Primary and Secondary (Gaseous Precursor) Emissions of PM 2.5. Number of samples: Fort Benning Flaming (5), Smoldering (5), Fort Gordon Flaming (4), Smoldering (3), Background (19).
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Number of samples:
Fort Benning Flaming (5), Smoldering (5),
Fort Gordon Flaming (4), Smoldering (3),
According to EPA’s emission inventory  18 % of primary PM2.5 emissions come from forest fires (wildfire and prescribed fire), 11.4 % and 5 %, for CO and Volatile Organic Compounds (VOC), respectively. Forest fire is a significant source of gaseous and particulate air pollutants, which are not well characterized in terms of their chemical composition and atmospheric reactivity. Some of the gaseous emissions are believed to be more reactive and act as precursors for secondary fine PM formation during atmospheric dispersion of the smoke plume. Secondary organic aerosol (SOA):
Organic compounds, some highly oxygenated, residing in the aerosol phase as a function of atmospheric gas or particle phase reactions.
SOA formation mainly depends on:
Emissions & forming potential of precursors
aromatics (BTX, aldehydes, carbonyls)
terpenes (mono-, sesqui-)
other biogenics (aldehydes, alcohols)
Presence of other initiating reactants
O3, OH, NO3, sunlight, acid catalysts
Mechanisms (with half hr to few hr yields):
e.g. terpene oxidation
aldehydes via hydration and polymerization, forming hemiacetal/acetal with alcohols
H2SO4-accelerated acetal formation
[Jang and Kamens, ES&T 2001]
Links to O3 Photochemistry:
Same precursors that form O3 play also a critical role in SOA formation. The determination of SOA contribution to total ambient PM2.5 mass observed at any receptor site is very difficult due to the above complex interactions, and can only be estimated from indirect methods. Due to the significant emissions of primary PM, however, EPA’s air quality regulations mandated by the Clean Air Act require the attainment of annual NAAQS for PM2.5, whereas O3 needs to be regulated only during the summer months.
5-year Average Monthly Totals of Prescribed Burns in GA
VOC canister sampling
Photochemical processes leading to SOA linked to O3 formation, hence SOA must be expected higher in summer than in winter.
with SOA formed during transport;
Decreasing Occurrence and Size of Wild Fires With Increasing Prescribed Burns on Fort Benning, GA
Case Study of Local PM2.5 Exceedance
2) PM2.5 Seasonal Differences in Diurnal Variability
Comparison of measured (OLC) and predicted (GFC) wind data (top), boundary layer mixing height (BLH) and atmospheric stability indicators (center, with daily T max/min difference), areas of prescribed burns and wild fires incl. their directions and distances from OLC with 24 h average [PM2.5] from OLC, Griffin, Macon, and Augusta (bottom), for 5 weeks in fall 2001. The blue open circles and triangles are the state’s regulatory FRM data from Columbus’ Cusseta Rd. (5 km N of OLC) and the Health Dept. (11 km N of OLC), respectively, both missing the exceedances of the continuous OLC measurements due to their 1/3 schedule.
Correlation of 24 h [PM2.5] at OLC with total acres burnt, considering the fire location (distance and direction) relative to OLC, and the projected plume trajectory as a measure for potential plume impact (largest if equal 1, placing OLC directly downwind), with the lower atmosphere stability indicator (Tmax - Tmin), wind speed (top), and with the GFC model predicted BLH for the day the burn or wild fire occurred as well as for the succeeding night (bottom). The date labels in the legend (right) point to a continued accumulation of fine PM pollution and contribution from smoldering fires until several days after the actual flaming stage.
Regional Non-attainment of the Annual NAAQS for PM2.5 During Dry Years
OM/OC 1.9 1.5 2.2 1.6 1.9 2.1 2.0
OC/EC 15 19 8 19 26 26 26
Acres burnt 0 937 1256 3770 4006 504 251
Midday minimum due to BL mixing in winter (right) seems compensated by SOA in summer (left);Similar bimodal variability at all sites except for summer 2000 (incomplete data);PM2.5 sources near Columbus drive nighttime averages in winter 2001/02;Standard deviations of those indicate rare occurrences of extreme values;Summer stagnation with high O3 also leads to high PM2.5 (e.g. 2000);Annual PM2.5 NAAQS (15 mg m-3) sensitive to:- SOA formed under regional stagnation in summer;- Primary PM2.5 from local sources at night in winter.
Prescribed Burning and the Development of a Smoke Management Plan (SMP) in Georgia
Karsten Baumann1, Sangil Lee2, Mark Clements3, Polly Gustafson4
1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
2School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA
3Southeast Regional Office, Installation Management Agency, U.S. Army, Fort McPherson, GA
4Environmental Management Divisio0n, U.S. Army Infantry Center, Fort Benning, GA
Prescribed Burning Activities in GA
Prescribed burning (PB) is a common land management practice in GA with 24.4 million acres of forested land. Of the 17.6 million acres privately owned forests alone, more than 1 million acres are burnt annually. Most forested areas are burnt in winter and spring. Agricultural burns gain importance in summer. Highest burn intensities occur on military installations where up to 5,000 acres can be burnt on a single day. The three largest military installations are Forts Stewart, Benning, and Gordon, which burn ~50,000, 30,000 and 12,000 acres every year, respectively. Here, PB emissions were determined at three different locations and evaluated in the context of long-term air quality measurements and the development of a Smoke Management Plan (SMP) for GA.
VOC Profile of Emissions from Flaming and Smoldering
Combustion efficiency (CE)
Flaming = 91-92 % vs.
Smolder = 81-82 %
ΔC: excess C concentration
[Ward and Hao, 1992]
Georgia’s economy is heavily supported by agriculture and forestry. Both vocations utilize prescribed burning practices to cultivate agriculture and maintain healthy forests. The State of Georgia regulates open burning to assure air quality, minimize fire danger and protect wildlife species such as bob-white quail, eastern wild turkey, white-tail deer, and red-cockaded woodpecker that are protected by the Endangered Species Act (ESA) or designated by state initiatives for wildlife management. Many native songbirds and plants also depend on a natural fire ecology. Fort Benning fire statistics also show that prescribed burning reduces the occurrence and size of unwanted wild fires, and ultimately protects human lives and property. Prescribed Burning is therefore considered in the U.S. government’s Healthy Forests Restoration Act as an important measure to reduce fuel loads and the risk of catastrophic wild fires across the Nation.
The Conflict With Air Quality
The general trend in annual [PM2.5] at the State’s regulatory monitoring network is a uniform decrease across all 26 sites since 1999. This trend seems climatologically driven by precipitation, the main sink for atmospheric PM. The annual state-wide totals for the years 1999 thru 2003 were 40.9, 41.7, 42.9, 50.3, and 58.2 inches, compared to a 30-year normal (1961-1990) of 50.8 inches. All sites outside metro Atlanta benefited from the last two wet years and attained the annual NAAQS of 15 mg m-3. While the metro Atlanta sites experience the highest concentrations, the coastal sites remain the cleanest, apparently benefiting from diluting effects associated with the land-sea breeze circulation.
PM2.5 Mass and Composition at OLC near Fort Benning in 2003
“Others” includes K+, Na+, Cl-, and “LOA” includes acetate, formate and oxalate. Acres burnt are prescribed burns conducted on the Fort during each given period. The OM/OC ratios derived from mass closure provide some measure of the degree of POC oxygenation showing a trend toward higher values later in the season. The less uncertain OC/EC indicates relative change in SOA contribution, which was low early in the season, when photo-chemical activity was low (see max-O3). More SOA from regional sources in aged air masses contributed to total POM at the end, while more primary OPOC contributed earlier in the season.
Conclusions and Outlook
Part of this work was funded by the EPA/DOD Region 4 Pollution Prevention Partnership Small Grants Program and the U.S. Army Corps of Engineers via Engineering & Environment, Inc. subcontract NC03-05SUB01. The FAQS is directed by Dr. Michael Chang from EAS at Georgia Tech. OLC members from Columbus State University and LMB Personnel from Forts Benning and Gordon assisted with the VOC sampling and provided burn data. The VOC analysis was performed by Dr. Don Blake at UC Irvine. Daniel Chan from the Georgia Forestry Commission (GFC) provided state-wide burn data and forecast products.