air pollutants in the troposphere basics: chemical fate of pollutants in the troposphere basics:...
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Air pollutants in the troposphere Air pollutants in the troposphere
•Basics: Chemical fate of pollutants in the troposphereBasics: Chemical fate of pollutants in the troposphere•Photochemical smog and ‘classical smog’Photochemical smog and ‘classical smog’•The Gothenburg protocolThe Gothenburg protocol•Norwegian emissionsNorwegian emissions•Air Quality Guidelines and exceedances in NorwayAir Quality Guidelines and exceedances in Norway•Heavy metalsHeavy metals•POPsPOPs
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2
O3
NO
NO2
O2O(3P)
NO
hM O2
HNO3
NO2
sink:OH, M
Wet depositionDry deposition
h
h310 nmO*
O2
M
H2O
OH. (hydroxyl radical)
CO
CO2
H.
O2
HO2 .
(hydroperoxyl radical)
NO
NO2
O2 HO2 .
H2O2
(hydrogen
peroxide)
h
Tropospheric chemistry in a nutshellThe ‘detergent’ of the atmosphere
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3
O3
NO
NO2
O2O(3P)
NO
h
O2, M
HNO3
NO2
sink:OH, M
Wet depositionDry deposition
h
h310 nmO*
O2
M
H2O
OH. (hydroxyl radical)
CH4
H2O
CH3.
O2
CH3O2 .
(methylperoxyl radical)
NO
NO2
O2 HO2 .
H2O2
(hydrogen
peroxide)
h
Oxidation of methane and other hydrocarbons
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CH3O2 .
(methylperoxyl radical)
NO2 CH3O .
NO
CH3O . O2
HCHO (formaldehyde)
HO2
Further degradation and oxidation of formaldehyde via photolysis or reaction with OH or HO2 to CO and finally to CO2
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Photochemical smogLos Angeles Smog
• Where there is much traffic and sunshine
• Main reagents:– NOx, VOC,
O3, CO
• Oxidative
Huston, Texas
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Fluctuations in concentrations of photochemical smog during the day
• Sunlight+ VOC + NOx = O3
The dominant oxidant is O3.
The figure is a generalisation based on various studies.
O3
Sunlight
and PAN
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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
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Both NOx and VOC emissions must be reduced
O3 concentration isolines
NOx conc.
VO
C c
onc.
100 ppb
160 ppb140 ppb
120 ppb
The non-linearity between NOx and VOC
At high NOx levels: NO is titrating O3 → O3 may increase if only NOx is reduced.
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Classic smogLondon smog
• Where there is much burning of fossil fuels
• Main constituents:– Particles (incl
soot), CO, S-compounds
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Comparison of Los Angeles and London smogCharacteristic Los Angeles
(Photochemical smog)London (Classic smog)
Air temperature 24 to 32C -1 to 4C
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, S-compounds
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
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Priorities given to local, regional and global Priorities given to local, regional and global pollution problemspollution problems
1960s 1970s 1980s 1990s 2000s
Regional
LRTAPGeneva 1979
SO2 NOx VOC MultiGothenburg
1999Climate Change
IPCC Rio Kyoto1997 Kyoto approved by China
2002
Marrakesh
LocalS-limits for residual oil
Limits for point sources
Catalytic cars
Focus on NO2 and PM
LRTAP: Long-range transboundary pollutionLRTAP: Long-range transboundary pollution
IPCC: Intergovernmental Panel on Climate ChangeIPCC: Intergovernmental Panel on Climate Change
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The Gothenburg protocol The Gothenburg protocol (1999) (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
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Emission
1990
Emission 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
Norwegian emissions and targets in the Gothenburg Protocol
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Trends in Norway
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Norwegian NOx emissions
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Norwegian SO2 emissions
• Commitment reached
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Historical development of sulphur dioxide emissions in Europe
(Source: Vestreng et al., 2007)
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European sulphur emissions 1980-2000Countries SO2
CE = Czech Rep., Hungary, Poland and Slovak Rep.
-73%
CW = Austria, Switzerland and Germany
-89%
E = Estonia, Latvia, Lithuania and Russia (European part)*
-73%
N = Denmark Finland Iceland, Norway and Sweden
-87%
NW = Belgium, Luxemburg, the Netherlands, Ireland and United Kingdom
-76%
S = France, Greece, Italy, Portugal and Spain
-62%
SE = Albania, Armenia, Belarus, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, Georgia, Kazakhstan, Republic of Moldova, Romania, Slovenia, The FYROM Macedonia, Turkey, Ukraine and Yugoslavia
-40%
TOTAL EUROPE (excluding ships )
-67%
The decrease is generally larger after 1990
Greater from sources that emit S that is deposited in sensitive regions
1000 tones/yr
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Norwegian NH3 emissions
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European nitrogen emissions 1980-2000
Countries NOx NH3
CE = Czech Rep., Hungary, Poland and Slovak Rep.
-42% -46%
CW = Austria, Switzerland and Germany
-49% -23%
E = Estonia, Latvia, Lithuania and Russia (European part)*
+21% -48%
N = Denmark Finland Iceland, Norway and Sweden
-21% -10%
NW = Belgium, Luxemburg, the Netherlands, Ireland and United Kingdom
-36% -13%
S = France, Greece, Italy, Portugal and Spain
-4% +1%
SE = Albania, Armenia, Belarus, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, Georgia, Kazakhstan, Republic of Moldova, Romania, Slovenia, The FYROM Macedonia, Turkey, Ukraine and Yugoslavia
-26% -12%
TOTAL EUROPE (excluding ships )
-24% -20%0
1000
2000
3000
4000
5000
6000
7000
1975 1980 1985 1990 1995 2000 2005
S
CE
SE
E
N
CE
CW
NW
E
Regional differences in N emission changes are more pronounced than for sulphur emissions.
1000 tones/yr
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Norwegian emissions of non-Methane Volatile Organic Compounds
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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
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PM is a mixture of components
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Classical air pollutants are generally reduced in Europe
Figure from Monks et al 2009
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(GHG emissions in Norway)
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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
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Trends of cadmium emissions and depositions in Europe for 1980-2000.
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Air quality guidelines for some pollutants (mg/m3)
• Concentration of air pollutant below which adverse effects to human health are acceptable.
CompoundAverag-ing time
WHO Norway Norway
CO 8 h 10 10 -
1 h 30 25 -
NO2 1 yr 0.04 - 0.03
6 months - 0.05 -
24 h - 0.075 -
1 h 0.20 0.10 -
NO 1h 0.60 - -
O3 8 h 0.10 0.08 0.06
1t - - 0.15
SO2 1 yr a - 0.02
6 months - 0.04 -
24 h 0.02 0.09 0.05
Particles, PM10
24 h1 yr
0.050.02
0.035 -
HEALTH VEGETATION
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
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PM is the most important local air pollutant in Norwegian cities
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Concentrations in Oslo (down town) air.
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0,45
1958
/59
1961
/62
1964
/65
1969
/70
1972
/73
1975
/76
1978
/79
1981
/82
1984
/85
1987
/88
1990
/91
1993
/94
1996
/97
1999
/00
2002
/03
mg
/m3
SO2
PM10
NO2
Guidelines
NOx
PM10
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Developed vs developing countries
Monks et al 2009
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China top SO2 emitter todaySO2 emissions in China, Europe and the USA
10,00
15,00
20,00
25,00
30,00
35,00
40,00
45,00
Mill
ion tons
SO2 China
SO2 USA
SO2 Europe
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Average annual PM10 concentrations (particular matter with diameter less than 10 μm) in selected Asian cities in
2003
0 20 40 60 80 100 120 140 160
Bangkok
Beijing
Busan
Colombo
Dhaka
Hanoi
Ho Chi M inh
Hong Kong
J akarta
Kathmandu
Kolkata
Manila
Mumbai
New Delhi
Seoul
Shanghai
Singapore
Surabaya
Taipei
Tokyo
PM10 annual average [ug/m3]
US EPA guideline (50 µg/m3)
WHO guideline
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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
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Ozone (surface level) – damage to crops
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0 10 20 30 40 50 60 70 80 90 100 110
M7 (Seasonal 7 hours-1 mean ozone (09.00-16.00), ppbv)
Rel
ativ
e yi
eld Rice
Wheat
Corn
Cotton
Vegetables
Soybean
Tuber
Sorghum
Exposure-response functions for yield loss
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Persistent Organic Pollutants (POPs)
The grasshopper effect”:
POPs evaporate and deposit several times(distillation)
Concentrations in cold polar areas may therefore become serious.
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POPs (Europe)Trends of PCDD and PCDF
C, Cl, O, H
2,3,7,8-tetrachlorodibenzodioxin
DIOXINS and FURANS
PCDD: Polychlorinated dibenzo-p-dioxins PCDF: Polychlorinated dibenzofurans
emissions concentrations in air and soil