Dust emissions from training and testing operations are of increasing concern because many military installations are either in nonattainment areas for PM10 or are near mandatory Class I air quality areas. Most fugitive dust mass is emitted in particles larger than 2.5 ìm in aerodynamic diameter, but it is the PM2.5 fraction (particles with aerodynamic diameters less than 2.5 ìm) that remains suspended and travels long distances impacting visibility and human health. Prior work on fugitive dust emissions from unpaved roads and industrial sites was not specific to PM2.5 or the alkaline desert soils that are typical of western military bases.

 The objective of this project was to provide installationlevel environmental staff with scientifically validated information for developing emissions inventories through the development of improved fugitive source chemical characterization profiles and the evaluation of the effects of vertical mixing and near-source redeposition.

Source apportionment of ambient particulate by chemical analysis of sources and of receptor samples is an important technique for studying causes of air pollution and for validating predictions from source inventory and transport models. Field studies evaluated site-specific fugitive dust particle characteristics using both the analytical techniques routinely used by ambient monitoring networks and research techniques for organic species. The field studies also tested the hypothesis that current PM2.5 emission factors overstate the regional impact of fugitive dust because they do not properly account for vertical mixing, deposition, and impaction near the source. This involved monitoring the dust plume using tower-mounted instruments combined with computational modeling.

This project addressed the question of whether dust from military training range activities could be distinguished from dust from other sources in an airshed. Database analysis and new field studies—including sites at Fort Bliss, Texas, at Camp Williams, Utah, and at Dugway Proving Ground, Utah—led to the unexpected finding that soil chemical composition was better correlated with U.S. Department of Agriculture soil unit than with surface land use. Also, the studies found that no major differences were present in the chemical composition of PM10, PM2.5, and PM1 fugitive dust from roads. Current fugitive dust emission factors do not consider the effect of surface roughness and atmospheric stability on the fraction of dust transported. Computational modeling combined with field studies at Dugway Proving Ground and Fort Bliss have shown that the fraction of initially suspended dust that is transported more than a few hundred meters from the source can vary from nearly 100% to less than 20% depending on site conditions.

Partitioning of dust between transport and redeposition may explain the difference between source inventory and receptor site estimates of PM2.5 emissions.

The results of this study were integrated with concurrent civilian fugitive dust studies to provide installation-level environmental staff with scientifically validated information for developing emissions inventories, environmental assessments, and cost-effective dust control measures that are compatible with mission readiness. (Project Completion - 2005)