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Though the current wave of electric vehicles is transforming the on-road passenger and commercial vehicle fleets, similar attempts in the off-road equipment sector appear to be lacking. Because of the diverse equipment categories and varied applications, electrifying off-road equipment requires significant research and development. A successful electrification of such equipment can offer an array of benefits, including reduced air and noise pollution, higher energy efficiency, and increased productivity. This paper provides a review of the current state of technology in off-road equipment electrification, with a focus on the equipment used in construction and agricultural applications. The paper also discusses advantages of, and challenges associated with, electrifying off-road construction and agricultural equipment. In addition, potential solutions for overcoming these challenges as well as opportunities to facilitate the electrification of off-road construction and agricultural equipment are identified. 

Abstract. Understanding the properties and life cycle processes of aerosol particles inregional air masses is crucial for constraining the climate impacts ofaerosols on a global scale. In this study, characteristics of aerosols in theboundary layer (BL) and free troposphere (FT) of a remote continental regionin the western US were studied using a high-resolution time-of-flight aerosolmass spectrometer (HR-AMS) deployed at the Mount Bachelor Observatory (MBO;2763 m a.s.l.) in central Oregon in summer 2013. In the absence of wildfireinfluence, the average (±1σ) concentration of non-refractorysubmicrometer particulate matter (NR-PM1) at MBO was 2.8 (±2.8)µg m−3 and 84 % of the mass was organic. The otherNR-PM1 components were sulfate (11 %), ammonium (2.8 %),and nitrate (0.9 %). The organic aerosol (OA) at MBO from these cleanperiods showed clear diurnal variations driven by the boundary layer dynamicswith significantly higher concentrations occurring during daytime, upslopeconditions. NR-PM1 contained a higher mass fraction of sulfate andwas frequently acidic when MBO resided in the FT. In addition, OA in the FTwas found to be highly oxidized (average O∕C of 1.17) with lowvolatility while OA in BL-influenced air masses was moderately oxidized(average O∕C of 0.67) and semivolatile. There are indications thatthe BL-influenced OA observed at MBO was more enriched in organonitrates andorganosulfur compounds (e.g., MSA) and appeared to be representative ofbiogenic secondary organic aerosol (SOA) originated in the BL. A summary ofthe chemical compositions of NR-PM1 measured at a number of otherhigh-altitude locations in the world is presented and similar contrastsbetween FT and BL aerosols were observed. The significant compositional andphysical differences observed between FT and BL aerosols may have importantimplications for understanding the climate effects of regional backgroundaerosols. 

Abstract. During the first phase of the Biomass Burn Operational Project (BBOP) fieldcampaign, conducted in the Pacific Northwest, the DOE G-1 aircraft was usedto follow the time evolution of wildfire smoke from near the point ofemission to locations 2–3.5 h downwind. In nine flights we maderepeated transects of wildfire plumes at varying downwind distances andcould thereby follow the plume's time evolution. On average there was littlechange in dilution-normalized aerosol mass concentration as a function ofdownwind distance. This consistency hides a dynamic system in which primaryaerosol particles are evaporating and secondary ones condensing. Organicaerosol is oxidized as a result. On all transects more than 90 % ofaerosol is organic. In freshly emitted smoke aerosol, NH4+ isapproximately equivalent to NO3. After 2 h of daytime aging, NH4+ increased and is approximately equivalent tothe sum of Cl, SO42, and NO3. Particle size increased with downwind distance,causing particles to be more efficient scatters. Averaged over nine flights,mass scattering efficiency (MSE) increased in ∼ 2 h by 56 % and doubled in one flight. Mechanisms for redistributing mass from small to large particles are discussed. Coagulation is effective at movingaerosol from the Aitken to accumulation modes but yields only a minor increase in MSE. As absorption remained nearly constant with age, the timeevolution of single scatter albedo was controlled by age-dependentscattering. Near-fire aerosol had a single scatter albedo (SSA) of 0.8–0.9. After 1 to 2 h of aging SSAs were typically 0.9 and greater. Assuming global-average surface and atmospheric conditions, the observedage dependence in SSA would change the direct radiative effect of a wildfire plume from near zero near the fire to a cooling effect downwind.