Particulate matter (PM) is one of the six pollutants regulated by National Ambient Air Quality Standards (NAAQS) issued by the United States Environmental Protection Agency (USEPA). Fugitive dust refers to the re-suspended dust from soil surfaces due to surface disturbance. The dust imposes considerable health concerns by carrying virus and bacteria, which can be inhaled into human respiratory tracts. Dust also obscures visibility and can impact the effectiveness of military training.  To protect visual air quality, the Regional Haze Rule was adopted during 1999 to protect visibility at Environmental Protection Agency-designated Class I areas, such as national parks, forests, and wilderness areas, by controlling anthropogenic PM emissions. The Regional Haze Rule requires that anthropogenic emissions to the atmosphere be reduced to the extent that visibility is not noticeably degraded more than it would be under natural conditions.

Helicopter-Generated Swirling Dust Clouds

The Department of Defense (DoD) has been concerned about the emissions of fugitive dust from its training and testing ranges; however, little is known about dust emissions from military activities. As a result, the objectives of this study were to: (1) identify, characterize, and monitor airborne PM with aerodynamic diameters ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5) from fugitive dust emissions that are caused by unique military sources; (2) develop and modify instrumentation, methods, and systems to determine PM emission factors; (3) determine PM dust emission factors for artillery back blasts, the movement of tracked and wheeled vehicles, and flying helicopters; (4) develop model components that better describe the generation of the DoD’s fugitive PM; and (5) quantify the variability and uncertainty of these emissions.

To quantify the PM mass emissions for dust plumes generated by unique military activities, a method was developed that used optical remote sensing (ORS) devices and DustTrak^TM (DT) aerosol monitors. Two versions of the ORS system were used in this study. The first version consisted of a ground-based Micro-Pulse Lidar (MPL) that was located on a positioner to control the vertical measurement angle of the MPL, two mono-static Open-Path Fourier Transform Infrared spectrometers (OP-FTIRs), and two Open-Path Laser Transmissometers (OP-LTs). The second version, which is also referred to as the hybrid version, consisted of an MPL, an OP-LT, and three ground-level DT aerosol monitors. The ground-level component was accomplished in partnership with SERDP project: Particulate Matter Emissions Factors for Dust from Unique Military Activities (RC-1399).

The ORS method developed in this research first determines the dust’s extinction profiles via inversion of the Lidar equation from the normalized relative backscattering (NRB) signals that are corrected from raw MPL signals. The one-dimensional (1-D) extinction profiles are combined to provide two-dimensional (2-D) extinction profiles by interpolating the data along all scan-paths in a scan cycle. These 2-D extinction profiles are then converted into 2-D PM mass concentration profiles by multiplying extinction efficiency factors, which are determined with two algorithms corresponding to the two previously described versions of the ORS systems.  Finally, emission factors are determined by integrating all vertical 2-D mass concentration profiles with the duration of each plume event and the wind speeds and directions measured by the co-located anemometers. 

Three types of military activities that generate fugitive dust were characterized during this research project. The activities included firing of artillery, movement of tracked and wheeled vehicles, and flying of helicopters. Regressions were developed to determine PM-mass emission factors based on type of fugitive source, speed of the mobile sources, and momentum of the mobile sources.

This project successfully developed and implemented a novel ORS technique to quantify fugitive dust PM emissions from unique military operations. 

Specific results from the four field campaigns include:

1.  Fugitive dust emission factors for tracked and wheeled vehicles were quantified for PM _2.5 and PM₁₀ and statistical trends were established based on vehicle speed and momentum providing two options to model the PM-mass emission factors when developing PM-mass emission inventories for DoD installations.

2.  Fugitive dust emission factors for tracked and wheeled vehicles were quantified for PM _2.5 and PM₁₀ and statistical trends were established based on vehicle speed and momentum providing two options to model the PM-mass emission factors when developing PM-mass emission inventories for DoD installations.

3.  The tested wheeled vehicle (i.e., HEMTT) generates approximately twice the amount of dust in comparison to the tested tracked vehicles. This suggests that the properties of the wheel and their enclosures are important considerations when determining methods to reduce dust emissions from select types of vehicles.

4.  Helicopter dust emission factors were successfully quantified with their dependence on helicopter speed with correlation coefficients ≥0.81. In contrast to vehicular travel, faster traveling helicopters generated less dust per unit distance traveled than slower traveling helicopters.

This research provides DoD installations with the capability to measure PM emission factors using real time, in-situ, continuous, simple and economical methods. Results from these methods can be used to estimate the generation of fugitive dust from military activities. These methods allow for the development of emission inventories for facilities and more effective environmental compliance and PM control strategies. In addition to cost savings, the PM data management and storage is simpler than conventional measurement technologies.