Characterisation of Diesel Exhaust from Military Vehicles

Introduction The Australian Defence Force (ADF) operates a large fleet of vehicles fitted with diesel engines of various types and age. They include special purpose vehicles such as tracked (M113A1) and wheeled (ASLAV) armoured personnel carriers with unusual exhaust configurations. This combined with the design of the vehicle and location of personnel can result in atypical exposures to engine exhaust emissions. Thus a study was undertaken to determine the concentrations and characteristics of diesel exhaust particulates (DPM) in the breathing zone of vehicle occupants. Experimental Vehicle trials were conducted on test circuits in a rural area, free from vehicular pollution. Continuous measurements of exhaust emissions were made at four locations in the vehicles for PM10, fine particles in the size range 0.3 μm – 20 μm, polynuclear aromatic hydrocarbon (PAH) concentrations, NOx, CO and VOCs. Quartz and Teflon filter samples were also obtained for PAH and soluble inorganic ion analyses but loadings were insufficient. Mass size distributions using the MOUDI multistage impactor were determined under engine idling conditions. Results and Discussion PM10 levels were found to vary with passenger location, vehicle speed and load, as expected (CARB 1998). Transient DPM concentrations ranged from 0.05-5 mg m. Mass size distributions, under idling conditions, were bimodal and differed between normally aspirated (M113A1) and turbo-charged engines (ASLAV) as shown in Fig. 1, consistent with findings reported elsewhere (Kittelson 2002). Particle number concentrations generally tracked mass concentrations and varied with time as the engine load and vehicle speed changed (Fig. 2). PAH measurements (Fig. 3) indicated good correlation with DPM concentrations. DPM levels also correlated with NOx, CO and VOCs, indicating little interference from road dust. Progress is underway to determine the size fractionated chemical composition of DPM using the Sioutas design multistage impactor (Misra 2002). Conclusions The exposure levels were affected by location of personnel and engine load conditions in both the M113A1 and ASLAV vehicles. MOUDI For M113 and Aslav