Reducing the exhaust emissions of unregulated pollutants from small gasoline engines with alkylate fuel and low-ash lube oil.

We report exhaust emissions of regulated and unregulated gaseous compounds (aromatic, oxygenated, and nitrogen-containing compounds), particle mass and soot content for a series of 5 utility hand-held machines typically used in gardening and forestry operation in Europe. The engines were tested in the Vehicle Emissions Laboratory of the European Commission - Joint Research Centre. Two fuels, standard and alkylate fuel (trace content of aromatics), and 2 lubricant oils (semi-synthetic and low-ash) were used. With the standard fuel, we observed average emissions from 8 g/h up to 103 g/h of hydrocarbons and from 162 g/h up to 275 g/h of carbon monoxide (regulated compounds). A consistent fraction of aromatics was identified in the exhaust: 5-10 g/h of toluene and 1.7-3 g/h of benzene for the 2-stroke engines (below 0.6 g/h for the 4-strokers). The use of the alkylate fuel resulted beneficial in the reduction of several chemical species, in particular all the monitored aromatics (70-100% reduction) and the soot content of the emitted particles (27-90% reduction). These reductions can mitigate the adverse health effects of some toxic or carcinogenic compounds (e.g. toluene and benzene) especially for professional users with high exposure risk. The use of the low-ash lube oil had a lower impact than the fuel change and was engine- and compound-specific. The carbon monoxide emission limit reduction and the introduction of the alkylate fuel would be already feasible actions based on this study and existing scientific literature.

Intercomparison of real-time tailpipe ammonia measurements from vehicles tested over the new world-harmonized light-duty vehicle test cycle (WLTC).

Four light-duty vehicles (two diesel, one flex-fuel, and one gasoline vehicle) were tested as part of an intercomparison exercise of the world-harmonized light-duty vehicle test procedure (WLTP) aiming at measuring real-time ammonia emissions from the vehicles' raw exhaust at the tailpipe. The tests were conducted in the Vehicle Emission Laboratory (VELA) at the European Commission Joint Research Centre (EC-JRC), Ispra, Italy. HORIBA, CGS, and the Sustainable Transport Unit of the Joint Research Centre (JRC) took part in the measurement and analysis of the four vehicles' exhaust emissions over the world-harmonized light-duty vehicle test cycle class 3, version 5.3 using a HORIBA MEXA 1400 QL-NX, a CGS BLAQ-Sys, and the JRC Fourier transform infrared spectrometer, respectively. The measured ammonia concentrations and the emission profiles revealed that these three instruments are suitable to measure ammonia from the vehicles' raw exhaust, presenting no significant differences. Furthermore, results showed that measurement of ammonia from the vehicle exhaust using online systems can be performed guaranteeing the reproducibility and repeatability of the results. While no ammonia was detected for any of the two diesel vehicles (even though, one was equipped with a selective catalytic reduction system), we report average ammonia emission factors 8-10 mg/km (average concentrations 20-23 ppm) and 10-12 mg/km (average concentrations 22-24 ppm) for the flex-fuel and gasoline vehicles, respectively.

Volatility of organic aerosol: evaporation of ammonium sulfate/succinic acid aqueous solution droplets.

Condensation and evaporation modify the properties and effects of atmospheric aerosol particles. We studied the evaporation of aqueous succinic acid and succinic acid/ammonium sulfate droplets to obtain insights on the effect of ammonium sulfate on the gas/particle partitioning of atmospheric organic acids. Droplet evaporation in a laminar flow tube was measured in a Tandem Differential Mobility Analyzer setup. A wide range of droplet compositions was investigated, and for some of the experiments the composition was tracked using an Aerosol Mass Spectrometer. The measured evaporation was compared to model predictions where the ammonium sulfate was assumed not to directly affect succinic acid evaporation. The model captured the evaporation rates for droplets with large organic content but overestimated the droplet size change when the molar concentration of succinic acid was similar to or lower than that of ammonium sulfate, suggesting that ammonium sulfate enhances the partitioning of dicarboxylic acids to aqueous particles more than currently expected from simple mixture thermodynamics. If extrapolated to the real atmosphere, these results imply enhanced partitioning of secondary organic compounds to particulate phase in environments dominated by inorganic aerosol.

Evaporation kinetics of a non-spherical, levitated aerosol particle using optical resonance spectroscopy for precision sizing.

We describe how a time series of optical resonance spectra of an evaporating, non-spherical, irregular aerosol particle levitated in an electrodynamic balance exhibits patterns which are related to its evaporation kinetics. Simulated spectra of an evaporating, model aerosol particle show comparable features. If these patterns are used to deduce the particle size change with time, the resulting vapor pressures and enthalpies of vaporization compare favorably with literature data for both crystalline ammonium nitrate and succinic acid particles.

White light Mie resonance spectroscopy used to measure very low vapor pressures of substances in aqueous solution aerosol particles.

We report a novel and fairly simple optical technique for sizing and measuring the evaporation rates of aqueous solution aerosol particles. A ball-lens LED with high degree of spatial coherence is used as a "white" light source to excite the Morphology Dependent Resonance (MDR) spectra of a microdroplet levitated in an electrodynamic balance (EDB). The spectra are recorded by an Optical Multichannel Analyzer. We show that very low vapor pressures of substances in aqueous solution particles can be measured for different temperatures and relative humidities (hence for different concentrations). As an application we measured the vapor pressure and the enthalpy of vaporization of aqueous malonic acid, a substance of interest for atmospheric science.