1. Giorgio Martini opened the meeting and welcomed the significant number of participants present as well as those joining the web conference.

2. Giorgio Martini introduced the presentation from JRC reminding the group that this was a literature survey study to determine the current state of play and knowledge on sub-23nm particles. The PMP group had delegated this activity to the JRC at the 27th meeting. Mr Martini also explained the basis of the existing legislation – which was developed to measure solid particles from diesel engines where a significant amount was known about the characterisation of the particles. The need for a robust solid particle number measurement and the state of the art of reliable measurement equipment led to the decision for a 50% cut off size of 23nm. As the PN (particle number) measurements are being extended to other technologies, so it is important to review the state of knowledge regarding the existence, characterisation and measurement possibilities for sub-23nm particles.

3. Barouch Giechaskiel gave the JRC presentation: Key points are summarised below:

• Nucleation mode is liquid mostly 10-20 nm. PN measurement to the PMP procedure evaporates the liquid particles and nucleation mode more or less disappears.
• Diesel literature in last 5 years shows separate modes (nucleation and accumulation) of solid particles in larger older diesel vehicles at low load, rarely seen in other diesel engines. Must be noted that these are from direct tailpipe measurements not from the dilution tunnel / CVS.
• Are the particles really solid or only defined as solid because they are measured after the VPR (evap tube 350 deg C)? TSI mentioned that if formed during combustion at same size as primary particles then this raises the question of why they don’t agglomerate. Ricardo suggested maybe more likely to see this in low soot engines. Others assume might be particles formed from combustion of lube oil.
• Primary particles approx. 25nm. GDI primary particle distribution is wider (7-60nm). Therefore % sub 23nm probably higher for GDI.
• GDIs show typically a shoulder at 20nm, a separate solid nucleation mode is not typical but size distribution can peak at 20nm in some operation modes (highly unlikely).
• Conventional gasolines show sub 23nm from metal additives of lube oil or fuel.
• Mopeds – quite a lot of solid sub-23nm particles seen even down to 6nm although this can also be a sampling artifact.

JRC has run some testing: not on NEDC, but using WLTP but using PMP protocol, PCRF 1000 and measuring in parallel sub and above 23 nm particles. No additional loss correction was included.

• Diesels less than 20% particles below 23nm
• GDI slightly higher age of solid sub 23nm particles compared to diesels but typically < 60
• GDI nucleation mode (as shoulder) peaked at 10nm
• Low temperature testing (-7 deg C) increased the percentage.
• Regeneration (one car, 2 regenerations) showed similar percentages and no distinct solid nucleation mode particles

• TSI mentioned to be very careful not to overemphasize the 3nm as many measuring issues with sizes this small.

• Even at tailpipe didn’t see high levels of solid nucleation particles. Thanasis Mamakos (AVL) wondered exactly what these particles were and what their origin was.

• Measurement Feasibility PNC:
  • Lowering cut off of PNC is potentially advantageous and reduces material dependency
  • Down to 10nm possible with existing PNCs but below would need different model and thus big modifications for existing PN systems. Might need for appropriate calibration material and would mandate use of an electrometer for both calibration and validation of the PMP system.
• Measurement Feasibility – VPR:
  • Penetration / losses: losses of VPR increase significantly as 50% cut off size reduced – feasible only as indication of existence. Generation of monodisperse particles < 30nm problematic but not impossible for characterising the VPR efficiency.
  • Formation of solid particles from volatiles (e.g. pyrolysis) – there are very few studies available – indications it may occur in the presence of sulphuric acid.
  • Hydrocarbons – Theoretical estimations show that they will renucleate at concentration of 3 mg/m³
  • Sulphuric acid renucleates at 0.7 to 3.5ug/m3 – fuel less than 10ppm and lube conversion translates to 300 ug/m³ – same order of magnitude.
  • Even when considering dilution in CVS and primary diluter – renucleation is likely – experimentally it has been shown in some cases sub 23nm were renucleated particles.
  • There was some discussion that presence of ammonia would increase the risk of renucleation. Note: Request for data on formation of solid particles from volatile material.
• Summary:
  • With existing equipment reducing cut off size is not recommended.
  • Decreasing size to 10nm is possible but addition of catalytic stripper to replace or complement the evaporation tube in the VPR is recommended.
  • Decreasing size below 10nm – Uncertainty very high – possible for research but not for legislation.
  • Open issues – regeneration, pyrolysis, catalytic stripper performance and update of calibration procedures (VPR and PNC).

4. Mr Martini concluded from the evidence presented that the VPR system is not suitable for measurements with D₅₀ < 23nm. However, the question of measuring during an active regeneration remains.

5. Given that for current GDI, it is shown that there is not a big difference between the particle emissions from GDI compared to diesels; the group discussion preliminary conclusions were that there is no clear driver to extend the D₅₀ to below 23 nm.

6. PMP group concluded that there is no justification for extending the D₅₀ to below 23 nm for diesels. Jürgen Stein reminded the group that higher injection pressures do not lead to the decreased size of the particles as is often feared.

7. Ms. Hosier wondered if the nucleation mode solid particles exist but are not independent of the accumulation mode and there are no separate or additional control technologies – does it make sense to regulate.

8. Mr. Stein (ACEA / EUROMOT) noted that industry has invested millions on the equipment and yet still today there is not a really good calibration procedure existing – therefore major focus should be on improving calibration on existing systems.

9. Reproducibility / repeatability questions need to be considered as the increase in uncertainty of measurement from reducing the D₅₀ would need to be compensated in the limit values.

10. Additives in fuel – for Europe not a big deal – but fuel borne cat additive only in conjunction with DPF.

11. Ms. Karlsson noted that it would be more productive to spend the time on improving calibration rather than chasing the extreme circumstances.

12. JRC agreed that we might be talking only about non DPF vehicles and extreme lubricants.

13. The discussion will continue at the next PMP meeting and focus on what elements need to be provided to the legislators to support policy decision making.

• Information on nature of the particles: Are the particles even real? Do they originate upstream or down stream of PF (particle filter)? If they come from downstream of the PF, then attention is needed, however the current review dosen’t support this assumption……
• Health effects depend on what’s in the particles.
• It makes sense only if relevant for human health and independent from accumulation mode already measured.
• What can we do about them if they exist? Feasibility to measure – reproducibility – changing the system ….

14. Jürgen Stein recommended to show the presentation and the ‘unknowns’ and clearly identifying where further investigations are required.

15. Mr. Andersson noted that it’s extremely clear from the JRC literature study that it is not possible to measure below 10nm. He recommended that with CVS need to stay at 23nm, with further research for a D₅₀ between 10 and 23nm.

16. Discussions stressed the need for further investigations as well as a need for guidelines for gathering future data to ensure it’s comparable. The group again suggested this is not the highest priority… Health relevance can be determined only after know what particles are – also what happens to the particles in the environment – do they persist?

17. JRC will prepare a summary of their findings, the group discussion and consensed points and a draft of the guidelines for gathering further data (eg tailpipe vs. CVS) for review at PMP 29th meeting.

18. Regarding active regeneration – need to develop some recommendations and procedures OICA tasked with collecting available data (if any) and prepare guidelines for measuring on standardized basis.

19. Investigating particle nature: Hans –Georg Horn (TSI) offered to check and report back what techniques are available.

20. EU Com (Mr Troppman ) gave a brief overview of the regulatory activities on NRMM PN. New NRMM impact assessment being completed – extension of scope of NRMM to additional power categories, inclusion of large LNG engines, adaptation of limit values particle number – similar to EU 6 heavy duty. EU Com needs a limit value for impact assessment – have looked at data for HD, non-road etc and determined a value of 1E+12 #/kWh for the impact assessment and most likely this will be carried into the draft proposal. This has raised some concern with EU Com internally. There is still a need for an experimental program, not only for this rule making but for the next revision clause.

21. EUROMOT (Paul Williams) presented some principles for NRMM PMP program. He briefly introduced EUROMOT as a new stakeholder to PMP. Essentially there are 40 member companies; in simple terms this covers a vast array of engines including everything which moves without a licence plate and everything which generates heat and power.

PMP-28-03 | Particle Measurement Programme: Euromot comments on NRMM engine work programme

22. EUROMOT expressed willingness to participate and identified the need for EU Com /JRC to take care of proper systems and testing – as this measurement is rather new. EUROMOT also requested EU Com to allow manufacturers in house data to be incorporated. Need to identify subject engines and test cycles.

• Specific attention must be paid to passive regeneration during test.
• Need to check both discrete and RMC (ramped modal cycle). On RMC need to take as much as possible from PN ECE-49-06.

23. EU Com mentioned that Co-Decision will start once the new Commission is in place during 2014 and therefore the data from the NRMM PN test program should be available to support this timing.

• Paul Williams (EUROMOT) reminded that rolling out Euro 4 during 2014 and their facilities are very busy.
• JRC (GM) mentioned they have some possibilities for testing but already they are also busy and won’t be able to install many engines.
• AECC noted also made some testing back in 2010 and would like to contribute. Paul Williams noted that the AECC testing was one engine / one size.
• Ricardo reminded of the need to use partial flow systems and that there is a good correlation between full and partial flow.
• Euro 3 engines with DPF tested but not the real Euro 4 engines – where there is a different proportion of manufacturers using passive regeneration.
• Clear R49.06 should be the basis but the next aspect is test cycles – transient vs. steady, engine power and technologies etc.

24. EU Com / JRC Giorgio will prepare a draft outline of the test program and then share with the group during the next PMP Jan GRPE.

25. Progress update of this project was given by Francesco Riccobono (JRC).

26. Stability of the aerosol (thermal) for calibration: In considering the aerosols most similar to soot, it was found that the counting efficiency variation due to material dependency was in same order of magnitude as the measurements – soot-like” seems not to be a good criteria to select the standard aerosol, although need for harmonisation remains.

27. The next experimental setup will be to test many silver (Ag) generators; note silver is the furthest away from today’s materials …. This has implications on pass / fail of measurement results. CAST generators optimised for small size are quite similar now and should be compared to silver.

28. EMRP will finish in 2014. Feb 2014 meeting will discuss next steps and recommendations. For more information, see the EMRP website.

29. JRC also provided an update on periodic emission control metrological validation – see also (GRPE-PMP-28-05) – 7 instruments reviewed and tested. Research on-going for instruments to replace todays opacimeters – instruments evaluated show large variability at low PN / mass conc. and sizes.

PMP-28-05 | Emerging requirements for measuring pollutants from automotive exhaust emissions Progress report on the European Metrology Research Programme.

30. Presentation provided by Dr Horn (TSI)

• Draft – DIS submitted for vote Oct 2013. Approved.
• FDIS to be submitted before 8 May, 2014.
• Publication mid 2014 (approx.).

31. The ISO standard focusses on how to do the calibration – a backbone document for metrology institutes – how to acquire the data, process the data etc …

32. ISO does not specify aerosol materials as this is application specific, nor will it provide information on how to generate the primary aerosols – on that a calibration aerosol must have very few multiply charged particles.

33. Method developed how to demonstrate linearity of CPC to much lower concentrations.

34. Discussion: EMRP will decide on candidate aerosols, potentially there will be a need for a round robin. The question is how to organise and co-ordinate the calibration aerosol discussion and testing requirements.

35. Giorgio Martini reminded the PMP group that the EU Com wanted to review because of GRPE documents from Russia. PMP agreed to start with a literature review, following which PMP could then decide whether to go forward, stop or assign to another group.

36. Giorgio Martini presented the interim status of the literature survey so far. A more comprehensive presentation will be available for discussion at the next meeting. Essentially there is a large body of work since 2000, but many issues in assessing the information due to non-standardised testing methods.

PMP-28-06 | Particle emissions from tyres ad brake wear: On-going literature review

37. Preliminary findings:

• Non exhaust emissions (includes resuspension) currently estimated for 50% of traffic related PM emissions in urban env. relatively increasing because other sources are decreasing rather than because absolute levels increase.
• Brake wear in urban location 16-55%, approx. 50% by mass brake wear particles become airborne – the others expected to be too big to be airborne.
• In coarse particle fraction mean diameter 5-6 um, but found transition metals in fine fraction of airborne brake wear particles
• Tyre wear: 5-30 % generated tyre wear particles emitted as PM10 depending on the driving conditions. Non exhaust PM10 contains 11-20% tyre wear particles
• Coarse fraction >7um, but PN 30-60nm mode has been reported at non-steady state driving conditions with stops.
• Transitions metals Fe, Cu, Zn, have been found in tyre wear debris – also organic compounds PAH, benzothiazole etc.
• Emission factors – major gaps in knowledge found.

PMP-28-06 | Particle emissions from tyres ad brake wear: On-going literature review

38. ERTICO reminded the group that we should refer to ‘tyre/road’ particles as without the road, the tyre does not wear. The group accepted the recommendation for clarity in future presentations.

39. The group briefly discussed other papers known to them and members – especially ERTICO offered to send papers / links to JRC for inclusion in their study. More details in Jan 2014 PMP-29th session.

40. Arrangements for the next meetings: Agreed that a doodle poll would be launched to establish the next meeting date (Feb / Mar 2014).