1. Uncertainties in the UK Heavy Metal Emissions Inventory
Chris Dore
AEA Energy and Environment
UK Emissions Inventory Programme
Funded by Defra: RMP2106

2. Contents 1. Principles of Uncertainty 2. Combustion Sources
3. Non-Combustion Sources
4. “Missing” & Non-Anthropogenic Sources
5. Mapping Emission Estimates
6. Conclusions

3. 1. Principles of Uncertainty
Combination of uncertainties
Point sources- combination of random independent errors
Area sources- one EF, prone to bias.

4. 1. Principles of Uncertainty

5. 2. Combustion Sources Solid
Coal, Coke, Anthracite & SSF
Important for As, Cd, Cr, Pb, Be and a major source of Mn, Hg & Se
Point Sources
Well characterised, and emissions data are reported. Hence no bias is expected.
But possible issues associated with extrapolation of few measurements
Concentrations (ppm) of metals in bituminous coals (Smith 1987)

6. 2. Combustion Sources Solid
Coal, Coke, Anthracite & SSF
In 2005, over 2/3 of UK steam coal was imported
~80% from Russia/South Africa, 13% from Columbia/Indonesia.
Distribution with the ranges shown is not known.
Fugitive emissions from Coke Ovens
Area Sources
Median values taken from a wide range
Fuels assumed to be the same as coal
Limited information on PM control
Potential for significant bias

7. 2. Combustion Sources Petroleum
Petroleum Fuels
Important for all metals except Cr and Hg, major sources of Be, Cd, Ni, Se, V & Zn
Metal emissions are primarily associated with petroleum coke, waste lubricants & fuel oil (higher metal contents)
However, large volumes of gas oil, DERV and petrol are consumed, giving notable contribution, despite their lower metal contents.
Point Sources
Variability would result in little impact on emissions total
Area Sources
Metal content taken from literature values
Fuel oil: variability of 2-4 times the mean value
Gas oil/DERV: very variable metal content data
Waste lubricants (10% of Pb): factor of ~10 variability metal content

8. 2. Combustion Sources Pb in Petrol
Pb in Petrol, and Unleaded Petrol
UK uses EF’s based on measurement data
Pb content of “unleaded” = 0.04 mg/l (UKPIA 2003)
70% assumed to be released to air
Small when compared to the limit value (5 mg/l)

9. 2. Combustion Sources Burning of CCA Treated Wood Cremation
“CCA” Cu, Cr As treated wood.
Major source for As, important for Cr
Data available on As consumed in CCA preservatives.
But v difficult to estimate the quantities of wood burned
Cr and Cu emissions extrapolated from As data
Estimates could be out by a factor of 20.
Cremation
Well characterised in the UK
Uncertainties of Hg would give a maximum impact of 10% increase to the UK total.
Other Fuels
Scrap tyres, MSW and wood in power stations
Not a particularly large source

10. 3. Non-Combustion Sources
Metal Industry Processes
Important for most metals
Includes processes at steelworks (sintering and blast, basic oxygen, & electric oxygen furnaces), foundries, 1° Al production, 2° Pb & Al production, and various other non-ferrous metal processes
Variety of point source data and literature data.
Estimates are likely to only include stack emissions, and fugitives are therefore not accounted for.
Chloroalkali Processes
Important for Hg
The main source is associated with the ventilation air from the cell room
Very difficult to asses for a variety of reasons, assume that the emission could be underestimated by a factor of five (also used for other fugitive emissions)

11. 3. Non-Combustion Sources
Tyre & Break Wear
Important for Zn and Cu
Estimates are a fixed fraction of PM10 emission from these sources
Tyre wear is easy to estimate, but PM10 emission less so. UK specific data. Metal concentrations in tyres are highly variable (less so for HGV’s).
Metal content of brake linings is fairly well characterised.
Emissions per vkm vary by nearly an order of magnitude. UK specific data.
“Odd and Ends”
A variety of other sources included in the inventory (fireworks, glass manufacture, waste incineration etc.)

12. 4. Missing & Non-anthropogenic Sources
“Missing” Sources
Accidental/malicious fires
dwellings, factories, other buildings, vehicle fires
Demolition
Corrosion/abrasion of metal structures
Galvanizing
Non-thermal processing of scrap metals
e.g. shredding of scrap metals
Part B industrial processes
e.g. cement batching, quarrying, powder coating
Abrasion of road surfaces by motor vehicles

13. 4. Missing & Non-anthropogenic Sources
Natural Sources
not currently included or estimated. Estimates available from Ilyin & Travnikov (2005)
Marine Sources
Resuspension
Estimates available from Ilyin & Travnikov (2005) suggest significant contributions for Pb and Cd (trebling the 2004 Cd emissions in the UK).
However estimates from Vincent and Passant (2006) for Cd, Pb, As, Ni suggested resuspension was not a major source.

14. 5. Mapping Emission Estimates

15. 6. Conclusions Conclusions Recommendations for Future work
There are areas where improvements need to be made
However we are currently limited by data availability
Recommendations for Future work
Point Sources: Obtain more information on whether fugitive emissions are included in current estimates
Combustion Sources: Obtain more comprehensive data on metal content of fuels
Brake and Tyre Wear: Review and consolidate existing literature information
“Missing” Sources: Make some initial estimates by improving PM10 estimates (not straightforward!)
Natural Sources: Incorporate estimates into emissions inventory
Validation & Verification
After conducting these improvements, reassess the estimates derived from modelling in light of updated emissions inventory estimates.

16. THANK-YOU FOR YOUR ATTENTION