Transcript garfield.chem.elte.hu

The quality of the air we breathe
Mike Pilling
School of Chemistry, University of Leeds
UK Air Quality Strategy, 2007
“Air pollution is currently estimated to reduce the life
expectancy of every person in the UK by an average of 7-8
months. The measures outlined in the strategy could help
to reduce the impact on average life expectancy to five
months by 2020, and provide a significant step forward in
protecting our environment.”
Defra estimate the health impact of air pollution in 2005
cost £9.1–21.4 billion pa.
Synopsis
1. Particulate matter: trends and origins.
2. NO2: increases in emissions of primary NO2 and its
impact on roadside and kerbside concentrations
3. Ozone
4. Air quality and climate change
Particulate matter PM
• categorised on the basis of the size of the particles (e.g.
PM2.5 is particles with a diameter of less than 2.5μm).
•comprises wide range of materials (soot, nitrate,
sulphate, organic compounds)
•primary particles emitted directly into the atmosphere
from combustion sources
•secondary particles formed by chemical reactions in the
air.
•derives from both human-made and natural sources (such
as sea spray and Saharan dust)
•health effects: inhaled into the thoracic region of the
respiratory tract. associated with respiratory and
cardiovascular illness
Particulate matter: trends in emissions and
measured concentrations (UK)
180
160
Black smoke, Lambeth,
1961 - 1997
Black smoke , ug/m3
140
600
500
120
100
80
60
20
400
0
1997
1995
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
1971
1969
1967
1965
300
1963
1961
40
200
35
100
30
Belfast Centre
Birmingham Centre
0
Bristol Centre
1970
1975
Public Power
Production Processes
Resuspension
1980
1985
1990
Comm.Res.&Instit. Comb.
Road Transport
1995
2000
Industrial Combustion
Other
PM10 TEOM , ug/m3
25
Cardiff Centre
London Bloomsbury
Edinburgh Centre
20
Leeds Centre
Leicester Centre
Liverpool Centre
Newcastle Centre
15
Southampton Centre
Swansea
Primary PM10 emissions sources
1970 – 2001 (AQEG: PM report)
Average
10
Annual mean PM10,
Urban Background sites
5
AQEG PM report
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
PM 10 emissions (kt)
40
Air quality – comparison of trends in
pollutants
relative annual mean concentration
120
100
80
60
40
SO2
PM10
CO
NOx
NO2
20
0
1997
1998
1999
2000
2001
Year
2002
2003
2004
Relative annual mean concentration (monthly intervals): selection
of monitoring sites in London.
AQEG PM report
Analysis of data
from 196 sites in UK in 2003
Annual Average PM10 Concentrations for 2003 (ugm TEOM) at Roadside, Urban and Rural Sites
-3
40
Annual PM10 TEOM
Average Annual PM10 TEOM
35
High rural
background
PM10 ugm -3 TEOM
30
25
20
15
10
5
Small number
of rural sites
0
AQEG PM report
Roadside, urban background and
rural annual average PM10
TEOM concentrations in 2003
Secondary PM
• PM is also formed as a secondary pollutant by chemical
reactions in the atmosphere.
• This includes oxidation reactions leading to the
formation of secondary PM containing:
• Sulphate
• Nitrate
• Organic compounds
• The chemistry involved is close to that involved in ozone
formation and explains why ozone episodes are
accompanied by enhanced PM
PM episodes – other sources
Saharan dust: e.g. 2-3 March
2002. Hourly mean of 292 g m-3
at Plymouth. 1-2 events per year
in UK. 23 in Spain!
Sea salt aerosol during gales,
especially coastal sites but also
inland. 1-5 episodes / year.
Biomass burning: Forest fires in
Russia, September 2002. Peak
hourly concentrations in were
reported on the 12th of
September in the range from 70
– 125 g m-3.
AQEG PM report
Biomass plumes, W Russia,
4 September 2002
Air Quality Strategy 2007 - PM
Dual approach:
air quality objective/limit value (backstop objective):
PM2.5: annual mean 25μg m-3 by 2020
Exposure reduction: an objective based on reducing
average exposures across the most heavily populated areas
of the country:
15 per cent reduction in average concentrations in urban
background areas across the UK between 2010 and 2020
NO2;
NOx = NO + NO2
All combustion processes in air produce oxides of nitrogen
(NOX).
Road transport is the main source, followed by the
electricity supply industry and other industrial and
commercial sectors.
NO2 is associated with adverse effects on human health:
causes inflammation of the airways. Long term exposure
may affect lung function and respiratory symptoms. Also
enhances the response to allergens in sensitive individuals.
NO2: EU Limit values
Hourly mean: 200 g m-3, not to be exceeded more than 18
times a year, to be achieved by 31st December 2010.
Annual mean: 40 g m-3, to be achieved by 31st December
2010.
Spatial distribution of
NOx emissions in the
UK
Maps of annual mean background NO2 concentrations
UK 2001
UK 2010
Key AQ objective is annual mean of
40 g m-3 to be achieved by
2010 (EU Directive)
Air quality – comparison of trends in
pollutants
relative annual mean concentration
120
100
80
60
40
SO2
PM10
CO
NOx
NO2
20
0
1997
1998
1999
2000
2001
Year
2002
2003
2004
Relative annual mean concentration (monthly intervals): selection
of monitoring sites in London.
AQEG PM report
NOx and NO2 emissions in London
Trends in annual mean NOx and NO2,
roadside and kerbside, 1996 - 2005
Lo ndo n M arylebo ne Ro ad
B ury Ro adside
Glasgo w Kerbside
Oxfo rd Centre Ro adside
Lo ndo n M arylebo ne Ro ad
B ury Ro adside
Glasgo w Kerbside
Oxfo rd Centre Ro adside
NOx, NO2 concentrations
Full lines NOx. Dashed lines NO2
450
Concentration (µg m-3, as NO2)
400
350
300
250
200
London Marylebone Road
Bury Roadside
Glasgow Kerbside
Oxford Centre Roadside
0.45
150
0.4
100
0.35
0
1998
1999
2000
2001
2002
2003
2004
2005
Year
• NOx shows downward trend,
compatible with improved emissions
reduction technologies
• This trend is not reflected in NO2.
• Measured NO2 / NOx ratio generally
increases with time.
• Not always the case – e.g. Glasgow
Ambient NO2/NOx ratio
50
0.3
0.25
0.2
0.15
0.1
0.05
0
1998
1999
2000
2001
2002
Year
Ratio NO2 / NOx
2003
2004
2005
Measured [NO2] / [NO] at a number of sites in London
Roadside and kerbside LAQN data
A30
BN1
1.2
BY7
CD1
NO2/NOx ratio relative to year 2006 = 1
1.1
CR2
CR4
CY1
1
EA2
EN2
0.9
GR5
HF1
HI1
0.8
HS1
HS4
HV1
0.7
HV3
KC2
0.6
MY1
RB3
RB4
0.5
SK2
TH2
WA4
0.4
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
HG1
All sites
Estimates of f(NO2) based on atmospheric
concentrations of NO and NO2
30
Marylebone Rd
f-NO2
20
10
1998
1999
2000
2001
2002
2003
2004
2005
year
30
2006
2007
All London sites
25
20
estimated f-NO2
0
1997
15
10
5
0
1997
1998
1999
2000
2001
year
2002
2003
2004
2005
Similar behaviour across Europe - Paris
700
600
100
500
80
400
60
300
40
NO2 FR0895A Roadside
200
NO2 FR0335A Roadside
NOx FR0895A Roadside
20
0
1995
100
NOx FR0335A Roadside
1996
1997
1998
1999
2000
2001
2002
2003
2004
0
2005
Annual mean concentration NOx (ugm-3, as NO2)
Annual mean concentration NO2 (ugm-3)
120
NO2 in Budapest and Hungary
in 2005
the percentage of urban major road length predicted to be above 40
g m-3 annual mean NO2 in 2010 for different f-NO2 percentages
(shown in brackets).
2004
base year
(10 - 15%)
2010
(10 - 15%)
2010
(15 - 23%)
2010
(20 - 30%)
2010
(25 - 38%)
2010
(30 - 45%)
London
84%
46%
52%
57%
62%
67%
Rest of
England
31%
11%
14%
16%
18%
20%
Scotland
22%
6%
8%
9%
10%
12%
Wales
13%
6%
7%
8%
8%
9%
Northern
Ireland
8%
0%
1%
1%
2%
3%
Total
35%
15%
17%
19%
21%
24%
AQEG conclusions on primary NO2
Measured NOx concentrations have declined in line with emission
changes but NO2 concentrations have not declined as expected,
particularly at the roadside and some sites have shown increases in
recent years.
Increases in NO2 / NOx ratios could be due to:
• increased penetration of Euro-III diesel vehicles fitted with
oxidation catalysts
• Fitting of catalytically regenerative particle traps to buses
Exact interpretation difficult given the observation of increases in
the NO2/NOx concentration ratio at only some roadside and
kerbside sites outside London. Is London particularly sensitive to
direct NO2 emissions, because of its size and emission density? But
what about Glasgow?
NB more analysis carried out for the sites in London because of the
greater availability of data in London.
Similar increases in NO2 / NOx observed in other European
countries.
Ozone
not emitted directly from any human-made source. Arises from
chemical reactions between various air pollutants, NOX and Volatile
Organic Compounds (VOCs), initiated by strong sunlight.
formation can take place over several hours or days and may have
arisen from emissions many hundreds, or even thousands of kilometres
away.
can damage airways leading to inflammatory reactions; reduces lung
function and increases incidence of respiratory symptoms
causes damage to many plant species leading to loss of yield and quality
of crops, damage to forests and impacts on biodiversity.
Air Quality Standards: Ozone
European Union Limit Value: Target of 120μg.m-3 (60 ppb)
for an 8 hour mean, not to be exceeded more than 25
times a year averaged over3 years. To be achieved by 31
December 2010.
UK Air Quality Objective: Target of 100μg.m-3 (50 ppb)
for an 8 hour mean, not to be exceeded more than 10 times
a year. To be achieved by 31 December 2005.
Methane oxidation
CH4 + OH (+O2)  CH3O2 + H2O
CH3O2 + NO  CH3O + NO2
CH3O + O2  HO2 +
HCHO
HO2 + NO  OH + NO2
HCHO + OH (+O2)
HCHO + hn
 HO2 + CO + H2O

H2 + CO
HCHO + hn (+2O2)  2HO2 + CO
Note:
2 x(NO  NO2) conversions
HCHO formation provides a route to radical formation.
General oxidation scheme for VOCs
O3 + hn  O1D + O2
O1D + H2O  2OH
OH + RH (+O2)  RO2 + H2O
RO2 + NO  NO2 + RO
RO  HO2 (+R’CHO)
HO2 + NO  OH + NO2
NO2 + hn  NO + O; O + O2  O3
OVERALL
NOx + VOC + sunlight  ozone
The same reactions can also lead to formation of
secondary organic aerosol (SOA)
Timescales of ozone chemistry
1. Global chemistry. Dominated by NOx + CH4 + sunlight.
Timescales are long as are transport distances.
2. Regional chemistry.
•
Many VOCs are emitted, e.g. over Europe. Each has
its own lifetime governed by its rate constant for
reaction with OH. The timescales of ozone production
takes from hours to days. The transport distance for
a wind speed of 5 m s-1 and a lifetime of 1 day is ~500
km.
3. In cities, there are high concentrations of NO from
transport sources. Ozone is depressed by the reaction:
NO + O3  NO2 + O2
01/12/2006
01/11/2006
01/10/2006
01/09/2006
01/08/2006
01/07/2006
01/06/2006
01/05/2006
01/04/2006
01/03/2006
01/02/2006
01/01/2006
O3, ug/m3
Sources of ozone in W Ireland
120
100
80
Europe-regional
North America
60
Asia
Europe-intercontinental
40
Extra-continental
Stratosphere
20
0
01/04/2006
01/04/2005
01/04/2004
01/04/2003
01/04/2002
01/04/2001
01/04/2000
01/04/1999
01/04/1998
01/04/1997
01/04/1996
01/04/1995
01/04/1994
01/04/1993
01/04/1992
01/04/1991
01/04/1990
01/04/1989
01/04/1988
01/04/1987
Monthly mean baseline ozone, ug/m3
Ozone mixing ratios at MaceHead
W. Ireland, under westerly airflows
110
100
90
80
70
60
50
40
Regional production of
ozone in Europe
Local effects – Ozone depression due to reaction with
high concentrations of NO in London. Transect of ozone
concentrations
70
Annual Mean Concentration (in g m-3)
60
50
40
30
20
10
0
465000
475000
485000
495000
505000
515000
525000
535000
545000
555000
Easting
PCM 2003
2003 AURN measurements
Ascot Rural
ADMS-Urban 2003
565000
575000
585000
Heat wave in Europe, August 2003
Monitoring stations in
Europe reporting high band
concentrations of ozone
>15 000 ‘excess deaths’ in
France; 2000 in UK, ~30%
from air pollution.
Temperatures exceeded
350C in SE England.
How frequent will such
summers be in the future?
Future summer temperatures
Using a climate model
simulation with greenhouse
gas emissions that follow an
IPCC SRES A2 emissions
scenario, Hadley Centre
predict that more than half
of all European summers are
likely to be warmer than that
of 2003 by the 2040s, and by
the 2060s a 2003-type
summer would be unusually
cool
2003: hottest on record (1860)
Probably hottest since 1500.
15 000 excess deaths in Europe
Stott et al. Nature, December 2004
ozone / microg/m3
Budapest, 1 – 31 August 2003
200
180
160
140
120
100
80
60
40
20
0
Széna tér
Baross tér
Pesthidegkút
Kőrakás park
Laborc u.
0
100
200
300
400
time
500
600
700
800
Diurnal variation
13th August 2003
Pesthidegkut
ozone/ microg/cm3
200
150
100
Ser i es1
50
0
-1
4
9
14
time of day
19
24
Climate change and air quality
Global-average radiative forcing (RF)
estimates and ranges in 2005
(relative to 1750) for anthropogenic GHGs
and other important agents and mechanisms
Air Quality and Climate Change
UK Air Quality Strategy (2007)
The Government’s environmental policies will be developed with a
consideration of their impact on climate change and greenhouse gas
emissions, and this is particularly true of air quality.
Where practicable and sensible, synergistic policies beneficial to both
air quality and climate change will be pursued.
Where there are antagonisms, the trade-offs will be quantified and
optimal approaches will be adopted.
Examples of difficult issues in assessing impact of
emissions on climate change and air quality
• Diesel vehicles:
• Need a more complete assessment of savings of CO2
emissions for diesel vs petrol
• Difficulties of defining metrics for black carbon
emissions (absorptive aerosol) for climate change and
in assessing the air quality (health) impacts relative to
climate change impacts of CO2 reduction.
• Ozone precursors:
• NOx emissions impact on global CH4 and O3, both of
which are greenhouse gases. Effects are of opposite
sign
• VOC emissions from biofuel crops could enhance
episodic ozone, especially as temperatures rise.
Acknowledgement
Air Quality Expert Group