Name: measuring sub-23 nanometer real driving particle number emissions using the portable downtoten sampling system
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Description: Watch this Scientific Journal Video about Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System at JoVE.com

This work is conducted in the framework of the H2020 project DownToTen. This project has received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under grant agreement Nr. 724085.

<ol>
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Official Journal of the European Union Available from: <a target="_blank" href="https://eur-lex.europa.eu/eli/reg/2017/1154/oj">https://eur-lex.europa.eu/eli/reg/2017/1154/oj</a> (2017)</li><li>Mamakos, A., Khalek, I., Giannelli, R., Spears, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+combustion+aerosol+produced+by+a+mini-CAST+and+treated+in+a+catalytic+stripper.">Characterization of combustion aerosol produced by a mini-CAST and treated in a catalytic stripper.</a> Aerosol Science and Technology. 47 (8), 927-936 (2013).</li><li>Jing, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+Combustion+Aerosol+Generator+(SCAG)+for+Calibration+Purposes.">Standard Combustion Aerosol Generator (SCAG) for Calibration Purposes.</a> Atmospheric Environment. 27 (8), 1271-1275 (1999).</li><li>Moore, R. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+operation+of+the+miniature+combustion+aerosol+standard+(Mini-CAST)+soot+generator.">Mapping the operation of the miniature combustion aerosol standard (Mini-CAST) soot generator.</a> Aerosol Science and Technology. 48 (5), 467-479 (2014).</li><li>Giechaskiel, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Implementation+of+portable+emissions+measurement+systems+(PEMS)+for+the+real-driving+emissions+(RDE)+regulation+in+Europe.">Implementation of portable emissions measurement systems (PEMS) for the real-driving emissions (RDE) regulation in Europe.</a> Journal of Visualized Experiments. (118), e54753 (2016).</li><li>EC Commission Regulation (EU) 2017/1151. Official Journal of the European Union Available from: <a target="_blank" href="https://eur-lex.europa.eu/eli/reg/2017/1151/oj">https://eur-lex.europa.eu/eli/reg/2017/1151/oj</a> (2017)</li><li>EC REGULATION (EC) No 715/2007 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL. Official journal of the European Union Available from: <a target="_blank" href="https://eur-lex.europa.eu/Legal-content/EN/ALL/?uri=CELEX:32007R0715">https://eur-lex.europa.eu/Legal-content/EN/ALL/?uri=CELEX:32007R0715</a> (2007)</li><li>EC DIRECTIVE 2007/46/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL. Official journal of the European Union Available from: <a target="_blank" href="https://eur-lex.europa.eu/Legal-content/EN/ALL/?uri=CELEX:32007L0046">https://eur-lex.europa.eu/Legal-content/EN/ALL/?uri=CELEX:32007L0046</a> (2007)</li><li>EC Commission Regulation 2790/99. 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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Aerosol technology: properties, behavior, and measurement of airborne particles. , (2012).</li><li>Badshah, H., Kittelson, D., Northrop, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+Emissions+from+Light-Duty+Vehicles+during+Cold-Cold+Start.">Particle Emissions from Light-Duty Vehicles during Cold-Cold Start.</a> SAE International Journal of Engines. 9 (3), 1775-1785 (2016).</li><li>First results of vehicle technology effects on sub-23nm exhaust particle number emissions using the DownTo10 sampling and measurement system. 22nd ETH-Conference on Combustion Generated Nanoparticles Available from: <a target="_blank" href="https://www.nanoparticles.ch/archive/2018_Andersson_PR.pdf">https://www.nanoparticles.ch/archive/2018_Andersson_PR.pdf</a> (2018)</li><li>Giechaskiel, B., Manfredi, U., Martini, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engine+exhaust+solid+sub-23+nm+particles:+I.+Literature+survey.">Engine exhaust solid sub-23 nm particles: I. Literature survey.</a> SAE International Journal of Fuels and Lubricants. 7 (2834), 950-964 (2014).</li><li>Including cold-start emissions in the Real-Driving Emissions (RDE) test procedure. Publications Office of the European Union Available from: <a target="_blank" href="https://op.europa.eu/en/publication-detail/-/publication/66874f0c-fd85-11e6-8a35-01aa75ed71a1/language-en/format-PDF/source-120155396">https://op.europa.eu/en/publication-detail/-/publication/66874f0c-fd85-11e6-8a35-01aa75ed71a1/language-en/format-PDF/source-120155396</a> (2017)</li><li>Mathissen, M., Scheer, V., Vogt, R., Benter, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+on+the+potential+generation+of+ultrafine+particles+from+the+tire-road+interface.">Investigation on the potential generation of ultrafine particles from the tire-road interface.</a> Atmospheric Environment. 45 (34), 6172-6179 (2011).</li><li>Grigoratos, T., Martini, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brake+wear+particle+emissions:+a+review.">Brake wear particle emissions: a review.</a> Environmental Science and Pollution Research. 22 (4), 2491-2504 (2015).</li></ol>

The authors have nothing to disclose.

This work presents the DTT sampling system and its application as a portable emission measurement system. The system was designed and constructed within the EU Horizon 2020 project DTT to enable particle number emission measurements below the current legislative particle size limit of 23 nm. The system&#8217;s versatility enables the assessment of the regulated solid particle number emissions as well as total particle emissions and studies on secondary aerosols. To interpret measurement results accurately, a calibration procedure is necessary with the DTT system. This is to evaluate the relative particle penetration for different particle sizes, to be able to calculate a correction factor that accounts for the particle losses. It is critical to provide sufficient warm up time for the sampling system itself and the rest of the experimental setup to reach thermal equilibrium and achieve accurate calibration measurement results.
The application of the DTT system for the measurement of solid particle number emissions with a lower particle size cutoff of 23 nm (current regulation) and 10 nm (experimental) is described. To be able to assess particle number emissions of a vehicle it is necessary to determine the particle number concentration and the exhaust mass flow rate. The DTT system covers the particle number concentration measurement. The exhaust mass flow is measured using an exhaust flow meter (EFM). It is critical to install the EFM according to the manufacturer&#8217;s instructions. Erroneous measurements of the exhaust flow rate directly affect the deduced emission rates. When processing the measured data, it is important to perform an accurate time alignment of the particle concentration data and the exhaust flow data. This is necessary because the emission rate is the exhaust flow rate multiplied by the particle number concentration. If the two signals are not aligned correctly, the emissions over the whole drive can significantly deviate from the real emissions.
The DTT system is not a commercial device but a versatile research tool. It is used to investigate unregulated vehicle emissions as opposed to performing certification measurements validating compliance with current regulations. The high versatility comes at the cost of increased energy and dilution air consumption. When using the system for mobile measurements, the weight added to the vehicle due to the battery (30 kg) and gas bottle (20 kg) to cover the energy and air consumption of the system must be kept in mind. The total weight added to the car when measuring the PN emissions with the DTT system is approximately 80 kg, which is comparable to another person being transported in the vehicle. The added weight can lead to slightly increased emissions, especially if the drive includes a great deal of acceleration and/or hills.
The DTT system can be used to investigate the unregulated &#60;23 nm particle number exhaust emissions. Both solid and total particle number emissions can be measured. Furthermore, it can be a useful tool to study the complex field of secondary aerosol formation. Another possible application of the system is the measurement of automotive brake wear particles. A significant fraction of the particles emitted during braking events can be smaller than 30 nm34. With a d50 of approximately 11 nm, the DTT system is suitable for studying these emissions. Although it is known that non-exhaust emissions contribute almost equally to traffic-related PM10 emissions35, non-exhaust particle emissions are still unregulated. This is due to the complex and seldom reproducible process of particle generation, making it very difficult to set regulatory actions. Furthermore, the chemical composition and the related toxicity of organic brake wear particles is still widely unknown35.
The DTT system is a useful tool to improve our understanding of both exhaust and non-exhaust traffic-related particle emissions.

The Particle Measurement Programme (PMP) was founded by the UK Government for the &#8220;development of type approval test protocols for assessing vehicles fitted with advanced particulate reduction technology that would complement or replace current legislative measurement procedures&#8221;1. The PMP is the world&#8217;s first particle number-based emissions regulation, targeted specifically at carbonaceous particles &#8805;23 nm. Recent measurements indicate that it may be necessary to include smaller particles.
Negative health impacts of diesel soot are well understood2, and therefore, the &#8216;precautionary principle&#8217; was invoked on the basis that the elimination of carbon particles from diesel exhaust, via the mandatory use of diesel particulate filters (DPFs), was imperative on health grounds. However, because in European legislation a limit value must force adoption of emissions control technologies, this could not be achieved without an appropriate measurement method. With strong political backing across Europe, the UK Government led the conception of the PMP to improve particulate measurements. The PMP, under the auspices of the United Nations Economic Commission for Europe (UN-ECE)3, included the expertise of others from around the globe. Two particle research projects were completed in 2001. One of them (Particulate Research4) was carried out by the UK Government Department of the Environment, Transport and the Regions (DETR), in partnership with the Society of Motor Manufacturers and Traders (SMMT) and the Oil Companies European Organisation for Environment, Health and Safety (CONCAWE). The other one (PARTICULATES5) was funded by the European Union&#39;s 5th Framework and was carried out by 14 different European partners. The results of both projects indicated that particle number-based procedures were promising, but that challenges for repeatable and reproducible measurements remained.
In 2007 the final report of the PMP Light-duty Inter-laboratory Correlation Exercise was published6, including some improvements on the filter-based mass measurement method, primarily demonstrating the feasibility of a number count-based method for regulatory purposes based upon a defined particle size range and particle volatility. Both methods were implemented based upon sampling from the existing constant volume sampler (CVS) dilution tunnel approach originally developed for particulate matter mass and bagged dilute gaseous emissions measurements.
Within the number count-based method, a lower particle size limit of ~20 nm was selected. The primary objective of the project was to ensure particles of this size and above were controlled by legislation. It is now known that the primary particle size in engine exhaust can be &#60;20 nm7,8,9. For practical reasons, a particle counter with a 50% counting efficiency (d50) at 23 nm was selected, and this size became the accepted lower size threshold. It was recognized that due to the high sensitivity to properties such as dilution, air temperature, humidity, and ratio10, volatile particle size distribution and integrated number measurements could be repeatable in one CVS-equipped facility with one vehicle, but much less so from facility to facility. Thus, for rigorous regulations, it was necessary to focus purely on nonvolatile particles, with the measurement approach effectively defining the regulatory particle boundary conditions on size and volatility. European diesel fuel has back-end volatility such that only a few percent boils at temperatures above 350 &#176;C, and early work within the PMP indicated that short residence times at this temperature were suitable for the complete evaporation of tetracontane, a linear hydrocarbon containing 40 carbon atoms with volatility towards the end boiling point of engine lubricant11. Consequently, a temperature of 350 &#176;C has become the de facto reference point for regulatory &#62;23 nm particle volatility.
The PMP measurement system specification comprises components for sampling, sample conditioning, and measurement, summarized in Table 1.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Stage</td>
			<td>Identity</td>
			<td>Purpose</td>
		</tr>
		<tr>
			<td>0</td>
			<td>Sample source</td>
			<td>Origin of sample</td>
		</tr>
		<tr>
			<td>1</td>
			<td>Particle Transport</td>
			<td>Conduct sample from origin to measurement system</td>
		</tr>
		<tr>
			<td>2</td>
			<td>Volatile Particle Remover</td>
			<td>Eliminate volatiles and define non-volatile particles to be measured</td>
		</tr>
		<tr>
			<td>3</td>
			<td>Particle Number Counter</td>
			<td>Enumerate non-volatile particles and define the lower size limit</td>
		</tr>
	</tbody>
</table>
Table 1: Elements of the PMP Measurement System.
The European PMP PN approach is being implemented and now applies to light-duty diesel (September 2011, EURO 5b) and GDI vehicles (September 2014, EURO 6), and to diesel and gas heavy-duty engines (February 2013, EURO VI).
Recent measurements showed that some light-duty vehicles and, in particular, spark ignition technologies, can emit substantial levels of particles &#60;23 nm12,13,14. This led the European Commission to fund research projects to develop new or extended methods that can be rapidly implemented as a replacement, or addition to, the current &#62;23 nm regulation.
One such project, DownToTen (DTT), aims to preserve the general approach of PMP and extend the measurement range down to a d50 &#8804;10 nm. To this end, the configuration of the DTT measurement system was designed to include the same basic elements described in Table 1, but with the conditioning and measurement steps optimized to enable efficient transport and detection of the &#60;23 nm particles. The DTT system was initially developed for laboratory use but was modified to operate as a portable emissions measurement system (PEMS). For the DTT PN-PEMS system, the components were optimized to reduce weight and power consumption and increase physical robustness without substantially diverging from the original design. For mobile application, the system must be resistant to harsher and erratic temperatures, pressures, and vibration environments likely encountered in light- and heavy-duty PEMS testing. The impact of pressure variations at the inlet of the system was modelled and studied experimentally15. The resistance to vibrations was assessed using a dedicated test bed16. Vibrations and accelerations that occur during typical RDE drives did not impair the measurement results of the condensation particle counters used. The DTT system is also designed for use at low temperatures, where the volatile removal function is inactive, to feed an aging chamber and study secondary organic aerosol formation17.
The thermal conditioning elements of the DTT measurement system that define the regulatory volatility boundary of particles closely parallel the elements of the PMP system in that both systems contain the sequence:
<ol>
	<li>First particle number dilution stage</li>
	<li>HC/volatile elimination stage</li>
	<li>Second particle number dilution stage</li>
</ol>
The primary differences between the DTT and PMP systems are that the DTT system components are selected to:
<ol>
	<li>Maximize transmission of ~10 nm PN from the sample source to the particle counter using low loss dilution and particle transmission approaches</li>
	<li>Comprehensively remove volatiles using oxidative particle elimination rather than merely reducing partial pressures of condensable HC species through evaporation and dilution</li>
	<li>Count particles of ~10&#8211;50 nm with greater efficiency than current PMP systems</li>
</ol>
The objective of this paper is to present the use of the DTT PN-PEMS system for measuring nonvolatile particles &#8805;10 nm from an in-use road vehicle. This includes an introduction to the measurement system and its main components, performing laboratory-based calibration measurements, installing the device for a mobile application, conducting a real driving emission measurement, and processing the collected measurement data.
Instrumentation
The DTT PN-PEMS was designed to provide high particle penetration down to a few nanometers, robust particle number dilution, removal of volatile particles, and prevention of artificial particle formation. The components of the system were selected based on results from laboratory experiments comparing a variety of technologies for dilution and aerosol conditioning. This section provides an overview of the system, its working principle, and the components used. Figure 1 shows a schematic of the system. Figure 2 shows a photo of the system. The DTT system is 60 cm high and has a footprint of 50 cm x 50 cm. The weight of the system is approximately 20 kg. Including the required peripheral elements (i.e., battery and gas bottle) the total weight is approximately 80 kg. The major elements of the system are the two dilution stages (i.e., first hot, second cold), a catalytic stripper, and at least one condensation particle counter (CPC).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61287/61287fig01.jpg" /> 
Figure 1: Schematic drawing of the DTT particle number portable emission measurement system. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61287/61287fig02.jpg" /> 
Figure 2: Top view picture of the DTT sampling system. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Two dilution stages reduce the particle number concentrations to levels measurable by condensation particle counters (&#60;104 #/cm3). Custom-made porous tube diluters are used for both dilution stages. This technology was selected because of its low particle loss18,19. The radial ingress of dilution air convectively keeps particles away from the walls, which reduces particle losses. Furthermore, these diluters can be very small and can withstand temperatures of 400 &#176;C. The porous material used is a sintered hastalloy X tube (GKN Filters Metals GmbH, Radevormwald, Germany). Static mixing elements inside the porous tube provide a well-mixed aerosol directly downstream of the diluter. This allows taking a representative sample of the diluted aerosol for further conditioning or measurement by splitting the aerosol flow directly downstream of the diluter, and allows for a compact sampling system. The primary dilution stage is typically heated to 350 &#176;C, while the second stage is operated at ambient temperature. The dilution factor of the system is approximately 80. The exact value is dependent on the inlet flow and the mass flow management: The flow rates in the sampling system are managed by a system of two mass flow controllers and two mass flow meters. The mass flow controllers control the dilution air flow rates. The mass flow meters monitor the flow rates extracted downstream of dilution stages 1 and 2. The differences between the flows extracted and the flows supplied can be changed. In other words, the net flow added or subtracted in one dilution stage can be defined. The sample flow rate, Qsample, is defined as the sum of all other flow rates: 1) Flow rate drawn by the measurement instruments (Qinst); 2) the dilution air flow rates (Qdil,i); and 3) the excess flow rates Qex,i. For the calculation of the sample flow, the contributions of the flows extracted from the system are positive and the contributions of the flows fed into the system are negative.
<img alt="Equation 1" src="/files/ftp_upload/61287/61287equ01.jpg" />
The total dilution ratio DR is calculated by:
<img alt="Equation 2" src="/files/ftp_upload/61287/61287equ02.jpg" />
A catalytic stripper (CS) is situated between dilution stage 1 and 2 and is operated at 350 &#176;C at a flow rate of 1 liter per minute (L/min). The catalytic stripper provides oxidation of organic compounds and sulphur storage. The removal of these substances ensures the isolation of the solid particle fraction. The undesired formation of volatile and semivolatile particles and growth of subcut size particles is prevented. The catalytic stripper used is commercially available (AVL GmbH). The volatile particle removal efficiency of the CS was verified with polydisperse emery oil particles &#62;50 nm and &#62;1 mg/m3 (3.5&#8211;5.5 mg/m3) showing an efficiency of &#62;99% (actual value 99.9%) as defined by RDE regulations20. This is a more rigorous test than the tetracontane test prescribed in the current PMP protocol.
One or more condensation particle counters are used to measure the particle number concentration downstream of the second dilution stage. A CPC with a d50 of 23 nm enables the measurement of the currently regulated emission of solid particles larger than 23 nm. Additionally, measuring the particle number concentration with one or more CPCs with a lower d50 cut point (e.g., 10 nm, 4 nm) enables the assessment of the currently unregulated solid particle fraction &#60;23 nm down to the d50 cut size of the applied CPC.
The dilution air supply line, the primary porous tube diluter, and the catalytic stripper have independent heating elements containing k-type thermocouples (TC). Independently heating different sections controls the temperature distribution in the system.
In addition to the thermocouples in the heating elements, two thermocouples are placed downstream of dilution stage 1 and 2. These two thermocouples directly measure the aerosol temperature.
Two absolute pressure sensors (NXP MPX5100AP) are used to monitor the pressure at the inlet and the outlet of the sampling system.
For mobile measurements, a Clayton Power LPS 1500 battery pack is used. A 10 L synthetic air bottle supplies the system with dilution air during mobile applications. The sizes of the battery and the gas bottle are chosen so that the system can operate independently for 100 min.
The system is controlled via a NI myRIO running a LabVIEW virtual instrument. The virtual instrument allows for control of the flow rates and heater temperatures. Apart from the controlled parameters, the aerosol temperatures, pressures, and acceleration (via the sensor integrated in myRIO) can be monitored and logged. A myRIO accessory GPS module enables logging of the position data. Figure 3 and Figure 4 show the user interface of the virtual instrument used for controlling the DTT system.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61287/61287fig03.jpg" /> 
Figure 3: DTT virtual instrument dilution stage parameter overview. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61287/61287fig04.jpg" /> 
Figure 4: DTT virtual instrument heater control panel. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Any kind of sampling procedure causes particle losses. To be able to account for these losses, laboratory measurements are performed to determine the particle size dependent particle penetration through the DTT sampling system. In these measurements, the particle concentration of monodisperse aerosol is measured upstream and downstream of the sampling system using two condensation particle counters. Figure 5 shows the experimental setup for the calibration measurements. In this setup, a Jing miniCAST is used as a particle source21,22. Mass flow controllers (MFC) are used to control the gas flows into the burner. A dilution bridge enables the adjustment of the particle number concentration. The dilution bridge is a high-efficiency particulate air (HEPA) filter parallel to a needle valve. Adjusting the position of the needle valve alters the dilution ratio by changing the ratio between the fraction of the aerosol passing through the HEPA filter and the fraction of the aerosol passing through the needle valve. The filtered and the unfiltered aerosols are recombined with a T-piece to form a diluted aerosol. A catalytic stripper is used to remove possibly abundant volatile compounds generated as byproducts of the combustion process. A TSI 3082 electrostatic classifier together with a TSI 3085 differential mobility analyzer (nano DMA) are used for the size selection of particles. Two TSI CPCs 3775 (d50 = 4 nm) are used to measure the particle number concentration upstream and downstream of the DTT sampling system. The counters&#8217; cut point of d50 = 4 nm allows for the penetration determination at particle sizes as low as 10 nm and below.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/61287/61287fig05.jpg" /> 
Figure 5: Schematic drawing of the experimental setup used for the calibration of the DTT sampling system. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>2x Condensation Particle Counter 4 nm</td><td>TSI</td><td>3775</td><td>Particle counter with a cut point of 4 nm</td></tr><tr><td>5x Mass Flow Controllers (MFC)</td><td>V&amp;ouml;gtlin</td><td></td><td>Mass flow controllers for controlling the miniCast gas flows</td></tr><tr><td>AVL M.O.V.E. EFM Exhaust Flow Meter</td><td>AVL</td><td></td><td>Device for the measurement of the exhaust flow rate of vehicles</td></tr><tr><td>Catalytic Stripper</td><td>Custom made</td><td></td><td>Device for the removal of volatile compounds in an aerosol by oxidation</td></tr><tr><td>Compressed Air</td><td></td><td></td><td>Oxidation and dilution air supply for miniCast</td></tr><tr><td>Condensation Particle Counter 10 nm</td><td>AVL</td><td></td><td>Particle counter with a cut point of 10 nm</td></tr><tr><td>Condensation Particle Counter 23 nm</td><td>TSI</td><td>3790A</td><td>Particle counter with a cut point of 23 nm</td></tr><tr><td>Differential Mobility Analyzer</td><td>TSI</td><td>3085</td><td>Part of the electrostatic classifier where the particle are separeted by mobility.</td></tr><tr><td>Dilution Bridge</td><td>Custom made</td><td></td><td>Needle valve in parallel to HEPA filters. Used to adjust particle concentrations for calibration purposes</td></tr><tr><td>DownToTen Sampling System</td><td>Custom made</td><td></td><td>Custom made sampling system for the assessment of automotive sub-23 nm particle emissions</td></tr><tr><td>Electrostatic Classifier</td><td>TSI</td><td>3082</td><td>Device for the classifaction of arosol particles by electrical mobility diameter</td></tr><tr><td>Hand held Mass Flow Meter (MFM)</td><td>V&amp;ouml;gtlin</td><td></td><td>Device for measuring the inlet flow of measurement instruments</td></tr><tr><td>miniCast Soot Generator</td><td>Jing Ltd</td><td></td><td>Combastion aerosol standard, soot generator</td></tr><tr><td>Mobile Battery LPS 1500</td><td>Clayton Power</td><td></td><td>Battery for power supply of the DTT measurement system</td></tr><tr><td>Nitrogen Gas Bottle</td><td></td><td></td><td>Nitrogen for Mixing gas and quench gas supply of miniCast</td></tr><tr><td>Propane Gas Bottle</td><td></td><td></td><td>Fuel for miniCast</td></tr><tr><td>Soft X-Ray Neutralizer</td><td>TSI</td><td>3088</td><td>Device for the establishmentof the equillibrium charge distribution of aerosol particles</td></tr><tr><td>Synthetic Air Bottle 10 L</td><td></td><td></td><td>Gas Bottle for the dilution air supply</td></tr></tbody></table>

measuring sub-23 nanometer real driving particle number emissions using the portable downtoten sampling system

The current particle size threshold of the European Particle Number (PN) emission standards is 23 nm. This threshold could change because future combustion engine vehicle technology may emit large amounts of sub-23 nm particles. The Horizon 2020 funded project DownToTen (DTT) developed a sampling and measurement method to characterize particle emissions in this currently unregulated size range. A PN measurement system was developed based on an extensive review of the literature and laboratory experiments testing a variety of PN measurement and sampling approaches. The measurement system developed is characterized by high particle penetration and versatility, which enables the assessment of primary particles, delayed primary particles, and secondary aerosols, starting from a few nanometers in diameter. This paper provides instruction on how to install and operate this Portable Emission Measurement System (PEMS) for Real Drive Emissions (RDE) measurements and assess particle number emissions below the current legislative limit of 23 nm.

Calibration Data (Particle Penetration):
Figure 11 shows an exemplary plot of the relative particle penetration of the DTT system as a function of the particle mobility diameter. The corresponding data have been measured and evaluated as described in instruction section 1. The plot shows that the deviations between two measurement points at the same mobility diameter were less than 5%. Deviations larger than 10% indicate instabilities in the experimental setup. In this case, the calibration had to be repeated with increased warm up stabilization times. Both the warm up time (typically 30 min) and the stabilization time (typically 30 s) increased by a factor of 1.5.
The particles passing through the DTT system were lost due to diffusion and thermophoresis. Thermophoretic losses were caused by a temperature gradient drawing particles towards the walls of the sampling system. This is a particle size independent effect29; in contrast, diffusion is highly particle size dependent. A concentration gradient caused a net particle flux towards the walls where particles were lost. The diffusivity rising with lower particle size made this the dominant loss mechanism for particles &#8804;10 nm. The lines in Figure 11 indicating thermophoretic, diffusional, and total losses demonstrate the respective particle size dependencies. For the diffusional losses, this function was used to illustrate the approximate particle size dependency:
<img alt="Equation 11" src="/files/ftp_upload/61287/61287equ11.jpg" />
The penetration P depends on a fit parameter a and the diffusion coefficient D:
<img alt="Equation 12" src="/files/ftp_upload/61287/61287equ12.jpg" />
The diffusion coefficient depends on the Boltzmann constant k, the absolute temperature T, the viscosity &#951;, the particle diameter dp, and the Cunningham slip correction factor Cc, which is a function of the mean free path and the particle diameter29.
The data illustrated in Figure 11 resulted in the following mean particle penetration efficiency Pmean:
<img alt="Equation 13" src="/files/ftp_upload/61287/61287equ13.jpg" />
The particle size where the penetration efficiency amounts to 50% is referred to as d50. The d50 describes the penetration cutoff characteristic of a system. For the DTT system the d50 was 11 nm. The d50 is shown in Figure 11.
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/61287/61287fig11.jpg" /> 
Figure 11: Particle penetration as a function of particle mobility diameter. 
Points marked in blue are measurement results. The dashed lines in orange and green indicate the losses associated with thermophoresis and diffusion, respectively. The red line represents the total losses as the sum of diffusional and thermophoretic losses. The dotdashed purple line shows the average particle penetration Pmean as calculated in the calibration measurement instruction section 1. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Solid Particle Number:
Figure 12 shows the particle number emission rate over time for the first ten minutes of an RDE measurement drive. The data from the DTT PEMS using a 10 nm and a 23 nm CPC are shown together with data from a commercially available 23 nm cut point system. The particle emission rates were calculated from the respective particle concentrations multiplied by the exhaust flow rate as described above in the data analysis instruction section 4. The reference instrument (AVL MOVE) relied on a diffusion charger for the particle number concentration measurement. Despite the different sensor principles, the data measured with the DTT PEMS were overall in very good agreement with the data measured by the commercially available PEMS. Sharp downwards pointing spikes in all three signals occurred because the particle measurement devices can report zero particle concentrations temporarily and zeros cannot be displayed in logarithmic plots. The particle emissions measured with the 10 nm CPC were very close to the emissions measured with the 23 nm CPC for the majority of the time period shown in Figure 12. However, right at the beginning between 10 s and 25 s there was an occurrence of significant &#60;23 nm particle emission. The DTT 10 nm signal was significantly higher than the 23 nm signal of the DTT system and the AVL MOVE. In this case, &#62;50% of the total number of particles emitted were between 10 nm and 23 nm. Cold start dynamic processes in non-thermal equilibrium can cause particle size distributions to differ from emissions from a hot vehicle30. The discussion of these complex processes is beyond the scope of this work. Further information on this topic can be found in the literature31,32,33.
<img alt="Figure 12" class="xfigimg" src="/files/ftp_upload/61287/61287fig12.jpg" /> 
Figure 12: The upper part of the figure shows the particle number emission rate over time for the first 10 mins of an RDE measurement drive. 
Data measured with the DTT PEMS using 10 nm and 23 nm CPC and a commercially available 23 nm cut point system (AVL MOVE) are used as a reference. The lower part of the figure shows the velocity of the vehicle. <a href="https://www.jove.com/files/ftp_upload/61287/61287fig12large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System at JoVE.com

Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System

Presented here is the DownToTen (DTT) portable emission measurement system to assess real driving automotive emissions of sub-23 nm particles.

The current particle size threshold of the European Particle Number (PN) emission standards is 23 nm. This threshold could change because future ...

measuring-sub-23-nanometer-real-driving-particle-number-emissions

Research

JoVE Journal

Engineering

5.4K Views.  Graz University of Technology. Presented here is the DownToTen (DTT) portable emission measurement system to assess real driving automotive emissions of sub-23 nm particles.

Video: Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System

Implementation of Portable Emissions Measurement Systems (PEMS) for the Real-driving Emissions (RDE) Regulation in Europe

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. However, on the road, ambient and driving conditions can vary over a wide range, sometimes causing emissions to be higher than those measured in the laboratory. For this reason, the European Commission has developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS) to verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. This paper presents the newly-adopted RDE test procedure, differentiating six steps: 1) vehicle selection, 2) vehicle preparation, 3) trip design, 4) trip execution, 5) trip verification, and 6) calculation of emissions. Of these steps, vehicle preparation and trip execution are described in greater detail. Examples of trip verification and the calculations of emissions are given.

Implementation of Portable Emissions Measurement Systems PEMS for the Real-driving Emissions RDE Regulation in Europe

The European Commission has developed a Real-Driving Emissions (RDE) test procedure to verify pollutant emissions during real-world vehicle operation using the Portable Emissions Measurement Systems (PEMS). This paper presents the experimental procedures required by the newly-adopted RDE test.

Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their official emission values and reference fuel consumption. ...

Environment

Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx

Nitrogen oxides (NOx = NO + NO2) are a family of atmospheric trace gases that have great impact on the environment. NOx concentrations directly influence the oxidizing capacity of the atmosphere through interactions with ozone and hydroxyl radicals. The main sink of NOx is the formation and deposition of nitric acid, a component of acid rain and a bioavailable nutrient. NOx is emitted from a mixture of natural and anthropogenic sources, which vary in space and time. The collocation of multiple sources and the short lifetime of NOx make it challenging to quantitatively constrain the influence of different emission sources and their impacts on the environment. Nitrogen isotopes of NOx have been suggested to vary amongst different sources, representing a potentially powerful tool to understand the sources and transport of NOx. However, previous methods of collecting atmospheric NOx integrate over long (week to month) time spans and are not validated for the efficient collection of NOx in relevant, diverse field conditions. We report on a new, highly efficient field-based system that collects atmospheric NOx for isotope analysis at a time resolution between 30 min and 2 hr. This method collects gaseous NOx in solution as nitrate with 100% efficiency under a variety of conditions. Protocols are presented for collecting air in urban settings under both stationary and mobile conditions. We detail the advantages and limitations of the method and demonstrate its application in the field. Data from several deployments are shown to 1) evaluate field-based collection efficiency by comparisons with in situ NOx concentration measurements, 2) test the stability of stored solutions before processing, 3) quantify in situ reproducibility in a variety of urban settings, and 4) demonstrate the range of N isotopes of NOx detected in ambient urban air and on heavily traveled roadways.

Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx

Previous work suggests that the nitrogen isotopic composition of atmospheric nitrogen oxides might distinguish the influence of different sources in the environment. We report on an automated, mobile, field-based method for the high collection efficiency of atmospheric NOx for N isotopic analysis at an hourly time resolution.

Nitrogen oxides (NOx = NO + NO2) are a family of atmospheric trace gases that have great impact on the environment. NOx concentrations directly influence ...

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the production of synthetic PM for laboratory studies have become a widespread necessity. Herein, experimental protocols demonstrate approaches to produce aerosolized organic PM by &#945;-pinene ozonolysis in a flow tube reactor. Methods are described for measuring the size distributions and morphology of the aerosol particles. The video demonstrates basic operations of the flow tube reactor and related instrumentation. The first part of the video shows the procedure for preparing gas-phase reactants, ozonolysis, and production of organic PM. The second part of the video shows the procedures for determining the properties of the produced particle population. The particle number-diameter distributions show different stages of particle growth, namely condensation, coagulation, or a combination of both, depending on reaction conditions. The particle morphology is characterized by an aerosol particle mass analyzer (APM) and a scanning electron microscope (SEM). The results confirm the existence of non-spherical particles that have grown from coagulation for specific reaction conditions. The experimental results also indicate that the flow tube reactor can be used to study the physical and chemical properties of organic PM for relatively high concentrations and short time frames.

This paper describes the operation procedure for the flow tube reactor and related data collection. It shows the protocols for setting the experiments, recording data and generating the number-diameter distribution as well as the particle mass information, which gives useful information about chemical and physical properties of the organic aerosols.

Organic particulate matter (PM) is increasingly recognized as important to the Earth's climate system as well as public health in urban regions, and the ...

Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering, which is a fundamental element to the approach of nanosafety-by-design of nanostructured products for their durable development. This approach is basically a preemptive one in which the focus is put on minimizing the emission of engineered nanomaterials' aerosols during the usage phase of the product's life cycle. This can be attained by altering its material properties during its design phase without compromising with any of its added benefits. In this article, an experimental protocol is presented to investigate the nanosafety-by-design of three commercial nanostructured products with respect to their mechanical solicitation and environmental weathering. The means chosen for applying the mechanical solicitation is an abrasion process and for the environmental weathering, it is an accelerated UV exposure in the presence of humidity and heat. The eventual emission of engineered nanomaterials is studied in terms of their number concentration, size distribution, morphology and chemical composition. The purpose of the protocol is to study the emission for test samples and experimental conditions which are corresponding to real life situations. It was found that the application of the mechanical stresses alone emits the engineered nanomaterials' aerosols in which the engineered nanomaterial is always embedded inside the product matrix, thus, a representative product element. In such a case, the emitted aerosols comprise of both nanoparticles as well as microparticles. But if the mechanical stresses are coupled with the environmental weathering, the experimental protocol reveals then the eventual deterioration of the product, after a certain weathering duration, may lead to the emission of the free engineered nanomaterial aerosols too.

In this article, an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental weathering is presented. Results on the emission of engineered nanomaterials, in the form of aerosols are presented. The specific experimental set-up is described in detail.

The present article presents an experimental protocol to investigate particle aerosolization of a product under abrasion and under environmental ...

A System to Create Stable Nanoparticle Aerosols from Nanopowders

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring minimal amounts of test materials (min. 200 mg), for studying powder aerosolization behavior and aerosol properties. The aerosolization procedure follows the concept of the fluidized-bed process, but occurs in the modified volume of a V-shaped aerosol generator. The airborne particle number concentration is adjustable by controlling the air flow rate. The system supplied stable aerosol generation rates and particle size distributions over long periods (0.5-2 hr and possibly longer), which are important, for example, to study aerosol behavior, but also for toxicological studies. Strict adherence to the operating procedures during the aerosolization experiments ensures the generation of reproducible test results. The critical steps in the standard protocol are the preparation of the material and setup, and the aerosolization operations themselves. The system can be used for experiments requiring stable aerosol concentrations and may also be an alternative method for testing dustiness. The controlled aerosolization made possible with this setup occurs using energy inputs (may be characterized by aerosolization air velocity) that are within the ranges commonly found in occupational environments where nanomaterial powders are handled. This setup and its operating protocol are thus helpful for human exposure and risk assessment.

We designed and developed an effective nanopowder aerosolization setup and operating protocol. The system generated nanoparticle aerosols with stable number concentrations and size distributions for long durations, requiring only small quantities of test material (min. 200 mg).

Nanoparticle aerosols released from nanopowders in workplaces are associated with human exposure and health risks. We developed a novel system, requiring ...

Testing of Nanoparticle Release from a Composite Containing Nanomaterial Using a Chamber System

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products containing nanomaterials is also increasing. Evaluating the nanomaterial release from products containing nanomaterials is a crucial step in assessing the safety of these products, and has resulted in several international efforts to develop consistent and reliable technologies for standardizing the evaluation of nanomaterial release. In this study, the release of nanomaterials from products containing nanomaterials is evaluated using a chamber system that includes a condensation particle counter, optical particle counter, and sampling ports to collect filter samples for electron microscopy analysis. The proposed chamber system is tested using an abrasor and disc-type nanocomposite material specimens to determine whether the nanomaterial release is repeatable and consistent within an acceptable range. The test results indicate that the total number of particles in each test is within 20% from the average after several trials. The release trends are similar and they show very good repeatability. Therefore, the proposed chamber system can be effectively used for nanomaterial release testing of products containing nanomaterials.

Nanoparticle release is tested using a chamber system that includes a condensation particle counter, an optical particle counter and sampling ports to collect filter samples for microscopy analysis. The proposed chamber system can be effectively used for nanomaterial release testing with a repeatable and consistent data range.

With the rapid development of nanotechnology as one of the most important technologies in the 21st century, interest in the safety of consumer products ...

Composition and Distribution Analysis of Bioaerosols Under Different Environmental Conditions

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, we described a protocol for multiple analyses of the biological compositions in environmental PM. Five experiments are presented: (1) PM number monitoring by using a laser particle counter; (2) PM collection by using a cyclonic aerosol sampler; (3) PM collection by using a high-volume air sampler with filters; (4) culturable microbes collection by the Andersen six-stage sampler; and (5) detection of biological composition of environmental PM by bacterial 16SrDNA and fungal ITS region sequencing. We selected hazy days and a livestock farm as two typical examples of the application in this protocol. In this study, these two sampling methods, cyclonic aerosol sampler and filter sampler, showed different sampling efficiency. The cyclonic aerosol sampler performed much better in terms of collecting bacteria, while these two methods showed the same efficiency in collecting fungi. Filter samplers can work under low temperature conditions while cyclonic aerosol samplers have a sampling limitation for temperature. A solid impacting sampler, such as an Andersen six-stage sampler, can be used to sample bioaerosols directly into the culture medium, which increases the survival rate of culturable microorganisms. However, this method mainly relies on culture while more than 99% of microbes cannot be cultured. DNA extracted from the culturable bacteria collected by the Andersen six-stage sampler and samples collected by cyclonic aerosol sampler and filter sampler were detected by bacterial 16S rDNA and fungal ITS region sequencing.All the methods above may have wide application in many fields of study, such as environmental monitoring and airborne pathogen detection. From these results, we can conclude that these methods can be used under different conditions and may help other researchers further explore the health impacts of environmental bioaerosols.

Understanding the biological composition of environmental particulate matter is important for the study of its significant impacts on human health and disease spread. Here, we used three types of bioaerosol sampling methods and a biological analysis of airborne microbes to better explore airborne microbial communities under different environmental conditions.

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, ...

Development of a Nose-only Inhalation Toxicity Test Chamber That Provides Four Exposure Concentrations of Nano-sized Particles

Using a numerical analysis based on computerized fluid dynamics, a nose-only inhalation toxicity chamber with four different exposure concentrations is designed and validated for flow field uniformity and cross-contamination among the exposure ports for each concentration. The designed flow field values are compared with the measured values from exposure ports located horizontally and vertically. For this purpose, nanoscale sodium chloride particles are generated as test particles and introduced to the inhalation chamber to evaluate the cross-contamination and concentration maintenance among the chambers, for each concentration group. The results indicate that the designed multiconcentration inhalation chamber can be used in animal inhalation toxicity testing without cross-contamination among concentration groups. Moreover, the designed multiconcentration inhalation toxicity chamber can also be converted to a single-concentration inhalation chamber. Further testing with gas, organic vapor, or non-nanoscale particles will ensure the use of the chamber in the inhalation testing of other test articles.

A nose-only inhalation toxicity chamber capable of testing inhalation toxicity at four different exposure concentrations was designed and validated for flow field uniformity and cross-contamination between the exposure ports for each concentration. Here, we present a protocol to confirm that the designed chamber is effective for inhalation toxicity testing.

Using a numerical analysis based on computerized fluid dynamics, a nose-only inhalation toxicity chamber with four different exposure concentrations is ...

Versatile Dual-Inlet Sample Introduction System for Multi-Mode Single Particle Inductively Coupled Plasma Mass Spectrometry Analysis and Validation

Metal-containing nanoparticles (NP) can be characterized with inductively coupled plasma mass spectrometers (ICP-MS) in terms of their size and number concentration by using the single-particle mode of the instrument (spICP-MS). The accuracy of measurement depends on the setup, operational conditions of the instrument and specific parameters that are set by the user. The transport efficiency of the ICP-MS is crucial for the quantification of the NP and usually requires a reference material with homogenous size distribution and a known particle number concentration.
Currently, NP reference materials are available for only a few metals and in limited sizes. If particles are characterized without a reference standard, the results of both size and particle number may be biased. Therefore, a dual-inlet setup for characterizing nanoparticles with spICP-MS was developed to overcome this problem. This setup is based on a conventional introduction system consisting of a pneumatic nebulizer (PN) for nanoparticle solutions and a microdroplet generator (&#181;DG) for ionic calibration solutions. A new and flexible interface was developed to facilitate the coupling of &#181;DG, PN and the ICP-MS system. The interface consists of available laboratory components and allows for the calibration, nanoparticle (NP) characterization and cleaning of the arrangement, while the ICP-MS instrument is still running.
Three independent analysis modes are available for determining particle size and number concentration. Each mode is based on a different calibration principle. While mode I (counting) and mode III (&#181;DG) are known from the literature, mode II (sensitivity), is used to determine the transport efficiency by inorganic ionic standard solutions only. It is independent of NP reference materials. The &#181;DG based inlet system described here guarantees superior analyte sensitivities and, therefore, lower detection limits (LOD). The size dependent LODs achieved are less than 15 nm for all NP (Au, Ag, CeO2) investigated.

Here we provide a protocol for the use of a dual-inlet system for single particle inductively coupled mass spectrometry which allows for a standard independent nanoparticle characterization.

Metal-containing nanoparticles (NP) can be characterized with inductively coupled plasma mass spectrometers (ICP-MS) in terms of their size and number ...

Chemistry

Additive Manufacturing-Enabled Low-Cost Particle Detector

As particles with a size of 1 &#181;m or smaller pose a severe health risk to the human body, the detection and regulation of particle emissions are of great importance. A large share of particulate emissions are emitted by the transport sector. Most of the commercially available particle detectors are bulky, very expensive, and need additional equipment. This paper presents a protocol to build and test a standalone particle detector that is small and cost-efficient. 
The focus of this paper lies in the description of the detailed construction manual with video and the sensor evaluation procedure. The computer-aided design model of the sensor is included in the supplemental material. The manual explains all the construction steps, from 3D printing to the fully operational sensor. The sensor can detect charged particles and is therefore suitable for a wide range of applications. A possible field of application would be soot detection from power plants, wildfires, industries, and automobiles.

Here, we present a protocol on how to build and test a simple but efficient low-cost particle detector.

As particles with a size of 1 &#181;m or smaller pose a severe health risk to the human body, the detection and regulation of particle emissions are of ...