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

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

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

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

Photochemical smogLos 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

• Sunlight+ VOC + NOx = O3

The dominant oxidant is O3.

The figure is a generalisation based on various studies.

O3

Sunlight

and PAN

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

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.

Classic smogLondon smog

• Where there is much burning of fossil fuels

• Main constituents:– Particles (incl

soot), CO, S-compounds

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

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

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

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

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 1980-2000Countries 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

Norwegian NH3 emissions

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

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 (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

PM is the most important local air pollutant in Norwegian cities

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

Developed vs developing countries

Monks et al 2009

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

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

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

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

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

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