1. PMP: SUB 23 NM MEASUREMENT RECOMMENDATIONS B. Giechaskiel, G. Martini Institute for Energy and Transport Joint Research Centre 3 April 2014

2. Sub23nm particles Percentages around 30-40% (over a cycle) Mamakos et al. 2011 ETH Giechaskiel, PMP 29

3. GDI, vehicle Khalek et al. 2010Ronkko et al. 2014 GDI, produces nanoparticles even when not fueled, coming from oil Monitoring GDI important

4. Formation of particles in the VPR Indications when sulfur exists Formed solid particles were <10 nm Difficult to justify (pyrolysis?) Example is reaction of sucrose with strong sulfuric acid Experimental suggestions: HC and sulfuric acid through PMP Both as gaseous and liquid droplets SMPS and CPC downstream PMP Check PCRF effect

5. Volatile Removal efficiency (ET) Hydrocarbons Tetracontane will re-nucleate at >10 7 p/cm 3 or 3 mg/m 3 Sulfuric acid Sulfuric acid will re-nucleate at 0.7-3.5 μg/m 3 Growth after the ET The re-nucleated nucleis are 1-2 nm. Organics are necessary for the nucleis to grow Theoretical calculations and experimental results show that they can grow to 6 nm (10 11 p/cm 3 organics) or 20 nm (10 14 p/cm 3 hexadecane, <5 ppm C3)

6. Sulfur compounds in DPFs Partial DPF Alumina based coating with Pt as active metal No artifact from sampling lines etc. Formation of sulfuric acid particles from SO2 to SO3 conversion Kajalainen et al. 2014 SO2

7. DPF regeneration Volatile artifact appears as solid particles <23 nm (CVS) PCRF: 100x10 No artifact >6 nm (tailpipe) PCRF: 15x15 Typically no artifact above 10 nm (Zheng et al. 2012, Mamakos et al. 2013)

8. DPF regeneration Gaseous HCs do not correlate with PN<23 Probably heavy HCs Sulfates probably important Artifact probably from desorption after tailpipe Pre-conditioning of setup is important

9. PCRF selection PCRF 100x10 Still >3nm artifact Lower solid surface nucleation vs condensation Probably no issues with >10nm measurements

10. Moped Volatile artifact even with high dilution (1000x10) With EEPS connected to PMP (350x20) no detectable artifact. Similarly with a 10 nm CPC Thus artifact around <6nm

11. Volatile Removal Efficiency (CS) Catalytic Stripper (CS) Removes volatiles by oxidation Even >35 times highest HC concentration (eg moped) Better removal efficiency of tetracontane Traps sulfur Up to 10 mg/m 3 Might oxidize SO 2 to SO 3 Particles might be formed if saturated Higher particle losses

12. CS has also limitations Silica-alumina coating with Pt and Barium oxide Amanatidis et al. 2013

13. Summary Monitoring of sub23nm is recommended Decreasing the size to ~10 nm is possible. VPRs should be used with high dilution (>1000:1) Special attention to GPFs and DPFs (no soot) The CS is an alternative solution that has to be investigated: Saturation with sulfur Formation of particles SO 2 to SO 3 conversion

14. Summary To measure below 10 nm: A dilution system with minimum losses of sub23 nm is necessary. A catalytic stripper well documented is necessary A full flow CPC with low cut-off size is necessary

15. Next steps The setup has to be well pre-conditioned Organics, sulfates would be useful Measurements in parallel with PMP systems with ET and CS devices with both 23nm and ~10 nm PNCs. Support from instrument manufacturers needed especially for CS, or setting a second CPC

16. Next steps Tests without CS should be conducted with as high PCRF as possible (at least 100x5) Note that even with PCRF 10000, and PNC concentrations <1000 p/cm3, artifacts can happen because they depend on the volatile species’ concentration. When high sub23nm concentrations are measured (>100%, at emissions 10^11 p/km) the tests should be repeated with 10x higher PCRF Lower concentrations could be background noise

17. Thank you for your attention! Draft report is ready for anyone interested! barouch.giechaskiel@jrc.ec.europa.eu