Air Pollution 1 What is Air Pollution? - School of …dstevens/teaching/MetAE_AirPoll1.pdf ·...

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1 Air Pollution 1 Grangemouth oil refinery, ~20 miles west of Edinburgh What is Air Pollution? Latin pollutus – foul, unclean, dirty Definition: ‘Air pollution is when a substance (an air pollutant) is present in the atmosphere at higher than ambient (clean) levels and produces significant effects on humans, animals, vegetation or materials’ Air pollutant may be man-made or natural, gaseous, or suspended liquid/solid particles (aerosols) Some typical effects: foul odours, irritation of senses, sickness, death, vegetation damage, damage to materials, obscuration of visibility, adverse weather or climate changes Primary and Secondary APs Primary air pollutants are directly emitted, e.g., Soot (a primary aerosol AP) – SO 2 Secondary APs form in-situ from precursors, via chemical transformation, e.g.: Ozone (O 3 ) is a gaseous secondary AP – formed from the NO x -catalysed oxidation of precursors such as CO (carbon monoxide) and hydrocarbons Sulphuric acid aerosol is an aerosol secondary pollutant, formed by the oxidation of SO 2 to H 2 SO 4 , which then condenses to form liquid aerosols Sources of Air pollution Anthropogenic Urban and Industrial – mainly from fossil fuel combustion Power generation (CO 2 , SO 2 , NO x , particles…) • Industry Transport (land, sea, air) Waste disposal (landfills, incineration…) Agricultural and Rural • Dust Slash and burn agriculture/waste burning Soil emissions (fertilizer) Livestock emissions – Domestic (e.g. local heating/cooking) Natural Desert dust Forest fires Volcanoes (particles, SO 2 ,…) Biogenic emissions – from vegetation and wetlands (incl. pollen) Sea spray & ocean emissions Soils and decaying matter (natural microbial activity) • Lightning… Indoor air pollution is the 2 nd largest contributor to the global burden of disease (after poor water and sanitation) – kills 1.6 million people annually (WHO, 2002) London smog, 1952 Estimated 12,000 total excess deaths High levels of Sulphuric acid aerosol from burning high-S coal. Trapped under inversion. Eventually led to the clean air act and other pollution control measures.

Transcript of Air Pollution 1 What is Air Pollution? - School of …dstevens/teaching/MetAE_AirPoll1.pdf ·...

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Air Pollution 1

Grangemouth oil refinery, ~20 miles west of Edinburgh

What is Air Pollution?

• Latin pollutus – foul, unclean, dirty

• Definition: ‘Air pollution is when a substance (an air pollutant) is present in the atmosphere at higher than ambient (clean) levels and produces significant effects on humans, animals, vegetation or materials’

• Air pollutant may be man-made or natural, gaseous, or suspended liquid/solid particles (aerosols)

• Some typical effects: foul odours, irritation of senses, sickness, death, vegetation damage, damage to materials, obscuration of visibility, adverse weather or climate changes

Primary and Secondary APs

• Primary air pollutants are directly emitted, e.g.,– Soot (a primary aerosol AP)

– SO2

• Secondary APs form in-situ from precursors, via chemical transformation, e.g.:– Ozone (O3) is a gaseous secondary AP – formed from

the NOx-catalysed oxidation of precursors such as CO (carbon monoxide) and hydrocarbons

– Sulphuric acid aerosol is an aerosol secondary pollutant, formed by the oxidation of SO2 to H2SO4, which then condenses to form liquid aerosols

Sources of Air pollution• Anthropogenic

– Urban and Industrial – mainly from fossil fuel combustion• Power generation (CO2, SO2, NOx, particles…)• Industry• Transport (land, sea, air)• Waste disposal (landfills, incineration…)

– Agricultural and Rural• Dust• Slash and burn agriculture/waste burning• Soil emissions (fertilizer)• Livestock emissions

– Domestic (e.g. local heating/cooking)

• Natural• Desert dust

• Forest fires• Volcanoes (particles, SO2,…)• Biogenic emissions – from vegetation and wetlands (incl. pollen)• Sea spray & ocean emissions• Soils and decaying matter (natural microbial activity)• Lightning…

Indoor air pollution isthe 2nd largest contributorto the global burden ofdisease (after poor waterand sanitation) –kills 1.6 million people

annually (WHO, 2002)

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London smog, 1952Estimated 12,000total excess deaths

High levels ofSulphuric acid aerosol from burning high-S coal.Trapped under

inversion.

Eventually led to the clean air act and other pollution

control measures.

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Air Quality

Source: UK National Air Quality Archive

www.scotland.gov.uk/stats/envonline

PM10 in Scottish cities 1993-2008

Particulate matter less than 10�m in diameter (PM10) concentrations (�g m-3)

1993-2008

Current exposure to PM from anthropogenic

sources leads to the loss of 8.6 months of life expectancy, as an average for Europe.

China: 1.3-1.7 years

US: 0.6 yrs per 10�g/m3

CA Pope et al (2009) New England Journal of Medicine 360

www.euphix.org/object_class/euph_airborne_particulate_matter.html

Observed visibility trends at a site in China, Observed visibility trends at a site in China,

19551955--20052005

Rosenfeld et al., 2007

Observed relationship between visibility and PM in Shanghai Mortality and visibilityMortality and visibility

Huang et al., 2009

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Air Quality

Ground level ozone concentrations in rural Scotland: 1990-2008

Source: UK National Air Quality Archive

Time and space scales

Local1-100 km

Regional102-103 km

Global103-104 km

minutes-hours

hours-days

days-years

Exposure tourban NO2 &PM pollution

Regional acidrain/deposition; ozone exposure;vegetation fires

Climate change dueto greenhouse gases/aerosols;

ozone depletion

Larger scaleAir pollution:Next lecture

SourcesDispersion

TransformationSinks

Concentrations Deposition

Impacts

Understanding air pollution

Buncefield oil depot fire, 2005

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Satellite image at 1045 GMT,~5 hours after start of fire

Nottingham Skew T-log P on day of

Buncefield Fire (12Z, 11 Dec 2005)

Top of BL

The Atmospheric Boundary Layer

• Layer of atmosphere next to surface

• Typically 1-2 km deep

• Strongly influenced by the surface (including friction), on timescales < 1 hour; diurnal cycle

• Dominated by turbulence, so well mixed; capped by an inversion or very stable layer

Diurnal variation of the Boundary Layer(idealised: sunny day, light winds)

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Buncefield oil depot fire, 2005

Top of BL

Buoyantthermal

plume roseto ~3 km

Very high concentrations

of soot, or ‘black carbon’

aerosol

Turbulent mixing on many scales

Settling outof largestaerosol

particles

Summary

• Understanding air pollution requires knowledge of the:1. Sources (man-made, natural; gases, aerosols; primary,

secondary)

2. Dilution, dispersion, and transformation processes

3. Sinks (removal mechanisms)

4. Impacts

• Meteorology is all important for (2), and can also affect the others

• Next time: (less obvious) air pollution on larger scales