Comprehensive Simultaneous Shipboard and Airborne Characterization of Exhaust from a Modern Container Ship at Sea

Abstract

We report the first joint shipboard and airborne study focused on the chemical composition and water-uptake behavior of particulate ship emissions. The study focuses on emissions from the main propulsion engine of a Post-Panamax class container ship cruising off the central coast of California and burning heavy fuel oil. Shipboard sampling included microorifice uniform deposit impactors (MOUDI) with subsequent offline analysis, whereas airborne measurements involved a number of real-time analyzers to characterize the plume aerosol, aged from a few seconds to over an hour. The mass ratio of particulate organic carbon to sulfate at the base of the ship stack was 0.23 ( 0.03, and increased to 0.30 ( 0.01 in the airborne exhaust plume, with the additional organic mass in the airborne plume being concentrated largely in particles below 100 nm in diameter. The organic to sulfate mass ratio in the exhaust aerosol remained constant during the first hour of plume dilution into the marine boundary layer. The mass spectrum of the organic fraction of the exhaust aerosol strongly resembles that of emissions from other diesel sources and appears to be predominantly hydrocarbon-like organic (HOA) material. Background aerosol which, based on air mass back trajectories, probably consisted of aged ship emissions and marine aerosol, contained a lower organic mass fraction than the fresh plume and had a much more oxidized organic component. A volume-weighted mixing rule is able to accurately predict hygroscopic growth factors in the background aerosol but measured and calculated growth factors do not agree for aerosols in the ship exhaust plume. Calculated CCN concentrations, at supersaturations ranging from 0.1 to 0.33%, agree well with measurements in the ship-exhaust plume. Using sizeresolved chemical composition instead of bulk submicrometer composition has little effect on the predicted CCN concentrations because the cutoff diameter for CCN activation is larger than the diameter where the mass fraction of organic aerosol begins to increase significantly. The particle number emission factor estimated from this study is 1.3 × 10 16 (kg fuel) -1 , with less than 1 / 10 of the particles having diameters above 100 nm; 24% of particles (>10 nm in diameter) activate into cloud droplets at 0.3% supersaturation.

Source apportionment of PM<sub>2.5</sub> in Cork Harbour, Ireland using a combination of single particle mass spectrometry and quantitative semi-continuous measurements

“…While local vehicular traffic was the largest source of ambient PM 2.5 mass in Cork Harbour during the sampling period, shipping traffic contributed significantly to ambient particle number concentrations (18%). Considering that fresh ship exhaust particles reside predominantly in the ultrafine mode and contain polycyclic aromatic hydrocarbons and transition metals with known toxicological effects, this source may have implications for human health in the area (Lippmann et al, 2006;Peltier et al, 2008;Murphy et al, 2009;Healy et al, 2009;Sodeau et al, 2009). …”

Global anthropogenic emissions of particulate matter including black carbon

“…load factors (Agrawal et al, 2008(Agrawal et al, , 2010Lack et al, 2008Lack et al, , 2009Moldanova et al, 2009;Murphy et al, 2009;Petzold et al, 2008Petzold et al, , 2010. Further studies have reviewed and compared emission factors (Buhaug et al, 2009;Dalsøren et al, 2009;Lack and Corbett, 2012).…”

A coupled observation – modeling approach for studying activation kinetics from measurements of CCN activity

“…To account for hygroscopicity and dry size differences between aerosol, both droplet sizes are selected from the point where activation is first observed. TDGA has been applied to several ambient aerosol samples (AsaAwuku et al, 2011;Bougiatioti et al, 2009Bougiatioti et al, , 2011Lance et al, 2009;Murphy et al, 2009;Padró et al, 2010Padró et al, , 2011Cerully et al, 2011), secondary organic aerosol (SOA) (Engelhart et al, 2008(Engelhart et al, , 2011Asa-Awuku et al, 2009 and laboratory-generated aerosol (Moore et al, 2008;Kumar et al, 2011a,b). In general, slower kinetics than calibration aerosol have been related to insoluble organics from SOA chamber experiments (Asa-Awuku et al, 2009), fresh exhaust plumes , and mineral dust particles when using a dry generation technique (Kumar et al, 2011a,b).…”

“…If critical supersaturation s c s after the instrument supersaturation develops (typical of large hygroscopic particles), one can assume that s − s eq ≈ s (Nenes et al, 2001). Then from applying the chain rule to Eq.…”

“…Subsaturated growth occurs in equilibrium with the ambient relative humidity, but growth and activation under supersaturated conditions are kinetically limited by the availability of water vapor and gas-and aerosol-phase mass transfer resistances (e.g. Chuang et al, 1997;Nenes et al, 2001). Consequently, droplet growth rates can be affected by delays in solute dissolution (Asa-Awuku and Nenes, 2007), formation of organic surface films (Chuang, 2003) and, possibly, glassy aerosol states (Zobrist et al, 2008;Virtanen et al, 2010;Tong et al, 2011;Koop et al, 2011).…”