TOPIC THREE

CHEMICAL MONITORING

AND

MANAGEMENT

Contextual Outline
The state of our environment is an important issue for society. Pollution of air, land and water
in urban, rural and wilderness areas is a phenomenon that affects the health and survival of all
organisms, including humans. An understanding of the chemical processes involved in
interactions in the full range of global environments, including atmosphere and hydrosphere, is
indispensable to an understanding of how environments behave and change.
It is also vital in understanding how technologies, which in part are the result of chemical
research, have affected environments. This module encourages discussion of how chemists can
assist in reversing or minimising the environmental problems caused by technology and the
human demand for products and services.
Some modern technologies can facilitate the gathering of information about the occurrence of
chemicals both those occurring in natural environments and those that are released as a
result of human technological activity. Such technologies include systems that have been
developed to quantify and compare amounts of substances.
This module increases students understanding of the nature, practice, applications and uses of
chemistry and the implications of chemistry for society and the environment.

Section ONE
Much of the work of chemists involves monitoring the reactant and
products of reactions and managing reaction conditions

Outline the role of a chemist employed in a name industry or enterprise

identifying the branch of chemistry undertaken by the chemist and
explaining a chemical principle that the chemist uses

Burhan Gemikonakli is a analytical chemist at Qenos, a major Australian Chemical

manufacturing company that makes ethylene from ethane and then polymerises it to
polyethylene.
His role is to

Monitor the quality of the ethylene produced by the plant to ensure that it meets the
requirement for the next stage of manufacture
o

Especially determining the nature and amount of impurities present

Monitoring waste water from the plant to ensure it meets environmental requirements
before it is discharged

Collaborating with process engineers to adjust operating conditions in order to optimise

product yield

The branch of chemistry used is mainly analytical chemistry which is concerned with
determining the nature and amount of substances present in each material.
The technique used is gas chromatography. It uses the chemical principles of adsorption and
solubility.

A liquid or gaseous mixture is vaporised into a stream of helium that flows over a
stationary phase. This is coated within a long thin glass capillary tube. The substances pass
through at different rates due to the solubility/adsorption and in accordance, a device at
the end of the column detects each substance as it passes out and measures it
quantitatively

Identify the need for collaboration between chemists as they collect and
analyse data

Chemistry is such a broad discipline that chemists specialise in particular branches. Solving
complex problems requires input from many chemists with different specialities. It is essential
that chemists work collaboratively and exchange their different view points as they collect and
analyse data.

Gather, process and present information from secondary sources about the
work of practising scientists identifying:
o The variety of chemical occupations
o Specific chemical occupation for a more detailed study

Environmental chemistry concerned with determining how substances interact in the

environment with monitoring concentrations of substances, particularly pollutants in air, water
and soil
Polymer chemistry a branch involved with developing new polymers with particular
properties, working on how polymerisation occurs and working on its efficiency while studying
the properties of polymers.

May also focus on creating new polymers with other properties for other uses

Aims to improve the structure and alter properties to create new substances

Food chemistry looks at chemical aspects of the production, preservation and use of foods
and chemicals added to food
Nuclear chemistry focuses on the production and uses of radioisotopes in medicine and
industry as well as studying the fundamental nature of nuclear reactions e.g. fusion/fission.

Describe an example of a chemical reaction such as combustion, where

reactants form different products under different conditions and thus would
need monitoring

Complete combustion this is combustion with an adequate supply of oxygen forming water
and carbon dioxide
CH4(g)

2O2(g)

CO2 (g)

2H2O(l)

Incomplete combustion this is combustion without an adequate supply of oxygen forming

water and/or carbon monoxide and carbon (soot)
2CH4(g)

CH4(g)

3O2(g)

O2(g)

2CO (g)

C (s)

4H2O(l)

2H2O(l)

Carbon monoxide is toxic gas as it irritates the breathing of humans

Carbon soot is carcinogenic
It is important to monitor the conditions in a reaction such as combustion in order to ensure

Minimising the production of CO or C as they are harmful substances

Section Two
Chemical processes in industry require monitoring and management to
maximise production

Identify and describe the industrial uses of ammonia

It is used for

Fertilisers

Fibres and plastics

Nitric acid

Household cleaners

Detergents

It is widely used as a fertiliser to grow crops for the growing population. Ammonia is reacted
with sulfuric acid or nitric acid to form ammonium sulfate or ammonium nitrates which is used
as fertilisers.

Identify that ammonia can be synthesised from its component gases,

nitrogen and hydrogen

The raw material for ammonia productions are nitrogen gas and hydrogen gas
Sources

Nitrogen can be obtained directly from the atmosphere via fractional distillation

Hydrogen can be obtained several ways depending on the available resources

Electrolysis of water 2H2O(l)

React natural gas (e.g. methane) with steam

+ H2O(g)

2H2(g) + O2(g)

CH4(g)

3H2(g)

+ CO(g)

CO(g) + H2O(g) H2(g)

The CO2 can further be used to be carbonated drinks

+ CO2(g)

Describe that synthesis of ammonia occurs as a reversible reaction that will

reach equilibrium
Identify the reaction of hydrogen with nitrogen as exothermic

Ammonia is prepared by the reversible reaction called the Haber process between hydrogen
and nitrogen gas. The forward reaction is exothermic

N2(g)

+ 3H2(g)

2NH3 (g)

H = - 96kj/mol

Explain why the rate of reaction is increased by higher temperatures

A chemical reaction involves the collision of particles. At higher temperatures, the particles
gain more kinetic energy and move more quickly. This increases the chance of collisions and
thus increases both the forward and backward rate of reaction.

Explain why the yield of product in the Haber process is reduced at higher
temperatures using le Chateliers principle

N2(g)

+ 3H2(g)

2NH3 (g)

H = - 96kj/mol

If the temperature is increased, the equilibrium will favour the endothermic reaction and
minimise the change by absorbing the heat. Thus in the Haber process, at higher
temperatures, the equilibrium will shift to the left, decreasing the yield of the product

Explain why the Haber process is based on a delicate balancing act involving
reaction energy, reaction rate and equilibrium
Analyse the impact of increased pressure on the system involved in the
Haber process

Pressure:

At high pressure, the rate of reaction will increase as the particles have more chance of
collisions

At high pressure, the yield of ammonia is increased as it the side with less gaseous
molecules and by Le Chateliers principle, the system will shift to this side to minimise the
high pressure changes

Impact of pressure High pressure systems is very costly and there is a risk of an explosion,
but does increase both the rate and yield. Thus a compromise of 250 350 atm is used
Temperature

At high temperature, there is a high rate of reaction, but low yield

At low temperature, there will be an increase in yield, but very slowly

A compromise for both temperature and pressure is required for a decent yield and a
reasonable rate of reaction. This is a temperature around 400 500oC

Explain that the use of a catalyst will lower the reaction temperature
required and identify the catalyst(s) used in the Haber process

The use of a catalyst lowers the activation energy for the reaction. This will increase the rate of
reaction at lower temperatures. The hydrogen and nitrogen molecules are adsorbed onto the
surface of the catalyst where they react to form ammonia
The catalyst is usually a mixture of iron and iron oxide or magnetite Fe3O4

Explain why monitoring of the reaction vessel used in the Haber process is
crucial and discuss the monitoring required

The condition of the reaction vessel must be monitored in order to ensure it is a safe and
optimised process. The conditions which are regularly monitored are:

Temperature this is compromised between the rate of reaction and yield of 400 to 500 oC.
This must be monitored to keep them in this range for optimum conversion of reactants to
products or else it will be too inefficient and costly to stabilise. Excess temperature may
damage the catalyst

Pressure This is kept in a range of 250 350 atm. Too high pressure may cause an
explosion

Composition of incoming gas must also be monitored

o

Ensure ratio of hydrogen gas to nitrogen gas is 3:1 which their stiochiometrical
ratio is. Excess of one reactant will slow down the reaction

Ensure there is no oxygen as it can cause an explosion

Ensure CO and sulfur containing species are removed as they poison the catalyst

Ensure there is no unreactive gases which may lower the efficiency

Also the ammonia is liquefied out so it shifts the equilibrium to the right, thus increasing the
yield

Gather and process information from secondary sources to describe the

conditions under which Haber developed the industrial synthesis of
ammonia and evaluate its significance at that time in world history

German scientist Fritz Haber first developed the method of synthesising ammonia from its
elements in which Bosch turned it into an industrial process. The main source of ammonia
before then was from imported from Chile, however this source was cut off by the British naval
blockade.
The production of ammonia was important for both the production of fertilisers and explosives.
Fertilisers were needed to grow food crops in order to solve the diminishing food supplies due
to the war to feed the population. Hence the Haber process was significant at that time as it
prolonged the length of the war and illustrates the impact of the development of science.

Section Three
Manufactured products including food, drugs and household chemicals,
are analysed to determine or ensure their chemical composition

Identifying ions refer to sheets + text book

The main ways are

Precipitation reactions

Flame tests (only for cations)

Some metallic atoms display a characteristic colour when subjected to a flame

When these atoms are subjected to an external energy supply, the electrons gain energy and
jump to the outer empty levels. When these electrons fall back down to their ground state,
they release this energy in the form of photons or light at a particular wavelength. The
wavelengths in the visible region will produce a set of distinctive colours known as the emission
spectrum. The wavelength of light emitted is unique to that particular element
Ba2+ - green
Ca2+ - red
Cu2+ - blue/green

Gather, process and present information to describe and explain evidence

for the need to monitor levels of one of the above ions in substances used in
society

Phosphate this often occurs in natural waterways at low concentrations, but if high enough
can cause eutrophication. This rapid algal bloom can completely cover the surface of the lake
or river, killing most marine life forms. It also increases the BOD and eventually uses up all the
DO in the water. It suppresses photosynthetic processes due to the blockage of sunlight and
also creates cyanobacteria. When it uses up all the phosphate, it dies and has further
detrimental effects on the waterway. Thus the monitoring of phosphate is essential to prevent
any harm
Lead this is a poison, it retards intellectual development and causes brain damage, leading
to neurological disorders. It was widely used in petrol and hence released into the atmosphere
and waterways. It was also a constituent of house paints which can release lead into the soil
and waterways. This is extremely dangerous for both the marine organisms and the humans
whom access this waterway. Thus it is extremely important the levels of lead are monitored in
a waterway.

Describe the use of atomic absorption spectroscopy (AAS) in detecting

concentrations of metal ions in solutions and assess its impact on scientific
understanding of the effect of trace elements.

The use of AAS

AAS allows us to measure the small concentrations of cations in a sample, it is highly

accurate and can go up to the ppm/ppb ranges

From the emission spectrum, we know the exact wavelengths absorbed or released by a
particular element (can be found by using AES). Hence if the element is supplied with those

wavelengths, the electrons of the atoms will absorb those wavelengths and undergo
transition

In AAS, a special light source producing specific wavelengths known to be absorbed by the
element tested is used. The light is passed through a flame containing a vapourised sample
of the test element

A filter is used to select a particular frequency and a detector is used to measure the
transmitted intensity after being passed through the atom. From a comparison between the
transmitted intensity and the original intensity, a percentage of absorption can be
determined. From a standard calibration graph, the concentration can be determined.

The Lamp: a hollow cathode lamp of the element being measured. The lamp generates
wavelengths of light specific to the element being analysed.

The Flame (Atomiser): the solution is sprayed into a flame or graphite furnace. At the
high temperatures of the flame/furnace, the element is reduced to its atomic state.

As light passes through the atomised sample some of the light is absorbed by the hot
atoms. The remaining light passes through a monochromators/filter to select only
the wavelength band to be measured.

The light beam then passes to a photomultiplier, which detects the intensity of the
light. The difference in intensity from the original value (no sample) to the final value
(with sample) is directly proportional to the concentration of the element in the
atomised sample.

AAS is used in measuring the concentration of trace elements. These are elements required by
living organises in very small amounts to help enzymes function. Common trace elements
required are Zn, Co, CU, Ni and Mn.
AAS can provide crucial evidence when dealing with soil or pasture deficiencies. It can identify
the particular trace element that needs to be added in order to improve animal health and
efficient agriculture which is of tremendous importance as it provides food sources where
previously no crops would grow.

South Western Australia animal health could not be maintained on seemingly good
pastureland. AAS showed cobalt deficiencies in the soil and the pasture

Parts of Victoria could not support crops until molybdenum deficiencies were detected by
AAS and rectified

Gather, process and present information to interpret secondary data from

AAS measurements and evaluate the effectiveness of this in pollution
control

The use of AAS can lead to improved environmental monitoring which has obvious positive
benefits for society and the environment. AAS can detect very small concentrations of metals,
especially heavy metals such as Pb, Cd, Hg, in the environment before those concentrations
are high enough to cause significant damage to the environment and those who access it. AAS
is an automated procedure and easy to use in providing quick and accurate results to monitor
and detect routinely harmful metals in food, effluent, waterways and the environment
Limitations

Lacking portability

AAS data on heavy metals is limited by the different sensitivity or detection limits for each
metal

Can only be used for cations

Evaluation hence the use of AAS in pollution is very effective.

Perform a first hand investigation to measure the sulfate content of lawn

fertiliser and explain the chemistry involved

Aim : to measure the sulfate of lawn fertiliser

1g of fertiliser was weighed ground in a mortar and pestle. This was then dissolved in
approximately 250ml HCl with staring

This was heated gently to near boiling and excess barium sulfate was added while stiring

The mixture was then cooled and filtered out

The mass was measured

Evaluate the reliability of the results of the above investigation and to

propose solutions to problems encountered in the procedure

The method is valid since BaSO4 has low solubility

Errors:

Passage of barium sulfate through the filter as the crystals are very small

The precipitate may bad adhered to the walls of the beaker while being transferred

Incomplete drying of precipitation which still contains water, gives inaccurate mass
measurement

Solutions

Use a desiccator to dry

Use a vacuum pump for filtration or use a sand/membrane filter

Section Four
Human activity has caused changes in the composition and the
structure of the atmosphere. Chemists monitor these changes so that
further damage can be limited

Describe the composition and layered structure of the atmosphere

At atmosphere is a blanket of gases above the earths surface. The gases are held together by
gravitational forces. It provides the gases essential for many life forms.
Layers of the atmosphere

Troposphere 0 15km
o

Closest to the earths surface

Provides gases essential for many life forms e.g. oxygen, CO2 and nitrogen

75% of the mass of the atmosphere is found here

Stratosphere 15 50km
o

Contains the ozone layer , its concentration varies between 2 to 8 ppm

Mesosphere 50 85km

Thermosphere 500km

Exosphere 1000km

Composition
Gases

Concentration (%v/v)

Nitrogen

78.1

Oxygen

20.9

Argon

0.93

Carbon dioxide

350ppm

Identify the main pollutants found in the lower atmosphere and their
sources

Carbon monoxide cars exhaust, Cigarettes, forest and farm fires

Oxides of nitrogen combustion from vehicles and power stations

Hydrocarbons unburnt exhaust, gases from vehicles and factories

Sulfur dioxide combustion of impurities in coal, metal extraction

Ozone high voltage discharges, photochemical smog

Describe ozone as a molecule able to act both as an upper atmosphere UV

radiation shield and a lower atmosphere pollutant

Ozone is an allotrope of oxygen. It is slightly polar due to its bent shape

In the troposphere, ozone is a pollutant. It is toxic for all life forms as it causing breathing
difficulties, aggravates respiratory problems and produces headaches and premature
fatigue. This is because ozone is a powerful oxidising agent; hence it can cause oxidation of
tissue in the living body. This disrupts normal biochemical reactions occurring in the body.

Ozone is formed in this layer when sunlight is very intense and the concentrations of No 2 are
well above clean air levels
NO2(g)

+ sunlight

O(g)

+ O2(g)

NO(g)

+ O(g)

O3(g)

But NO can also destroy ozone

NO(g)

O3(g)

NO2(g)

+ O2(g)

The formation of ozone depends on the ratio of the concentration of NO2 to NO. When the ratio
is about 0.3, the ozone is destroyed as quickly as it is formed. However if the ratio is too high,
ozone is formed at a greater rate than it is produced, then there may be a build up of ozone
concentration (ratio of 3 : 1)

In the stratosphere, it acts as a radiation shield by absorbing all the harmful UV rays which
may damage living tissue. It absorbs most UV-B and UV C.

(this type of formation is only possible in this layer)

O2(g)

+ UV radiation -- 2O(g)

O(g)

O2(g)

O3(g)

[exothermic reaction]

Describe the formation of a coordinate covalent bond

A coordinate covalent bond forms when one atom in a provides both electrons in the covalent
bond. Once formed this coordinate bond is indistinguishable from other covalent bonds.

Demonstrate the formation of coordinate covalent bonds using Lewis

electron dot structures

Compare the properties of the oxygen allotropes O2 and O3 and account for
them on the basis of molecular structure and bonding

Property
Colour

Oxygen
-

Ozone
colourle

ss gas
-

- colourless gas
- distinct blue

pale

liquid

blue liquid
-1830C

Boiling point

Explanation

-111oC

Ozone has a greater

molecular mass than
oxygen and is more
polar, hence greater
dispersion forces

Stability

Very stable

Easily decomposes to

Reactivity

Less reactive

O2
More reactive. It is a

Due to the weak co-

very strong oxidising

ordinate covalent

agent
High

bond
Ozone is a powerful

Oxidising

Low

oxidising agent to its

high tendency to
receive electrons

Solubility in water

Less soluble

More soluble

O3 is slightly polar
due to its bent shape
where as O2 is nonpolar

Compare the properties of the gaseous forms of oxygen and the oxygen free
radical

Oxygen radical

This is the oxygen atom in its ground state has 3 pairs of electrons in its valence shell.

This is the most reactive due to the unpaired electrons

Formed by the splitting of a normal oxygen gas molecule by UV radiation

Oxygen gas

very stable

Ozone:

Poisonous and powerful oxidant

Less reactive than the oxygen radical, but more reactive than hydrogen gas

Identify the origins of chlorofluorocarbons (CFCs) and halons in the

atmosphere

CFCs

These are Halo alkanes with all hydrogen atoms replaced by chloro or fluoro functional
groups

Since they were inert, non-toxic, and not soluble in water, they were the best replacement
for ammonia as coolants in refrigerants

They were used in air conditioners and propellants such as aerosol

Halons

Used in fire extinguishers

Identify and name examples of isomers(excluding geometrical and optical)

of halo alkanes up to eight carbon alkanes

Isomers are molecules with the same molecular formula but have a different structural
formula. The longer the chain, the more isomers possible.

Discuss the problems associated with the use of CFCs and assess the
effectiveness of steps taken to alleviate these problems
Present information from secondary sources to write the equations to show
the reactions involving CFCs and ozone to demonstrate the removal of
ozone from the atmosphere
Present information from secondary sources to identify alternative chemicals
used to replace CFCs and evaluate the effectiveness of their use as a
replacement for CFCs

Ozone depletion is a major issue as it results in more UV radiation reaching the earths surface.
This causes:

Increased incident of sunburns and skin cancers

Increased risk of eye cataracts

Increased risk of disease and illness

Increased plant growth

Increase damage to synthetic materials

It was found that CFCs and halons are the main factor that destroys the ozone layer in the
stratosphere. CFCs are not destroyed at low altitudes by sunlight and oxygen as they are inert
and insoluble, thus not removed by rain. Hence once released, CFCs remain in the troposphere
for a very long period of time and slowly diffuse into the stratosphere.
In the stratosphere CFCs break up by sunlight and form a reactive chlorine radical
CCl3F(g)

Cl(g)

UV light

O3(g)

Cl(g)

+ CCl2F(g)

ClO(g)

O2(g)

The free chlorine oxide radical can react with the oxygen present in the stratosphere to
regenerate this chlorine atom
ClO(g)

O(g)

Cl(g)

O2(g)

As the Cl free radical is regenerated in this continual process (a chain reaction), each CL radical
can destroy thousands of ozone molecules before being removed by other process such as
chain carrier removers. Hence the use of CFCs is highly dangerous as it has high ozone
depletion potential.
Steps taken to alleviate these problems
Since it is not possible to remove the CFCs from the atmosphere, the only way to rid the
atmosphere of them is to cease any emissions of CFCs

International agreements:
o

There have been several agreements in which nations have undertaken to phase
out the use of CFCs and other ozone destroying compounds. The original one
was the Montreal protocol but amended and steps accelerated by the one in
Copenhagen

Stop using halons by the end of 1994

Case the use and manufacture of CFCs by 1996

Phase out HCFCs

Allow less developed countries some period of grace and financial

assistance

This has proven to be effective as CFC production in developed countries have ceased and the
atmospheric concentrations of CFCs have been reduced

CFC replacements
o

HCFCs- These compounds contain C=H bonds and are oxidised in the
troposphere to form carbon dioxide, water and hydrogen halide molecules.
Hence only a small portion reaches the stratosphere and their ozone depletion
potential is less. However it is still significant and were only used as a temporary
substitute for CFCs until better replacements found.

HCFs These compounds do not contain chlorine atoms, only hydrogen and
fluorine atoms. Hence their ozone destroying capacity is close to zero and
decomposes easily in the troposphere. However they are more expensive and
less efficient than CFCs, but alleviates the problems to the ozone hole

Evaluation
The steps taken to alleviate the problems associated with the use of CFCs have been extremely
effective as current evidence suggests that the ozone hole is closing and ozone levels in the
stratosphere is increasing. However it will take a long period of time before the problems
associated are solved.

Analyse the information available that indicates changes in atmospheric

ozone concentrations, describe the changes observed and explain how this
information was obtained

Measurements of the total amount of ozone in a column of atmosphere have been recorded
since 1957. It was discovered that in the 1970s, CFCs were depleting the ozone layer.
Observations around the world have shown that the ozone layer thickness is significantly
thinner than in the previous years and being most depleted over the Antarctic during spring.
Seasonal influences

During winter, it is a period of continuously darkness and the stratosphere at this location is
extremely cold. Under these conditions, certain solid particles catalyse a reaction between
hydrogen chloride and chlorine nitrate

HCl

ClONO2

Cl2

+ HNO3

When sun comes in spring, the sunlight splits the chlorine molecule into two separate
chlorine atoms and these process to destroy the ozone layer

Monitoring Stratospheric Ozone

Ground based instruments are UV spectrophotometers pointing vertically up at the

atmosphere. They measure the intensity of light received at a wavelength at which ozone
absorbs and then at wavelengths to either side of this one. A comparison of these gives a
measure of the total ozone in the atmosphere per unit area of the earths surface at this
location

Total Ozone mapping spectrophotometers These are onboard satellites and apply the
same principle, but are able to provide for a much larger scale as they orbit the earth

Atmospheric instruments Huge helium balloons carry instruments such as the UV

spectrophotometers and measure the concentrations of various substances at high altitudes

Section FIVE
Human activity also impacts on waterways. Chemical monitoring and
management assists in providing safe water for human use and to
protect the habitats of other organisms

Identify that water quality can be determined by considering:

o Concentration of common ions
o TDS
o Hardness
o Turbidity
o Acidity
o DO and BOD

Concentration of Common ions

Most metal cations can be detected with AAS which is most practical as they are generally in
very small concentrations. These need to be monitored as they can indicate water quality
TDS
Total Dissolved Solids are typically dissolved salts, generally reported in ppm. Healthy water
should have a TDS of less than 100ppm. Any higher and the water is considered as
contaminated with levels of greater than 1000ppm signifies very unhealthy water which has
limited use.
It can be measured in two ways, evaporation or electrical conductivity
Evaporation The amount of TDS can be measured by evaporating a filtered sample of water
to dryness and weighing the residue. The evaporation must be carried out slowly to prevelt
loss by turbulent bubbling and spitting
Conductivity Nearly all solids dissolved are ionic salts. Therefore it this is commonly used as
it is much quicker and can be done in the field
Water Hardness
Hard water is described as water that does not form a good lather with soap due to the
presence of Ca and Mg ions, instead it forms a grey scum. Water with low concentrations of
these ions is called soft water
Soap is sodium stearate C17H35COONa and is used to lower the surface tension so water can
stick to oily particles which then can be removed. Instead with hard water the stearate ions
precipitate with magnesium or calcium.
Water hardness can be measured by titration with EDTA
Solutions to water hardness would be using a water softener where an ion exchange would
occur. The calcium/magnesium ions were replaced with sodium with the disadvantaged that it
needed to be replaced regularly. Another solution is to use synthetic detergents instead of
soap.

Turbidity
Turbidity in water means cloudiness of lack of transparency due to suspended solids. It
indicates the ability of water to support life as very turbid water systems will suppress
photosynthetic activity, dangerous for animals inhabiting the water system and those accessing
it. Sources include such as clay, silt, plankton, industrial waste and sewage
This can be qualitatively measured by using a turbidimetry tube with a secchi disc.
Acidity
The pH of aquatic systems are dependent upon the water source, geology and levels of
biological activity. Freshwater bodies near limestone soils will be slightly alkaline. Pollution
sources such as acid rain, exposure to sulfide ores can result in low pHs.
Dissolved Oxygen and Biochemical Oxygen demand
Oxygen has a very low solubility in water (healthy water is 9ppm at 20 degrees). However this
small amount that is dissolved is of vital importance to fish and other aquatic life forms. If the
water is depleted of dissolved oxygen, it can suffocate fish as well as causing stress to many
aquatic organism.
DO is a good indicator of water quality. Sources of dissolved oxygen include photosynthesis of
plants and surface water directly absorbing oxygen. If it falls below 5ppm, many aquatic
species will die or fail to reproduce, making it eventually unfit for human consumption.
The DO can be measured by using an electronic oxygen sensor for the winkler method
The biochemical oxygen demand is a measure of the concentration of dissolved oxygen
required for the complete breakdown of the organic matter in the water by aerobic bacteria. In
order to measure this, firstly measure the DO on the first day, then put it in a sealed container
without sunlight for 5 days. Measure the Do every day and compare, the difference between
the first and last day is the BOD

Identify the factors that affect the concentration of a range of ions in

solution in natural bodies of water such as rivers and oceans

The pathway, frequency and temperature of the water.

o

Rain travelling into streams will dissolve ions in natural nutrients and
decomposing minerals along the way. Rain that leeches deep in the earth
contains more heavy metal ions due to the minerals present in the rocks and
soils through which ground water passes through

The more frequent rain, the more possible ions

Higher temperatures will allow more ions to be dissolved in the run off

The presence of human practices

Agricultural practices such as the use of fertiliser and manure which contains
anions such as phosphate, sulfate and nitrates

Land clearing, allows water to rapidly run across the land and into streams,
increasing turbidity and facilities the dissolution of ions

Discharges of waste from industries and mines

Leeching from poorly designed rubbish tips and dumps

pH of rain

Describe and assess the effectiveness of methods used to purify and

sanitise mass water supplies

There are 6 basic steps :

Aeration -> Flocculation -> Sedimentation -> Filtration -> Chlorination ->
Fluoridation
1. Aeration The water is sprayed into the air to increase the concentration of DO
2. Flocculation by adding iron sulfate or aluminium sulfate (alum) along with sodium
hydroxide, precipitates called flocs are formed. These are jelly like substances that can
trap suspended particles
3. Sedimentation the flocs are settled to form sludge
4. Filtration water is passed through layers of sand and gravel to remove any remaining
particles
5. Chlorination This is the sanitising process where chlorine gas is bubbled through to kill
bacteria and other microbes.
6. Fluoridation Fluorine ions are added which help prevent tooth decay
These processes are used by Sydney water and are currently effective for a mass scale water
supply. However there are viruses such as Giardia and Cryptosporidium that cannot be
removed from the water supply. For this, the more expensive ozone sanitising with membrane
filters can be used to purify the water supply.

Describe the design and composition of microscopic membrane filters and

explain how they purify contaminated water

Membrane filters essentially use a thin film of inert and synthetic polymer through which there
are pores of fairly uniform size. They can be used to remove suspended particles that normal
treatment processes cannot.
A simple membrane filter is inert and does not react with water or corrode. It is a thin film of
porous polymer. When the filter cartridge is mounted into the water pipe, the contaminates are
trapped as the water flows through it

A more complex design is the capillary membrane filter where a pourous material is made into
many hollow capillaries with. It has pore sizes of 02-0.5 um. Dirty water is poured on the wall
of the capillary and clean water passes through.

Gather, process and present information on the range and chemistry of the
tests used to
o Identify heavy metal pollution of water
o Monitor possible eutrophication of waterways

Heavy metal pollution

In identifying and monitoring heavy metal pollution of water, AAS is the most effective and
quickest means of determining the concentration of heavy metals.
Also, by adding sodium sulfide, a precipitate will indicate the presence of heavy metals.
However this may identify the presence and overall concentration, it may not work if the
concentration is too low.
Heavy metals that are dangerous include Pb, Hg, Cd, Cr, Zn,
Eutrophication
This is the process where excess nutrients from phosphates and nitrates cause a subsequent
algal bloom.
Effects

Water becomes unsuitable for its normal uses

It creates cyanobacteria that process poisons which is harmful for humans accessing the
water way and livestock

The abundance of algae increases the BOD which, even though it generates oxygen during
daylight, consumes DO from the water at night. This may cause fish to suffocate and die.
Further more once the phosphate/nitrates are used up, the algae will die and have further
detrimental effects on the water way.

Suppresses photosynthetic activities of deeper plants as light cannot penetrate as far in the
water. It also interferes with the diffusion of oxygen from the air into the water.

Sources of Phosphate and Nitrate

Sewage
o

Organic matter contains a large amount of nitrogen and phosphorus which is

then converted into phosphates and nitrates

Laundry washing powder and detergents contain nitrates

Fertiliser
o

Fertiliser run off is the most direct way that farming contributes

Monitoring Eutrophication
This can be monitored by directly measuring the levels of phosphate in the water. This can be
done spectrophotmetrically or colorimetrically.