Transcript Air Pollution & Air Quality Monitoring

Air Pollution & Air Quality
Monitoring
Assessment

Written Tests (2)
60

Practical Reports (min 5)
40

Assignment


In order to pass this subject you will be required to
obtain at least a minimum of 40% in any test and
hand in 5 practical reports.
Assessment will be competency based with grades
of A, B, C, and F.
2
Introduction

functions of the atmosphere include:
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protection from harmful radiation

moderating the surface temperature

providing a medium (air) that allows organisms
to exchange gases in order to survive
(breathing).
3
Introduction
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Any substantial change in the nature or
contents of the atmosphere has a direct
consequence on how well the atmosphere
performs these tasks
Are there any current scenarios that this
relates to?
4
Introduction
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Historically air pollutants of greatest concern
have been TSP, and oxides of sulfur,
More sophisticated processing industries =
longer list of significant pollutants NOx and
photochemical oxidants as routine pollutants,
and often include Pb, asbestos, Hg, H2SO4
and many others that require careful
monitoring.
5
Introduction
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
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Non-pollutants e.g. CO2 also a problem
Wastes released into the atmosphere are
diluted and dispersed in the air, and are
processed and recycled through a variety of
natural physical, chemical and biological
mechanisms.
the atmosphere is continually cleaned of
pollutants
6
Introduction
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
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Atmospheric problems are made worse by
weather conditions
The residence time determines significance
of pollution problem
compared to natural sources, man’s activities
produce a much smaller amount of global
pollution.
7
Introduction
Global Emissions form Natural & Man Made Sources
120
100
80
% Emissions from Natural
Sources
60
% Emissions from man made
sources
40
20
0
SOx
CO
NOx
NH3
H/C
Dust
Pollutant
8
Introduction
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Dispersal of pollutants is a very important
consideration – as the atmosphere is not
homogeneous - pollutants tend to concentrate in
specific areas – most of which are near where large
human populations reside
means that pollutant levels around residential areas
are often much greater than would be expected in
ambient air
9
Introduction
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
Natural sources are in general more evenly spread,
but there are exceptions such as extremely high
levels of dust and acidic gases associated with
volcanic activity.
Man's activities (anthropogenic) release heat,
gases, aerosols and other wastes into the
atmosphere in high conc's overloading the natural
dispersal, dilution and recycling systems
10
Introduction

Very little is known about the dispersal
processes and the passage through
ecological systems of pollutants. Many are
resistant to degradation, some are
cumulative and harmful.
11
Introduction
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Air pollution definition
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WHO
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“Air is polluted when one or several pollutants are
present in the atmosphere at such a conc. and for
so long a time that they are harmful to man,
animals, plants or material property, cause harm or
reduce well-being or disturb appreciably its
application”.
12
Introduction
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NSW Protection of the Environment
Operations Act as “any deviation from the
natural combination of gases in our
atmosphere”.
13
Introduction


Definition fails to mention is that the natural
combination of gases in our atmosphere
must be taken as dry air at sea level.
Neither completely cover other factors that
we might also call pollution such as the
release of energy, radiation, odour or noise.
14
Introduction


Most air pollution concerns are associated
with ambient air (outdoors and free flowing)
– hence most control programs focus on
ambient air pollution,
significant pollution now occurs in
occupational environments which are
indoors.
15
The Atmosphere
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Earth’s atmosphere 160 kilometers deep, 95% of
air mass lies within 20 kilometers of the surface.
atmosphere is neither uniform, nor static in nature.
Its characteristics vary widely with altitude, season,
location and solar flare activity.
Air within a few kilometers of the earth’s surface
will typically contain the components
16
Element
% (by volume) in the
atmosphere
Total Mass in the
Atmosphere (x1012
tonnes)
nitrogen
78.08
3900
oxygen
20.95
1200
argon
0.934
67
carbon dioxide
0.035
2.5
Neon
0.0018
0.065
Helium
0.00052
0.004
Methane
0.00015
0.005
Krypton
0.0001
0.017
Carbon Monoxide
0.00001
0.0006
Ozone
0.000002
0.0003
Nitrogen Dioxide
0.0000001
0.000013
Sulfur Dioxide
0.0000001
0.000018
0.1 – 5 (normal range 1-3)
Varies according to location
water
17
The Atmosphere
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

The pollutants with which we have the most
problems make up an extremely small part of the
atmosphere.
In polluted city areas these % conc's will change
markedly for some pollutants.
The conc's of N, O, Ar, Ne, He, Kr, H and Xe remain
essentially constant (most are inert and play little
or no role in atmospheric chemistry).
18
The Atmosphere
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N is a precursor for other species such as NO3-, as
well as amino acids and nucleic acids (amongst
others) which are essential for life, and reacts with
O.
O2 important for the nurturing of life, and forming
ozone (O3), acts as a heat and radiation shield for
the planet – maintaining fairly constant
temperatures that allow life to exist.
19
The Atmosphere
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At 0.035%, CO2 in the atmosphere is very low enormous significance as the raw material used by
plants for carbon fixation to produce the
compounds used for energy by almost all forms of
life.
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also a significant greenhouse gas – which serves to
keep the planet warm.
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Water vapour is the most variable (from 0.1 –
30,000ppm).
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allows the transport of energy around the planet.
20
The Atmosphere
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Forms clouds that are responsible for the
Earth’s albedo – the ability of the Earth to
radiate sunlight back into space –controlling
the Earth’s surface temperature
trace gases produced from biological or
geological processes, NH4, CH4, H2S, CO and
SO2
21
The Atmosphere
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The avg. person breathes 20,000L of air per
day
995 of which is N or O.
1% is a mixture of gases and particulates,
many of which are pollutants.
we breathe as much as 200L of pollutants
per day!
22
Stratification of the Atmosphere
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stratification – or layering of the atmosphere
95% of the atmosphere’s air mass is found in the
troposphere. The upper troposphere has a temperature of 56ºC.
At the top of the troposphere is the tropopause layer - a
barrier to prevent water vapour rising much higher as it
causes ice formation.
Water vapour cannot pass through it.
stratosphere, - The ozone layer is within the stratosphere,
and reaches levels of up to 10ppm in the middle of the
stratosphere – gets hotter due to this.
23
The Atmosphere
24
The history of air pollution


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Air pollution was probably as much a problem to
cave men as it is today.
Reports of air pollution and decimation of forests
have been recorded since the 14th C.
mostly linked with the burning of soft coal with a
high sulfur content. This activity produces smoke,
sulfur dioxide and particulate matter containing
HCs.
25
The history of air pollution

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London "pea souper" fogs.
type of smog is grey in colour and is generally
referred to as London type smog.
Meuse Valley of Belgium 60 deaths. 21 people were
killed in Donora, Pennsylvania,
Most victims died of lung and breathing disorders.
Of the survivors, 7000 of the total population of
14000 became seriously ill.
26
The history of air pollution


Los Angeles type smogs conditions different
to those in London
Large amounts of NO2 and unburnt HC’s,
which then react in the atmosphere in the
presence of UV light and oxidants to form a
brown photochemical smog.
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Haze or smog?
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Haze, but how is it different to smog?
Both typified by a reduction in visibility, but the
intensity varies.
Haze is a condition where the reduction in visibility
is not great, and is generally applied to describe
the atmospheric conditions over a very large area
Smog is significant reductions in visibility, generally
in metropolitan areas
28
Factors that make things worse
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calm conditions
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low level emission sources
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temperature inversions
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high buildings and narrow streets
29
The POEO Act
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This act specifies all legal requirements for
the control of air pollution in NSW.
The current regulation pertaining to air
pollution control (in NSW) is called the;
Protection of the Environment Operations
(Clean Air) Regulation 2002
30
Chapter 2
Sources, Types & Distribution of
Air Pollution
Major Sources of Air Pollution
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The number of different types of pollution sources
in modern society is almost endless.
We look at only the most significant sources of air
pollutants.
Mobile (50 - 70%), and stationary sources.
15-25% from heavy industrial stationary sources
and as much as 25% from other stationary
sources.
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Major Sources of Air Pollution
Emissions (106 tonnes / year)
Source
CO
Particles
H/C’s
NOx
SOx
Total
%
Transport
40.7
1.4
6.0
8.4
0.9
57.4
44.9
Stationary fuel
combustion
7.2
1.8
2.3
10.3
16.4
38.0
29.7
Industrial
Processes
4.7
2.5
8.3
0.6
3.1
19.2
15.0
Solid waste
disposal
1.7
0.3
0.6
0.1
0
2.6
2.0
Miscellaneous
7.1
1.0
2.4
0.1
0
10.6
8.3
Total
61.4
7.0
19.6
19.5
20.4
127.8
%
48.0
5.5
15.3
15.3
15.9
100
33
Major Sources of Air Pollution
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
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The table is from USA. The total amount
emitted in Australia will be far less
A significant reduction in the amounts of CO
and H/C’s when compared to the previous
decade
levels of other pollutants has been steady or
shown only a slight increase
34
Transportation Combustion Sources
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The most important transportation sources
at present are major polluters
Motor vehicles CO, CO2 H/C’s, NOx and small
amounts of SOx
Motor vehicle exhaust accounts for 40% of
all H/C air pollutants and 90% of all NO2
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Transportation Combustion Sources
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Motor vehicles pollutants react to form more
reactive (and dangerous) pollutants such as
photochemical smog.
diesel fuel = a source of very dangerous H/C’s
(PAH’s).
Pb has decreased in significance, and according to
the latest national SoE report, is no longer
considered a problem
vehicles running on unleaded fuels emit lower
levels of NOx and SOx
36
Transportation Combustion Sources
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Aircraft and trains are less significant sources of
pollution compared with road transport vehicles.
Aircraft run on kerosene, burnt efficiently, but they
fly very high in the atmosphere the pollutants –
most of which are H/C’s – are spread and diluted in
the upper atmosphere. DISCUSS NEW PROBLEM
Trains mostly run on electricity = contribute very
little to air pollution (except CO2 & some ozone)
37
Stationary Combustion Sources
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Some of the more important sources include
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furnaces - and their combustion of
carbonaceous fuels
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boilers
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ovens and dryers
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process systems which produce volatile
chemicals, gases, etc.
38
Stationary Combustion Sources
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Solvent evaporation (fugitive) from;
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solvent-based materials
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leaking pipe joints
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maintenance work
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spills, unloading /loading procedures
an important part of photochemical pollution
39
Stack Emissions
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Emission of waste gases, fumes, vapours
and smokes to the atmosphere are usually
by the use of a smoke stack or chimney.
stack emission becomes a plume in the
atmosphere.
The plume is an area of concentrated waste
emissions that slowly become diluted with
the other atmospheric gases.
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Stack Emissions
How dilution happens depends on many factors
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Nature of the waste emission
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Volume of the waste
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Toxic emissions need to be very dilute
Is emission constant or only at certain times in the process.
Local topography
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Many cities located in areas surrounded by hills or mountains.
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low wind and cooler temperatures = photochemical smog.
41
Stack Emissions
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Prevailing climate
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direction of prevailing winds
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e.g. Queenstown, Tasmania
The Existing Atmosphere
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In very polluted cities, more stack emissions not
desirable.
e.g. build power stations in the country away
from NOx from cars
42
Plume Behaviour
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Effects of plumes are considered local within
500 metres of the stack, and regional
beyond this.
Mixing or dispersion of the waste gases and
products into the atmosphere = plume
behaviour.
43
Types of Plumes
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Fanning plumes
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Looping plumes
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Coning plumes
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Fumigating
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Lofting
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The Fanning Plume
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Fanning Plumes
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Require stable air and slow vertical movement of the
emission
common after calm clear nights
temperature inversion limits the rise of the plume into
the upper atmosphere
45
The Fanning Plume
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creates a higher conc. of polluted air at lower levels

exists for several hours
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Commonly seen from Eraring Power station
46
Looping plumes
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Looping plumes
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Require windy conditions which cause the plume can
swirl up and down
common in the afternoon.
Moderate and strong winds are formed on sunny days
creating unstable conditions
Exists for several hours.
47
Coning plumes
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Coning plumes
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Require moderate winds and overcast days
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wider than it is deep, and is elliptical in shape
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exists for several hours.
48
Fumigating plume
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Fumigating plume
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Is short-lived (fraction of an hour), but reaches the
earth's surface.
occur when the conditions move from stable to unstable
A fanning plume develops overnight under stable
conditions but as the day heats up, unstable air is
produced
49
Fumigating Plume
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Fumigating plume (cont)
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
unstable air causes the plume to move up and down can cause localised pollution.
become looping or coning plumes as the air conditions
stabilise.
50
Lofting plume

Lofting plume
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
When plume is above the inversion layer (or there is no
inversion), it becomes a lofting plume.
Normal wind direction and speed will disperse the plume
into the atmosphere without effect from ground warming
or cooling.
51
Stack emissions

factors used to establish the amount of stack
emission allowed, and its conc. to the atmosphere
include:



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
smoke stack (chimney) height,
local topography,
temperature,
emission rates,
chemical reactivity, and
existing air pollution problems
wind allow rapid dispersal of pollutants.
52
Fugitive Emissions

Fugitive emissions are emissions which
escape from a process rather than being
discharged

They often have serious consequences
because their levels are not monitored and
they are untreated when entering the
atmosphere
53
Fugitive Emissions

There are many sources of fugitive emissions
including:
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industrial sources (particulate fluorides from aluminium
smelters)
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small business (e.g. dry cleaning solvents)
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agriculture (e.g. dust from ploughing)

natural sources (e.g. volcanoes, forest fires)
54
Fugitive emissions
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

Often the result of poor maintenance of
plant and equipment
Can be eliminated by SOP’s that involve
timed maintenance and quality control
checks
Some are almost impossible to control (e.g.
natural sources)
55
Types of air pollutants
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There are four types of air pollutants;

particulate pollutants and
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gaseous pollutants,
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odour and

noise.
56
Primary vs Secondary pollutants
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
Not all of the pollutants found in the
atmosphere are the direct result of
emissions.
Many pollutants arise from chemical
reactions in the atmosphere with other
substances or light (photochemical
reactions).
57
1° vs 2° pollutants


Pollutant substances that are directly emitted
into the atmosphere = primary pollutants.
Substances not directly emitted into the
atmosphere, formed by chemical reactions in
the atmosphere = secondary pollutants.
58
Particulate Pollutants
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

Very small solid or liquid particles
Individual particles may vary in size,
geometry, chemical composition and physical
properties
May be of natural origin (pollen or sea spray)
or man made (dust, fume and soot)
59
Particulate Pollutants



Provide a reactive surface for gases and
vapours in the formation of secondary
pollutants
Particles also diffuse light reducing visibility
Come from stack emissions, dusty processes,
unsealed roads, construction work and many
other sources
60
Particulate Pollutants

Dusts


large solid particles
Fume

solid particles (metallic oxides) formed by
condensation of vapours from a chemical
reaction process or physical separation process
61
Particulate Pollutants

Mist

liquid particles formed by condensation of vapours or
chemical reaction.
SO3 + H2O

Smoke


H2SO4
solid particles formed as a result of incomplete
combustion of carbonaceous materials.
Spray

a liquid particle formed by the atomisation of a parent
liquid.
62
Particle Size
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

Particles range in size from 0.005 - 500m.
Smallest of these are clusters of molecules
whilst the largest are easily visible with the
naked eye.
Sizes given are not the physical size, but
rather the aerodynamic equivalent diameter
which relates the particle to the behaviour of
an equivalent spherical particle.
63
64
Particle Size
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Particles less than 1m in diameter behave like
gases (remain suspended, may coalesce, move in
fluid streams),
Larger particles act like solids (affected by gravity,
don’t stay suspended long, don’t coalesce).
Smaller particles generally derive from chemical
reactions, whereas the larger particles (10m or
greater) are usually generated mechanically and
tend to be basic.
65
Particle Size




Smaller particles most dangerous to health,
In urban areas there is an approx. even distribution
between fine and coarse particles, this is weather
dependent.
Calm conditions more fine particles than coarse,
Fine particulate matter spread over much greater
distances
66
Particle behaviour in the atmosphere

Particles can undergo many physical and chemical
changes;

grow in size,

absorb or desorb gases from their surfaces,

change electrical charge,
67
Particle behaviour in the atmosphere

Particles can undergo many physical and
chemical changes;

collide or adhere with other particles,

absorb water.

changes the particle size and affect its
atmospheric lifetime.
68
Total Suspended Particles (TSP)



Most particles concentrated into three main
size groups
Larger particles around 10m in size
Smaller particles in size groups centred
around 0.2 and 0.02m.
69
TSP
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

Only particles of <10m penetrate into the
human lung
Analyse air for only this fraction to estimate
its potential danger to human health = PM10
sampling.
Particles <2.5m in size can penetrate deep
into the lung tissue and are especially
dangerous = PM2.5 sampling
70
Organic Particulates



PAH most significant
Found on soot and dust particles, and are
formed from smaller H/C’s at high
temperatures (coal furnace effluent may
contain 1mg/m3 of PAH cigarette smoke
0.1mg/m3)
Urban atmospheres PAH levels ~20 ug/m3
but is highly variable
71
Lead Particulates


Was the most serious atmospheric heavymetal pollutant, but is no longer
primary source was exhaust from vehicles
72
Gaseous Pollutants


CO, H/C’s, H2S, NOx, O3 and other oxidants,
and SOx
Measured in micrograms per cubic meter
(ug/m3) or parts per million (ppm).

1 ppm = 1 volume of gaseous pollutant

106 volumes of (pollutant + air)
73
Gaseous Particulates

At 25°C and 101.3 kPa the relationship
between ppm and ug/m3 is;
ug/m3 = ppm x molecular weight x 103
24.5
74
Carbon Monoxide




a colourless, odourless and tasteless gas.
atmosphere has an avg. burden of around 530
million tonnes (about 0.00001%),
avg. residence time of 36 to 100 days.
Much of the CO in the atmosphere occurs naturally
from volcanic eruptions, photolysis of methane and
terpenes, decomposition of chlorophyll, forest fires
and microbial action in oceans.
75
Carbon Monoxide



Anthropogenic sources = transportation, solid
waste disposal, agricultural burning, steel
production, etc.
emitted directly into the atmosphere through the
inefficient combustion of fossil fuels.
removed by reactions in the atmosphere which
change it to CO2 and by absorption by plants and
soil micro-organisms.
76
Carbon Monoxide


It is removed by reactions in the atmosphere
which change it to CO2 and by absorption by
plants and soil micro-organisms.
In combustion, carbon is oxidised to CO2 in a
two step process.
2C + O2
2CO + O2
2CO
2CO2
77
Carbon Monoxide

Typical conc's




Background levels of CO tend to vary greatly depending
on location.
avg. global levels = 0.2ppm.
Peak conc's during autumn months when large volumes
are generated by the decomposition of chlorophyll in
leaves.
In urban areas = diurnal conc. pattern
78
79
Carbon Monoxide



The internal combustion engine contributes much
of the anthropogenic CO (up to 90% in the Sydney
region)
Maximum levels of this gas tend to occur in
congested urban areas at times when the
maximum number of people are exposed, such as
during rush hours.
At such times, CO levels in the atmosphere may
become as high as 50-100ppm.
80
Carbon Dioxide


Since the Clean Air Act in NSW in 1972 (and
subsequent acts), the levels of CO in Sydney
have dropped from an avg. of 25ppm to
around 10ppm
The accepted standard is 9ppm over an
eight-hour period
http://www.environment.nsw.gov.au/air/24hr.htm
81
Carbon Monoxide

Sinks



CO is removed from the air mostly by conversion
to CO2
This may occur through aerial oxidation or
through the action of soil micro-organisms
The reason for very high conc's occurring in
urban areas is that high emission rates are
combined with a lack of soil
82
Carbon Dioxide


Carbon dioxide is produced when organic matter is;

combusted

weathered

biologically decomposed
It is removed from the atmosphere by plants in
photosynthesis and released by biological reactions
83
Carbon Dioxide



Over hundreds of millions of years CO2 has been
withdrawn from the atmosphere and stored in coal,
oil and natural gas.
The intensive use of these fuels has resulted in
significant CO2 emissions and an increase of
atmospheric conc's
Since 1958, CO2 values measured at Mauna Loa
Observatory in Hawaii have increased from 310 to
more than 350ppm.
84
Carbon Dioxide


Significant seasonal variations are also
observed to occur in CO2 levels
This seasonal variability appears to be
associated with growing season
photosynthetic needs and metabolic releases
of CO2 in excess of plant uptake at the end
of the growing season.
85
Carbon Dioxide



Not all CO2 emitted to the atmosphere from
anthropogenic sources contributes to
increased atmospheric levels.
Because of its solubility in water, the oceans
are a major sink for CO2, absorbing 50% of
all man made emissions.
The world's forests, particularly tropical
forests, also serve as a sink.
86
Carbon Dioxide


As a thermal absorber (read greenhouse
gas), CO2 prevents some IR emissions from
the Earth being radiated back to space
Greenhouse Effect.
87
Sulfur Compounds


A variety of sulfur compounds are released to the
atmosphere from both natural and anthropogenic
sources
The most important of these are the sulfur oxides
(SOx) and hydrogen sulfide (H2S)

Significant SOx emissions may occur from volcanic
eruptions and other natural sources

Man made emissions are responsible for much of
the atmospheric emissions
88
Sulfur Oxides


These are produced by roasting metal sulfide
ores and by combustion of fossil fuels
containing appreciable inorganic sulfides and
organic sulfur
Of the four known sulfur oxides, only SO2 is
found at appreciable levels in the
atmosphere.
89
Sulfur Oxides


Sulfur trioxide (SO3) is emitted directly into
the atmosphere in ore smelting and fossil
fuel combustion and is produced by the
oxidation of SO2.
Because it has a high affinity for water, it is
rapidly converted to sulfuric acid.
90
Sulfur Oxides

The formation of SO2, SO3, and sulfuric acid
in the atmosphere is summarised in the
following equations.
S + O2
SO2
2 SO2 + O2
2SO3
SO3 + H2O
H2SO4
91
Sulfur Dioxide


Sulfur dioxide may be directly absorbed by
water bodies such as the oceans to form
sulfurous acid.
This is one of the sources of acid rain,
which has dramatically affected the
environment in Europe and North America.
92
Sulfur Dioxide



SO2 is an acidic colourless gas which may
remain in the atmosphere for periods up to
several weeks
It can be detected by taste and odour in the
conc. range of 0.38 - 1.15ppm
Above 3 ppm, it has a pungent, irritating
odour
93
Sulfur Dioxide


It is estimated that 65 million tonnes of SO2
per year enter the atmosphere as a result of
man's activities, primarily from the
combustion of fossil fuels.
Of these, coal (and oil) is by far the greatest
contributor, even in Australia
94
Sulfur Dioxide


Background levels of SO2 are very low, about
1ppb
In urban areas maximum hourly conc's vary
from less than 0.1 to more than 0.5ppm.
95
Sulfur Dioxide
Sinks



SO2 is removed from the atmosphere by both dry
and wet deposition processes.
It is believed that plants are responsible for most
SO2 removal that occurs by dry deposition.
SO2 can also dissolve in water to form a dilute
solution of sulfurous acid (H2SO3). This water can
be in clouds, in rain droplets, or at the surface.
96
Sulfur Dioxide


A major sink process for SO2 is its gas-phase
oxidation to H2SO4 and subsequent aerosol
formation by nucleation or condensation
Sulfuric acid will react with ammonia (NH3)
to form a variety of salts
97
Sulfur Dioxide

About 30% of atmospheric SO2 is converted to
sulfate aerosol

Sulfate aerosols are removed from the atmosphere
by dry and wet deposition processes.



In dry deposition, aerosol particles settle out or impact
on surfaces.
In wet deposition, sulfate aerosol is removed from the
atmosphere by forming rain droplets (in cloud) or being
captured by falling rain droplets (below cloud).
These removal processes are called rainout and
washout.
98
Hydrogen Sulfide


H2S is a very toxic gas with a characteristic
rotten egg odour.
The principal concerns associated with H2S
are its smell (foul) & toxicity (same as HCN)
99
Hydrogen Sulfide



Background levels of H2S are approx.
0.05ppb
Natural sources, which include anaerobic
decomposition of organic matter, natural hot
springs and volcanoes
Anthropogenic sources include oil and gas
extraction, petroleum refining, paper mills,
rayon manufacture, and coke ovens
100
Hydrogen Sulfide


The major sink process for H2S is its
atmospheric conversion to SO2.
This SO2 is then removed from the
atmosphere in the gas phase or as an
aerosol by wet or dry deposition processes.
101
Nitrogen Compounds


There are five major gaseous forms of nitrogen in
the atmosphere.
These include

molecular nitrogen (N2),

ammonia (NH3),

nitrous oxide (N2O),

nitric oxide (NO), and

nitrogen dioxide (NO2).
102
Nitrogen Compounds




N2 the major gas in the atmosphere.
N2O present in unpolluted air due to
microbial action
NO and NO2 significant air pollutants
NH3 not considered a significant man made
pollutant, but enormous quantities generated
through natural emissions.
103
Elemental Nitrogen (N2)

~78% of the air we breathe

Relatively inert (unlike O2)

Significant biological use by microbes
104
Nitrous Oxide (N2O)





colourless, slightly sweet, non-toxic gas.
natural part of the atmosphere avg. conc.
0.30ppm.
used as anaesthetic in medicine and dentistry
(laughing gas)
product of natural soil processes, produced by
anaerobic bacteria.
photolytically dissociates in stratosphere to NO.
105
Nitric Oxide (NO)


colourless, odourless, tasteless, relatively
non-toxic gas.
produced naturally by;


anaerobic biological processes in soil and water,
combustion processes and by photochemical
destruction of N compounds in stratosphere.
106
Nitric Oxide (NO)

Major anthropogenic sources include;

automobile exhaust

fossil fuel-fired electric generating stations

industrial boilers

incinerators

home space heaters
107
Nitric Oxide

Nitric oxide is a product of high-temperature
combustion.
N2 + O 2
2NO
108
Nitrogen Dioxide (NO2)



light yellow to orange colour at low conc’s
and brown at high conc’s.
pungent, irritating odour , and extremely
corrosive especially in wet environments
toxic - can cause anoxia
109
Nitrogen Dioxide (NO2)

Some of the NO2 in air produced by direct
oxidation of NO
2NO + O2
2NO2
110
Nitrogen Dioxide (NO2)


At low atmospheric NO levels, oxidation is
slow, accounts for <25% of NO conversion
Photochemical reactions involving O3, peroxy
radical (RO2) and reactive hydrogen species
such as OH, HO2, H2O2, are primary means
by which NO is converted to NO2 in the
atmosphere.
111
Nitrogen Dioxide (NO2)

Other NO2 formation mechanisms
NO + O3
RO2 + NO
HO2 + NO
NO2 + O2
NO2 + RO
NO2 + OH
112
Nitrogen Dioxide



Background conc’s of NO and NO2 are
approx. 0.5 and 1ppb respectively
In urban areas, 1 hour avg. conc’s of NO
may reach 1-2ppm, with max NO2 levels of
approx. 0.5ppm.
decay of NO rapid as polluted air moves from
urban to rural areas, with conc’s dropping to
near background levels.
113
Nitrogen Dioxide



Atmospheric NO level related to
transport/work cycle.
Peak conc's observed in early morning hours,
with a second smaller peak late in the day
(See Figure 2.8).
Peak morning NO conc's followed several
hours later by peak levels of NO2 produced
by the chemical and photochemical oxidation
of NO.
114
Nitrogen Dioxide



Atmospheric levels of NO and NO2 also show
seasonal trends
Emissions of NO greater during winter when
there is increased use of heating fuels
Since the conversion of NO to NO2 is related
to solar intensity, higher NO2 levels occur on
warm sunny days.
115
Nitrogen Dioxide




NOx in vehicle exhausts controlled by legislation as
with CO
catalytic converter in the exhaust system increases
reduction of NOx to N2.
Australian Design Rules limit emission of NOx from
exhausts to 1.9g/km
to maintain the levels in Sydney below the
recommended standard of 0.16ppm (1 hour avg.).
116
Figure 2.8 – Levels of NO, NO2, and ozone on a smoggy day in Los Angeles
117
Nitrogen oxides (NOx)
Sinks


most significant sink for NO is conversion by
both direct oxidation and photochemical
processes to NO2
A major sink process for NO2 is its
conversion to nitric acid
118
Nitrogen Oxides (NOx)
OH + NO2 + M
HNO3 + M
M is an energy-absorbing species (generally O2 or N2). NO2 is also converted to nitric acid by
night-time chemical reactions involving O3.
NO2 + O3
NO3 + O2
NO2+ NO3
N2O5
N2O5 + H2O
2HNO3
119
Nitrogen Oxides (NOx)

NO3 is nitrate free radical

key factor in night-time chemistry

reaction product of NO2 and NO3 is
dinitrogen pentoxide (N2O5) - reacts with
water rapidly to produce HNO3
120
Nitrogen Oxides (NOx)


Some of the HNO3 in the atmosphere reacts
with ammonia (NH3) or other alkaline species
to form salts such as NH4NO3
Nitrate aerosol is generally removed by the
dry and wet deposition processes in much
the same way as sulfate aerosol
121
Ammonia (NH3)

relatively unimportant man made pollutant

Most comes from biological decomposition

Background conc's vary from 1 to 20ppb

The avg. atmospheric residence time is
approx. 7 days
122
Organic Nitrates



produced in the atmosphere by reaction of
NOx and hydrocarbons
Examples are peroxyacyl nitrates (PAN’s) and
peroxybutylnitrates (PBN’s).
discussed in detail in photochemical smog
section
123
Hydrocarbons


organic materials in the atmosphere.
In the atmosphere simple hydrocarbons react with
substances containing

oxygen,

nitrogen,

sulfur,

chlorine

bromine

even some metals (Pb)
124
Hydrocarbons



Atmospheric hydrocarbons exist in gas, liquid
and solid phases
gases and volatile liquids the most
significant pollutants
Solid hydrocarbons generally of higher MW
and exist as condensed particles in
atmospheric aerosols
125
Hydrocarbons


Methane (CH4) most common hydrocarbon in
the atmosphere - formed from many natural
sources;

termites,

cows

decomposition of organic matter
It and the other alkanes found in the
atmosphere are fairly un-reactive
126
Hydrocarbons


atmospheric hydrocarbons of most
significance in terms of chemical reactivity
are the alkenes
highly reactive alkene hydrocarbons are
formed naturally by plants (e.g. terpenes
from citrus plants and eucalyptus haze)
127
Hydrocarbons


greatest source of non-methane
hydrocarbons are motor vehicles and
petroleum processing
Alkenes are the major air pollutant
responsible for photochemical smog and
other gross oxidants in the atmosphere
128
Hydrocarbons

Once in the atmosphere non-methane H/C’s
combine with O2 to form many different
oxygenated H/C’s including;

alkanones

alkanals

alkanoic acids

alkanols

ethers
129
Hydrocarbons

Aromatic H/C’s not very reactive, but can
react with other very reactive chemical
oxidants to form toxic substances, such as;

benzo[]pyrene

poly-aromatic hydrocarbons (PAH’s)
130
Benzo[]pyrene
131
Hydrocarbons



H/C’s emitted from a variety of natural and
man made sources
important pollutants because of their role in
atmospheric photochemistry
biological and geological processes release
hydrocarbon compounds naturally
132
Hydrocarbons
Sources include;

plant and animal metabolism

vaporisation of volatile oils from plant surfaces

biological decomposition

emission of volatiles from fossil fuel deposits
133
Hydrocarbons
Sinks

most important sink processes are;



photochemical conversion of hydrocarbons to CO2 and
H2O or
to soluble or condensable products such as dicarboxylic
acids - a major component of photochemical aerosol.
aerosols are removed from the atmosphere by both
dry and wet deposition processes.
134
Methane



was initially considered an unimportant H/C
Measurements of total H/C subtracted the
conc. of CH4
Hence ambient air quality standard for H/C’s
is a non-methane hydrocarbons standard
135
Methane

recognised as one of the trace gases that
may have significant greenhouse effect on
global climate
136
Methane


by far the most abundant H/C in the
atmosphere, with a 1980 conc. of 1.65ppm.
It has been increasing at a rate of 1.2-1.9%
per year. The rate itself is also increasing.
137
Methane
Ozone & Photochemical Smog



O3 a normal component of the atmosphere
mostly in the middle stratosphere where it
controls UV light reaching the planet’s
surface
here depletion of the substance results in air
pollution – loss of ozone is causing
deterioration in quality of life
139
Ozone



not listed as a major primary air pollutant in
the lower atmosphere
high toxicity and involvement in production
of other pollutants - very important
atmospheric pollutant
Over 90% of photochemical smog is ozone
140
Ozone
Sources


Electrical discharges, e.g. lightning and
electrical devices
Light driven upper atmospheric chemical
reactions e.g. reaction of molecular oxygen
with oxygen atoms
141
Ozone
O2 + O + M

O3 + M
In this reaction M is any third substance (usually O2 or N2) that removes the
energy of the reaction and stabilises O. In the lower atmosphere (troposphere)
the only significant source of atomic oxygen is the photolysis of NO2.
NO2 + h

NO + O*
The reaction of O* with O2 produces O3, which reacts immediately with NO to
regenerate NO2.
NO + O3
NO2 + O2
142
Ozone



All reactions proceed rapidly with approx.
conc. of 20ppb
atmospheric NO2/NO conc. ratios can be
equal to 1
Hence conc's of ozone remain low unless
imbalances in the levels of NO2 or other
alternate chemical reactants are available
143
Oh dear! The chemistry!

We need to look closely at the chemistry we
have seen thus far.

144
Photochemical Smog



refers to an atmosphere laden with
secondary pollutants that form in the
presence of sunlight as a result of chemical
reactions in the atmosphere
arises in urban areas, where there is a heavy
build-up of vehicle exhausts
greatly exacerbated by weather conditions
145
Photochemical Smog




normally primary air pollutants are dispersed over a
large region or to the upper atmosphere
A good prevailing wind is important for cities and
large urban areas to reduce smog
At certain times of the year, when wind is very still,
primary pollutants build up over cities.
Autumn worst for photochemical smog
146
Photochemical Smog
147
Photochemical Smog




In autumn, days are sunny and warm, with cool
nights
Under still conditions, a warm inversion layer forms
under a layer of higher cooler ai
Large urban areas store heat, which provides the
warmth for the inversion layer
The inversion layer limits air mixing and dispersal
trapping primary pollutants at lower altitudes over
urban areas
148
Photochemical Smog
149
Photochemical Smog

primary pollutants (NOx), and H/C’s trapped
in the lower atmosphere are subjected to UV
radiation from the sun – photochemical
smog forms.
150
Photochemical Smog


products called gross photochemical oxidants,
defined by their ability to oxidise I- to I2.
They include

ozone (O3)

hydrogen peroxide (H2O2)

organic peroxides (ROOR')

organic hydroperoxides (ROOH) and

by far the most serious to health, peroxyacyl nitrates
(RCO3NO2), known as PAN's.
151
Photochemical Smog



The key chemical reactants in the formation
of photochemical smog are NOx and
hydrocarbons.
The reactions undergone by these
substances in the atmosphere are many and
varied.
Many of the reaction mechanisms are not
well understood.
152
Photochemical Smog



In the lower atmosphere O3 conc's are often much
higher than those that occur from NO2 photolysis
alone.
This is because there are chemical reactions that
convert NO to NO2 without consuming O3.
In polluted atmospheres, these changes in O3
chemistry can be attributed to peroxy radicals
(RO2) and other species produced by the oxidation
of hydrocarbons as shown in the reactions below.
153
Photochemical Smog
RO2
+ NO
NO2 + h
O* + O2 + M
Net:
RO2 + O2 + h
NO2 + RO
NO + O*
O3 + M
RO + O3
154
Photochemical Smog
155
Photochemical Smog



The rate of O3 formation is closely related to
the conc. of RO2.
Peroxy radicals are produced when hydroxy
radicals OH and HOx react with
hydrocarbons.
Hydroxy radicals are produced by reactions
involving the photolysis of O3, carbonyl
compounds (mostly alkanals), and nitrous
acid.
156
Photochemical Smog

In polluted atmospheres, O3 conc's are directly
related to;





the intensity of sunlight,
NO2/NO ratios,
the hydrocarbon type and conc's,
and other pollutants, such as alkanals and CO, which
react photochemically to produce RO2.
The increase in NO2/NO ratios caused by
atmospheric reactions involving RO2 results in
significant increases in lower atmosphere O3 levels.
157
Photochemical Smog


summary of reactions in smog formation
can be compressed into 4 stages.
explains time variations in levels of H/Cs,
ozone, NO2 and NO (see Figure 2.13).
158
Photochemical Smog

1. Primary photochemical reaction producing oxygen atoms:
NO2 + h

NO + O*
2. Reactions involving oxygen species (M is an energyabsorbing third body):
O* + O2 + M
NO + O3
O3 + M
NO2 + O2
159
Photochemical Smog


Because last reaction is rapid, the conc. of
O3 remains low until that of NO falls to a low
value.
Automotive emissions of NO tend to keep O3
conc's low along freeways.
160
Photochemical Smog

3.Production of organic free radicals from
hydrocarbons, RH:
O + RH
O3 + RH
R + other products
R + and/or other products
(R is a free radical that may or may not contain oxygen.)
161
Photochemical Smog

4. Chain propagation, branching, and
termination by a variety of reactions such as
the following:
NO + ROO
NO2 + R
NO2 + and/or other products
products (e.g. PAN)
162
Photochemical Smog







Some of the many other reactions which are known
to occur in photochemical smog formation are listed
below.
O + hydrocarbons
HO + O2
HO3 + H
HO3 + NO
HO3 + O2
HOx + NO2
HO
HO3
alkanals, alkanones
HO2 + NO2
O3 + HO2
PAN's
163
Photochemical Smog




all H/C’s may form smog, but there are
considerable differences in their reactivities
methane, very slow to react, having an approx.
atmospheric lifetime of more than 10 days
branched alkenes and aromatic compounds the
most reactive
naturally-occurring alkenes (d-limonene) the most
reactive compounds
164
Photochemical Smog


With complex reactions and changing vehicle
emissions during a day, conc's of the major
components vary considerably over a 24hour period.
typical pattern of variations shown in fig2.13.
165
166
Photochemical Smog



morning rush hour begins, NO rises rapidly,
followed by NO2.
NO2 reacts with sunlight giving ozone and
other oxidants
H/C level increases in the morning, then
decreases as compounds are oxidised to
form PAN's and other species.
167
Photochemical Smog



air mass moves toward an urban center, picks up
NO, and H/C’s.
OH begins to degrade H/C’s, producing RO2 while
O3 precursors peak and then decline with
increasing downwind distance.
Ozone conc's increase and are sustained over a
period of 1-5 hours as more reactive alkene and
aromatic H/C’s are depleted by photochemical
reactions.
168
Photochemical Smog



After 5-10 hours, moderately reactive H/C’s
play a more important role in O3 production
O3 levels decrease due to dilution,
conversion of NO2 to HNO3, and surface
adsorption
At night no O3 produced
169
Photochemical Smog



Under inversion layer, O3 may persist for 80
hrs.
allows O3 to be transported over long
distances
At sunrise, inversion breaks up, bringing O3
and other products to the ground, where
they mix with the pollutants held in by the
inversion layer, and begin cycle all over again
170
Photochemical Smog



In unpolluted atmospheres O3 conc's near
ground are 10-20ppb (0.01-0.02ppm) during
the warm months
O3 conc's over landmasses with large motor
vehicle numbers often well above this even
at remote sites
Los Angeles basin 1 hour conc's are 0.200.40ppm
171
Photochemical Smog


warm, sunny NSW central coast means
Sydney Basin has high photochemical smog
production
(NHMRC) ozone standard of 0.12ppm (1hr
avg.) should not be exceeded on more than
one day per year.
172
Photochemical Smog



Ozone removed from the atmosphere by reactions
with plants, soil, and man made materials (rubber)
O3 produced in the atmosphere removed by
chemical processes involving NOx
principal scavenger of O3 is NO – Night reactions
with NO2 destroy O3
173
Chlorofluorocarbons (CFC’s)
What are they?

halogenated H/C compounds used as
refrigerant gases and propellants in aerosol
cans
174
Chlorofluorocarbons (CFC’s)

unique because of their environmental persistence

examples




DDT, Chlordane, Dieldrin, and Aldrin (pesticides)
polyhalogenated biphenyls (PCB’s, PBB’s) solvents and
fire retardants
dichloromethane, trichloroethene, perchloroethene,
tetrachloroethene, and tetrachloromethane (solvents)
CFC’s - refrigerants, degreasing agents, foaming agents,
aerosol propellants
175
Chlorofluorocarbons (CFC’s)


serious atmospheric threat because of their great
stability - leads to damage the O3 layer
Also absorb IR energy and are greenhouse gases
176
Chlorofluorocarbons (CFC’s)

most commonly used (most common
atmospheric contaminants) are;

Trichlorofluoromethane (CFC13)

Dichlorodifluoromethane (CF2C12),

Trichlorotrifluoroethane (C2C13F3).
177
Chlorofluorocarbons (CFC’s)


no sink in the lower atmosphere - CFC
conc's increase with time
For CFC-11 and CFC-12, atmospheric
lifetimes are 75 and 111 years, respectively
178
Chlorofluorocarbons (CFC’s)
Naming CFC’s

The decoding system for CFC-01234a is:

0 = Number of double bonds (omitted if zero)

1 = Carbon atoms -1 (omitted if zero)

2 = Hydrogen atoms +1

3 = Fluorine atoms

4 = Replaced by Bromine ("B" prefix added)
179
Fluoride


Aluminium smelters major source of both
gaseous and particulate fluorides, as are;

brick and glass works

some smelters

steel plants and

coal fired power stations
Fluoride is a localised problem
180
Minor Gaseous Pollutants

Hydrogen sulfide

odour

noise
181
Odour as air pollution


odour pollution increasing importance
from a regulatory point of view, seen as a
welfare not a health issue – this is changing
182
Odour as air pollution


odour is response to the inhalation of a
chemical substance - cannot yet be reliably
measured by chemically
sensory attributes of odours measured by
exposing individuals under controlled
conditions
183
Odour as air pollution

Elements of odour subject to measurement
are:

detectability

intensity

character (quality)

hedonic tone (pleasantness, unpleasantness)
184
Odour as air pollution

limit of detection = odour threshold
characterized in 2 ways;


detectable difference from the background
first conc. at which an observer can positively
identify quality of odour
185
Odour as air pollution


characters of a variety of selected chemicals
summarised in Table 2.2
For example, dimethylamine is described as
fishy, phenol as medicinal, 1,4dihydroxybenzene (paracresol) as tar-like.
186
Chemical
ethanal (acetalydehyde)
Odour Threshold (ppm)
Odour Character
0.21
Green, sweet
propanone (acetone)
100.0
Chemical sweet, pungent
dimethylamine,
0.047
Fishy
ammonia
46.8
Pungent
benzene
4.68
Solvent
butanoic acid
0.001
Sour
dimethylsuffide
0.001
Vegetable sulfide
ethanol
10.0
Sweet
ethyl mercaptan
0.001
Earthy, sulfide
formaldehyde
1.0
hydrogen sulfide
methanol
0.00047
Hay, straw-like, pungent
Egg like sulfide
100.0
Sweet
10.0
Sweet
1,4-dihydroxybenzene
(paracresol)
0.001
Tar-like, pungent
perchloroethene
4.68
Chlorinated solvent
phenol
0.047
Medicinal
sulfur dioxide
0.47
Pungent Sulfur
toluene
2.14
Moth balls, rubbery
2-butanone
or MEK)
(methylethylketone
187
Odour as air pollution


olfactory response to an odourant decreases
as the odourant conc. decreases (nonlinear)
responses to malodours include;

Nausea and vomiting

Headaches and other sensory disturbance

Coughing respiratory ailments

Depression
188
Odour as air pollution

Odour Problems


Bad odours generate complaints to regulatory
agencies more than any other form of air
pollution
A new area of management that deals with
odour and noise is called modelling
189
Odour as air pollution
Odour Problems

Likely sources of bad odours include;

soap-making facilities

petrochemical plants and refineries

pulp and paper mills

food-processing plants

sewage treatment plants

abattoirs
190
Odour as air pollution

Bad odours associated with;

amines

sulfur gases (e.g. H2S)

phenol, ammonia etc

Hydrocarbons

And many more…
191
Odour and the Law

Legal/Regulated aspects of odour

Local Council
192
Air Pollution and Health


specific sections of the public most affected
by air pollution
diseases of the cardiorespiratory system asthmatics and smokers far more likely to be
affected
193
Air Pollution and Health
194
Air Pollution and Health




Pollutants act on surfaces of respiratory system =
chronic respiratory and cardiovascular disease
alter O2 exchange in lungs, and transport in blood
Irritant pollutants = long term damage to eyes,
nose, throat and wet surfaces of body
H2SO4 particles irritate mucous membranes and
cause bronchial constriction
195
Air Pollution and Health




gaseous effects more acute than chronic (as
opposed to the particulate pollutants)
SO2, O3 and NO2 are pulmonary irritants, may
cause congestion, oedema and haemorrhage
NO, H2S and CO are asphyxiant gases
organic gas pollutants e.g. acrolein (1-propenal) as
well as those gaseous pollutants mentioned above
produce eye irritation
196
Synergism



Interaction between pollutants may be
additive, synergistic, or antagonistic
Synergistic effects are those where the sum
of the effects of two or more pollutants is
less than the combined effect i.e. 1 + 1 = 3
The great majority of pollutant effects are
additive.
197
How are we affected?
three main routes by which pollutants enter
the body:

absorption through the skin

ingestion, and

inhalation
198
Air Pollution and Health
199
Carbon Monoxide



preferentially and irreversibly binds to haemoglobin
in blood forming carboxyhaemoglobin
reduces blood's capacity to carry O2 as CO has a
higher affinity (200X greater) for haemoglobin than
O2
medical evidence suggests that continued exposure
to low levels of CO may cause nervous disorders
and be a factor in the cause of heart disease
200
Carbon Monoxide



CO in urban environments usually only a fraction of
those levels that cause asphyxiation
low level effects = behavioural changes, decreased
time interval discrimination, impairment of
brightness discrimination, increased reaction time
to visual stimuli, and lowered performance in
driving simulations
may be the cause of many motor vehicle accidents
in peak hour traffic of cities where peak hour CO
levels may rise above 50ppm
201
Carbon Monoxide

For cigarette smokers,
CO exposures far more
significant (an average
3 – 8%
carboxyhaemoglobin
saturation) than those
experienced under
urban ambient
conditions
Concentration of CO (ppm)
Physiological Effect
10
Lowered awareness and
driving performance
50 - 100
Headaches and
drowsiness, changes in
driving performance and
increased reaction time
to visual stimulation
>250
Death
202
Sulfur Compounds
Sulfur Dioxide and Particulates



Analysis of the effects of SO2 complicated by association
with particulate pollutants – direct effects of each individual
pollutant are difficult to separate.
often produced by a common source, (combustion of coal),
hence high SO2 levels often associated with high particulate
matter levels - forming sulfate aerosols
aerosols just the right size to be retained in the lungs so
cause maximum physiological damage
203
Sulfur Compounds
Sulfur Dioxide

primary effect on respiratory tract, producing
irritation and difficulty breathing

affects most strongly people with respiratory
problems


children known to suffer increased frequency of
infection upon prolonged exposure to SO2
long term effects of exposure not well understood
204
Sulfur Compounds
Table 3.2 – Acute effects on humans of different atmospheric SO 2 levels
[SO2] in g/m3
Effect
500
Lowest level of human
sensation
Threshold of taste
Threshold of odour
Threshold for reversible
bronchial constriction
Immediate
throat
irritation
Immediate eye irritation
Immediate coughing
800
1400
4400
20000
30000
50000
205
Sulfur Compounds
Sulfur Dioxide




London smog of 1952 averaged about 40005000g/m3
Street levels in Wollongong in the late 1970’s
recorded values of 2250g/m3 – due to smelting
operations
water solubility - SO2 almost entirely removed in
the mouth, throat, and nose through normal
breathing
< 1% of inspired SO2 reaches lung tissue (alveoli)
206
Sulfur Compounds
Sulfur Dioxide



principal effect of SO2 exposure is to alter
the mechanical function of the upper airway
SO2 exposure at low levels (0.25 and
0.5ppm) produce acute bronchoconstriction
on inhalation
likely that health effects of SO2 are due to
the highly irritant effects of sulfate aerosols,
such as sulfuric acid, which are produced
from SO2
207
Nitrogen Compounds
Nitrogen Oxides

NO not health threat but is converted to NO2

NO2 exposure at low levels (0.5ppm) destroy
cilia and obstruct respiration

NO2 at 5ppm minor respiratory problems –
100ppm non-fatal inflammation – higher
levels fatal
208
Hydrocarbon Compounds
Hydrocarbons



Most H/C’s relatively nontoxic at the ambient
levels found in normal atmospheres
Form photochemical smog = very deleterious
to health - reduce visibility, have unpleasant
odours and cause skin and eye irritation at
higher levels - some carcinogenic, benzo[a]pyrene
H/C air quality standards not based on
health effects, but an attempt to reduce
photochemical smog
209
Ozone and Photochemical Smog
Ozone



Ozone = the most toxic pollutant regulated
under ambient air quality standards
may cause significant physiological and
pathological changes in animals and humans
at conc’s within range measured in polluted
ambient environments
The ambient air quality standard for O3 is
0.12ppm (235g/m3) averaged over 1 hour
210
Ozone and Photochemical Smog
Ozone



O3 may cause significant lung function
changes even with exposures in the 0.100.40ppm range of for 1-2 hours
Exposure to O3 levels above 0.12ppm, may
lead to a variety of symptoms including
throat dryness, chest tightness, coughing,
pain, shortness of breath, lassitude, malaise,
headache, and nausea
may inhibit immune system's ability to
defend the body against infection
211
Particulate Matter



exhibits toxic effects due to direct irritant
action of particles (such as H2SO4) and
substances readily adsorbed to the large
surface area of small particles
concentration of adsorbed substances may
be considerably greater than in ambient
atmosphere
adsorbed substances of particular concern
include SOx, PAH, and heavy metals e.g. Pb,
Cd, Zn and Hg
212
Particulate Matter
Retention



health consequences depend on ability to
penetrate respiratory defence mechanisms
remove inhaled particles in excess of 10m,
but particles smaller than can enter =
inhalable particles
Particles < 2.5m = respirable, enter pulmonary
tissue
213
Particulate Matter
Retention
214
Particulate Matter
Retention



deposition is slightly higher in smokers and
greatly increased in individuals with lung
disease
retention varies greatly among the different
regions of the respiratory tract
ciliated airways of the nose and upper
tracheobronchial zone, clearance in healthy
individuals is achieved <1 day
215
Particulate Matter
Retention
3

deeper in the
lungs the time
required for
clearance greatly
increases - 2
weeks to months
1
Total Suspended Particulate Level (ug/m )
Effect
1000
250 – 500
Increased mortality
Aggravation
of
bronchitis
Small reversible changes
in lung function of
children
200
216
Particulate Matter
Lead



Atmospheric lead normally a chronic cumulative
poison, mostly affecting the central nervous
system, blood & kidney
at highest concentrations in particles of 0.2m or
less, which increases its access to animals by
allowing access to the deep lung tissue
lead crosses the placenta, resulting in high lead
levels in the foetus, which may lead to mental
retardation - blood lead much higher in smokers
217
Particulate Matter
Asbestos



inhalation of the fibres causes the lung disease
asbestosis –characterised by scarring of the lower
lungs and lowered breathing function
Some forms of asbestos are responsible for causing
lung cancer and mesothelioma (cancer of the lining
of the body cavity)
Asbestos fibres are chronic toxins with very long
latency periods - 1 fibre can kill eventually
218
Effects on Plants



Plants often the first to show damage
associated with increased ambient levels of
air pollution
effects of SO2, HCl and HF reported as early
as the middle of the 19th century
most severe damage associated with high
levels of SO2 and heavy metal particulates
associated with mining and smelting
219
Effects on Plants


visible effects involve changes in leaf
structure such as chlorophyll destruction
(chlorosis), tissue death (necrosis) and
pigment formation
subtle effects include inhibition of growth
and lowered photosynthesis
220
Effects on Plants
Sulfur Dioxide



harmful to certain plants at levels below 1ppm,
causing tissue damage and destruction of
chlorophyll
enters plant tissues through stomates where it
comes into contact with the spongy mesophyll cells
of the leaf causing tissue collapse
injury extends from the bottom to the top of the
leaf and is visible on both surfaces - alfalfa most
affected – injury at 1ppm for 1 hour
221
Effects on Plants
Sulfur Dioxide
Figure 3.4 – Tissue injury symptoms associated with exposure
to high levels of SO2
222
Effects on Plants
Ozone



also enters the leaf through the stomates
symptoms of acute injury are visible on the
upper leaf surface - younger plants more
sensitive and older plants more resistant
most common O3-induced symptom patterns
observed on dicots are upper surface flecks
and some bronzing
223
Effects on Plants
Ozone
Figure 3.5 – Leaf tissue injury associated with ozone exposure
224
Effects on Plants
Ozone
Figure 3.6 – Leaf tissue injury associated with ozone exposure
225
Effects on Plants
Ozone



sensitivity varies from species to species and from
variety to variety within species
more toxic to plants than SO2. Symptoms may be
observed on sensitive plants from exposures of as
little as 0.10 - 0.30ppm for a few hours
estimated to be the cause of over 90% of all plant
injury due to air pollution in North America
226
Effects on Plants
Peroxyacyl Nitrate (PAN)



causes glazing/browning appearance on the lower
surface of the leaf
PAN injury often appears as bands at the apex of
the youngest sensitive leaf, the middle of an
intermediate-aged leaf and the base of the oldest
sensitive leaf
Young, rapidly developing leaves on young rapidly
growing plants are most sensitive to PAN
227
Effects on Plants
PAN
228
Effects on Plants
Fluoride



substantial effects on growing plant tissue
Injury from gaseous HF through the
stomates or from soluble particulate fluorides
absorbed through the leaves and/or roots
fluorides enter veins and are transported to
leaf margins and/or the leaf tip, where they
accumulate - appears as tip burn
229
Effects on Plants
Fluoride
230
Effects on Plants
Particulates

Direct effects such as those for cement kiln dust
include a variety of plant responses, such as

reduction in yield and growth without visible injury,

increase in disease incidence,

severe injury to leaf cells,

suppression of photosynthesis, and

death of trees
231
Effects on Buildings



soiling building surfaces, clothing and other
articles
Most important are effects on metals,
carbonate building stones, paints, textiles,
fabric dyes, rubber, leather, and paper
Physical damage from abrasive effect of
wind-driven particulate matter - chemical
reactions when pollutants and materials
make direct contact
232
Accepted Levels of Pollutants
Air Pollutant
CO
Acceptable Level
1 hour ave. 30ppm (60ppm detrimental)
8 hour ave. 9ppm (20 ppm detrimental)
1 hour alert level 150ppm
NO2
1 hour ave. 0.12ppm (0.25ppm detrimental)
8 hour ave. 0.06ppm (0.15 ppm detrimental)
1 hour alert level 0.50ppm
1 year 0.03ppm
NH3
Ground level conc. 0.83ppm (0.6 mg/m 3)
HNO3
Ground level conc. 0.067ppm (0.17 mg/m3)
SO2
1 hour ave. 0.20ppm (0.34ppm detrimental)
8 hour ave. 0.06ppm (0.11 ppm detrimental)
1 day ave. 0.08ppm
1 year ave. 0.02ppm
1 hour alert level 0.50ppm
H2S
Ground level conc. 0.0001ppm (0.00014 mg/m 3)
Photochemical oxidants
(as O3)
1 hour ave. 0.10ppm (0.15ppm detrimental)
4 hour ave. 0.08ppm (0.15ppm detrimental)
8 hour ave. 0.05ppm (0.08 ppm detrimental)
1 hour alert level 0.25ppm
Respirable particles
24 hour ave. 120 mg/m3 (240mg/m3 detrimental)
1 year ave. 40 mg/m3 (80mg/m3 detrimental)
PM10 Respirables
1 day ave. 50g/m3
Atmospheric Lead
3 month ave. 1.0 g/m3
1 year ave. 0.50g/m3
Benzo[]pyrene
1 year ave. 5.0ng/m3
Benzene
1 year ave. 10.0ng/m3
Fluorine
Ground level conc. 0.033ppm (0.067 mg/m 3)
233
Air Quality Measurement
What is air quality?



complicated by a lack of knowledge as to
what is "clean" and what we mean by quality
main reason for air pollution control
programs is to protect public health - define
air quality based on its effects on people and
the environment
effects of air pollution are chronic and not
immediately obvious
234
Air Quality Measurement

Measurements of air quality generally fall into three
classes:



Measurements of Emissions - also called source
sampling - when a particular emission source is
measured, generally by on the spot tests
Meteorological Measurement - Measures
meteorological factors that show how pollutants are
transferred from source to recipient
Ambient Air Quality - Measures the quality of all the
air in a particular place. Almost all the evidence of health
effects is based on these measurements
235
Air Quality Measurement

Also now have:


Industrial Hygiene sampling - for testing
the air quality inside of factories and places of
work
Residential Indoor sampling - to evaluate
the quality of air in living spaces
236
Air Quality Measurement
Air Sampling Techniques



Most air pollution monitoring equipment performs
the act of sampling and analysis in one action =
real time measurement
older equipment = intermittent sampling (time lag
between when the sample was obtained and when
data was available)
Almost all gaseous pollutants are monitored by real
time analysis - Particulate pollutants are still
mostly monitored by intermittent sampling, even
though real time methods are available
237
Air Quality Measurement
Air Sampling Techniques

When obtaining a sample for air pollution analysis




should be sufficient sample for analysis. Most pollutants
= very low levels and require a large volume of gas for
accurate measurement
pollutants in very small quantities are easy to
contaminate. Take care to purge sampling containers if
grab samples are used
Collection and analysis limitations may require collection
over extended periods means data may only be a 24 hr
avge.
real time produces so much data - are often set to give
hourly avge. to make data more understandable
238
Air Quality Measurement
Air Sampling Systems



require gases or particles to be drawn to the
surface of a collecting medium or a sensor
sampling trains, which may include a vacuum
pump, vacuum trap, a flow regulator and a
collecting device or sensing unit
Sampling trains for gases may also utilize
filters to present particles from entering the
collection unit
239
Air Quality Measurement
Air Sampling
Systems

impingers
240
Air Quality Measurement
Air Sampling Procedures



conducted by static, grab, intermittent or
continuous procedures
first air monitoring used static sampling simple and cheap – requires days for data
e.g. deposit gauge
Grab sampling not commonly used to
monitor ambient air quality – uses bladders
of syringes
241
Air Quality Measurement
Site Selection

General Requirements for Site Selection

purpose of monitoring

number and type of instruments required

duration of measurements

best available general guide comes from AS2922

should be easily accessible

242
Air Quality Measurement
Meteorological Monitoring


changing weather conditions can produce dramatic
changes in air quality and ambient pollution levels
Factors such as:

wind dispersion rates (velocity and direction)

temperature inversions

photochemical reactions, and

rain
243
Air Quality Measurement
Choice of Monitoring Equipment

For almost every type of air pollutant there are several
different acceptable methods of analysis

The type of equipment and methodology used for analysis
may be determined by many factors such as

cost

the number of data points required

the purpose for which the data are being used

the time interval required between data points

the devices power requirements

the type of air pollutant, and

the environment in which the monitoring equipment is being placed
244
Air Quality Measurement
Calibration Procedures



When a device uses airflow input need to calibrate
the airflow system
involves using a device or a pre-calibrated gas flow
meter to check on the ambient airflow into the
device
All devices MUST be calibrated according to
manufacturer’s spec’s in maintenance
manual - times and results of these MUST be
kept in the instrument logbook
245
Air Quality Measurement
Calibration Procedures



two types of calibration procedures commonly used
on air monitoring equipment – static methods and
dynamic methods
Static methods - involve a simple one point
electrical or chemical test
Dynamic methods - based on generating a
flowing stream of calibration gas – which is used to
calibrate the whole instrument = preferred method
for calibration
246
Air Quality Measurement
Data Handling



range from the simplest manual methods to
very sophisticated electronic devices
Manual methods - use field data sheets or
log books, where all parameters are entered
manually – not suitable for remote sites
Dataloggers - electronic devices that store many
data points in an electronic memory. They can be
attached to a device and accumulate the data for
long periods of time if required
247
Air Quality Measurement
Reference Methods




consider only those which are Australian
Standards or where no Australian Standards
exists US EPA Methods
first generation devices - low cost unpowered devices require long time to accumulate data e.g. deposit gauge
second generation devices - powered and require small
amounts of time to produce data e.g. high volume sampler
third generation devices - produce instant (continuous
data) e.g. nephelometer, gravimetric microbalance, remote
UV-visible detectors and remote infra red sensors
248
Air Quality Measurement
Source Sampling


some sources are monitored continually
with automated instruments (real time
analysers)
manual sampling techniques and testing are
often required e.g. Pitot Probe
249
Air Quality Measurement
Source Sampling



introduce a probe into a waste gas stream flowing
in smokestack - probe withdraws sample of waste
gas, which is analysed in laboratory
Gaseous pollutants collected by absorption in
impingers, adsorption on charcoal or other media,
or condensation in collecting traps
Particulate matter be collected by a variety of
techniques including wet scrubbing, filtration,
impaction, and electrostatic precipitation
250
Air Quality Measurement
Stack Sampling



emissions associated with combustion, velocity
and temperature may be much higher than
ambient conditions - measure to correct to
standard conditions
Velocity data determined from pressure
measurements utilising a pitot-tube are
necessary to calculate mass loading to the
atmosphere, i.e., plant emission rates
requires airflow through the sampling probe to be
at the same rate as that flowing in the waste gas
stream = isokinetic
251
Air Quality Measurement
252
Air Quality Measurement
253
Air Quality Measurement
254
Air Quality Measurement
Real Time Analysis

Several methods provide real time analysis,
the most popular is remote UV detection for
SO2
255
Air Quality Measurement
Particulates – Deposit Gauge



involves simple collection of dust that
settles to the earth by gravitation
generally over a period of 30 days - 1 data
point per month (See AS3580.9 for details)
suffer from many problems (uncooperative
pigeons and drunks who can’t find
anywhere else to go)
256
Air Quality Measurement
257
Air Quality Measurement
Particulates – Hi Vol Sampler



most commonly used particle sampling
method
analysis is gravimetric - filter is weighed
before and after the analysis on an
analytical balance, and difference is
particulates collected
A standard high volume sampler collects
particles in the size range from 0.1 - 100m
258
Air Quality Measurement
Particulates – Hi Vol Sampler



airflow is measured by a small flow meter
(calibrated in m3 air/minute)
particulate concentration measured is
referred to as the Total Suspended
Particles (TSP), = combination of
settleable particles and suspended particles
expressed as g/m3 for a 24hour period –
normally as part of 6 day cycle
259
Air Quality Measurement
Particulates – Hi Vol Sampler



More information and the correct operating
procedures on high volume samplers is available
in Australian Standard AS3580.10 - 1990
PM10 and PM2.5 high volume samplers –only collect
particles with aerodynamic sizes of 10m or less,
or 2.5m or less
recognised by PM10 head, which looks like a cross
between a flying saucer and an overgrown wok!
260
Air Quality Measurement
261
Air Quality Measurement
Particulates – Nephelometers



devices which use the scattering of light to
measure the size and number of particles in a
given air sample
best used to determine the amount of particulate
matter in different size fractions
usually used to examine the amount of particulate
material in the 0.1 – 2.5m size range – that
which presents the greatest risk to human health
262
Air Quality Measurement
263
Air Quality Measurement
Gases – Sulfur Dioxide

many methods available for determination of SO2

AS3580.4.1 - 1990. appropriate for SO2 0-5ppm

permits the use of any of the following detection
methods;

UV fluorescence analyser

flame photometric detector (with or without gas
chromatograph)

electrochemical (coulimetric detector)

most widely used method in this country is the UV
fluorescence analyser
264
Air Quality Measurement
Gases – Sulfur Dioxide



UV Fluorescence = air sample drawn into a
scrubber chamber (removes PAH) and then
on into an irradiation chamber where it is
exposed to UV light
SO2 absorbs in 190-230nm
The amount of fluorescent radiation is
directly proportional to the concentration of
SO2
265
Air Quality Measurement
Gases – Sulfur Dioxide


SO2
+
SO2*
UV
SO2*
SO2 + light
266
Air Quality Measurement
Gases – Oxides of Nitrogen



determined using chemiluminescence
specific for NO, but total oxides of nitrogen
determined by passing sample over a
catalyst to convert NO2 to NO
suitable for ambient air containing NOx (NO
and NO2) at levels less than 1 mL/m3
267
Air Quality Measurement
Gases – Oxides of Nitrogen


reaction of NO with ozone in a dark enclosed
chamber to produce light - detected by a pmt
Provided the ozone is present in excess the light
output is directly proportional to the concentration
of NO

NO +

NO2*
O3
NO2*
+ O2
NO2 + h (light)
268
Air Quality Measurement
Gases – Ozone



determined either by chemiluminescence methods
or direct reading UV detectors. AS3580.6 - .6.1 1990
sample drawn into a mixing chamber mixed with a
stream of ethene - causes a chemiluminescent
reaction and the subsequent emitted light at
about 430nm
direct reading UV method - stream of gas in the
sample is drawn through a flow cell where it is
irradiated with UV light at 254nm
269
Air Quality Measurement
Gases – Carbon Monoxide



non-dispersive infra red (NDIR) devices,
suitable for detection from 0-500ppm by
volume
sample through a flow cell in the instrument
where it is irradiated with infrared radiation
essentially just a modified dual beam
infrared spectrophotometer
270
Air Quality Measurement
IR source
Chopper
CO
free
air in
Reference
cell
CO
free
air out
0.1
2
Ambient sample in
Sample cell
Ambient sample out
IR transmitting
windows
Detector
diaphragm
&
capacitance plate
271
Air Quality Measurement
Gases – Non-methane H/C



essential to discriminate between methane and
other H/C’s, as it is the only hydrocarbon that
naturally occurs in large amounts in the
atmosphere - remember those cows & termites!
feed a continuous stream of gas sample into a GC
with a FID
hand held field gas chromatographs now available
which allow sampling and analysis to be done in
the field – eliminating sampling error
272
Air Quality Measurement
Gases – Fluoride



AS2618.2-1984 which is suitable for
determining levels of 0.1g/m3 or greater
automatic sampler draws ambient air through an
inlet tube which passes it through an acid
impregnated paper tape (initial filter tape) to
collect particulate fluorides and then through an
alkali-impregnated paper tape (final filter tape) to
collect acidic gaseous fluorides
New methods impinge the gas and use F- ISE
273
Air Quality Measurement
Gases – Hydrogen Sulfide



Automatic Intermittent Sampling Gas
Chromatographic Method as outlined in
AS3580.8.1 - 1990
applicable to ambient air with H2S
concentrations in the range 0.003 - 2ppm
and is totally specific
GC is designed to sample air automatically
at least ten times per hour
274
Control of Air Pollutants
Air Quality Standards


Air quality standards are provided by many groups
and organisations such as:
National Environment Protection Council
Standards

WHO

US EPA

NSW EPA/DECC standards

Standards Australia
275
Control of Air Pollutants
Particulates

Particulate matter the most obvious form of air
pollution – therefore receives the most effort in
pollution reduction measures

Process Modifications

fuel substitution

encapsulation and wet operation can also greatly
reduce the amount of fugitive particles emanating
from a potential pollutant source
276
Control of Air Pollutants
Particulates – Cyclones



separation by centrifugation - most
common form of particulate removal
gas is spun rapidly - heavier particulate
matter to collect on outside of separator by
centrifugal force, where it is collected and
removed
cyclone separator
277
Control of Air Pollutants
cleaned gas
outlet
dirty
gas inlet
particulate outlet
278
Control of Air Pollutants
Particulates – Filtration



Fibre bags commonly used for control of
particulate emissions with very high dust loadings
and smaller particles
As the gas changes direction, large particles are
removed by inertial separation and collected in the
hopper
dust is collected on the inside of the bag
surface and the filtered gas is discharged to
the atmosphere - 99% efficient
279
Control of Air Pollutants
280
Control of Air Pollutants
Particulates – Wet Scrubbers



spray systems where fine water droplets are
sprayed at high velocity at right angles to the
emerging gas
Most of the particles in the gas stream are
scavenged by the water droplets, which fall and
are collected along with the particles
relatively low efficiencies (80-90%) and is usually
employed as a pre-cleaner to remove particles
larger than 5m
281
Control of Air Pollutants
282
Control of Air Pollutants
Particulates – Electrostatic Precipitators



pass dirty gas through a series of fine wires
(coronas) charged with DC current – causes
particles to coalesce & precipitate
Alternatively corona produces negative ions that
cause particles in the gas stream to become
negatively charged, and attracted to positive
terminal – where they coalesce and fall into a
collection hopper
Large precipitators and low gas flow rates give
better results
283
Control of Air Pollutants
soot free gas escape
charged electrodes
soot laden smoke
inlet
earth point
removal of soot particles
284
Control of Air Pollutants
Gaseous pollutants - Process Modifications



simplest and least expensive methods for the
control of gaseous pollutants
fuel substitution e.g. low sulfur coal, or fuel oils in
place of cheaper coal can greatly reduce the
amount of SO2 emissions at the source
This type of source control is always the best
approach wherever possible
285
Control of Air Pollutants
Gaseous pollutants - Combustion



involves a series of complex chemical
reactions in which oxygen is combined with
organic molecules, to form CO2 and H2O
commonly referred to as incineration or
afterburning
afterburning is applicable when the
treatment process is located downstream of
a primary combustion process
286
Control of Air Pollutants
Gaseous pollutants - Combustion

Incineration applied to effluent streams containing
combustible gases

Incineration can be used to eliminate;

malodourants such as mercaptans and H2S

organic aerosols and visible plumes such as those
produced by coffee roaster and enamel bake
ovens

combustible gases produced by refineries, and

solvent vapours produced by a variety of industrial
287
processes
Control of Air Pollutants
Gaseous pollutants - Combustion

3 types of combustion systems commonly
utilised for pollution control

direct flame,

thermal, and

catalytic incineration systems
288
Control of Air Pollutants
Gaseous pollutants - Adsorption



physical adsorption to solid surfaces
Reversible - adsorbate removed from the
adsorbent by increasing temp. or lowering
pressure
widely used for solvent recovery in dry
cleaning, metal degreasing operations,
surface coating, and rayon, plastic, and
rubber processing
289
Control of Air Pollutants
Gaseous pollutants - Adsorption



limited use in solving ambient air pollution
problems – with its main use involved in the
reduction of odour
Adsorbents with large surface area to
volume ratio (activated carbon) preferred
agents for gaseous pollutant control
Efficiencies to 99%
290
Control of Air Pollutants
Gaseous pollutants - Absorption



Scrubbers remove gases by chemical
absorption in a medium that may be a
liquid or a liquid-solid slurry
water is the most commonly used scrubbing
medium
Additives commonly employed to increase
chemical reactivity and absorption capacity
291
Control of Air Pollutants
292
Control of Air Pollutants
Gaseous pollutants – Dry Scrubbing


used to remove large amounts of SOx from flue
gases using a dry alkaline absorbent (usually lime
or sodium carbonate)
several advantages over wet scrubbers.


do not suffer from scaling or residue build up
do not require elaborate sludge handling systems for
waste materials

less maintenance as there is less corrosion

they use up to 50% less power and water
293
Control of Air Pollutants
Gaseous pollutants – Odour
The main approaches include

wet scrubbing,

charcoal filtration and

incineration
294
Control of Air Pollutants
Gas pollutants – Vehicle emissions



generally involve simple procedures such as
maintaining the correct tuning for the engine, or
the use of catalytic converters
catalytic converters use Pt and Pd attached to
some form of ceramic material
extremely high surface area (in hundreds of m2)
allows catalytic materials to contact exhaust
gases, oxidising them to CO2 and water vapour
295
Control of Air Pollutants
Gas pollutants – Vehicle emissions


all the measures which decrease CO and
hydrocarbon emissions, increase NOx
emissions
measures such as changing engine spark
plug timing and reduction of compression
ratios allow NOx emissions to be lowered
without greatly increasing other pollutant
emissions
296
Control of Air Pollutants
297