Characterization of Submicron Exhaust Particles from Engines Operating Without Load on Diesel and JP-8 Fuels

Diluted exhaust from a selection of Air Force ground support vehicles was subjected to gravimetric, carbon, and size distribution analyses in September 1999. The vehicles operated on diesel and JP-8 fuels. In most cases, the engines involved were similar to civilian counterparts. The tests involved "low" and "high" idle settings but no external loads were imposed. Particle size distribution data, obtained over the 10 to 352 nanometer diameter range using an SMPS instrument, showed that the relative number count of accumulation mode particles increased with respect to nucleation mode particles as the engine rpm increased. The SMPS distributions often explained the main variations in the integrated PM 2.5 gravimetric mass data. Particulate mass derived from the SMPS data and from cascade impactor measurements were well correlated (regression slope 1.02). Empirically determined "elemental" carbon (EC) and "organic" carbon (OC) were the main constituents of the PM 2.5 gravimetric mass (regression slope 0.89). EC contributed less, and OC contributed more to the PM 2.5 mass than was found in some recent studies of exhaust from vehicles operated under external loads. The observed particle nucleation modes were attenuated by coagulation with accumulation mode particles, but it does Address correspondence to C. Fred Rogers, Desert Research Institute, Division of Atmospheric Sciences, University and Community College System of Nevada, 2215 Raggio Parkway, Reno, NV 89512. E-mail: [email protected] not appear that artifact particle formation was operative in these experiments. The estimated ±1σ measurement precisions range from about ±4% for the largest impactor mass concentration determinations to ±24% for some of the SMPS mass concentration estimates

Perchlorate behavior in the context of black carbon and metal cogeneration following fireworks emission at Oak Lake, Lincoln, Nebraska, USA

The imprints of fireworks displays on the adjacent water body were investigated from the perspective of cogeneration of black carbon, metals and perchlorate (ClO4?). In particular, the mixing and dissipation of ClO4? were studied at Oak Lake, Lincoln, Nebraska, following fireworks displays in 2015 and 2016. Following the display, ClO4? concentration in the water increased up to 4.3??g/L and 4.0??g/L in 2015 and 2016, respectively. A first-order model generally provided a good fit to the measured perchlorate concentrations from which the rate of dissipation was estimated as 0.07 d?1 in 2015 and 0.43 d?1 in 2016. SEM images show imprints of soot and metal particles in aerosol samples. EDS analysis of the lake sediment confirmed the presence of Si, K, Ca, Zn and Ba, most of which are components of fireworks. The ?13C range of ?7.55� to ?9.19� in the lake water system closely resembles fire-generated carbon. Cogeneration of black carbon and metal with perchlorate was established, indicating that ClO4? is an excellent marker of fireworks or a burning event over all other analyzed parameters. Future microcosmic, aggregation and column-based transport studies on black carbon in the presence of perchlorate and metals under different environmental conditions will help in developing transport and fate models for perchlorate and black carbon particles.by Manish Kumar, Daniel D. Snow, Yusong Li and Patrick J.She