The objectives of this project were twofold. The first objective was to conduct real-time non-refractory chemical content and size distribution characterization of the fine particulate fraction (0.04 to approximately 1.0 mm diameter) of aerosol generated during the open-air discharge of select Army artillery. The second objective was to conduct an assessment of potential health hazards gun crews may be exposed to from respirable fine particles and selected toxic gases during real-world firing conditions.

The aerosol mass spectrometer (AMS) and a complementary suite of aerosol and gas-phase instruments have the necessary time-response and sensitivity to monitor gun-discharge plumes in real-time and in an open environment. The instrument suite was installed on a mobile laboratory and coupled to a customized, multiline sampling system. The mobile laboratory provided the flexibility to maneuver close to any particular gun and deploy relatively short sampling lines to interrogate the time-dependent aerosol and gaseous pollutant loading around the gun position.

Emission indices (mass of pollutant/mass of propellant energetic material) for quantified gaseous and particulate matter (PM) chemical species or species classes were computed from emission plume trace species and major carbon gas (CO + CO₂) concentrations. Propellant carbon mass balances were used to correct for plume dilution by ambient air. Time traces of solider breathing zone trace gas and fine PM emissions concentrations for the relatively high wind conditions present during the sampled firing sequences were also determined along with representative ambient background measurements before and after firing sequences. The plume emission indices and breathing zone data have been provided to the U.S. Army Center for Health Promotion and Preventive Medicine for evaluation of potential health risks for gun crews and individual weapons operators under weapons training conditions.

Given the results of this project, it is possible that under some scenarios Army gun crews may be subject to extremely high transient loadings of fine respirable particulates. Using the AMS, the characterization of airborne fine particle content was possible on time scales as short as 1-3 seconds. Data obtained from this project can be analyzed to determine the health risk of personnel downwind of the gun. (Project Completed – 2008)