Martin Mohr

Oxidative stress and inflammation response after nanoparticle exposure: differences between human lung cell monocultures and an advanced three-dimensional model of the human epithelial airways

Combustion-derived and manufactured nanoparticles (NPs) are known to provoke oxidative stress and inflammatory responses in human lung cells; therefore, they play an important role during the development of adverse health effects. As the lungs are composed of more than 40 different cell types, it is of particular interest to perform toxicological studies with co-cultures systems, rather than with monocultures of only one cell type, to gain a better understanding of complex cellular reactions upon exposure to toxic substances. Monocultures of A549 human epithelial lung cells, human monocyte-derived macrophages and monocyte-derived dendritic cells (MDDCs) as well as triple cell co-cultures consisting of all three cell types were exposed to combustion-derived NPs (diesel exhaust particles) and to manufactured NPs (titanium dioxide and single-walled carbon nanotubes). The penetration of particles into cells was analysed by transmission electron microscopy. The amount of intracellular reactive oxygen species (ROS), the total antioxidant capacity (TAC) and the production of tumour necrosis factor (TNF)-α and interleukin (IL)-8 were quantified. The results of the monocultures were summed with an adjustment for the number of each single cell type in the triple cell co-culture. All three particle types were found in all cell and culture types. The production of ROS was induced by all particle types in all cell cultures except in monocultures of MDDCs. The TAC and the (pro-)inflammatory reactions were not statistically significantly increased by particle exposure in any of the cell cultures. Interestingly, in the triple cell co-cultures, the TAC and IL-8 concentrations were lower and the TNF-α concentrations were higher than the expected values calculated from the monocultures. The interplay of different lung cell types seems to substantially modulate the oxidative stress and the inflammatory responses after NP exposure.

Particulate Emissions from a Low-Speed Marine Diesel Engine

This study presents results from tail pipe emissions of particulate matter from a turbocharged common rail 2-stroke marine diesel engine (4RTX-3 from Wärtsilä) investigated at various operating conditions and using two different fuels. Size distributions were measured with a SMPS (Scanning Mobility Particle Sizer). A thermodesorber (TD) was applied to remove volatile material. In addition, filter samples were taken for gravimetric and chemical analysis. The mean diameters of the particles ranged between 20–40 nm, which is considerably smaller than the diameter of particles known from 4-stroke diesel engines as used in cars. A TD operated at 400°C evaporated the majority of the particles. The particle mass is dominated by volatile organic material, the fraction of which is significantly higher than for engines in cars. A high nucleation mode was found instead of a pronounced accumulation mode as known from 4-stroke diesel engines.

Sampling Conditions for the Measurement of Nucleation Mode Particles in the Exhaust of a Diesel Vehicle

A novel porous tube diluter was characterized to define sampling parameters for repeatable measurements of nucleation-mode particles (NMPs) in the exhaust of a modern diesel passenger car at moderate engine load. This porous tube diluter permits the variation of sampling parameters independently and in a wide range. We investigated the sampling parameters: primary dilution temperature (PDT; 15–55°C), primary dilution ratio (PDR; 8–45), residence time (RT; 0.5–4.0 s), and relative humidity of primary dilution (PRH; 5–90%). Decreased PDT and increased PRH led to a growth of particle number and size in the nucleation mode. While a maximum number of NMPs was found at moderate PDRs between 20 and 30, a maximum volume of NMPs was achieved at PDRs below 20. Coagulation explains the number reduction of NMPs under sampling conditions of prolonged RT and decreased PDR. However, the size growth of the nucleation mode can only partly be attributed to coagulation, and thus growth due to organic compounds from the exhaust probably plays an important role. Sensitivity analysis was conducted as a function of PDR-PDT and revealed two optimal sampling conditions for repeatable NMPs in number or repeatable maximum NMPs in volume. In addition to the sampling parameters, exhaust line conditioning was found to affect NMPs strongly and thus needs to be controlled to minimize effects on the history of measurements.

Performance Evaluation of a Novel Sampling and Measurement System for Exhaust Particle Characterization

This paper presents a novel partial flow sampling system for the characterization of airborne exhaust particle emissions. The sampled aerosol is first conditioned in a porous dilutor and then subsequent ejector dilutors are used to decrease its concentration to the range of the instrumentation used. First we examine the sensitivity of aerosol properties to boundary sampling conditions. This information is then used to select suitable sampling parameters to distinguish both the nucleation and the accumulation mode. Selecting appropriate sampling parameters, it is demonstrated that a distinct nucleation mode can be formed and measured with different instruments. Using these parameters we examine the performance of the system over transient vehicle operation. Additionally, we performed calculations of particle losses in the various components of the system which are then used to correct signals from the instruments. Several quality characteristics are then discussed, such as the repeatability and reproducibility of the measurements and the potential to derive total emission rate with a partial flow sampling system. Comparisons in different laboratories show that repeatability (intra-laboratory variability) is in the order of 10% for accumulation mode particles and 50% for nucleation mode ones. Reproducibility (inter-laboratory variability) values are in the range of ±20-30%. Finally, we compared laboratory size distributions with ambient samples obtained chasing a vehicle. This demonstrated that the sampling system accurately reproduced the accumulation mode particles as well as the potential for nucleation mode formation. This sampling system has been used in the framework of a European project for measurement of emissions of a number of light duty vehicles and heavy duty engines.

Effects of combustion-derived ultrafine particles and manufactured nanoparticles on heart cells in vitro

Evidence from epidemiological studies indicates that acute exposure to airborne pollutants is associated with an increased risk of morbidity and mortality attributed to cardiovascular diseases. The present study investigated the effects of combustion-derived ultrafine particles (diesel exhaust particles) as well as engineered nanoparticles (titanium dioxide and single-walled carbon nanotubes) on impulse conduction characteristics, myofibrillar structure and the formation of reactive oxygen species in patterned growth strands of neonatal rat ventricular cardiomyocytes in vitro. Diesel exhaust particles as well as titanium dioxide nanoparticles showed the most pronounced effects. We observed a dose-dependent change in heart cell function, an increase in reactive oxygen species and, for titanium dioxide, we also found a less organized myofibrillar structure. The mildest effects were observed for single-walled carbon nanotubes, for which no clear dose-dependent alterations of theta and dV/dt(max) could be determined. In addition, there was no increase in oxidative stress and no change in the myofibrillar structure. These results suggest that diesel exhaust as well as titanium dioxide particles and to a lesser extent also single-walled carbon nanotubes can directly induce cardiac cell damage and can affect the function of the cells.

Submicron fly ash penetration through electrostatic precipitators at two coal power plants

ABSTRACT Simultaneous measurements of the size distribution were performed for fine particulate matter (diameter d < 0.5 μm) at the inlet and outlet of the electrostatic precipitators (ESP) of two full-scale pulverized coal power stations (615 MW, 510 MW). For a comparative study of the performance of the ESP the same high resistivity coal was burned at both sites. In addition, measurements were carried out for an easy to handle coal at the newer state-of-the-art power station. Effects on the size distribution caused by nonintermittent pulse energization of the ESP were also investigated. The results revealed a significantly stronger influence of the boiler than of the coal type on the size distribution at the inlet of the ESPs. In all cases the distribution was unimodal and a pronounced peak could be observed around 100 nm particle diameter. The ESP outlet distributions varied much more and showed also a dependence on the coal type. The maximum of the penetration through the ESP was determined in the ran...

Particle Characterisation of Modern CNG, Gasoline and Diesel Passenger Cars

Tailpipe particle measurements have been performed in Euro-4 passenger cars. The investigation included compressed natural gas fuelled (bifuel vehicle concepts, commercially available) spark-ignition vehicles, gasoline port-injection spark-ignition vehicles, gasoline direct injection spark-ignition vehicles as well as compression ignited, diesel vehicles with and without particle filters. Particle number and soot mass was measured. In addition particle number size distributions have been recorded at constant vehicle speed operation. In the current study, the particle emissions of Compressed Natural Gas (CNG) vehicles are significantly lower than the corresponding ones of the other sparkignition vehicles. While direct injection spark-ignition vehicles exhibited high particle emission, only topped by the diesel vehicles without a particle filter, diesel vehicles with particle filters had lowest particulate emission, provided the diesel particulate filter was not regenerated shortly prior to the measurement cycle. CNG vehicles had almost as low particulate emissions in all cycle parts with low and moderate vehicle speeds. At typical highway driving speeds CNG vehicle particle emissions were significantly higher than the corresponding ones of the diesel particulate filter equipped vehicles. The enrichment of fuel-air mixture was identified as the main reason for the particle emission of the CNG vehicles at high vehicle speeds. We believe this enrichment to be a remnant from the gasoline operation the engine was originally designed for. In gasoline engines enrichment of the mixture reduces process and exhaust gas temperatures mainly due to fuel evaporation during and following the intake, protecting the catalyst from high temperatures. In parallel it improves engine performance and torque due to increased flame velocity. Since CNG-rich mixtures only slightly reduce process or exhaust temperatures and the maximal flame speed is at nearly stoichiometric air-fuel ratios we identify there a relatively easy to capture potential which, if reaped, may lead to the cleanest possible vehicle propulsion system. INTRODUCTION A significant reduction of CO2 emissions in the mobility sector is a major challenge for the next decades. In combination with efficient powertrain technologies, the potential of natural-gas is excellent for a comparably high as well as cost effective reduction in CO2 and toxic emissions in the near future. In the recent past our laboratory in collaboration with the Federal Institute of Technology of Zurich (ETHZ) has demonstrated the potential of a natural-gas optimised engine vehicle with the Clean Engine Vehicle (CEV) project. The vehicle used was a production line small sedan (model year 2000) with a curb weight of 1020kg. The achieved goal was 30% lower CO2 emissions than the gasoline vehicle while staying in compliance with Euro-4 as well as SULEV emission limits [1]. Also recently major passenger car manufacturers have modified gasoline fuelled spark-ignition engines for bifuel operation with CNG and gasoline. As a result, some bifuel CNG-gasoline vehicles have been introduced on the European market. While the bifuel concept is an important feature for customers, given the scarcity of CNG refuelling stations, it inhibits the exploiting of the full potential of CNG powertrains. In parallel, the relative low numbers of CNG vehicles on the road still constrains the resources dedicated by automotive industries to their development. CNG vehicles have to use established parts as well as concepts from their pure gasoline counterpart models. A main issue concerns the emissions from such vehicles. Certainly, they comply with the recent legislation limits, but are they better or worse than their peers? We are not aware of any systematic recent studies and comparisons. In this paper we examine the particle emissions of typical Euro IV propulsion systems for passenger cars. Typically particles are measured with gravimetric methods. The newest vehicle technologies, though, result in emissions often in the resolution domain of gravimetric methods. We used the gravimetric as well as the particle counting method in order to achieve comprehensive results. The counted particles from internal combustion engines are usually divided into solid and volatile particles. The solid particles mainly consist of agglomerated carbonaceous primary particles, which are in general referred to as soot. The volatile nanoparticles are usually formed by nucleation of sulfuric acid, water, and other species. These two different kinds of particles form clearly distinguishable modes in the number size distributions, designated as “accumulation” and as “nucleation mode” [2]. Extensive comparison of different powertrain technologies was carried out by [3], though no CNG systems had been included. Further investigations moved in the direction of emission modeling and inventory building [4] or assessing cold start influence on diesel and/or gasoline passenger car engines [2, 5]. Again no comparisons concerning CNG system were reported there. In the present paper we aim to address the questions of particle emission from current market-available CNG vehicles and compare them to other current technologies. The comparison extends only to EURO-IV vehicles including modern direct injected (DI) gasoline powered vehicles as well as conventional multi-point intake manifold injected (MPI) gasoline vehicles. As comparable peers from the diesel side, we chose a series of vehicles equipped with, as well as without, a particulate filter.

Efficient multiple charging of diesel particles by photoemission

ABSTRACT Particle charging of real combustion aerosols by exposure to ultraviolet irradiation has been investigated. Using a tandem mobility analyzer (TDMA) we determined charge distributions as function of particle size (d = 60, 75, 90, and 120 nm) and relative intensity of the irradiation for two photon energies (hv = 5.6 and 6 eV). For diesel particles a significantly higher charge level was achieved by photoemission compared to the calculated charging mechanism of ion attachment due to corona discharge. For example, we obtained an average charge per particle of up to 25 elementary units on particles with 100 nm in diameter.

ACEA Programme on the Emissions of Fine Particulates from Passenger Cars(2) Part 2: Effect of Sampling Conditions and Fuel Sulphur Content on the Particle Emission

The results of an investigation of the influence of the sulphur fuel content and different dilution techniques on fine particulate emissions are reported in this paper. Fuels with two different sulphur contents (<10 ppm and approx. 200 ppm) were used for a Diesel and a gasoline vehicle in order to compare four different dilution procedures. These comprised the standard CVS tunnel and two pre-heated and one non-heated direct dilution systems. Various particulate measurement instruments were employed simultaneously, including SMPS, CPC, and ELPI for number and size, the standard gravimetric filter method for mass. In addition, Soxhlet extraction for chemical composition was carried out. A higher fuel sulphur content was found to clearly increase particulate emissions from the Diesel and the gasoline vehicle for higher load. The increase in emissions was due to the contribution of condensed material and most of it could be clearly brought into relation with to sulphur compounds. The comparison between the different dilution systems showed a good agreement for the accumulation mode in number and size. Drastic differences were observed concerning the nucleation mode for the tests with high sulphur fuel. Whereas the pre-heated dilution systems do not show a nucleation at all, the total number concentration was increased up to an order of magnitude for the non-heated systems.

Charakterisierung der Partikelemission von modernen Verbrennungsmotoren

Im Rahmen eines interdisziplinaren Projekts unter der Federfuhrung des Laboratoriums fur Verbrennungsmotoren und Verbrennungstechnik (LVV) der ETH Zurich sind an Motoren mit verschiedenen Brennverfahren — vom langsam laufenden Zweitakt-Schiffsdieselmotor bis zum Versuchs-Ottomotor mit direkter Einspritzung — Partikelmessungen zur Erfassung der Anzahlgrosenverteilungen und der chemischen Zusammensetzung durchgefuhrt worden. Mit der Variation einer Vielzahl von Betriebsparametern sind die Moglichkeiten und Grenzen der Beeinflussung der Partikelemissionen ausgelotet worden.