Particulate matter (PM) emission is a critical problem for the Department of Defense (DoD). PM emitted during DoD testing and training activities threatens the safety and respiratory health of military personnel and can impact the health of urban populations encroaching on military installations. Moreover, new regulations protecting visibility at Environmental Protection Agency-designated Class I national parks, forests, and wilderness areas mandate reductions in PM emissions and their chemical precursors over the next 60 years. Because many military installations are located near Class I areas, these regulations have the potential to affect training activities in coming years. Military activities have unique dust emission sources not encountered in the civilian environment, which have not been accurately characterized and quantified. Without source-specific emissions factors of known precision and accuracy, the uncertainties on these estimates are high.

This project focused on developing an understanding of the dust emission process and strength of these emissions for artillery backblast on improved gun-sites (surface treated with dust palliatives), tracked and wheeled vehicles travelling on unpaved surfaces, and rotary-winged aircraft travelling close to desert surfaces.  The main objective was to develop PM emission factors for military-unique activities in support of a documented database and dust dispersion model that could be used to estimate DoD impacts to air quality.

Field-based in situ measurement campaigns were carried out to quantify dust emissions and to develop emission factors for unique DoD sources. In partnership with SERDP project: Development of Emission Factors for Dust Generated by Unique Military Activities (RC-1400), a hybrid measurement system for estimating fugitive emissions of dust also was tested, which combined elements of optical remote sensing and the in situ measurements. These various campaigns were undertaken at the Yuma Proving Ground (YPG), Yuma, Arizona; Yakima Training Center (YTC), Yakima, Washington; and Ft. Carson, Colorado. Measured emission factors were linked with indices of surface dust emission potential using a new portable wind tunnel and an on-vehicle measurement system, thereby creating a cost-effective mechanism to extend the use of the emission factors into different environments (i.e., establish transfer standards). A database was developed from the field and laboratory measurements to characterize the chemical, physical, and optical properties of the dust emissions, which are important for assessing source contribution estimates and impacts on regional visibility degradation.

Based on the measured dust emissions from unique DoD sources, the greatest amount of emissions is from tracked and wheeled vehicles because of their high emission rates and frequency of use. Dust emissions from both artillery backblast and rotary-winged aircraft are representative of only minor contributing sources in the overall attribution of airborne particulates to DoD sources.

The hybrid approach showed that such a system will enable the development and eventual deployment of other open path extinction measurements tools, such as LIDAR or digital cameras, which can be used to develop fugitive PM emission factors.

The dust emission relationships and defined emission factors developed as part of this project were incorporated into the DUSTRAN model developed in SERDP project: Development of a GIS-Based Complex Terrain Model for Atmospheric Dust Dispersion (RC-1195), which can be used to forecast and hind-cast dust emissions based on testing and training scenarios involving these source types with knowledge of the meteorology.

The successful completion of this project also produced valuable information on the comparability of in situ and remote sensing measurements to quantify fugitive dust emissions. In addition, this research made advances in the understanding of the physics of the dust emission processes for sources that have not been previously quantified. This insight is not only of direct importance to the DoD, which now has access to the developed emission factor relationships to improve upon their emission inventories, but also has the potential to assist with other problems faced by the DoD regarding operations of their vehicles and aircraft under conditions impacted by dust.