Air pollutants in the troposphere
•Basics: Chemical fate of pollutants in the troposphere
•Photochemical smog and ‘classical smog’
•The Gothenburg protocol
•Norwegian emissions
•Air Quality Guidelines and exceedances in Norway
•Heavy metals
•POPs
Tropospheric chemistry in a nutshell
hn l<310 nm
O3
O2
H2O
O*
hn
NO
The ‘detergent’ of the atmosphere
OH.
M
(hydroxyl radical)
CO
M
O2
O2
O(3P)
CO2
hn
hn
NO2
NO2
sink:
OH, M
NO2
NO
H.
NO
O2
H2O2
(hydrogen
peroxide)
HNO3
Wet deposition
Dry deposition
O2
HO2 .
HO2 .
(hydroperoxyl radical)
2
Oxidation of methane and other hydrocarbons
hn l<310 nm
O3
O2
H2O
O*
hn
NO
OH.
(hydroxyl radical)
M
CH4
O2, M
O2
O(3P)
H2O
hn
hn
NO2
NO2
sink:
OH, M
NO2
NO
CH3.
NO
O2
H2O2
(hydrogen
peroxide)
HNO3
Wet deposition
Dry deposition
O2
HO2 .
CH3O2 .
(methylperoxyl radical)
3
CH3O2
.
NO
2
(methylperoxyl radical)
O2
CH3O .
NO
CH3O .
HO
2
HCHO
(formaldehyde)
Further degradation and oxidation of formaldehyde via
photolysis or reaction with OH or HO2 to CO and finally
to CO2
Photochemical smog
Los Angeles Smog
• Where there is much
traffic and sunshine
• Main reagents:
– NOx, VOC,
O3, CO
• Oxidative
Huston, Texas
Fluctuations in concentrations of photochemical
smog during the day
and PAN
• Sunlight
+ VOC
+ NOx
= O3
Sunlight
O3
The dominant oxidant is O3.
The figure is a generalisation based on various studies.
Why is the oxidant concentration in photochemical smog
(mainly ozone) increasing during mid-day?
When exposed to sunlight,
NO2 can cause formation of ozone:
• First atomic oxygen is formed
• Atomic oxygen can react with
O2 to form ozone
Since mainly NO is emitted,
we need a reaction that gives NO2.
• However, oxidation by O3 would
reverse the reaction, i.e. decrease O3
•
Reactions with free peroxyl radicals may
instead oxidise NO to NO2
•
RO2• radicals may have been formed through
reactions involving hydrocarbons, e.g.:
•
A chain reaction involving CO, OH•
and HO2•
may also produce NO2 (net reaction):
•
•
NO2 + hν (λ< 400 nm)  NO + O
O + O2 + M  O3 + M*
NO2 + O2  O3 + NO
•
O3 + NO  NO2 + O2 (O3 is often low within cities)
•
NO + HO2•  NO2 + HO•
NO + RO2•  NO2 + RO•
•
•
OH• + CH4 CH3• + H2O
CH3• + O2 + M CH3O2• + M*
•
CO + NO + O2  CO2 + NO2
VOC conc.
The non-linearity between NOx and VOC
O3 concentration isolines
160 ppb
140 ppb
120 ppb
100 ppb
At high NOx levels: NO
is titrating O3 →
O3 may increase if only
NOx is reduced.
NOx conc.
Both NOx and VOC emissions must be reduced
Classic smog
London smog
• Where there is
much burning of
fossil fuels
• Main
constituents:
– Particles (incl
soot), CO,
S-compounds
Comparison of Los Angeles and London smog
Characteristic
Los Angeles
(Photochemical smog)
London
(Classic smog)
Air temperature
24 to 32C
-1 to 4C
Relative humidity
< 70%
85% (+fog)
Visibility
< 0.8 to 1.6 km
< 30 m
Months of most frequent
occurrence
August – September
December – January
Time of max. occurrence
Mid-day
Early morning
Major fuels
Oil
Coal and oil products
Principle components
O3, NOx, CO, VOC
Particles (incl. soot), CO, Scompounds
Chemical condition
Oxidative
Reductive, acidic
Principal health effects
Lung function, cough, shortness of
breath O3)
Temporary eye irritation (PAN
Peroxyacetylnitrate)
Bronchial irritation, coughing
(particles/SO2)
Effects on materials
Rubber cracked (O3)
Corrosion of many materials (iron,
zinc, sandstone)
Effects on plants
Ozone damage many plants
SO2, particles and acid fog damage
many plants
Priorities given to local, regional and global
pollution problems
1960s
1970s
1990s
1980s
2000s
Local
S-limits for residual oil
Catalytic cars
Limits for point sources
Focus on NO2 and PM
Regional
LRTAP
Geneva
1979
SO2
NOx VOC
IPCC
Rio
Multi
Gothenburg
1999
Kyoto
1997
Marrakesh
Kyoto approved by China
2002
LRTAP: Long-range transboundary pollution
IPCC: Intergovernmental Panel on Climate Change
Climate
Change
The Gothenburg protocol (1999)
A sophisticated environmental agreement
 Addresses three different air pollution
problems:
- Acidification
- Eutrophication
- Ground-level ozone
 Four different gases/groups
of gases:
- Sulphur dioxide (SO2)
- Nitrogen oxides (NOx)
- Ammonia (NH3)
- Volatile organic compounds
(NMVOCs)
 Based on scientific studies through an
integrated assessment of critical loads,
deposition patterns and abatement costs
Norwegian emissions and targets in the
Gothenburg Protocol
Emission Emission
1990
2008
Target
2010
Required
reduction
(%)
NOx
204
176
156
20 (11)
SO2
52
20
22
OK
NMVOC
300
170
195
OK
NH3
20
23
23
OK
In 1000 tonnes
Trends in Norway
Norwegian NOx emissions
Norwegian SO2 emissions
• Commitment reached
Historical development of sulphur dioxide
emissions in Europe
(Source: Vestreng et al., 2007)
European sulphur emissions 1980-2000
 The decrease is generally larger after 1990
Countries
SO2
 Greater from sources that emit S that is
deposited in sensitive regions
CE =
-73%
CW =
Austria, Switzerland and
Germany
-89%
E =
Estonia, Latvia, Lithuania and
Russia (European part)*
-73%
1000
tones/yr
Czech Rep., Hungary, Poland
and Slovak Rep.
N = Denmark Finland Iceland, Norway
and Sweden
-87%
NW =
Belgium, Luxemburg, the
Netherlands, Ireland and United
Kingdom
S = France, Greece, Italy, Portugal and
Spain
-76%
-62%
SE =
Albania, Armenia, Belarus,
Bosnia-Herzegovina, Bulgaria,
Croatia,
Cyprus,
Georgia,
Kazakhstan,
Republic
of
Moldova, Romania, Slovenia,
The
FYROM
Macedonia,
Turkey, Ukraine and Yugoslavia
TOTAL EUROPE
(excluding ships )
-40%
-67%
Norwegian NH3 emissions
European nitrogen emissions 1980-2000
Regional differences in N emission changes are
more pronounced than for sulphur emissions.
Countries
NOx
NH3
CE =
-42%
-46%
Austria, Switzerland and
-49%
-23%
E =
Estonia, Latvia, Lithuania and
Russia (European part)*
+21%
-48%
N = Denmark Finland Iceland, Norway
-21%
-10%
-36%
-13%
-4%
+1%
-26%
-12%
-24%
-20%
Czech Rep., Hungary, Poland
and Slovak Rep.
CW =
1000
tones/yr
Germany
7000
and Sweden
6000
NW =
E
4000
3000
2000
Belgium, Luxemburg, the
Netherlands, Ireland and United
Kingdom
S
5000
S = France, Greece, Italy, Portugal and
SE
Spain
NW
CE
SE =
E
CE
Albania, Armenia, Belarus,
Bosnia-Herzegovina, Bulgaria, Croatia,
Cyprus, Georgia, Kazakhstan, Republic
of Moldova, Romania, Slovenia, The
FYROM Macedonia, Turkey, Ukraine
and Yugoslavia
CW
N
1000
TOTAL EUROPE
0
1975
1980
1985
1990
1995
2000
2005
(excluding ships )
Norwegian emissions of non-Methane Volatile
Organic Compounds
Norwegian emissions of particles (PM10)
• Particles less than 10
μm are along with CO
and NOx of largest
importance for air
quality in cities
• Burning of biomass and
metallurgic industry the
most important sources
PM is a mixture of components
Classical air pollutants are
generally reduced in Europe
Figure from Monks et al 2009
(GHG emissions in Norway)
Norwegian emissions of environmental toxins
• Large reductions due
to
– Improved flue
cleaning technology
• Esp. waste
incineration
– Shutdown of
chemical and
metallurgic industry
– Pb reduction due to
unleaded petrol
Trends of cadmium emissions and depositions
in Europe for 1980-2000.
Air quality guidelines for some pollutants
HEALTH
VEGETATION
3
(mg/m
) WHO Norway Norway
AveragCompound ing time
• Concentration of
air pollutant
below which
adverse effects
to human health
are acceptable.
a. WHO argue that if
the 24 hour limit is
satisfied, the annual
average will be
satisfactory.
Guideline for 10 min:
0.5 mg/m3
CO
8h
10
10
-
1h
30
25
-
1 yr
0.04
-
0.03
6 months
-
0.05
-
24 h
-
0.075
-
1h
0.20
0.10
-
NO
1h
0.60
-
-
O3
8h
0.10
0.08
0.06
1t
-
-
0.15
1 yr
a
-
0.02
6 months
-
0.04
-
24 h
0.02
0.09
0.05
24 h
1 yr
0.05
0.02
0.035
-
NO2
SO2
Particles,
PM10
PM is the most important local air
pollutant in Norwegian cities
19
58
/
19 59
61
/
19 62
64
/
19 65
69
/
19 70
72
/
19 73
75
/
19 76
78
/
19 79
81
/
19 82
84
/
19 85
87
/
19 88
90
/
19 91
93
/
19 94
96
/
19 97
99
/
20 00
02
/0
3
mg/m3
Concentrations in Oslo (down town) air.
0,45
0,4
0,35
0,3
0,25
SO2
PM10
NO2
0,2
0,15
0,1
0,05
0
Guidelines
NOx
PM10
Developed vs developing countries
Monks et al 2009
China top SO2 emitter today
SO2 emissions in China, Europe and the USA
45,00
SO2 China
SO2 USA
35,00
SO2 Europe
30,00
25,00
20,00
15,00
20
06
20
04
20
02
20
00
19
98
19
96
19
94
19
92
10,00
19
90
Million tons
40,00
Average annual PM10 concentrations (particular matter
with diameter less than 10 μm) in selected Asian cities in
2003
B angko k
B eijing
B usan
Co lo mbo
Dhaka
Hano i
Ho Chi M inh
Ho ng Ko ng
Jakarta
Kathmandu
Ko lkata
M anila
M umbai
New Delhi
Seo ul
Shanghai
Singapo re
Surabaya
US EPA guideline (50 µg/m3)
Taipei
To kyo
0
20
40
WHO guideline
60
80
100
PM10 annual average [ug/m 3]
120
140
160
Air pollution – not only local and
regional problem anymore
Increasing evidence that many air pollutants are transported on
a hemispheric or global scale. Observations and model
predictions show the potential for intercontinental transport
of
–
–
–
–
–
ozone and its precursors
fine particles
acidifying substances
mercury
persistent organic pollutants
Ozone (surface level) – damage to crops
Exposure-response functions for yield loss
1.00
0.90
0.80
Relative yield
0.70
0.60
Rice
Wheat
0.50
Corn
Cotton
0.40
Vegetables
Soybean
0.30
Tuber
Sorghum
0.20
0.10
0.00
0
10
20
30
40
50
60
70
80
M7 (Seasonal 7 hours-1 mean ozone (09.00-16.00), ppbv)
90
100
110
Persistent Organic Pollutants (POPs)
The grasshopper
effect”:
POPs evaporate and
deposit several times
(distillation)
Concentrations in
cold polar areas may
therefore become
serious.
POPs (Europe)
Trends of PCDD and PCDF
DIOXINS and FURANS
PCDD: Polychlorinated dibenzo-p-dioxins
PCDF: Polychlorinated dibenzofurans
C, Cl, O,
H
2,3,7,8-tetrachlorodibenzodioxin
emissions
concentrations in air and soil