Hugo Denier van der Gon & Jeroen Kuenen With emphasis on recent TNO Improvements to metal emission estimates

11 May 2009Improvements to metal emission estimates2 Contents Background Case I - Metal contents of diesel and petrol fuel Conclusions fuel analysis Case II - Copper from brake wear Implications for EF guidebook? Outlook

11 May 2009Improvements to metal emission estimates3 Background (heavy) metals (HM) Elevated presence and availability of HM in ecosystems and the urban environment due to human activities HM (e.g. lead, cadmium) are toxic causing adverse health effects Main anthropogenic sources of heavy metals are Industrial sources (e.g., mining activities, foundries and smelters) & Diffuse sources (e.g., combustion by-products, traffic, etc..) Considerable attention over the last decades (Pb, Hg, Cd) In recent years two European HM inventories: TNO (Denier van der Gon et al.) and ESPREME (Reiss et al.) – both presented at TFEIP meetings in 2005 & 2006.

11 May 2009Improvements to metal emission estimates4 Comparison of modelled and measured lead concentrations in air using official/ TNO (blue) and ESPREME (red) emissions. Natural and historical emissions are included. Issue: Current knowledge is not able to explain the ambient concentrations of many heavy metals (60-75% explained). Source: Sliggers et al. (2007) Difference mostly due to Pb in fuels

11 May 2009Improvements to metal emission estimates5 Lead emission in the UK from 1970 to 2004 (t/yr) for road transport and other sources + (correction for potential resuspension of Pb containing dust, and necessary emission input to explain observed concentrations (black line) Source: Dore et al., (2006) Major Pb emission Reduction! But gap increases! Still Pb in fuels?

11 May 2009Improvements to metal emission estimates6 Case I - Pb in petrol The problem: Leaded fuels have been used for a long period, clear adverse health effects have been reported. As a result leaded fuels have been banned in Europe. Lead emission from unleaded road transport fuel combustion has been suggested as a missing source to explain the discrepancy between measured and modeled Pb concentration in air (Pacyna et al., Atmospheric Environment 2007, 41: ) Reason: Pb is present in the crude and even Pb contents below the EC limit value (<5mg/l) can be a significant source give the large quantities of petrol consumed Is this realistic?

11 May 2009Improvements to metal emission estimates7 Study: Metal contents of diesel and petrol fuel sold on the European Market Objective: to obtain high quality analytical data on the concentrations of dissolved metals in petrol and diesel as sold in nine European countries. Methodology: Fuel samples collected at service stations - The distribution of fuel samples selected by CONCAWE with sensitivity to various issues in different Member States, including: Petrol and diesel fuel consumption (also as % of EU-27), Penetration of biofuel components, Extremes in climactic conditions, and Supply and distribution logistics. Reference: Denier van der Gon et al., Metal contents of diesel and petrol fuel sold on the European Market, TNO report 2009 Final draft submitted to CONCAWE, status not final yet.

11 May 2009Improvements to metal emission estimates8 ES 5 20 PL 5 NL 5 DE IT UK 15 FR SE 5 FI 5 Country Nr. of Petrol samples Nr. Of Diesel samples ES 5 20 PL 5 NL 5 DE IT UK 15 Fuel consumption in the covered countries represents over 80% of the consumption in the EU-27.

11 May 2009Improvements to metal emission estimates9 Metals analyzed in transport fuels AQ interest defined as – included in UNECE HM Protocol Metals outside AQ interest not further discussed here Note: Finnish data not included in presented results due to possible contamination – coverage of EU petrol and diesel still > 80%

11 May 2009Improvements to metal emission estimates10 Just to prove we do have instruments… Inductively coupled plasma –mass spectroscopy X2 QAPEX ICP-MS

11 May 2009Improvements to metal emission estimates11 Examples of results - I Dot = average value; the bar indicates high-low value (range) All Pb values in ppb (ug/kg) range! The Pacyna et al. paper (AE, 2007) used mg/kg range – overestimated!

11 May 2009Improvements to metal emission estimates12 Examples of results - II Considerable range in Cu values but average values are below 10 ug/kg Note: guidebook EF is currently 1700 ug/kg (to be discussed later)

11 May 2009Improvements to metal emission estimates13 Average metal content of transport fuel by country DieselPetrol - All concentrations in ppb (ug/kg) range - No specific country pattern - Petrol slightly higher than diesel but essentially comparable

11 May 2009Improvements to metal emission estimates14 Summary: Average metal contents in EU Concentrations of the priority heavy metals (Cd, Hg, Pb) and other metals (As, Cu, Cr, Ni, Se and Zn) listed in the UNECE Heavy metal protocol in road transport fuels are currently low (below 10 ug/kg), Zn is slightly elevated but still low Implications? To be discussed…

11 May 2009Improvements to metal emission estimates15 Case II: Brake wear, an important source for particulate copper Brake wear generates brake lining particles, which were until now not accounted for in emission inventories for copper because EFs were old and based on asbestos brake pads. We assessed the importance of brake wear to explain atmospheric copper concentrations. We also used preliminary fuel analysis measurements to reassess the EF for transport fuel combustion Conclusion: fuel combustion no longer important, brake pads are dominating source in EU Reference: Denier van der Gon et al., A revised estimate of copper emissions from road transport in UNECE-Europe and its impact on predicted copper concentrations, Atmospheric Environment, Volume 41, , 2007

11 May 2009Improvements to metal emission estimates16 Copper content of brake pads and linings Copper content (% wt) Westerlund (2001) HDV- Volvo 0.01HDV-Scania 11.8New passenger cars (1997) - front 9.2New passenger cars (1997) - rear 7.2Old a) passenger cars-front 5.1Old a) passenger cars-rear This type of data combined with brake wear PM emission factors gives the emission of your component of study (here: copper) Elevation should be visible in vicinity of the source:

11 May 2009Improvements to metal emission estimates17 Copper concentration of ambient PM confirms source relevance

11 May 2009Improvements to metal emission estimates18 Implications for guidebook? Please join the discussion! Road transport wear emissions are important metal sources –review of literature for al HM is relevant. (Updates may be needed – e.g., because of change in materials) Guidebook EF for exhaust is expressed in ug/kg fuel but 1.EF = EF_f(uel) + EF_m(otor oil burning) + EF_e(ngine attrition) 2.EF_f = low : High EFs for e.g. Cu and Zn do not originate from fuels and EF_m + EF_e are independent of fuel 3.So, LPG is no different from petrol and diesel? 4.Few measurements available for HM in exhaust PM (Vouitsis et al., 2007) = direct quantification ( -> low Pb, Cu substantial Zn, Fe and Sb depending on lube oil and driving cycle) 5.This information should be combined with information on EF_m and EF_e to better understand the contribution of Road transport to total HM emissions.

11 May 2009Improvements to metal emission estimates19 Outlook Through identification of major sources and uncertainties for a particular metal or source hypothesises can be formulated These can be verified (e.g. Cu from brake wear) or falsified (e.g., Pb from unleaded petrol) This is progress! Accuracy increases, uncertainty reduces. Information from emission inventories and model results (regional under- / overestimation) to define the “candidates” for further investigation. Ex. 1 - metal contents of representative lube oils used in Europe, lube oil losses during driving and fraction of the lost lube oil burned would be a next step in dissecting the exhaust metal emissions and tracing the origin of measured metals in exhaust PM. Ex. 2 – Diffuse industrial emissions? Difficult to get on the research agenda…..  (Yes, we always complain a bit…..)

11 May 2009Improvements to metal emission estimates20 Acknowledgements The project Metal contents of fuels sold on the European market was funded by CONCAWE. Contact: