Downwind real-time PM2.5 and CO monitoring during prescribed forest burns at Fort Benning, GA
MetadataShow full item record
Background: Prescribed forest burning has long been recognized as a significant source of various air pollutants including particulate matter with an aerodynamic diameter ≤ 2.5 μm (PM2.5) and carbon monoxide (CO). However, few studies have evaluated downwind exposures, especially using real-time monitoring methods with a strategy to capture instantaneous downwind exposures with mobile samplers to accommodate change of wind directions. Objectives: Our specific objectives were to: 1) estimate ground-level smoke exposure levels (as indicated by PM2.5 and CO); 2) determine if distance to the fire and time since burn ignition have any significant effect on the exposure levels of PM2.5 and CO. Methods: Smoke data was collected from air samplers mounted on three trucks that were assigned to three different sampling zones downwind from the prescribed forest burns. Sampling zones were within a 60 degree arc started downwind from the center of the burn with a sampling scale of 1-3 kilometers (Km) in Zone 1; 3-5 Km in Zone 2; 5-7 Km in Zone 3. In order to capture as much smoke as possible, trucks moved within their designated sampling zones to the best degree possible to remain under the plume. PM2.5 was sampled using TSI DustTrak Model 8520 aerosol monitors. CO was sampled with Langan CO Monitor Model T15v and Draeger PAC III CO Monitors. Sampling started around 12:00 and continued until approximately 15:30 for each of the 11 sampling days. Results: Exposure to PM2.5 was highly variable and significantly affected by the distance to burn area (P = 0.018) and the time since burn ignition (P < 0.001). Geometric mean (GM) concentrations of PM2.5 calculated from 15-minute moving averages ranged from 3 μg/m3 to 104 μg/m3, with a maximum 15-minute moving average of 403 μg/m3. In comparison with PM2.5, CO levels were fairly low, with a highest maximum 15-minute moving average at 3.1 ppm and all daily (3-hour sampling duration) GM values less than 2 ppm. Conclusion: Our findings suggest that smoke exposures downwind from prescribed forest burns may at times be high enough to warrant public health concern.