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Ozone & Particulate Matter: Key U.S. Air Pollutants & their Impact on Quality, Slides of Chemistry

Chaudhary Charan Singh Haryana Agricultural University Chemistry

An in-depth analysis of ozone and particulate matter (pm) in the u.s., focusing on the number of people living in areas exceeding national ambient air quality standards, typical aerosol size distribution, fine aerosol composition, and the formation and impact of sulfate-nitrate-ammonium aerosols. The document also covers worldwide measurements of fine aerosol composition, u.s. So2 emissions, and the global sulfur budget.

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OZONE AND PARTICULATE MATTER (PM):

THE TOP TWO AIR POLLUTANTS IN THE U.S.

# millions of people living in areas exceeding national ambient air quality

standards (NAAQS) in 2007

15 g m-3 (day), 65 (annual)

75 ppb (8-h average)

65 g m-3 (24-h), 15 (annual)

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OZONE AND PARTICULATE MATTER (PM):

THE TOP TWO AIR POLLUTANTS IN THE U.S.

millions of people living in areas exceeding national ambient air quality

standards (NAAQS) in 2007

g m

(day), 65 (annual)

75 ppb (8-h average) 65

g m

(24-h), 15 (annual)

TYPICAL AEROSOL SIZE DISTRIBUTION

fine

coarse

ultrafine

accumulation

PM

dN/d(log

(Diam))

health**(UFP 10x) lightscatteringmetric aciditymetric

nucleation

metrics

WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION

U.S. SO

EMISSIONS

IndustrialVolcanoesBiomassburningOceans

Sulfur emissions,Tg a

GLOBAL

UNITED STATES

Main source iscoal combustion

SO

+ OH·

HOSO

which is followed by:HOSO

· + O

HO

· + SO

In the presence of water, sulfur trioxide (SO

) is

converted rapidly to sulfuric acid:SO

(g) + H

O (l)

H

SO

(l)

(SO

can also be hydrated to form H

SO

in the gas

phase in a multi-step process, giving rise to newparticles)

Oxidation of SO

to sulfuric acid: gas phase

SO

(g) + H

O

SO

·H

O

SO

·H

O

H

+ HSO

−

HSO

−

H

+ SO

−

There are a large number of aqueous reactions thatoxidize sulfur from S(IV) to S(VI), leading to theformation of sulfuric acid. The most important oxidationreactions are with ozone, hydrogen peroxide andoxygen (reactions with oxygen are catalyzed by iron andmanganese in the cloud droplets). Reaction with H

O

is

acid catalyzed, so the process proceeds faster as SO

levels (or other sources of acidity) increase.

Oxidation of SO

to sulfuric acid: in cloud

droplets or aqueous aerosols (liquid phase)

In solution, reaction with O

(low solubility, K

= 0.011 mol/kg/bar)

< SO

> + O

< SO

> + O

S IV

SVI

d [ S(IV)]/dt = k

[SO

H

O] + K

[HSO

] + K

[ SO

]

M

FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS

(

)

(

) (

)

(

)

(

)

(

)



























H O

H SO

HNO

NH NO

aerosol

Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosoltotally or until titration of acidity, whicheverhappens first

Nitrate is taken up by aerosol if (and only if)excess NH

is available after sulfate

titration

HNO

and excess NH

can also form a solid aerosolif RH is low

Thermodynamic rules:

Highest concentrationsin industrial Midwest(coal-fired power plants)

Condition

aerosol pH

Low RH

High RH

[S(VI)] > 2[N(-III)]

acid

H

SO

•nH

O,

NH

HSO

4 ,

(NH

SO

(NH

, H

, SO

solution

[S(VI)]

2[N(-III)]

neutral

(NH

SO

NH

NO

(NH

,NO

solution

SULFATE-NITRATE-AMMONIUM AEROSOLS IN U.S.

Highest concentrationsin industrial Midwest(coal-fired power plants)

Sulfate

Nitrate

Ammonium

Acidity

CARBONACEOUS AEROSOL SOURCES IN THE U.S.

Fossil fuelBiofuelBiomass burningVegetation

ORGANIC CARBON

2.7 Tg yr

ELEMENTAL CARBON

0.66 Tg yr

Annual mean concentrations (2001)

elemental

organic

EPA REGIONAL HAZE RULE: WILDERNESS AREAS MUST

ACHIEVE NATURAL VISIBILITY CONDITIONS BY 2064

GlacierNationalPark

7.6 μgm

12.0 μgm

21.7 μgm

65.3 μgm

U.S. air quality standard

Visibility degradation by aerosols at Glacier National Park, MontanaNatural aerosol concentrations are typically less than 2

g m

VISIBILITY IN U.S. WILDERNESS AREAS

Statistics for 20% worst visibility days

Deciviews

2001 observations

Natural

Background; includestransboundary pollution

Visual

range (km)

Park et al. [2006]

WILDFIRES: A GROWING AEROSOL SOURCE

S. California fire plumes,Oct. 25 2004

Total carbonaceous (TC) aerosol averaged over U.S. IMPROVE sites

Interannual variability is drivenby wildfires

Ozone & Particulate Matter: Key U.S. Air Pollutants & their Impact on Quality, Slides of Chemistry

Related documents

Partial preview of the text

Download Ozone & Particulate Matter: Key U.S. Air Pollutants & their Impact on Quality and more Slides Chemistry in PDF only on Docsity!

OZONE AND PARTICULATE MATTER (PM):

THE TOP TWO AIR POLLUTANTS IN THE U.S.

millions of people living in areas exceeding national ambient air quality

TYPICAL AEROSOL SIZE DISTRIBUTION

PM

PM

dN/d(log

(Diam))

WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION

U.S. SO

EMISSIONS

GLOBAL

UNITED STATES

SO

+ OH·

HOSO

which is followed by:HOSO

· + O

HO

· + SO

In the presence of water, sulfur trioxide (SO

) is

converted rapidly to sulfuric acid:SO

(g) + H

O (l)

H

SO

(l)

(SO

can also be hydrated to form H

SO

in the gas

phase in a multi-step process, giving rise to newparticles)

Oxidation of SO

to sulfuric acid: gas phase

SO

(g) + H

O

SO

·H

O

SO

·H

O

H

+ HSO

HSO

H

+ SO

O

is

acid catalyzed, so the process proceeds faster as SO

levels (or other sources of acidity) increase.

Oxidation of SO

to sulfuric acid: in cloud

droplets or aqueous aerosols (liquid phase)

< SO

> + O

< SO

> + O

S IV

SVI

[SO

H

O] + K

[HSO

] + K

[ SO

]

M

M

M

FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS

HNO

[S(VI)] > 2[N(-III)]

H