attaining urban air quality objectives- links to transboundary air pollution
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Attaining urban air quality objectives- links to transboundary air pollution. Helen ApSimon, Tim Oxley and Marios Valiantis UK Centre for Integrated Assessment Modelling Imperial College London. CO 2 N2O CH4 C L I M A T E. - PowerPoint PPT PresentationTRANSCRIPT
Attaining urban air quality objectives- links to transboundary air pollution
Helen ApSimon, Tim Oxley and Marios Valiantis
UK Centre for Integrated Assessment Modelling
Imperial College London
SOURCES EMISSION EXPOSURE EFFECTS/RECEPTORS
Energy
Agriculture
Industry
Traffic
Sulphur dioxide
Ammonia
Nitrogen oxides
VOCs
Sulphur deposition
Nitrogen deposition
SO2,SO4 air concns
NO2,NO3 air concns
Ozone
Acidification
Eutrophication
Human health
Materials
Yield losses
Surface waters
Terrestial ecosystems
Marine ecosystems
Crops
Forests
Domestic
Particles PM10/2.5
NH4 concn
CO2
N2O
CH4
C
L
I
M
A
T
E
AIR QUALITY
NO2
Particulate matter
PM10: Limit values (max. conc at hot-spots)
Annual mean conc. 40g.m-3
24 hr conc 50 g.m -3 < 35 days per year
Targets proposed for PM2.5
Limit values 25 g.m -3
and “exposure reduction”: 20% at urban background sites
BENEFITS e.g. in UK 2005 baseline-> £9 to £21 bn/y for life years lost (DEFRA: Air Quality Strategy for England, Scotland, Wales and N Ireland- consultation document April 2006)
NITROGEN DIOXIDE
Limit values:
Annual mean conc. 40 g.m -3 (21 ppb)
I hr mean 200 g.m -3 (105 ppb) <18 times /yr
Wide-spread exceedence in European cities, especially at road-side sites.
Adds to importance of reducing NOx, but emphasizes urban sources, particularly traffic
Illustrate other links to CLRTAP
ASAM- European scale (50km)
UKIAM- UK scale (5km)
BRUTAL- Background Road & Urban Transport modelling of Air quality Limit Values->
Superimpose road-side on background
Road network + traffic data-> traffic emissions individual roads and gridded
Pop. Data -> urban areas/roads (canyons etc)
Modelled background concentrations:-
First model NOx using same model, PPM, used for primary PM .
Then convert to NO2 using relationship between NO2 and NOx
NB Good agreement with measurements , but requires added rural background
Background NOx inferred from rural diffusion tube network
->10 g.m -3 most of England
Preliminary calculations suggest that imported NOx contributes to this background including shipping- so some transboundary component. Applies to other countries too?
EMEP source apportionment: relative importance of transboundary and own country:
NOx/ NO2 conc. not given by EMEP, but probably more like reduced N deposition and PMcoarse?
SCENARIO ANALYSIS
Superimpose roads:
Traffic emissions: traffic flows and vehicle mix combined with speed-dependent emission factors (individual roads and summed over grid square)
Scenarios:
Tech. measures e.g. EGR, early introduction Euro V,VI ; hybrids/LEVs
Local measures/ reduced traffic volumes: congestion zones; :LEZs etc.
PRELIMINARY RESULTS
Projections of NO2 for 2010 at road-side sites: contributions from roads superimposed in each 1x 1 km grid square on top of background-> mapping of peak concns at hot-spots
BAU
LEZ
Max. tech. reduction case
+ factors ~CLRTAP
-> section across London
BRUTAL (15.5.06): Scenario transects across London for peak NO2 at road-side sites in each grid-cell
Changes in NO2/NOx relationships
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
NOx X 10 ppb
NO2 base
20% prim NO2
5ppb more O3
NO2 secondary- NO2 primary fraction- evidence
depends on O3 of increase - PMtraps
Example: 50 ppb NOx -> 25 ppb NO2 (limit value 21 ppb)
Reduce to 35 ppb NOx-> 20 ppb NO2 (OK). BUT!
5 to 20% prim. frac-> 22 ppb NO2; plus more O3 -> 23ppbNO2 (not OK)
NO2 ppb
Similar analysis PM10
e.g. benefits of PM traps
NB importance of non-exhaust emissions- brakes/tyres
Summary: links UAQ and CLRTAP
1.Local control of urban air quality puts extra emphasis on traffic emissions detailed modelling of scenarios
2. High economic benefits(PM)
3. Some direct transboundary contribution to NOx/NO2 ?
4. NO2-NOx ratios dependent on ozone NB background ozone increasing
5. Interaction other pollutants- PM trap-> increased primary NO2.