Characterisation of particulate matter and gaseous emissions from a large ship diesel engine

Composition of exhaust from a ship diesel engine using heavy fuel oil (HFO) was investigated onboard a large cargo vessel. The emitted particulate matter (PM) properties related to environmental and health impacts were investigated along with composition of the gas-phase emissions. Mass, size distribution, chemical composition and microphysical structure of the PM were investigated. The emission factor for PM was 5.3 g (kg fuel)^?1. The mass size distribution showed a bimodal shape with two maxima: one in the accumulation mode with mean particle diameter D_P around 0.5 μm and one in the coarse mode at D_P around 7 μm. The PM composition was dominated by organic carbon (OC), ash and sulphate while the elemental carbon (EC) composed only a few percent of the total PM. Increase of the PM in exhaust upon cooling was associated with increase of OC and sulphate. Laser analysis of the adsorbed phase in the cooled exhaust showed presence of a rich mixture of polycyclic aromatic hydrocarbon (PAH) species with molecular mass 178–300 amu while PM collected in the hot exhaust showed only four PAH masses.Microstructure and elemental analysis of ship combustion residuals indicate three distinct morphological structures with different chemical composition: soot aggregates, significantly metal polluted; char particles, clean or containing minerals; mineral and/or ash particles. Additionally, organic carbon particles of unburned fuel or/and lubricating oil origin were observed. Hazardous constituents from the combustion of heavy fuel oil such as transitional and alkali earth metals (V, Ni, Ca, Fe) were observed in the PM samples.Measurements of gaseous composition in the exhaust of this particular ship showed emission factors that are on the low side of the interval of global emission factors published in literature for NO_x, hydrocarbons (HC) and CO.     

Ion-soot interaction: a possible mechanism of ion removal in aircraft plume

The phenomenon of the ion-soot interaction in the aircraft plume at the ground conditions is investigated. The ion-soot attachment coefficients, taking into account the polarization of the soot particles in the ion electric field, are calculated. It is shown that the ion-soot attachment may play the important role in the evolution of the ion concentrations in the plume. Comparison of the model results with the ground-based measurements for the ion depletion along the plume demonstrates that the concentration of the positive and negative ions at the nozzle exit for these observations is close to 1.2 x 10(8) cm(-3).     

Wetting and hydration of insoluble soot particles in the upper troposphere

Wettability and hydration are determined for aircraft combustor and laboratory-made soots which are used as surrogates for the insoluble part of aircraft-generated black carbon particles in the upper troposphere (UT). The measured water/ice contact angles on the soot surfaces are in the range 60-80 degrees. Factors influencing the soot wetting show a tremendous dependence on the surface chemical composition and microstructure. Wetting characteristics of soots are directly related to its hydrophilicity. The inverse Kelvin effect is considered as a mechanism of ice nucleation which is facilitated by the soot agglomerated structure with interparticle cavities in which condensation takes place on the insoluble surface with a high water contact angle. Estimations of the critical supersaturations needed for the ice condensation growth of particles are provided to determine which of the wetting characteristics are required for cirrus cloud formation in ice saturated regions of the UT.