1. Application of Anion Exchange Chromatography with Pulsed Amperometric Detection for Measurement of Levoglucosan in Ambient Aerosol Samples
Amanda S. Holden, Amy P. Sullivan, Sonia Kreidenweis, Jeffrey L. Collett, Jr., Colorado State University, Department of Atmospheric Science, Fort Collins, Colorado Bret Schichtel, William Malm, National Park Service/CIRA, Colorado State University, Fort Collins, Colorado 80523; Graham Bench, Lawrence Livermore National Laboratory, Livermore, California 94551
Background
Fire is an important contributor to regional haze and elevated concentrations of particulate matter,
especially in the western U.S.
Levoglucosan used as a tracer for biomass burning
This study uses a new method to measure levoglucosan in ambient samples
Goal: to estimate biomass burning contributions to PM2.5 concentrations in several locations
Because these samples are from the summer, we can assume that biomass burning is primarily from prescribed
fires, rather than residential wood combustion (e.g. fires in fireplaces)
Most literature source profiles are from residential wood combustion
Figure 7. Contemporary, fossil, and biomass carbon concentrations (as TC), given for each sampling period and as an overall average for each site. Contemporary and fossil carbon are stacked to show the total carbon concentration for that sample.
Results
Biomass carbon not a big contributor to PM2.5 in
Phoenix
Urban site: high fossil carbon
Mid- to high-contributions of biomass carbon in
Grand Canyon and Tonto National Forest
Significant fossil carbon in Tonto National Forest as
well
Possible transport from Phoenix
Rocky Mountain shows highest biomass burning
influence
Some weeks show biomass carbon concentrations
higher than total carbon
Possibly due to sampling error- biomass carbon
calculated from different data than fossil +
contemporary carbon
Source profile used possibly not appropriate for
this site
Smoke plume images did not show all biomass
contributions
Some smoke plumes too small to be seen by satellite
Possible false negatives
For the most part, smoke plume presence
corresponded with higher biomass carbon
These calculations only include primary aerosol
Do not include secondary organic aerosol (SOA)
contributions from reactions within aged smoke plumes
Additional “smoke SOA” might contribute to additional
contemporary carbon not attributed to primary biomass
burning aerosol using this method
The two “mystery” peaks (“a” and “b”) in our chromatogram appear to contain extra information about fuel type (Figure 8)
Each fuel type dominated by peak “b”
Branches show the highest dominance of peak “b”
Different fuel types (grasses, branches, needles, leaves) yield
chromatograms with various ratios of the sizes of the two mystery peaks
Ambient IMPROVE site data fall along certain fuel type lines
PHOE and TONT peak ratios agree with grass ratios
HANC peak ratios are similar with leaf ratios
ROMO peak ratios look like grass or branch ratios
Grasses: easterly winds
Branches: westerly winds
Figure 8. Response at mystery peaks “a” and “b”, split into fuel type and IMPROVE sampling site. Linear trendlines, and their corresponding equations and R2 values, are shown for each fuel type.
1:1
Figure 1. Organic carbon shown as % PM2.5 mass according to IMPROVE measurements.
Methods
Ambient Sampling
6-day samples taken during winter and summer at 12 IMPROVE sites
4 locations analyzed for summer 2005
2 remote: Grand Canyon, AZ (HANC) and Rocky Mountain National Park, CO
(ROMO)
1 urban: Phoenix, AZ (PHOE)
1 “near-urban”: Tonto National Forest, AZ (TONT)
Samples collected using Hi-vol sampler
Source Profiles
Levoglucosan/TC (total carbon) ratios from source filters
FLAME study: various fuels burned at the USDA-USFS Fire Science Lab
Sampled using Hi-vol samplers with 2.5μm size cut
Split into geographical regions: Southwest and North/Central U.S.
Within regions, split into fuel types
Compared individual fuel types to all fuel types for each region
Regional average ratio applied to IMPROVE samples
Figure 3. Levoglucosan to TC ratios for FLAME fuels used in calculating source profiles. Fuels are separated into different compositions. Striped bars are Southwestern fuels, while solid bars are North/Central fuels.
Figure 2. Map showing locations of IMPROVE sampling sites and the origin of FLAME fuels used as source profiles. Table inset gives fuel name and composition.
Smoke/Fire Presence
Back trajectories
From HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) On-line Transport and Dispersion Model
NOAA and Australia’s Bureau of Meteorology
Gives advection of a single particle using meteorological data
Examined 48-hour back trajectories ending each sampling day
Region where air parcels originated used in determining which source profile region to use
Smoke/fire images
From NOAA NGDC (National Geophysical Data Center) Satellite Fire Detections map
Smoke plumes and fire locations from HMS (Hazard Mapping System) Fire and Smoke Product
HMS uses images from GOES, AVHRR, and MODIS satellites
Looking at back trajectories with smoke/fire images gives an estimate of which samples should be influenced by biomass burning
Figure 4. Images for the ROMO site, 8/16/2005-8/23/ (below left) Image from HYSPLIT. Black star indicates location of IMPROVE sampling site. Colored lines indicate 48-hour back trajectories, corresponding to the time periods shown on the table below the image. (below right) Image from Satellite Fire Detections map. Red circle indicates location of IMPROVE sampling site. Grey areas indicate analyzed smoke plumes, boxes indicate locations of fires (different colored boxes corresponding to different satellite sources).
Conclusions and Future Work
HPAEC-PAD provides a simple, cost-effective analytical method for looking at smoke markers in ambient aerosol samples
Estimates of biomass combustion contributions to ambient aerosol carbon are mostly consistent with 14C contemporary/fossil splits: few instances
of over-prediction (ROMO site)
It is important to use wild fire source profiles for this type of analysis, as they are very different from residential wood combustion source profiles
Will look soon at additional IMPROVE sites as well as winter samples
“Mystery” peaks in HPAEC-PAD chromatograms could be useful as additional biomass burning source markers, especially for providing more
information about types of fuels combusted
For more about FLAME source profiles, see Amy Sullivan’s platform presentation, 3:50 p.m. Tuesday, #5B.1
Sample Analysis and Calculations
Analyzing concentrations for FLAME and IMPROVE filters
Levoglucosan and other sugars measured using High-Performance Anion Exchange
Chromatography with Pulsed Amperometric Detection, with a Dionex CarboPac
column (PA10) and a gradient of H2O/NaOH eluent
Organic carbon (OC) and elemental carbon (EC) measured using a Sunset Labs
carbon analyzer
TC = OC + EC
All concentrations were blank corrected
Estimation of biomass combustion contributions
Biomass carbon (μgC/m3) =
Compared biomass combustion carbon to fossil and contemporary carbon
Fossil and contemporary carbon concentrations calculated from carbon isotope
measurements using accelerated mass spectrometry at the Lawrence Livermore
National Laboratory
Contemporary carbon: biomass burning, biogenic emissions
Different from modern carbon, which includes inputs from atomic bomb testing
Fossil carbon: fossil fuel combustion
Figure 5. HPAEC-PAD setup used for analyzing sugars in FLAME and IMPROVE filters.
levoglucosan
Figure 6. Sample carbohydrate chromatogram for a FLAME burn of longleaf pine needles. Peaks corresponding to known sugars are labeled. Two “mystery” peaks regularly appear; these are denoted “a” and “b” (retention times 3.24 and 3.65 minutes, respectively).
Acknowledgements
Funding: Joint Fire Science Program and the National Park Service
Sample collection: Chuck McDade and the IMPROVE team at U.C. Davis
Support during FLAME: Cyle Wold, Wei Min Hao, and the Fire Science Lab staff b
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