The current study investigates the nonvolatile particle number emissions of three bi-fuel passenger cars (Euro 6_b, 6_d-temp), which operate on compressed natural gas (CNG), as a primary fuel, and gasoline as a secondary one. The CNG fuel was injected into the engine using port fuel injection (PFI) while the gasoline fuel was either by PFI or by direct injection (GDI). A novel exhaust gas sampling and dilution system was employed for the determination of solid particle number (SPN) emissions at 10 nm (SPN_>10nm) and 2.5 nm (SPN_>2.5 nm). The vehicles were tested in the laboratory over different test cycles where the CNG solid particle number emissions greater than 23 nm (SPN_>23nm) were an order of magnitude lower than GDI and PFI gasoline emissions. However, when the size threshold was lowered to 10 nm or 2.5 nm, emissions were similar for both fuels. Particularly, SPN_>2.5 nm emissions of the Euro 6 b vehicle exceeded the Euro 6 emission standard for both fuels while the SPN_>23nm emissions were between 40 and 2.8 times lower than the limit for CNG and gasoline, respectively. Particle size distributions show a significant number of particles reside below the regulated limit of 23 nm, even lower than 10 nm. The results have significant implications in setting a particle number limit for alternative fuel vehicles while indicating that the current size threshold (23 nm) is insufficient for particle emission testing. Copyright © 2020 American Association for Aerosol Research

Particulate and gaseous emissions were studied from a large two-stroke slow-speed diesel engine equipped with an open-loop scrubber, installed on a 78,200 metric tonnes (deadweight) containership, under real operation. This paper presents the on-board emission measurements conducted upstream and downstream of the scrubber with heavy fuel oil (HFO) and ultra-low sulfur fuel oil (ULSFO). Particle emissions were examined under various dilution ratios and temperature conditions, and with two thermal treatment setups, involving a thermodenuder (TD) and a catalytic stripper (CS). Our results show a 75% SO₂ reduction downstream of the scrubber with the HFO to emission-compliant levels, while the use of the ULSFO further decreased SO₂ levels. The operation of the scrubber produced higher particle number levels compared to engine-out, attributed to the condensational growth of nanometer particle cores, salt and the formation of sulfuric acid particles in the smaller size range, induced by the scrubber. The use of a TD and a CS eliminates volatiles but can generate new particles when used in high-sulfur conditions. The results of this study contribute to the generally limited understanding of the particulate and gaseous emission performance of open-loop scrubbers in ships and could feed into emission and air quality models for estimating marine pollution impacts.

Current legislations typically characterize systems of aerosols, such as from vehicle exhaust, primarily by number concentration and size distributions. While potential health threats have a dependence on the particle size, the chemical composition of particles, including the volatile and semi-volatile components adsorbed onto nonvolatile particle cores present at roadside and urban settings, is important in understanding the impact of exhaust particles on health. To date, the only tools suitable for an online in-depth chemical aerosol characterization are aerosol mass spectrometers, which are typically composed of complex and cost intensive instrumentation. We present a new analytical system, which combines a novel inexpensive infrared-radiation-based evaporation system (HELIOS) with a commercially available highly efficient atmospheric ionization source (SICRIT) connected to a rather low-price ion-trap mass spectrometer. Our inexpensive, robust and mobile aerosol characterization HELIOS/SICRIT/Mass Spectrometry system enables highly sensitive chemical analysis of particle-associated volatile substances. We validate the HELIOS/SICRIT/Mass Spectrometry system in laboratory experiments with coated particles generated under controlled conditions, and show that the system is capable of identification of combustion-generated polycyclic aromatic hydrocarbons and relative quantification of individual chemical species adsorbed on particle surfaces. We then employ our system to analyze real-world vehicle engine exhaust aerosol and show through time-resolved measurements with high time resolution (<10 s) that the chemical composition of the particles changes during different parts of an engine test cycle. Copyright © 2021 American Association for Aerosol Research