Two-stroke scooters are a dominant source of air pollution in many cities.

Fossil fuel-powered vehicles emit significant particulate matter, for example, black carbon and primary organic aerosol, and produce secondary organic aerosol. Here we quantify secondary organic aerosol production from two-stroke scooters. Cars and trucks, particularly diesel vehicles, are thought to be the main vehicular pollution sources. This needs re-thinking, as we show that elevated particulate matter levels can be a consequence of 'asymmetric pollution' from two-stroke scooters, vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. Further, we demonstrate that oxidation processes producing secondary organic aerosol from vehicle exhaust also form potentially toxic 'reactive oxygen species'.This work was supported by the Swiss Federal Office for the Environment (FOEN), the Federal Roads Office (FEDRO), the Swiss National Science Foundation (Ambizione PZ00P2_131673, SAPMAV 200021_13016), the EU commission (FP7, COFUND: PSI-Fellow, grant agreement n.° 290605), the UK Natural Environment Research Council (NERC), the French Environment and Energy Management Agency (ADEME, Grant number 1162C00O2) and the Velux Foundation.This is the accepted manuscript version. The final version is available from http://www.nature.com/ncomms/2014/140513/ncomms4749/full/ncomms4749.html

Quantification of organic P and low-molecular-weight organic acids in ferralsol soil extracts by ion chromatography

A better understanding of the composition of organic phosphorus (organic P) and low-molecular-weight organic acids (LMWOAs) in soil will make it possible to predict phosphorus cycling, improve biomass production and help phosphorus management in forest plantations. The method for quantifying organic P and LMWOAs in soil extracts was developed using ion chromatography (IC). Sodium hydroxide (0.5 N) was validated as an extractant for both organic P and LMWOAs. A mixture of 200 mM NaOH and ultrapure water was used to create a linear gradient elution. The eluent program separated five different organic P forms (glucose-6-phosphate, AMP, fructose-1,6-bisphosphate, ATP and phytate) as well as pyrophosphate from inorganic P (Pi), and four LMWOAs (malate, malonate, oxalate and citrate) in a 25 minute run through an AS11 column. The variability of the quantification was expressed as the relative standard deviation which was less than 20% for most of the analytes. The recovery rate of organic P assayed by IC to colorimetry was 110 +/- 20%. This chromatographic method was shown to be suitable for the quantification of organic P and LMWOAs in soil samples and could be an easier alternative to P-31 Nuclear Magnetic Resonance (NMR) measurement

Particle number measurements in the European legislation and future JRC activities

The solid particle number method was introduced in the European Union (EU) light-duty legislation for diesel vehicles to ensure the installation of the best-available technology for particles (i.e., wall-flow diesel particulate filters) without the uncertainties of the volatile nucleation mode and without the need of large investment for purchasing the equipment. Later it was extended to gasoline vehicles with direct injection engines, heavy-duty engines (both compression ignition and positive ignitions) and non-road mobile machinery engines. Real Driving Emissions (RDE) testing on the road with Portable Emissions Measurement Systems (PEMS) for particle number (and NOx) during type approval and in-service conformity testing was recently (in 2017) introduced for light-duty vehicles, and is under discussion for heavy-duty vehicles in-service conformity testing. This paper will summarize the existing legislation regarding solid particle number and discuss the on-going activities at EU level. The main focus at the moment is on improving the calibration procedures, and extending the lower detection size below 23 nm with interlaboratory exercises. In parallel, discussions are on-going to introduce testing at low ambient temperature, regeneration emissions in the light-duty regulation, a particle limit for other technologies such as gasoline port-fuel injection vehicles, and the feasibility of particle measurements to L-category vehicles (mopeds, motorcycles, tricycles and minicars). A short overview of periodical technical inspection investigations and the situation regarding non-exhaust traffic related sources with special focus on brakes and tyres will be described

Real-time analysis of aromatics in combustion engine exhaust by Resonance-Enhanced Multiphoton Ionisation Time-Of-Flight Mass Spectrometry (REMPI-TOF-MS): A robust tool for chassis dynamometer testing.

Resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry (REMPI-TOF-MS) is a robust method for real-time analysis of monocyclic and polycyclic aromatic hydrocarbons in complex emissions. A mobile system has been developed which enables direct analysis on site. In this paper, we utilize a multicomponent calibration scheme based on the analytes' photo-ionisation cross-sections relative to a calibrated species. This allows semi-quantification of a great number of components by only calibrating one compound of choice, here toluene. The cross-sections were determined by injecting nebulised solutions of aromatic compounds into the TOF-MS ion source with the help of a HPLC pump. Then, REMPI-TOF-MS was implemented at various chassis dynamometers and test cells and the exhaust of the following vehicles and engines investigated: a compression ignition light-duty (LD) passenger car, a compression ignition LD van, two spark ignition LD passenger cars, 2 two-stroke mopeds, and a two-stroke engine of a string gas trimmer. The quantitative time profiles of benzene are shown. The results indicate that two-stroke engines are a significant source for toxic and cancerogenic compounds. Air pollution and health effects caused by gardening equipment might still be underestimated

Chemical analysis and ozone formation potential of exhaust from dual-fuel (liquefied petroleum gas/gasoline) light duty vehicles.

Measures must be undertaken to lower the transport sector's contribution to anthropogenic emissions. Vehicles powered by liquefied petroleum gas (LPG) are an option due to their reduced emissions of air pollutants compared to engines with conventional fuels. In the present study, ten different dual-fuel LPG/gasoline light duty vehicles were tested, which all complied with European emission level legislation EURO-4. Tests with LPG and gasoline were performed on a chassis dynamometer by applying the New European Driving Cycle (NEDC) and emission factors and ozone formation potentials of both kinds of fuels were compared. The components investigated comprised regulated compounds. CO(2), volatile hydrocarbons and carbonyls. On-line analysis of aromatic species was carried out by resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS). We demonstrate that utilization of LPG can entail some environmental benefits by reducing emissions. However, for dual-fuel LPG/gasoline vehicles running on LPG the benefits are less than expected. The main reason is that dual-fuel vehicles usually start the engine up on gasoline even when LPG is selected as fuel. This cold-start phase is crucial for the quality of the emissions. Moreover, we demonstrate an influence on the chemical composition of emissions of vehicle performance, fuel and the evaporative emission system of the vehicles

A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra

Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM<sub>1</sub> (particulate matter with an aerodynamic diameter <I>d</I><sub>a</sub> < 1 μm) mass. Secondary organic aerosol (SOA) is an important contributor to the OA and can be formed from biogenic and anthropogenic precursors. Here we present results from the characterization of SOA produced from the emissions of three different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from α-pinene. <br><br> The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. <br><br> Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra showing Pearson's r values >0.94 for the correlations between the four different SOA types after five hours of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, <I>m/z</I> 43 and 44, are dominated by the oxygenated ions C<sub>2</sub>H<sub>3</sub>O<sup>+</sup> and CO<sub>2</sub><sup>+</sup>, respectively, similarly to the relatively fresh semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The atomic O:C ratios were found to be in the range of 0.25–0.55 with no major increase during the first five hours of aging. On average, the diesel SOA showed the lowest O:C ratio followed by SOA from wood burning, α-pinene and the scooter emissions. Grouping the fragment ions revealed that the SOA source with the highest O:C ratio had the largest fraction of small ions. <br><br> The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended

Application of modern online instrumentation for chemical analysis of gas and particulate phases of exhaust at the European Commission heavy-duty vehicle emission laboratory.

The European Commission recently established a novel test facility for heavy-duty vehicles to enhance more sustainable transport. The facility enables the study of energy efficiency of various fuels/scenarios as well as the chemical composition of evolved exhaust emissions. Sophisticated instrumentation for real-time analysis of the gas and particulate phases of exhaust has been implemented. Thereby, gas-phase characterization was carried out by a Fourier transform infrared spectrometer (FT-IR; carbonyls, nitrogen-containing species, small hydrocarbons) and a resonance-enhanced multiphoton ionization time-of-flight mass spectrometer (REMPI-TOFMS; monocyclic and polycyclic aromatic hydrocarbons). For analysis of the particulate phase, a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS; organic matter, chloride, nitrate), a condensation particle counter (CPC; particle number), and a multiangle absorption photometer (MAAP; black carbon) were applied. In this paper, the first application of the new facility in combination with the described instruments is presented, whereby a medium-size truck was investigated by applying different driving cycles. The goal was simultaneous chemical characterization of a great variety of gaseous compounds and particulate matter in exhaust on a real-time basis. The time-resolved data allowed new approaches to view the results; for example, emission factors were normalized to time-resolved consumption of fuel and were related to emission factors evolved during high speeds. Compounds could be identified that followed the fuel consumption, others showed very different behavior. In particular, engine cold start, engine ignition (unburned fuel), and high-speed events resulted in unique emission patterns