UFP instrument comparison at an urban background location in Antwerp

Distribution: Restricted Final report UFP instrument comparison at an urban background location in Antwerp Evelien Frijns, Jo Van Laer, Wim Aerts, Rob Brabers, Patrick Berghmans Study accomplished under the authority of 2013/MRG/R/172 July 2013

All rights, amongst which the copyright, on the materials described in this document rest with the Flemish Institute for Technological Research NV ( VITO ), Boeretang 200, BE-2400 Mol, Register of Legal Entities VAT BE 0244.195.916. The information provided in this document is confidential information of VITO. This document may not be reproduced or brought into circulation without the prior written consent of VITO. Without prior permission in writing from VITO this document may not be used, in whole or in part, for the lodging of claims, for conducting proceedings, for publicity and/or for the benefit or acquisition in a more general sense.

Distribution List DISTRIBUTION LIST Christine Matheeussen, VMM Jeroen Staelens, VMM Edward Roekens, VMM I

Table of Contents TABLE OF CONTENTS Distribution List I Table of Contents II List of Figures IV List of Tables VI CHAPTER 1 Introduction 1 1.1. Background 1 1.2. Aim 2 CHAPTER 2 Site Description 3 2.1. Location 3 2.2. Measuring Cabins 5 CHAPTER 3 Materials and Methods 7 3.1. Material 7 3.1.1. EPC (TSI 3783) 7 3.1.2. UFP (TSI 3031) 8 3.1.3. SMPS (Grimm 5420/L-DMA) 9 3.1.4. IfT Customized SMPS 11 3.1.5. Sampling system 11 3.2. Methods 12 3.2.1. Sampling period 12 3.2.2. Diffusion correction 13 CHAPTER 4 Results and Discussion 15 4.1. Number Concentration epc 15 4.1.1. Time profiles 15 4.1.2. Correlation 19 4.1.3. Box plot 22 4.1.4. Inlet Configurations 23 4.1.5. Conclusions 24 4.2. Size Distribution UFP monitor 25 4.2.1. Time Profile Size Channel comparison 25 4.2.2. Contour Plot 27 4.2.3. Correlation for six channels and total 30 4.2.4. Box plot 34 4.2.5. Conclusion 35 4.3. Size Distribution SMPS 36 4.3.1. Time Profile 36 4.3.2. Contour Plot 36 4.3.3. Correlation for seven size ranges and total 40 II

Table of Contents 4.3.4. Box plot 45 4.3.5. Conclusions 45 4.4. Comparison ECN reference instruments EPC, UFP monitor and SMPS 45 4.4.1. Time Profile 45 4.4.2. Correlation 46 4.4.3. Conclusion 50 4.5. Comparison ISSEP 50 4.5.1. Time profile SMPS week 6 incl ISSEP 50 4.5.2. SMPS Correlation for seven size ranges and total 51 4.5.3. Time profile EPC week 7 56 4.5.4. EPC Correlation 57 4.5.5. Box Plot 58 4.5.6. Conclusion 59 4.5.7. Diffusion versus non-diffusion corrected 59 4.6. Indoor conditions 61 4.7. Outdoor conditions 62 4.8. UFP Pollution Rose 65 CHAPTER 5 Conclusion/summary 66 5.1. Conclusion and summary 66 5.2. Recommendations 66 References 67 Annex A Maintenance Log Book 68 III

List of Figures LIST OF FIGURES Figure 1 Overview of the urban background location in the Antwerp city region 3 Figure 2 Detail of the site in Wilrijk (A) 4 Figure 3 Location measuring cabins 4 Figure 4 Cabins, trailers and truck 5 Figure 5 Condensation particle counter TSI 3783 (VMM) in TSI trailer 7 Figure 6 Schematic of condensation particle counter TSI 3783 8 Figure 7 UFP monitor TSI 3031 (UoL) in TSI trailer 8 Figure 8 Flow schematic of UFP monitor TSI 3031 9 Figure 9 Grimm SMPS+C 5420 with L-DMA in Grimm cabin 10 Figure 10 Photo and schematic drawing of TSI 3031200 Environmental Sampling System 11 Figure 11 Time profile EPC week 1 (not diffusion corrected) 15 Figure 12 Time profile EPC week 2 (not diffusion corrected) 16 Figure 13 Time profile EPC week 3 (not diffusion corrected) 16 Figure 14 Time profile EPC week 4 (diffusion corrected from 11 th of January) 17 Figure 15 Time profile EPC week 5 (diffusion corrected) 17 Figure 16 Time profile EPC week 6 (diffusion corrected) 18 Figure 17 Correlation plot ECN EPC (reference) versus VMM, VITO and GGD EPC with inlet screen assembly attached Not diffusion corrected (period 1) 20 Figure 18 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached Diffusion corrected (period 2) 20 Figure 19 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached, before changing the wick - Diffusion corrected (period 2A) 21 Figure 20 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached, after changing the wick Diffusion corrected (period 2B) 22 Figure 21 Box plot EPC data period 2b (no inlet screen assembly, new wick) (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 23 Figure 22 Time profile total number concentration UFP monitors week 4 25 Figure 23 Time profile total number concentration UFP monitors week 5 26 Figure 24 Time profile total number concentration UFP monitors week 6 26 Figure 25 Contour plot ECN UFP monitor 28 Figure 26 Contour plot VITO UFP monitor 28 Figure 27 Contour plot UoL UFP monitor 29 Figure 28 Correlation plot number concentration UFP monitors channel 1 (20-30 nm) 30 Figure 29 Correlation plot number concentration UFP monitors channel 2 (30-50 nm) 31 Figure 30 Correlation plot number concentration UFP monitors channel 3 (50-70 nm) 31 Figure 31 Correlation plot number concentration UFP monitors channel 4 (70-100 nm) 32 Figure 32 Correlation plot Number Concentration UFP monitors channel 5 (100-200 nm) 32 Figure 33 Correlation plot number concentration UFP monitors channel 6 (>200 nm) 33 Figure 34 Correlation plot UFP monitors total number concentration (20 - >200 nm) 33 Figure 35 Box plot UFP monitor (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 35 Figure 36 Time profile SMPS total number concentration week 6 36 Figure 37 Contour plot ECN SMPS 37 Figure 38 Contour plot VMM SMPS 38 Figure 39 Contour plot GGD SMPS 39 Figure 40 Correlation plot number concentration SMPS particle size <20 nm 40 Figure 41 Correlation plot number concentration SMPS particle size 20-30 nm 41 Figure 42 Correlation plot number concentration SMPS particle size 30-50 nm 41 IV

List of Figures Figure 43 Correlation plot Number concentration SMPS particle size 50-70 nm 42 Figure 44 Correlation plot number concentration SMPS particle size 70-100 nm 42 Figure 45 Correlation plot number concentration SMPS particle size 100-200 nm 43 Figure 46 Correlation plot number concentration SMPS particle size >200 nm 43 Figure 47 Correlation plot SMPS total number concentration (10 1094 nm) 44 Figure 48 Box plot SMPS systems (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 45 Figure 49 Time profile Total Number concentration ECN EPC, SMPS and UFP monitor in week 5 _ 46 Figure 50 Correlation plot total number concentration EPC ECN with ECN UFP monitor and SMPS 47 Figure 51 Correlation plot total number concentration ECN SMPS with ECN UFP monitor 48 Figure 52 Box plot 10-minute average data ECN (reference) monitors (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 48 Figure 53 Correlation plot Total Number concentration ECN EPC (non-diffusion corrected) with UPF monitors (partly diffusion corrected) and SMPSs (non diffusion corrected) 49 Figure 54 Correlation plot Total Number concentration ECN EPC with UPF monitors and SMPSs diffusion corrected 49 Figure 55 Time profile total number concentration SMPS (VMM, ECN, GGD & ISSEP) week 6 51 Figure 56 Correlation plot number concentration SMPS particle size <20 nm 52 Figure 57 Correlation plot number concentration SMPS particle size 20-30 nm 52 Figure 58 Correlation plot number concentration SMPS particle size 30-50 nm 53 Figure 59 Correlation plot number concentration SMPS particle size 50-70 nm 53 Figure 60 Correlation plot number concentration SMPS particle size 70-100 nm 54 Figure 61 Correlation plot number concentration SMPS particle size 100-200 nm 54 Figure 62 Correlation plot number concentration SMPS particle size >200 nm 55 Figure 63 Correlation plot SMPS total number concentration 55 Figure 64 Time profile total number concentration EPC (ECN & ISSEP) week 7 57 Figure 65 Correlation plot total number concentration of EPC connected to ISSEP sampling system and EPC connected to Joaquin sampling system 58 Figure 66 Box plots ECN SMPS and EPC and ISSEP SMPS and EPC 59 Figure 67 Indoor temperature time profiles 61 Figure 68 Indoor relative humidity time profiles 62 Figure 69 Wind rose total period 63 Figure 70 Daily average wind directions 64 Figure 71 Time profile outdoor temperature and relative humidity 64 Figure 72 Pollution rose total number concentration EPC ECN 65 V

List of Tables LIST OF TABLES Table 1 Instrument distribution in the cabin, trailer and truck 6 Table 2 EPC regression coefficients for VMM, GGD, UoL and VITO compared to ECN 21 Table 3 Inlet configurations: total average number concentration and RCs compared to ECN 24 Table 4 UFP monitor RCs UoL and VITO compared to ECN 34 Table 5 SMPS RCs VMM and GGD compared to ECN 44 Table 6 SMPS RCs and R 2 ISSEP compared to ECN 56 Table 7 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected EPC data 60 Table 8 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected UFP monitor data 60 Table 9 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected SMPS data 60 Table 10 Minimum, maximum and average temperatures inside the different cabins, trailers and truck 61 Table 11 Minimum, maximum and average relative humidity inside the different cabins, trailers and truck 62 Table 12 Minimum, maximum and average outdoor temperature (T) and relative humidity (RH) 65. VI

CHAPTER 1 Introduction CHAPTER 1 INTRODUCTION 1.1. BACKGROUND Joaquin (Joint Air Quality Initiative) is a new EU cooperation project supported by the INTERREG IVB North West Europe program (www.nweurope.eu). The aim of the project is to support healthoriented air quality policies in Europe. To achieve this, the project will provide policy makers with the necessary evidence on the current local and/or regional situation (e.g. measurements of emerging health relevant parameters), provide them with best-practice measures that can be taken and motivate them to adapt and strengthen their current air quality policies The project is divided into 3 work packages, each of which is specifically tailored to target the aim identified above. WP1 will focus on the development and implementation of novel air quality monitoring infrastructure for pollutants associated with the most dangerous aspects of air pollution on human health. Action 1 of work package 1 (WP1A1) is entitled Setup and operation of a next generation Watchdog Network for health pertinent pollution parameters. In four cities in NWE Europe, cutting edge instrumentation will be used to measure airborne concentrations of black carbon and the number concentration and size distribution of ultrafine particles (UFP). The monitors will be located at sites where statutory air quality parameters are measured such as nitrogen oxide (NOx) concentrations and the mass concentration of particulate matter (PM). To achieve this goal, a new monitoring infrastructure will be constructed (part of a NWE air quality Observatory and complementary to the existing EU network), comprising four new monitoring stations in Antwerp, Amsterdam, Leicester and Brighton. Real-time measurements of UFP number and size distribution and of black carbon concentrations will be made. As a first step, the instrumental approaches used for UFP monitoring were assessed. From literature review and a laboratory test, an evaluation was made of current commercial available UFP devices in order to choose appropriate instrumentation and methodology to measure number concentration and size distribution under routine measuring network conditions. Based on the evaluation three different monitors were selected and purchased: 3 x Grimm SMPS 5420 with L-DMA (GGD, VMM, ECN) 3 x TSI UFP monitor 3031 (UoL, UoB, ECN) 5 x TSI EPC 3783 (GGD, VMM, ECN, UoL, UoB) Before positioning these instruments in their new monitoring stations across Europe the instruments were compared at a temporary test site in Antwerp. This report describes the results of this instrument comparison. The instruments from UoB were not available for the instrument comparison in Antwerp. Instead two identical instruments from VITO were used: one UFP monitor 3031 and one EPC 3783. 1

CHAPTER 1 Introduction 1.2. AIM The aim of the instrument comparison at the urban background location in Antwerp was to determine: - The comparability of three identical SMPSs; - The comparability of three identical UFP monitors; - The comparability of five identical EPCs; - Comparability of SMPSs with UFP monitors; - Comparability of number concentration determined with SMPS / UFP monitor and EPC s The hypothesis for the study was that instruments are comparable within a type class (SMPS/UFP/EPC) when the number concentration and/or size differs less than 10 %. 2

CHAPTER 2 Site Description CHAPTER 2 SITE DESCRIPTION 2.1. LOCATION The instruments were compared at a temporary test site in Antwerp Wilrijk located at the Vuurkruisenplein. Figure 1 shows an overview of the location of this site in the Antwerp city region. Figure 2 and Figure 3 show a detail of the test location. Figure 1 Overview of the urban background location in the Antwerp city region The Wilrijk site is located in an urban-residential area and is surrounded by roads: - a busy road with 2x2 lanes in the north (Groenenborgerlaan); - a less busy road in the west (Oosterveldlaan), with a bus stop near the roundabout; - a smaller street in the south (Vuurkruisenplein), which is part of a triangular square where cars pass by when seeking parking space. 3

CHAPTER 2 Site Description Figure 2 Detail of the site in Wilrijk (A) Figure 3 Location measuring cabins 4

CHAPTER 2 Site Description 2.2. MEASURING CABINS Two measuring cabins were installed at the location marked in Figure 3. The measuring cabins were equipped with air conditioning and 19 racks in each cabin. The ground surface of each cabin is 4 x 2.4 m. The height of the roof is about 2.55 m above ground level (5 cm paving stone + 7 cm floor + 2.3 m inner height + 13 cm roof). Figure 4 Cabins, trailers and truck Close to the cabins two trailers (ECN, VMM) and one truck (VITO) were positioned (Figure 4). The instruments were distributed according to Table 1. Only meteorological instruments were situated in the VMM trailer. 5

CHAPTER 2 Site Description Cabin Partners VMM GGD ECN UoL VITO Grimm cabin Grimm SMPS Grimm SMPS TSI Cabin EPC EPC EPC UFP monitor ECN trailer VITO truck Grimm SMPS EPC UFP monitor Table 1 Instrument distribution in the cabin, trailer and truck NSAM EPC UFP monitor The results of the UoL NSAM (Nanoparticle Surface Area Monitor, TSI 3550) were not included in this report. These results can be used to compare surface estimates from NSAM with calculated surface data based on an SMPS system. 6

CHAPTER 3 Materials and Methods CHAPTER 3 MATERIALS AND METHODS 3.1. MATERIAL 3.1.1. EPC (TSI 3783) Particle number concentration was measured with a water-based condensation particle counter (CPC) (TSI model 3783, Figure 5). Figure 5 Condensation particle counter TSI 3783 (VMM) in TSI trailer The operation principle of TSI 3783 (also called Environmental Particle Counter; EPC) is illustrated in Figure 6. The aerosol sample is pulled through a conditioner that is saturated with water vapor, and then passes to a warmer growth section with thermodynamic super saturation conditions. As a result, the small particles act as condensation nuclei and grow into micron size droplets, which are detected individually by a light pulse when passing through a laser beam. 7

CHAPTER 3 Materials and Methods Figure 6 Schematic of condensation particle counter TSI 3783 As the EPC uses water as condensation liquid, this mode of operation differs slightly from the more common butanol-based CPCs. When an alcohol is used as condensation liquid, after the conditioning phase, particles pass through a condenser region (10 C). In an EPC, in contrast, after conditioning the particles pass through a warmer growth tube (60 C). The EPC can be used with a high-flow (3 L/min) or low-flow (0.6 L/min) inlet. The aerosol flow rate is 0.12 L/min. The response time (95%) is <3 s (high-flow) or <5 s (low-flow). The averaging interval can be set from 1 to 60 s. The EPC measured every second with an averaging interval of 60 seconds. All EPCs measured in high flow mode (3 L/min) except for the ECN EPC. This EPC measured in low flow mode from the start of the campaign till the 17 th of December 2012. 3.1.2. UFP (TSI 3031) The particle size distribution was measured by an UFP monitor TSI model 3031 (Figure 7). Figure 7 UFP monitor TSI 3031 (UoL) in TSI trailer 8

CHAPTER 3 Materials and Methods The operational principle is based on diffusion charging of particles, followed by size segregation with a differential mobility analyzer (DMA) and detection of the aerosol via an electrometer. The flow schematic is shown in Figure 8. Figure 8 Flow schematic of UFP monitor TSI 3031 The main components of the UFP monitor are: - Diffusion charger: unipolar corona charger, with counter flow diffusion charging (after flow splitting) - Differential mobility analyzer (DMA): size classification by stepwise change in DMA voltage - Faraday cup electrometer: current allows detection of particle concentration per size class The TSI 3031 UFP monitor needs no working fluid or radioactive source. The sample flow rate is 5 L/min. Sampling intervals are 7.5, 10 or 15 min, including 1 min for zeroing. The 7.5 min interval is less accurate than longer sampling times. The UFP monitor software corrects for diffusion losses due to the sampling system, but there is no correction for multiple charging of particles. Note that ISO 15900:2009 states that Unipolar charging leads to both a higher fraction of multiple-charged particles and higher charge levels on these particles. This has the adverse effect of reducing the size resolution of the differential electrical mobility classifier. The sample flow rate of all UFP monitors was set to 5 L/min and a sampling interval of 10 min was chosen. 3.1.3. SMPS (GRIMM 5420/L-DMA) The particle size distribution was also measured by a scanning mobility particle size spectrometer (Grimm CPC 5420 with L-DMA; Figure 9). 9

CHAPTER 3 Materials and Methods Figure 9 Grimm SMPS+C 5420 with L-DMA in Grimm cabin The main components of this Grimm SMPS are: - Neutralizer: 85 Kr source, 185 MBq, obtained from Eckert & Ziegler; - DMA: Vienna type L-DMA (~50 cm long), with up to 255 size channels per scan; - CPC: butanol-based condensation particle counter. The flow rate of the CPC is 0.3 L/min. To measure a 10-1100 nm range, the sheath air flow rate is 3 L/min. A complete particle sizing scan for 32 channels can be done in 5 min. The software corrects for internal diffusion losses and multiple charging. During the comparison scanning time was set to 10 min (precision 4, wait time 60 sec). 10

CHAPTER 3 Materials and Methods 3.1.4. IFT CUSTOMIZED SMPS From the 4 th of January till the end of the measurement campaign ISSEP joined the comparative study and measured total number concentration and number size distribution with a customized SMPS in a separate trailer at the Wilrijk location. The customized SMPS consisted of an IFT long DMA, a TSI butanol CPC 3772, a Ziegler 64 Ni nuclear source (100 MBq) measuring in the size range from 8.5 to 850 nm. The SMPS was set to a 5 minute sampling interval. 3.1.5. SAMPLING SYSTEM The sampling inlets of the sampling systems were positioned at 3.5 m height above ground surface. TSI The TSI instruments of UoL (EPC, UFP and NSAM) were connected to one environmental sampling system (TSI 3031200; Figure 10). In the ECN trailer, the same was done for the EPC and UFP monitor. In contrast, the EPCs of VMM, GGD and VITO were individually connected to the TSI sampling system as well as the UFP monitor from VITO. The main components of TSI 3031200 are a PM10 inlet, sharp cut PM1 cyclone, flow splitter and Nafion dryer (reduces humidity to less than 50 %). Figure 10 Photo and schematic drawing of TSI 3031200 Environmental Sampling System The recommended flow rate is 16.7 L/min at the inlet and up to 5 L/min sample flow. According to TSI, the particle transmission efficiency (with the given flow rates) is 82 % at 25 nm, 87 % at 40 nm, 93 % at 60 nm, 97 % at 150 nm and 100 % at 300 nm. 11

CHAPTER 3 Materials and Methods The sample and purge flow settings were: UoL EPC = 3 L/min, UFP = 5 L/min, NSAM = 2.5 L/min, Purge = 6.2 L/min ECN, setting 1 (till 17-12-2012) EPC = 0.6 L/min, UFP = 5 L/min, Purge = 11.1 L/min ECN, setting 2 EPC = 3 L/min, UFP = 5 L/min, Purge = 8.7 L/min VMM/GGD/VITO EPC = 3 L/min, Purge = 13.7 L/min VITO UFP = 5 L/min, Purge = 11.7 L/min Grimm All SMPS devices were connected to an individual Grimm sampling system with TSP sampling pipe, including sensors for temperature, relative humidity and pressure, and with a Nafion dryer and vacuum system. The length of the Grimm sampling pipe is 1.5 m. The inlet flow rate is 1.2 L/min, of which 0.3 L/min goes to the SMPS. ISSEP sampling system The ISSEP environmental sampling system consisted of a PM10 head, long stainless steel sampling line with a high flow rate (2.4 m 3 /h) and a stainless steel isokinetic splitter (five positions). 3.2. METHODS 3.2.1. SAMPLING PERIOD The instrument comparison took place from the 6 th of December 2012 till the 4 th of February 2013. Not all instruments were measuring continuously during this period. This was caused by: Sampling pipes from the VMM and GGD EPC that could not be fitted at the installation date at the 6 th of December 2012 but were installed at the 13 th of December. In between the instruments were sampling cabin air. The arrival of the VITO truck with UFP monitor and EPC on the 7 th of December 2013. The arrival of the ECN trailer with UFP monitor, EPC and SMPS on the 12 th of December. An old software version on the VITO UFP monitor including wrong algorithm. The new and correct software version was installed at the 10 th of January 2013 18 h. The delayed delivery of the SMPS nuclear sources from VMM and GGD. They were delivered at the 10 th of January 2013 9 h. The delayed delivery of the UFP monitor and EPC from UoL. They were delivered at the 10 th of January 2013 and operational from 18 h. The initial settings of the UoL UFP monitor. TSI selected the user-algorithm at the starting date which was changed to the ambient-algorithm at the 16 th of January 2013 13 h. Also at the 16 th of January the UFP monitor flow was adjusted from 4.7 to 5.0 L/min. The ECN UFP monitor reported too high number concentrations from the 25 th of January 22 h without reporting an error. The data from the 25 th of January 22 h till the end of the campaign was discarded. The 28 th of January the VITO EPC was switched to the ISSEP cabin. 12

CHAPTER 3 Materials and Methods The end of the campaign for all the partners at the 30 th of January, except for ECN. They measured till the 4 th of February. Trimming bushes and trees on the 23 rd and 24 th of January resulting in some outliers. The software on all SMPS instruments was updated at: 12 December 2012; 8 January 2013. In the report the following periods were compared: Number Concentration EPC data from 13 December 2012 till 30 January 2013 for VMM, GGD, ECN and VITO, including UoL from 10 till 30 January 2013; Size and Number Concentration - UFP monitor data from 16 till 25 January 2013 22 h; Number Concentration - SMPS data 13 December 2012 till 30 January 2013; Size - SMPS data from 10 till 30 January 2013. During the measurement campaign VITO visited the location at least once a week for simple maintenance tasks: instrument check, zero-check, flow check, butanol/water levels, SMPS impactor cleaning. The log book is shown in annex A. 3.2.2. DIFFUSION CORRECTION There are five main mechanisms which may lead to particle losses on to the surface of a sampling tube; these are sedimentation (gravitational), thermophoresis, electrostatic, inertial impaction and diffusion (Friedlander, 2000, Hinds, 1999). Of all potential losses, those due to diffusion and inertial impaction are most important for ambient particle measurements (Hinds, 1999). The second of these is only important under turbulent flow conditions and for particles larger than 100 nm (Lee and Gieseke, 1994). Gormley and Kennedy (1949) first derived the equation for diffusional losses in a fully developed laminar flow through a tube of circular cross section. Hinds (1999) developed a simplified expression (accuracy of 1%) for calculating the penetration efficiency P which was used in this study. The penetration efficiency P is the fraction of entering particles (N in ) that exit (N out ) through a tube. The formula used (Hinds, 1999) is presented below: P = 1-5.5µ 2/3 + 3.77 µ for µ<0.009 P = 0.819 exp(-11.5 µ ) + 0.0975 exp(-70.1 µ ) for µ>0.009 µ = DL/Q D = diffusion coefficient of the particles L = length of the tube Q = volume flow rate through the tube The IfT customized SMPS (see paragraph 3.1) and EPC (last two weeks) connected to the high flow sampling system were corrected using the following formula from Gormley and Kennedy (1949): P = 1-5.5µ 2/3 + 3.77 µ for µ<0.007 P = 0.819 exp(-11.5 µ ) + 0.0975 exp(-70.1 µ ) + 0.0325 exp(-179 µ ) for µ>0.007 13

CHAPTER 3 Materials and Methods The difference between the outcomes of the two formulas is limited. A description for each instrument type correction, is given below. Grimm SMPS The Grimm SMPS software already takes internal diffusion losses into account. Only diffusion losses were calculated for the sampling system and sampling lines. For all Grimm SMPS monitors the same penetration factors were used, because of the identical configuration. TSI UFP Monitor In the UFP Monitor software the option Environmental Sampling System was checked resulting in automatic internal diffusion loss correction and correction for diffusion losses in the sampling system. The transmission efficiencies in the UFP Monitor manual (Models 3031/3031-1, Ultrafine Particle Monitors User s Manual, P/N 6001716, Revision D, March 2011) that are used in the software only apply for one UFP Monitor connected (sample flow 5 LPM, purge flow 16.7 LPM). For ECN also an EPC and for UoL an EPC and NSAM were connected to the sampling system changing the sample and purge flow. The higher sample flow of 8 lpm (ECN) and 10.5 lpm (UoL) resulted in less diffusion losses which was manually corrected. An extra correction for diffusion losses in each size range was made manually for the length of the sampling line from the sampling system to the instrument. IfT custom. SMPS (ISSEP) For each size bin of the IfT customized SMPS three penetration factors were calculated: one for determining the internal diffusion losses for the CPC (D 50 ), one for determining the internal diffusion losses in the SMPS and one for determining the losses in the sampling system including sampling lines. The combination of all three was used for determining the losses for the SMPS system. EPC To calculate diffusion losses a size distribution is necessary. Because size distribution monitors were present also diffusion losses for the EPC s were calculated. Raw size distribution data (ECN as reference) and calculated EPC penetration factors were used to calculate diffusion corrected size distribution data. The diffusion corrected total number concentration determined with the size distribution monitors was divided by the raw total number concentration determined with the size distribution monitors and this factor was used to correct the 10 minute averaged EPC data. 14

CHAPTER 4 RESULTS AND DISCUSSION 4.1. NUMBER CONCENTRATION EPC Five EPCs (VMM, GGD, ECN, VITO, UoL) situated in three different cabins (VMM, GGD, UoL in TSI cabin / VITO in truck / ECN in trailer) measured the UFP total number concentration at the Wilrijk location. The data were compared using time profiles and correlation plots. 4.1.1. TIME PROFILES Figure 11 till Figure 16 show time profiles (half hour average values) for the first till the sixth week of the measurement campaign. Total number concentrations in Figures 11, 12 and 13 were not diffusion corrected because the reference SMPS was set to a different size range until the 8 th of January (5 350 nm). A calculated total diffusion correction factor for the 5-350 nm range is much higher than for the 10-1000 nm range resulting in faulty comparisons. Figure 11 Time profile EPC week 1 (not diffusion corrected) 15

Figure 12 Time profile EPC week 2 (not diffusion corrected) Figure 13 Time profile EPC week 3 (not diffusion corrected) 16

Figure 14 Time profile EPC week 4 (diffusion corrected from 11 th of January) Figure 15 Time profile EPC week 5 (diffusion corrected) 17

Figure 16 Time profile EPC week 6 (diffusion corrected) The same trend in number concentration was found for all five EPCs. During peak events the differences between instruments were more pronounced. The ECN EPC gave higher number concentrations from the beginning till the 11 th of January probably due to combined installation of the EPC with a UFP monitor on one Environmental Sampling System (ESS). The other EPCs were each separately connected to one ESS. The higher ECN number concentrations could be explained by a higher combined sample flow resulting in lower diffusion losses. From the 11 th of January the data was diffusion corrected and the difference between the ECN EPC and other EPC s decreased. When UoL joined the measurements (11 th of January) their EPC also experienced relatively higher concentrations. Multiple instruments (UFP monitor, EPC and NSAM) were also connected to one ESS for UoL, but also their wick was new. At that moment the other wicks were approximately 4 weeks old. To rule out the effect of wick age all instruments were provided with a new wick on the 23th of January. From the installation of the new wicks the ECN, GGD, VMM and VITO EPC showed comparable number concentrations and the UoL EPC lowest. The wick age could explain the higher UoL number concentrations during their start. The lower UoL number concentrations could be explained by the use of a combined sample flow for three instruments and a flow splitter in the sampling line resulting in higher losses which are apparently not taken into account in the diffusion loss correction formula. 18

4.1.2. CORRELATION The half hour average values were also used to create correlation plots. In the Joaquin project the ECN trailer and their instruments will be used as mobile validation laboratory in the future. For this reason the ECN instruments were selected as reference instruments. Four different correlation plots were created corresponding to different settings during the comparison: 1. With inlet screen assembly and 3.0 L/min period 1 (Figure 17); 2. Without screen assembly and 3.0 L/min period 2 (Figure 18). In period 2 two comparisons: A. Before changing wick (Figure 19); B. After changing wick (Figure 20). Only Figure 18, Figure 19 and Figure 20 contains diffusion corrected data because the period with inlet screen assembly (period 1) coincide with the lower selected SMPS size range (5-350 nm) resulting in too high diffusion correction factors compared to period 2. 19

Figure 17 Correlation plot ECN EPC (reference) versus VMM, VITO and GGD EPC with inlet screen assembly attached Not diffusion corrected (period 1) Figure 18 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached Diffusion corrected (period 2) 20

Figure 17 shows that with the inlet screen assembly installed in all EPCs the difference between the reference (ECN) and the others was more than 10 %. The regression coefficients (RCs) of the single linear regression lines are also presented in Table 2. Without inlet screen assembly attached (Figure 18) the difference between the reference and other EPCs was less than 10 %, but during this period also the wick was changed. For this reason the data of period two was split: before changing the wick (Figure 19) and after changing the wick (Figure 19). Before changing the wick the GGD EPC deviated 11 % from the reference. The others deviated less than 10 %. After wick changing the UoL EPC deviated 13 % from the reference, the others less than 10 %. From these results we can conclude that the wick age is very critical. Also it can be concluded that the UoL set-up results in lower concentrations than the reference set-up. Conditions ECN VMM GGD UoL VITO With inlet screen Not 1 0.8648 0.7787-0.8452 Without inlet screen diffusion corrected 1 0.9372 0.9152 0.9011 0.962 Old wick, except UoL New wick for all instruments Diffusion corrected 1 0.9974 0.8923 0.9964 0.9693 1 0.9969 0.993 0.8716 1.0313 Table 2 EPC regression coefficients for VMM, GGD, UoL and VITO compared to ECN Figure 19 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached, before changing the wick - Diffusion corrected (period 2A) 21

Figure 20 Correlation plot ECN EPC (reference) versus VMM, VITO, UoL and GGD EPC without inlet screen assembly attached, after changing the wick Diffusion corrected (period 2B) When comparing the situation with and without inlet screen assembly the other units improve in efficiency and the ECN EPC decreases in efficiency. The reason is an unexplained decrease in number count in the ECN EPC data. In all four cases the coefficient of determination (R 2 ) was larger than 0.9 indicating a very strong correlation. The regression lines fit the set of data well for all instruments. 4.1.3. BOX PLOT A box plot of the 10 minute average number concentration data from the period without inlet screen assembly and with a new wick (period 2B) is shown in Figure 21. The bottom and top of the box represents the 25th and 75th percentile (the lower and upper quartiles), respectively, and the band near the middle of the box represents the 50th percentile (the median). The ends of the whiskers represent the 5 th and 95 th percentile. The plot shows that the spread of the data is comparable for all instruments. The VMM, ECN, GGD and VITO EPC have comparable medians and percentiles. The UoL EPC is characterized by the lowest median and percentiles. 22

Figure 21 Box plot EPC data period 2b (no inlet screen assembly, new wick) (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 4.1.4. INLET CONFIGURATIONS The following inlet configurations were tested to find out the optimal configuration for the Joaquin network: A. ECN 0.6 L/min directly connected and others 3 L/min via screen assembly and screen; B. All units 3 L/min with screen assembly and screen; C. ECN with screen assembly and screen, others without screen assembly and thus without screen; 23

ECN GGD VMM VITO UoL A Total Average NC 11307 10122 10572 10679 - RC with Hi Conc 1.00 0.90 0.94 0.94 - RC without Hi Conc 1.00 0.92 0.96 0.95 - B Total Average NC 9757 7645 8314 7812 RC 1.00 0.78 0.85 0.80 C Total Average NC 14149 11503 12941 13081 13801 RC 1.00 0.81 0.91 0.92 0.98 Table 3 Inlet configurations: total average number concentration and RCs compared to ECN The results of the tests are shown in Table 3. These data was not corrected for diffusion losses because this coincides with the lower selected SMPS size range (5-350 nm). In test A ECN sampled in low flow mode (0.6 L/min) without inlet screen assembly, the others in high flow mode (3 L/min) via inlet screen assembly. ECN had more counts than the rest, probably due to the absence of the inlet screen assembly. This was confirmed in test B when all units were sampling in high flow mode (3 L/min) with inlet screen assembly. When comparing the results from test A and B (ECN changed from 0.6 L/min without to 3 L/min with inlet screen assembly) the ECN EPC gave a remarkably higher efficiency. To be sure that the inlet screen assembly caused this difference test C was performed. In test C ECN installed the screen assembly while the others did not have the screen assembly installed. From test C can be concluded that EPCs without assembly show a higher efficiency, as expected, due to avoided losses caused by the screen and sharp edges in the assembly. 4.1.5. CONCLUSIONS Changing low flow (0.6 L/min) to high flow (3 L/min) gave higher efficiencies; Wick replacement <4 weeks; Inlet screen assembly results in diffusion losses due to the fitted screen and sharp edges. The assembly should be removed and conductive tubing should be fitted instead when using also an ESS with PM10 & PM1 pre-separator; A strong correlation was found between the five EPCs (R 2 >0.99); With a new wick installed and without inlet screen assembly all instruments, except UoL (13 %), differed less than 10 % from the EPC reference (ECN); The number of instruments connected to one ESS is relevant. 24

4.2. SIZE DISTRIBUTION UFP MONITOR Three UFP monitors (ECN, VITO, UoL) situated in three different cabins (UoL in TSI cabin / VITO in truck / ECN in trailer) performed size distribution measurements at the Wilrijk location. The data were compared using time profiles, contour and correlation plots. 4.2.1. TIME PROFILE SIZE CHANNEL COMPARISON Figure 22 till Figure 24 show total number concentration time profiles (half hour average values) for the fourth till the sixth week of the measurement campaign. Figure 22 Time profile total number concentration UFP monitors week 4 25

Figure 23 Time profile total number concentration UFP monitors week 5 Figure 24 Time profile total number concentration UFP monitors week 6 26

Because the UoL UFP monitor arrived at the 10 th of January and the VITO UFP monitor used the wrong firmware version/algorithm till the 10 th of January only the data from the 11 th of January onwards were reported. The same trend in number concentration was found for all three UFP monitors considering figures 22, 23 and 24. Figure 22 and Figure 23 show that until the 16 th of January the UoL UFP monitor reported lower number concentrations. This was caused by the user profile. From the start the UoL UFP monitor was set to user and the VITO and ECN used ambient. In each profile a different algorithm is used. Figure 24 shows that the ECN UFP monitor reported too high number concentrations from the 25th of January 22 h. No error was reported and the cause was not found yet. For this reason the contour and correlation plots include only the data from the 16 th till the 25 th of January. 4.2.2. CONTOUR PLOT In Figure 25, Figure 26 and Figure 27 contour plots are shown from the ECN, VITO and UoL UFP monitor data. To create the plots a maximum of 8000 particles per channel was set to be able to obtain enough contrast in the graph. The six channels correspond to the following size ranges: - channel 1: 20-30 nm; - channel 2: 30-50 nm; - channel 3: 50-70 nm; - channel 4: 70-100 nm; - channel 5: 100-200 nm; - channel 6: >200nm. There were no big differences between the three graphs. 27

Figure 25 Contour plot ECN UFP monitor Figure 26 Contour plot VITO UFP monitor 28

Figure 27 Contour plot UoL UFP monitor 29

4.2.3. CORRELATION FOR SIX CHANNELS AND TOTAL To compare each size channel more in detail also correlation plots were made (Figure 28 - Figure 34). The RCs of the regression lines are also presented in Table 4. Figure 28 Correlation plot number concentration UFP monitors channel 1 (20-30 nm) 30

Figure 29 Correlation plot number concentration UFP monitors channel 2 (30-50 nm) Figure 30 Correlation plot number concentration UFP monitors channel 3 (50-70 nm) 31

Figure 31 Correlation plot number concentration UFP monitors channel 4 (70-100 nm) Figure 32 Correlation plot Number Concentration UFP monitors channel 5 (100-200 nm) 32

Figure 33 Correlation plot number concentration UFP monitors channel 6 (>200 nm) Figure 34 Correlation plot UFP monitors total number concentration (20 - >200 nm) 33

Channel Size range ECN UoL VITO 1 20-30 nm 1 0.7107 0.8492 2 30-50 nm 1 0.8763 0.9464 3 50-70 nm 1 0.9865 1.0431 4 70-100 nm 1 0.987 1.029 5 100-200 nm 1 1.0153 1.013 6 >200 nm 1 0.9745 1.3788 20 - >200 nm (total) 1 0.8991 0.9924 Table 4 UFP monitor RCs UoL and VITO compared to ECN The correlation plots show that the correlation between the reference (ECN) and the two others (UoL and VITO) was lowest for the size channel with particles >200 nm (R 2 = 0.60 for VITO and 0.36 for UoL). For all other size channels the correlation was strong (R 2 > 0.9) The biggest difference between the reference and UoL and VITO monitor could be found in the smallest size channel (20-30 nm). The difference was approximately 29 % for UoL and 15 % for VITO. In the second smallest channel the difference was 12 % for UoL and 5 % for VITO. The VITO size range >200 nm differed about 38 % from the reference. All other size channels (3, 4 and 5) differed less than 10 %. Looking at the total number concentration the difference was 10% for UoL and 0.78% for VITO). The difference in the smallest size channels could be explained by diffusion differences due to the different number of monitors connected to the ESS. The diffusion correction formula probably did not correct completely for the actual losses. 4.2.4. BOX PLOT A box plot of the total number concentration of the UFP monitor data is shown in Figure 35. This plot shows that the spread of the VITO and ECN data is comparable. The UoL data is characterized by a lower median and the concentrations are less spread out. 34

26000 24000 22000 20000 18000 Total nc (pt/cm³) 16000 14000 12000 10000 8000 6000 4000 2000 VITO ECN UoL Figure 35 Box plot UFP monitor (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 4.2.5. CONCLUSION Select the same profile (ambient); Except for the highest size channel (particles >200 nm) the correlation between the reference and the UoL and VITO UFP monitor was strong; When comparing the total number concentration the UoL UFP monitor differed 10 % from the EPC reference and VITO 0.8%; Number of instruments connected to one ESS is relevant. 35

4.3. SIZE DISTRIBUTION SMPS Three SMPSs (ECN, VMM and GGD) situated in two different cabins (GGD and VMM in TSI cabin / ECN in trailer) performed size distribution measurements at the Wilrijk location. The data were compared using time profiles, contour and correlation plots. 4.3.1. TIME PROFILE Figure 36 shows the total number concentration time profile (half hour average values) for the sixth week of the measurement campaign measured with the three SMPS systems. Not only during this week but also during the entire measurement campaign the total number concentrations of all SMPS monitors were comparable. Figure 36 Time profile SMPS total number concentration week 6 4.3.2. CONTOUR PLOT In Figure 37 till Figure 39 contour plots are shown from the ECN, VMM and GGD SMPS data. To create the plots the maximum number concentration in the plot was set to the 95% percentile (approximately 15000 particles) to obtain enough contrast in the graph. There were no big differences between the three graphs. 36

Figure 37 Contour plot ECN SMPS 37

Figure 38 Contour plot VMM SMPS 38

Figure 39 Contour plot GGD SMPS 39

4.3.3. CORRELATION FOR SEVEN SIZE RANGES AND TOTAL To compare the size distributions of the three instruments more in detail the data were split into the seven size ranges from the UFP monitor (20-30, 30-50, 50-70, 70-100, 100-200, >200 nm, total). The size range <20 nm was added. The number concentration in these eight size ranges was compared using correlation plots (Figure 40 - Figure 47). The ECN SMPS served as reference. The RCs of the regression lines are also presented in Table 5. The correlation plots show that the correlation between the reference (ECN) and the two others (GGD and VMM) was strong for all size channels (R 2 > 0.95). Figure 40 Correlation plot number concentration SMPS particle size <20 nm 40

Figure 41 Correlation plot number concentration SMPS particle size 20-30 nm Figure 42 Correlation plot number concentration SMPS particle size 30-50 nm 41

Figure 43 Correlation plot Number concentration SMPS particle size 50-70 nm Figure 44 Correlation plot number concentration SMPS particle size 70-100 nm 42

Figure 45 Correlation plot number concentration SMPS particle size 100-200 nm Figure 46 Correlation plot number concentration SMPS particle size >200 nm 43

Figure 47 Correlation plot SMPS total number concentration (10 1094 nm) Size range ECN VMM GGD <20 nm 1 1.0173 0.9640 20-30 nm 1 0.9201 0.9214 30-50 nm 1 0.9647 0.9879 50-70 nm 1 0.9650 0.9920 70-100 nm 1 0.9645 0.9951 100-200 nm 1 0.9754 1.0140 >200 nm 1 1.0275 1.0616 10-1094 nm (total) 1 0.9767 0.9835 Table 5 SMPS RCs VMM and GGD compared to ECN When comparing the number concentrations in the different size ranges the difference between the VMM or GGD SMPS and ECN SMPS was less than 10 %. The biggest difference between the reference and VMM and GGD SMPS could be found in the size range 20-30 nm. The difference was approximately 8 % for VMM as well as GGD. Looking at the total number concentration the difference was also less than 10 %. The difference in number concentrations between the instruments could not be explained by differences in the set-up but are probably partly the result of local conditions or instrumental calibration differences. 44

4.3.4. BOX PLOT A box plot of the total number concentration of the SMSP data is shown in Figure 48. This plot shows that the spread of data from all three SMPS systems is similar. Figure 48 Box plot SMPS systems (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 4.3.5. CONCLUSIONS The correlation between the reference (ECN) and the two others (GGD and VMM) was strong for all size channels (R 2 > 0.95); The difference in number concentrations between the VMM or GGD SMPS and ECN SMPS was less than 10 % for all size channels; The biggest difference was found in the size range 20-30 nm (8 %). 4.4. COMPARISON ECN REFERENCE INSTRUMENTS EPC, UFP MONITOR AND SMPS The three different types of instruments (EPC, UFP monitor and SMPS) were also compared using total number concentration. Only the ECN instruments were compared in the time profile. In the correlation plots not only the ECN instruments were compared, but also the ECN EPC with all other size distribution monitors. 4.4.1. TIME PROFILE The time profile of the total number concentration (30 min average) of the ECN EPC, UFP monitor and SMPS during week 5 is shown in Figure 49. 45

Figure 49 Time profile Total Number concentration ECN EPC, SMPS and UFP monitor in week 5 The same trend in number concentration was found for all three instruments. The ECN EPC gave higher number concentrations probably because of a lower detection limit (EPC 7 nm, UFP monitor 20 nm, SMPS 10 nm). 4.4.2. CORRELATION The half hour average values were also used to create correlation plots between the EPC and UFP monitor or SMPS (Figure 50) and the SMPS and UFP monitor (Figure 51). 46

Figure 50 Correlation plot total number concentration EPC ECN with ECN UFP monitor and SMPS The correlation plot (Figure 50) shows that the correlation between the EPC and the two size distribution monitors was strong (R 2 = 0.88 for the UFP monitor, R 2 = 0.87 for the SMPS). Based on the RCs of the linear regressions the difference in total number concentration between the EPC and UFP monitor was 24 % and between the EPC and SMPS was 20 %. The graph of the comparison between the two size distribution monitors (Figure 51) shows that the correlation between the UFP monitor and SMPS was strong (R 2 = 0.92). The total number concentrations of both instruments were comparable. A box plot of all data from the ECN instruments (EPC, UFP monitor & SMPS) is shown in Figure 52. This plot shows that the EPC median was higher and the data more spread. The higher EPC number concentrations could be explained by a lower minimal detectable particle size (D50) (EPC 7 nm, SMPS 10 nm, UFP monitor 20 nm). The difference in minimal detectable particle size will have a significant influence in environments where a nucleation mode is frequently present. The ECN EPC data was also plotted against the non-diffusion corrected data of all other size distribution monitors (Figure 53) and the diffusion corrected size distribution data (Figure 54). The UFP monitors correlate a little less (R 2 = 0.86-0.89) with the EPC than the SMPS monitors (R 2 = 0.92) when looking at the non diffusion corrected data. When comparing them with the corrected data the correlation coefficient and the regression coefficient decrease both caused by the application of one average diffusion correction factor for the total EPC number concentration. The size distribution monitors were size bin corrected. 47

s Figure 51 Correlation plot total number concentration ECN SMPS with ECN UFP monitor 35000 30000 25000 Total NC (pt/cm 3 ) 20000 15000 10000 5000 0 SMPS EPC UFPmon Figure 52 Box plot 10-minute average data ECN (reference) monitors (band: median, box: 25 and 75 percentile, whiskers: 5 and 95 percentile) 48

Figure 53 Correlation plot Total Number concentration ECN EPC (non-diffusion corrected) with UPF monitors (partly diffusion corrected) and SMPSs (non diffusion corrected) Figure 54 Correlation plot Total Number concentration ECN EPC with UPF monitors and SMPSs diffusion corrected 49

4.4.3. CONCLUSION A strong correlation was found between the EPC and SMPS/UFP monitor (R 2 = 0.88 UFP monitor, R 2 = 0.87 SMPS); Total number concentration measured with the UFP monitor was 24 % lower and measured with the SMPS 20 % lower than measured with the EPC; The correlation between the UFP monitor and SMPS was strong (R 2 = 0.92). The total number concentrations of both instruments were comparable. 4.5. COMPARISON ISSEP From the 4 th of January till the end of the measurement campaign ISSEP joined the comparative study and measured total number concentration and number size distribution with a customized SMPS in a separate trailer at the Wilrijk location. During the last week of the measurement campaign the VITO EPC was removed from the VITO truck and placed in the ISSEP trailer and connected to the ISSEP sampling system. The difference between an EPC connected to the Joaquin environmental sampling system or connected to the ISSEP sampling system could be examined. 4.5.1. TIME PROFILE SMPS WEEK 6 INCL ISSEP Figure 55 shows the total number concentration time profile (half hour average values) for the sixth week of the measurement campaign measured with all SMPS systems, including the ISSEP system. Not only during this week but also during the entire measurement campaign the total number concentrations of the ISSEP SMPS monitor followed the same trend but gave slightly higher number concentrations probably resulting from the use of a different sampling system. Sampling from a high flow rate will reduce diffusion losses. 50

Figure 55 Time profile total number concentration SMPS (VMM, ECN, GGD & ISSEP) week 6 4.5.2. SMPS CORRELATION FOR SEVEN SIZE RANGES AND TOTAL To compare the size distributions of the ISSEP SMPS with the Joaquin SMPS the data was split into the seven size ranges from the UFP monitor (20-30, 30-50, 50-70, 70-100, 100-200, >200 nm, total) and the size range <20 nm was added. The number concentration in these eight size ranges was compared using correlation plots (Figure 56 - Figure 63). The ECN SMPS served as reference. The RCs and R 2 of the regression lines are also presented in Table 6. The correlation plots show that the correlation between the reference SMPS (ECN) and the ISSEP SMPS was strong for all particles sizes (R 2 = 0.71-0.98 / r = 0.84-0.99). 51

Figure 56 Correlation plot number concentration SMPS particle size <20 nm Figure 57 Correlation plot number concentration SMPS particle size 20-30 nm 52

Figure 58 Correlation plot number concentration SMPS particle size 30-50 nm Figure 59 Correlation plot number concentration SMPS particle size 50-70 nm 53

Figure 60 Correlation plot number concentration SMPS particle size 70-100 nm Figure 61 Correlation plot number concentration SMPS particle size 100-200 nm 54

Figure 62 Correlation plot number concentration SMPS particle size >200 nm Figure 63 Correlation plot SMPS total number concentration 55

Size range ECN ISSEP RC ISSEP R 2 ISSEP r <20 nm 1 1.0992 0.7721 0.8787 20-30 nm 1 0.9489 0.713 0.8444 30-50 nm 1 0.9557 0.8751 0.9355 50-70 nm 1 0.9668 0.9369 0.9679 70-100 nm 1 0.9919 0.9664 0.9831 100-200 nm 1 1.0471 0.9816 0.9908 >200 nm 1 1.132 0.9848 0.9924 ISSEP 8.5-850 nm ECN 10-1093 nm 1 1.0312 0.8863 0.9414 Table 6 SMPS RCs and R 2 ISSEP compared to ECN When comparing the number concentrations in the different size ranges the biggest difference between the ECN SMPS and the ISSEP SMPS was found for particles bigger than 200 nm. The ISSEP SMPS gave 13% higher particle number concentrations in the size range > 200 nm. The particle number concentration in the size range <20 nm was 9% higher. Looking at the total number concentration the difference was only 3 %. The small difference could be explained by the slightly underestimated particle number concentrations in the particle size range 20-100 nm which compensates the overestimation in the <20, 100-200 and >200 nm size ranges. Sampling from a main sampling line with a high flow rate could be responsible for the differences in number concentrations between the two systems. 4.5.3. TIME PROFILE EPC WEEK 7 During the last week of the measurement campaign the VITO EPC was moved from the VITO truck to the ISSEP trailer and connected to the ISSEP sampling system. Figure 64 shows the number concentration time profile (30 min average) from the EPC in the ISSEP trailer (ECPC ISSEP). This figure also shows the time profile of the reference EPC (ECPC ECN) during this period for comparison. Both total number concentration profiles followed the same trend. The EPC connected to the ISSEP sampling system gave only higher number concentrations. 56

Figure 64 Time profile total number concentration EPC (ECN & ISSEP) week 7 4.5.4. EPC CORRELATION The correlation between the EPC connected to the ISSEP sampling system and the EPC connected to the Joaquin sampling system (ECN) is shown in Figure 65. The regression line shows that the particle number concentrations measured with the EPC connected to the ISSEP sampling system were about 25 % higher than the number concentrations measured with the EPC connected to the Joaquin sampling system. The difference that was found when the EPC in the VITO truck was compared to the ECN EPC was about 3 %. The total difference in particle number concentration between the sampling systems was about 22 %. The correlation between the reference EPC connected to the Joaquin sampling system (ECN) and the EPC connected to the ISSEP sampling system was strong (R 2 = 0.95 / r =0.9733). 57

Figure 65 Correlation plot total number concentration of EPC connected to ISSEP sampling system and EPC connected to Joaquin sampling system 4.5.5. BOX PLOT Box plots of the ECN SMPS and EPC and the ISSEP SMPS and EPC are shown in Figure 66. This plot shows that the ISSEP SMPS and EPC median were higher than the ECN SMPS and EPC median. The biggest difference was found for the EPC data. The data was more spread (box and whisker) because higher peak concentrations were measured. The use of the ISSEP sampling system resulted in the measurement of higher particle number concentrations. 58

35000 30000 25000 Total nc (pt/cm 3 ) 20000 15000 10000 5000 0 ECN SMPS ECN EPC ISSEP SMPS EPC ISSEP Figure 66 Box plots ECN SMPS and EPC and ISSEP SMPS and EPC 4.5.6. CONCLUSION The correlation between the ECN SMPS and the ISSEP SMPS was strong for all particles sizes (R 2 = 0.71-0.98 / r = 0.84-0.99); The ISSEP SMPS measured 3% more particles in the total size range compared to the ECN SMPS; The particle number concentrations measured with the EPC connected to the ISSEP sampling system were about 22 % higher than the number concentrations measured with the EPC connected to the Joaquin sampling system; The correlation between the reference EPC connected to the Joaquin sampling system (ECN) and the EPC connected to the ISSEP sampling system was strong (R 2 = 0.95); Higher peak concentrations were found for the instruments connected to the ISSEP sampling system; Sampling from a main sampling line with a high flow rate will improve sampling efficiency and result in higher particle number concentrations. 4.5.7. DIFFUSION VERSUS NON-DIFFUSION CORRECTED The non diffusion versus diffusion corrected regression coefficient and coefficients of determination are summarized in Table 7 (EPC), Table 8 (UFP monitor) and Table 9 (SMPS). 59

EPC VMM GGD UoL VITO ISSEP Non diffusion rc 0.9369 0.9313 0.8791 0.9716 - R 2 0.9889 0.9913 0.9923 0.992 - Diffusion rc 0.9969 0.993 0.8716 1.0313 1.24673 R 2 0.9902 0.9941 0.9917 0.9933 0.9473 Table 7 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected EPC data UFP monitor Size range UoL VITO Non diffusion Diffusion Non diffusion Diffusion rc R 2 rc R 2 rc R 2 rc R 2 20-30 nm 0.7083 0.9019 0.7107 0.9019 0.8534 0.9385 0.8492 0.9385 30-50 nm 0.8746 0.9345 0.8763 0.9345 0.9491 0.9397 0.9464 0.9397 50-70 nm 0.9854 0.9402 0.9865 0.9402 1.0448 0.9464 1.0431 0.9464 70-100 nm 0.9870 0.9553 0.9877 0.9553 1.029 0.9513 1.0279 0.9513 100-200 nm 1.0148 0.9532 1.0153 0.9531 1.0063 0.9589 1.013 0.9525 >200 nm 0.9743 0.3641 0.9745 0.3614 1.3791 0.6043 1.3788 0.6043 20 - >200 nm (total) 0.9009 0.9719 0.8991 0.9715 0.9956 0.9762 0.9924 0.9755 Table 8 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected UFP monitor data SMPS Size range VMM GGD Non diffusion Diffusion Non diffusion Diffusion rc R 2 rc R 2 rc R 2 rc R 2 < 20 nm 1.0108 0.9617 1.0173 0.9569 0.9567 0.956 0.9640 0.9507 20-30 nm 0.9213 0.9548 0.9201 0.9503 0.9234 0.9511 0.9214 0.9474 30-50 nm 0.9650 0.9878 0.9647 0.9833 0.9871 0.9577 0.9879 0.9533 50-70 nm 0.9654 0.9888 0.9650 0.9843 0.9932 0.982 0.9920 0.978 70-100 nm 0.9641 0.9933 0.9645 0.9891 0.9946 0.9921 0.9951 0.9882 100-200 nm 0.9752 0.9962 0.9754 0.9922 1.0139 0.9959 1.0140 0.9919 >200 nm 1.0216 0.9933 1.0225 0.9894 1.0610 0.9967 1.0616 0.9927 10-1094 nm 0.9751 0.9919 0.9767 0.9879 0.9848 0.9905 0.9835 0.9859 Table 9 Regression coefficient and coefficient of determination for non diffusion and diffusion corrected SMPS data 60

The instrumental correction factors were derived from the diffusion corrected regression coefficients in Table 7, Table 8 and Table 9. 4.6. INDOOR CONDITIONS The temperature and relative humidity were determined inside all measurement cabins, truck and trailers. The temperature profiles are presented in Figure 67 and the minimum, maximum and average temperature can be found in Table 10. Figure 67 Indoor temperature time profiles VITO truck SMPS cabin Trailer ECN TSI cabin VMM trailer Minimum 17.7 16.7 17.7 15.7 7.0 Maximum 28.3 28.0 19.6 27.7 15.1 Average 22.6 23.6 18.7 18.3 10.1 Table 10 Minimum, maximum and average temperatures inside the different cabins, trailers and truck The temperature in the ECN trailer was characterized as the most stabile. The VITO truck and VMM trailer followed the same trend, only the temperature in the VMM trailer was much lower compared to the VITO temperature profile (>2x). During the measurement campaign the temperature in all enclosures with UFP instruments was above 15.7 degrees Celsius. The relative humidity profiles are presented in Figure 68 and the minimum, maximum and average relative humidity can be found in Table 11. 61

Figure 68 Indoor relative humidity time profiles VITO truck SMPS cabin Trailer ECN TSI cabin VMM trailer Minimum 19.6 14.1 26.2 16.7 25.4 Maximum 55.3 47.0 56.1 70.4 96.3 Average 32.4 26.7 44.8 39.0 68.5 Table 11 Minimum, maximum and average relative humidity inside the different cabins, trailers and truck Figure 68 and Table 11 show that relative humidity in the ECN trailer was most stabile compared to the relative humidity in the other cabins, truck and trailer. Highest relative humidity was found in the VMM trailer. The relative humidity range between the enclosures was smaller from the 11 th till the 26 th of January. This was the result of colder weather. During the measurement campaign the relative humidity in all enclosures with UFP instruments was below 70.4 %. Average relative humidity was between 27 and 45 %. 4.7. OUTDOOR CONDITIONS In Figure 69 the wind rose is presented graphically showing the wind conditions, direction and speed, during the measurements campaign (13 December-1 February) at the Wilrijk location. 62

Figure 69 Wind rose total period The daily average wind directions are also shown in Figure 70. The dominant wind direction during the measurement campaign was West South West to West North West. From the 11 th till the 26 th of January the dominant wind was North East to East resulting in colder weather (Figure 70). The temperatures dropped below 0 C (Figure 71). 63

Figure 70 Daily average wind directions Figure 71 Time profile outdoor temperature and relative humidity 64

T RH Minimum -7.2 57.0 Maximum 13.4 100 Average 4.5 92.1 Table 12 Minimum, maximum and average outdoor temperature (T) and relative humidity (RH) As can be seen from the table above (Table 12) average temperature was 4.5 C and average relative humidity was 92.1 %. 4.8. UFP POLLUTION ROSE The pollution rose correlates wind direction data with a pollutant concentration value. The total number concentration from the ECN EPC was correlated with the wind direction in a pollution rose shown in Figure 72. The non diffusion corrected data was used for the pollution rose because diffusion correction was only possible after arrival of the nuclear source at the 10 th of January reducing the dataset considerably. The pollution rose does not show a clear relation between the total number concentration and a specific wind direction. During prevailing wind directions local roads did not influence total number concentrations much at the location. Figure 72 Pollution rose total number concentration EPC ECN 65