Using DUSTRAN to Simulate Fog-Oil Dispersion and Its Impacts on Local Insect Populations at Ft. Hood: Final Report

Abstract

SummarySmokes and obscurants (S&O) are important screening agents used during military training exercises on many military installations. Although the use of S&O is subject to environmental laws, the fate and effects of S&O on natural habitats are not well documented. One particular concern is the impact S&O may have on local insect populations, which can be important components of terrestrial food chains of endangered species. Fog-oil (FO) is an S&O that is of particular concern. An important part of assessing potential ecosystem impacts is the ability to predict downwind FO concentrations.This report documents the use of the comprehensive atmospheric dispersion modeling system DUST TRANsport (DUSTRAN) to simulate the downwind transport and diffusion of a hypothetical FO release on the U.S. Army installation at Ft. Hood, TX. FO is used as an obscurant during certain training exercises at Ft. Hood, which is home to two endangered migratory avian species-the black-capped vireo and golden-cheeked warbler-from April to August. These birds forage on local insect populations, some of which potentially could be affected by FO releases.Meteorological and source-term inputs required for DUSTRAN are explained, and representative values for the Ft. Hood site are presented. These values are used in simulating a hypothetical FO release. Modeled concentration results are compared with toxicological thresholds developed by project biologists at Pacific Northwest National Laboratory for certain insect types. Simulated results suggest that FO impacts to specific insect types, if any, will occur very near the source. To further support this finding, the conservative, straight-line Gaussian plume equation is used to estimate maximum downwind distances of possible toxicological effects for common meteorological stability classes. Conservative results indicate that impacts are likely to be within 400 meters of the FO source.Several advanced analysis topics are reviewed that, in conjunction with the DUSTRAN User's Guide (Allwine et al. 2006), can be used to further investigate FO releases and their potential toxicological impacts. Specific guidance is provided on adjusting concentration levels and contour colors within the DUSTRAN modeling system; such functionality can be useful for identifying and plotting lethal-dose concentrations that cause a toxicological response in specific insect types. The "Polygon Layer Creator" utility is introduced and can be used to create polygons (i.e., areas) that represent insect populations for specific insect types. These polygons can be added and displayed within the DUSTRAN modeling system, and the area shared with model-calculated concentration contours can be determined. A sample stepwise procedure for setting up such a query is presented in Appendix B.