Bay (Antarctica) Size-Segragated Aerosol Using a Laser Desorption Ionization - TOF Mass Spectrometer

The Antarctic tropospheric aerosol is of increasing research interest. The remote localization of Antarctica makes it the ideal site for the study of atmospheric global change (Artaxo 1990). Antarctica is expected to suffer minimally from anthropogenic activities while the biogenic activity of the surrounding ocean is very intense, allowing for the determination of natural aerosol components (sulfates, nitrates and halogens). Sulfur containing particles have a primary role in global climate change. Sulfate aerosols affect the planet albedo by increasing cloud condensation nuclei (CCN) number. The halogens, iodine, and in a minor extent bromine compounds, play a role in Antarctic tropospheric chemistry by reacting with ozone and DMS (Chatfield 1990). Experimental observation of aerosol composition is required for improving modeling of Antarctic tropospheric chemistry and characterizing the potential anthropogenic aerosols generated from the research stations.

The sampling campaign was performed near Terra Nova Bay Italian Base, at the coastal site Campo Icaro (lat. 72°42 '43" S, long. 164°06 '58" E) 3 km south of the base. Sampling was performed during January 2003 (austral summer) by means of a 12-stage SDI impactor, working with a 11.3 L min-1 air flux. The aerodynamic cut diameters of the 12 stages are respectively 0.045, 0.086, 0153, 0.231, 0.343, 0.591, 0.796, 1.06, 1.66, 2.68, 4.08 and 8.39 mm; the upper dimensional limit for the 12th stage is 10 mm, due to the use of a total suspended particulate sampling head. The sampling time was 24 hours.

Laser desorption ionization spectra were recorded using a custom-built TOF mass spectrometer operating in the linear mode. To desorb and ionize the analytes, a pulse UV radiation at 266 nm was used. The carbon cluster pattern was observed from stage 1 to stage 7- 8 (particles smaller than 1 mm). The small dimension of stage 1 particles indicate that carbon clusters have been recently produced near the sampling site (fresh particles). The nearby scientific bases are the most probable sources for the detected carbon particles. Particles larger than 1 mm do not show carbon cluster signals. This suggests that carbon rich particles were removed from the atmosphere by deposition before further growth. Sulfate was observed below 0.6 mm, suggesting sulfate comes primarily from gas phase condensation events (non-sea salt sulfate). In addition sulfate in smaller stages was always detected with the simultaneous presence of MSA, indicating that these two ions are internally mixed. Nitrate and nitrite appear with strong signals in particles with aerodynamic diameter larger than 1.0/1.6 mm. Our results agree with other observations (Teinila 2000) and support the hypothesis that nitrate presence in aerosol phase is due to the interaction of gaseous nitric acid with sea salt particles in the coarse mode. Chlorine was detected only in the coarse fraction and its desplacement by nitrate was observed. Iodine was observed in particles smaller than 0.5 mm. Our data indicate that iodine compounds condense from the gas-phase onto particle surface. 

Investigators: Stefania Gilardoni and Peter Kelly

Collaborators: Francesco Chiminello and Paolo Mittner   (Department of Physics, University of Padua Italy)

 

 

Time Resolved Chemical Analysis of Anthropogenic Aerosols in Norway, a Study of Long-Range Transport

Anthropogenic fine particulate matter produced by the burning of carbonaceous fuels is a complex issue that transcends political and geographical boundaries. Anthropogenic fine aerosols are tranported to Norway from the British Isles and continental Europe. Two 3-DRUM impactor samplers were used to generate size-separated PM2.5 aerosol samples (2.5 – 1.15, 1.15-0.34, 0.34-0.1 µm Da) at two sites, Birkenes and Kjeller for a six-week period in June and July.  The samples were analyzed with three-hour time resolution by Synchrotron X-ray Fluorescence and Time-of-Flight Mass Spectrometry. S-XRF determined three-hour mass averages for elements above Na, while the TOFMS data indicated the positive and negative ions present as a function of time and size. Positive spectra showed K+,  Na+ and organic molecular ions between 200 – 400 m/z. Negative ion spectra detected carbon clusters, Cl-, Br-, I-, NO2-, NO3-, CN-, CNO-, SO3-, HSO4-, MSA, and various organic acid salts. A different ion signature was detected by size and during different transport events in correlation with the S-XRF data. The chemistry of the long-range aerosol events and size distributions of the anthropogenic species is examined and connected to source using air mass back trajectories.  Thus specific chemistry and transport effects can be detected with high time resolution and size segregation in combination with meteorological data.

Investigators: Hege Indresand, Jeremy Waddell and Peter Kelly

Collaborators: Christian Dye and Karl-Espen Yttri at the Norwegian Institute for Air Research (www.nilu.no), Steve Cliff with the UC Davis Department of Applied Science, and Kevin Perry at the University of Utah Meteorology Department.

 

 

C14 AMS Analysis of Urban Carbonacous Aerosols in Oslo, Norway

Oslo, Norway,  experience severe inversions during the winter months, trapping high concentrations of particulate matter. The city is situated at the north end of the Oslofjord with surrounding hills of 300-500 m. The organic fraction is of concern due to the associeted health effects. The two main sources of fine inhalable particles are woodburning and traffic. The objectives of the present study was to quantitively find the ratio between biogenic and fossil fuel contributions to the fine particulate matter in Oslo. The AMS facility at Lawrence Livermore National Lab, USA, was used to analyze the samples for PM2.5. Sampling was done in a collaboration with the Norwegian Institute of Air Research (NILU) at Sofienberg Park,  an urban background site. Sampling was done with a LVS1.0 quartz filter sampler with an exposure time of 48 hours. Night and day variations were taken into account by allowing half of the filters to only run at night (6 pm to 6 am) and day (6 am to 6 pm), respectively. Preliminary results show that the total carbon was twice as high at night versus day during the coldest periods. The biogenic contribution was also higher during night time. Overall the total carbon concentration showed a very high correlation (r > 0.93) with temperature. LDI TOF MS and S-XRF measurements of 8-stage DRUM samples taken during the same sampling period are in progress.

Investigators: Hege Indresand,and Peter Kelly

Collaborators: Christian Dye and Karl-Espen Yttri at the Norwegian Institute for Air Research (www.nilu.no) and Graham Bench at the Center for Accelerated Mass Spectrometry Lawrence Livermore National Lab, USA (http://cams.llnl.gov)

 

Chemical Analysis of Aerosols for Characterization of Long-Range Transport at Mt. Lassen, CA

Effective regional air pollution regulation requires an understanding of long-range aerosol transport and natural aerosol chemistry.   Sample collection was performed at the Interagency Monitoring of Protected Visual Environments (IMPROVE) sampling site on Mt. Lassen in the Sierra Nevada range at 1755 m elevation.  The site is in Northern California at Longitude 121° 34’ 40”, Latitude 40° 32’ 25”.  Size segregated and time resolved aerosol samples were collected with an 8 DRUM sampler from April 15th to May 24th 2002 as part of the NOAA Intercontinental Transport and Chemical Transformation Experiment (ITCT). The samples were analyzed with Synchrotron X-Ray Fluorescence (S-XRF) and Time of Flight mass spectroscopy (TOFMS).    The total aerosol concentration exhibits a clear daily cycling of total mass, due to a nighttime down-slope air circulation from the free troposphere.  The sulfate peaked in concentration during the night. Elemental data is suggestive of dust transport from continental Asia.  The micron size ranges were dominated by nitrate, while the sub-micron size ranges had high levels of sulfate.  Chemical analysis shows oceanic influence through strong correlations between methyl sulfonic acid (MSA), iodine, and oxalate.  The appearance of the oceanic biogenic tracers in the sub-micron fraction is most likely a result of vertical mixing over the Pacific Ocean.  MSA follows a diurnal pattern similar to sulfate, however the differences suggest both an oceanic and continental source for sulfate.  The carbon particulate signal did not show any diurnal pattern during the measurement period.

Investigators: Yutaka Harada Jeremy Waddell and Peter Kelly

Collaborators: Steve S. Cliff and Kevin Perry (see above)

Prior Studies and Projects