Acid Rain

A  number of oxides can be used to produce acid rain.

Sulphur in coal will combine with oxygen to form sulphur dioxide. 

Sulphur + oxygen   sulphur dioxide

S + O2          SO2

Sulphur dioxide can react with water directly to form sulphurous acid

sulphur dioxide + water    sulphurous acid

SO2  +  H2O H2SO3

Sulphurous acid can react with oxygen and water to form sulphuric acid.

sulphur dioxide + oxygen + water    sulphuric acid

2SO2 + O2 + H2O    2H2SO4

As stated in previous posts, vehicle exhausts produce nitrogen dioxide as follows

nitrogen + oxygen   nitrogen dioxide

N2 + 2O2    2NO2

This in turn reacts with water to form nitric acid and nitrous acid

nitrogen dioxide + water    nitric acid + nitrous acid

2NO2 + H2O    HNO3  + HNO2

Acid rain forms in the atmosphere as these gases react with the water that is already in the atmosphere has a number of consequences.  When it reaches the ground, it can have a number of consequences:

1. Damaging the foliage of plants
2. Rapid leaching of essential nutrients from the soils
3. Releasing heavier metals from the soil (e.g. copper, zinc) so that they have toxic effects on plants.
4. Acidifying waterways causing fish kills.
5. Damaging statues or parts of buildings made of limestone and marble (some types of sandstone are also candidates for damage)

As the cartoon implies, the acid emissions of one country can affect neighbouring areas.  This was the case in Canada where northern USA emission damaged the environment.  In Scandinavia acid forming pollution from western Europe again caused damage.

In 1983 an international treaty, The  Convention on the Long-Range Transport Air Pollutants (LRTAP) came into force with 50 signatories to try and reduce the emissions that produce acid rain.  More on this later.

Global warming and Greenhouse Gases

This is a topic that has been in the news lately. A number of scientists and authorities are stating that without rapid action, the earth could warm by up to 6 degrees before the end of the 21st century.  Changing weather patterns and climates may have dire consequences in the long term.

The greenhouse effect occurs because greenhouse gases let sunlight (shortwave radiation) pass through the atmosphere. The earth absorbs sunlight, warms then reradiates heat (infrared or long wave radiation). The outgoing long wave radiation is absorbed by greenhouse gases in the atmosphere. This heats the atmosphere which in turn re-radiates long wave radiation in all directions. Some of it makes its way back to the surface of the earth. So with more carbon dioxide in the atmosphere, we expect to see less long wave radiation escaping to space at the wavelengths that carbon dioxide absorb. We also expect to see more infrared radiation returning back to Earth.


Greenhouse gases include:

1. Carbon dioxide.

The biggest contributor to global warming by volume produced and net effect.  CO2 is produced by the combustion of fossil fuel in a combustion reaction, which should be familiar to you from junior classes.  It is also caused by the breakdown of carbon in soils as a result of deforestation.

Fuel + oxygen         Carbon dioxide + water.

2. Methane.

This is significant because 1 part of methane is up to 20 times better at reflecting infrared radiation compared to CO2.  It is produced by ruminant animals (burping, not farting), rice paddies and landfills.

3. Nitrogen dioxide

This gas is becoming more problematic due to its increasing levels.  This gas is produced by the by combination of nitrogen and oxygen in car engines.  Because air is a mixture of these 2 gases, when it is drawn into the cylinder, some of the energy produced by the burning of the fuel combines to form nitrogen dioxide

N2  +   202        2NO2

Graphs showing the levels of these gases follow below

I should point out that this temp data does require some processing, but the link between historical temps and CO2 levels is striking. Of concern is the spike in the blue line at the end, that is a result of our activity.  This is unprecedented in the 450,000 year history of the atmosphere preserved in ice cores.





There is now pretty much consensus that global warming is happening now and that it will get worse in the next 100 years.  For example the average global temps for 11 of the last 12 years have been the warmest recorded.  There is no evidence to suggest a change in solar activity or other geological phenomenon. Only a small group of people feel that there is no such thing as climate change.  The part up for debate now is the extent that global warming will happen.

Water Licencing

Prior to the 1980's most of Australia had unregulated water usage from the rivers and bore supplies.  What this meant was that anyone who wanted draw water from a river or bore applied for a licence and got it.  At its peak the entire flow of the Murray River could be drained by NSW users if they acted on thier permits.  With the drought that occurred in the late 1970's early 1980's, and the deteriorating condition of the Murray Darling system at this time, it was decided to begin water regulation, particularly for the these rivers and the catchment areas.

So all existing licence users had to reapply for water rights.  If they applied they got them.  However if you did not then your licence lapsed.  This has reduced the amount of water that was drawn from water supplies.

Licences are now traded on the market so if you want to increase the amount of water usage, you needed to buy one off someone who was selling.  These were not transferable to different waterways.  The amount of water that could be captured was limited to 10% of the water falling on a stakeholders land. Beyond that a water licence was again needed.

To this day there is considerable tension between irrigators and conservationists about what the right balance of water is for maintaining the environment while not decreasing food production.

The reason that Australia has a problem with water largely revolves around its scarcity. Because of this whole ecosystems have evolved to rely on seasonal variations of water like in the Snowy River, or cycles of drought and flood like the Murray Darling.  Alterations to this can affect ecosystems and river health. In the worst case scenario the river may be classed as dead and the quality of the water decline to the point where it is unusable by all. 

Pesticides Alternatives

One of the problems of repeated applications of pesticide is the emergence of resistant populations and the removal of beneficial species, often the predators of the pests.  Generally predators take longer to have their numbers recover after the application of pesticide compared to the pests.  This window of time allows the pest to increase its numbers unchecked.  As a result the farmer is required to apply more pesticide, making it harder for predators to recover.  This cycle is perpetuated and is called the pesticide treadmill.

By trying alternative methods, there are many benefits:

1. Only the pest species are targeted.
2. No chemical residues
3. Often more cost effective (particularly in the long term)
4. May lead to the eradication of the pest all together.


Some examples of this are:

1. Pheromone traps, these are effective when females use a chemical scent to signal to males they are ready to mate. By using the hormone, males can be lured to traps.

2.  Introduction of diseases - disease tends to be pest specific.  However it may require regular reapplication and disease resistance may emerge.

3. Introduction of predators - Again this can be considered if the predator does not target non pest species.  A case where this went horribly wrong was the cane toad.

4.  Sterile male release.  By releasing sterile males, the females lay eggs that wont hatch.  However, sterile males need to be released repeatedly.    

DDT - a quick finishing comment

As you would now be aware, DDT appears to have many long term environmental effects particularly the problems of biomagnification and bioaccumulation.  When levels get to a certain point, it then begins to have noticeable effects on animals, such as eggshell thickness in birds etc.  I should also point out that if enough DDT or other toxic substance accumulates in your body, it will eventually kill you.  Combined effects of biomagnification and bioaccumulation meant that the effects of DDT were first noticeable in fish eating birds.  The reason for this because the food chain can have 4-5 links which enhances the biomagnification effect for the top predator.

In addition, the effects of DDT and similar pesticides may affect nervous system development in young children. Evidence for this was shown comparing 2 groups of children with varying degrees of exposure.  The high exposure kids had reduced coordination, memory and fine motor skills.

Potentially more alarming is the estrogenic (feminising) effect that DDT and its breakdown products have.  It could well be affecting fertility of many male animals, including humans and, may be linked to other defects involved in the formation of male reproductive systems.

DDT is also non specific, that is it will kill target species, but also species that just have the misfortune to be around.  This includes potential pollinators.  As a result farmers have looked beyond pesticides when they can, and are trying differing strategies.  This is the basis of our next module.

Work to do for the next week

We have finished Salinity!

This is a topic that is asked either directly or indirectly without fail in the HSC exams in the extended response section.  The case study is often referred to as well.

Make sure that you have a good idea about causes of salinity, types of salinity, combating salinity AND the reasons the methods to treat salinity are used.


At the end of next week I would like the section 3 of your dot point summary notes completed.  This includes everything about salinity.  If you have not completed your class notes regarding the Wagga Wagga case study, you will need to do this in your own time.  I will be  more than happy to help at homework club or a nominated lunchtime.

Next thing we do is start looking at the effects on the environment of pesticides. 

DDT and other pesticides

Brief History

DDT was introduced into the environment on a large during the latter parts of WWII to eradicate malaria which is transmitted by mosquitoes.  It was so effective that it was offered to farmers to spray on crops and to local governments to control mosquitoes and other biting insects which cause human discomfort.

In the late 1950's and early 1960's a number of wildlife ecologists had noticed a decline in a number of fish eating birds in a number of ecosystems.  This was caused by thinning of eggshells when the bird laid eggs.  When they sat on them to incubate they broke and so the chicks failed to develop.

Another problem was that DDT was being detected in significant amounts in dairy products in Europe.  This is because the substance is soluble in fat and so would appear in high amounts.  Then it was detected in human breast milk.

DDT has a number of characteristics that lead to these observations:
1. Long stability and activity.  It can act in a sprayed area for a long time.
2. Fat soluble.  This means that it is stored in the fats and oils that are produced by plants and animals.
3.  It is not metabolised (broken down) by living things very easily.

Because of this, the amount of DDT can build up in tissues, if the rate of intake is more rapid than breakdown.  This is called BIOACCUMULATION.  For example if a human can break down 5 units of DDT/year but takes in 11, he/she will accumulate 6 units DDT every year.  After 10 year, 60 units will be stored.

On top of this there is also BIOMAGNIFICATION.  This is where the accumulation of DDT is magnified every level on the food chain.



Looking at the example here the DDT is in very low levels in the water.  However, it is picked up and stored in the tissues of zooplankton.  Then if the minnows eat 12 zooplankton, they get 0.48 ppm DDT, then if the needlefish eat 4 minnows they get their 2 ppm of DDT.  The bird only has to eat 13 needlefish to get the dosage as shown in the figure.  Biomagnification shows large jumps in the amount of DDT at each stage of a food chain, that is, the dose is magnified.  Even though low levels of environmental DDT wouldn't affect the bird if it was the only means of exposure, the fact that the concentrations get so high through the food chain means that it will have an effect on birds, and in this case its eggshells.

With the detection of DDT in human breast milk and foods that humans consume at levels considered high, countries began banning its use in that late 1960's onwards.  Other pesticides such as organophosphates suffered the same fate a bit later for the same reasons.

DDT is still used in limited amounts in countries with high malaria risks. 

Case Study on Salinity Wagga Wagga

The case study is something that has been directly asked about in many past HSC examinations. In recent years, there has been a more indirect but a 7-8 mark question asked at the end of the core section.  Part of the answer needs to discuss salinity in some detail and Wagga Wagga could be used as an example.

The initial act that culminated in Wagga Wagga having a salinity problem was the clearing of vegetation.  In balanced systems where there existing salt, but no salinity problems, the amount of water in (recharge from rain) equals the amount of water out.  The "out" that water can have in that area is by groundwater entering the the Murrumbidgee River or more importantly, by the removal of water by deep rooted native plants.  In doing this, the water table is kept well away from the surface, and any salt that is in the soil remains solid.  As a result, it cannot cause any harm.

By removing the vegetation, the balance is tipped so that recharge is greater than removal.  Therefore, the water begins to build up in the soil and as the levels move closer to the surface, salt is dissolved.

There have also been additional water inputs into the soil which contributed to the salinity problem.  These are:
1. Rubble pits for stormwater runoff from roofs.
2. Planting shallow rooted non-natives and grasses.

By the early 1990's Wagga Wagga council realised that they had to take steps to or face an annual bill of $6 million/year (1995 dollars) to maintain infrastructure damaged by salt.

This rising groundwater was not only damaging buildings and roads but was having other effects on the biotic (living) and abiotic (non-living) parts of the environment.  You are expected to know and describe some of these.

They did this in a number of ways:
1. Groundwater pumping
2. Draining waterlogged areas into evaporation basins
3. Tree replanting.

You are also expected to know the scientific reasoning behind this and the success/failures of these strategies.

Salinity - Types, Causes and Effects

In this section salinity will be discussed.

The single biggest cause of salinity in Australia is land clearing.

In the figure below, deep rooted native vegetation removes the water added to the system by rainfall, from the soil by transpiration.  As a result, the salt cannot dissolve and is locked in the soil in a form that can cause no harm.  




By removing the vegetation the water loss from the soil is reduced, as less evaporation/transpiration can take place.  The water rises and salt contained in the soil is dissolved.  The water being added by rain continues to also raise the water table.  This is the cause of dryland salinity. 

In the case where water is being added to the system by irrigation (such as on the left side of the bottom figure), this will be the cause of irrigation salinity. 

Finally, when this salt affects  built structures in residential areas, its called urban salinity.

Over time, as the water table rises, the salty water will reach the surface soil.  The water will evaporate and the solid salt is left behind. When salt gets to the surface, very little can grow, and it is very time consuming and expensive to rehabilitate the land.

The best way that salinity can be dealt with is by lowering the groundwater level by either pumping the water out and discharging the water somewhere it cannot cause further harm or by replanting the vegetation so that the roots remove the water and any salt left being is re-solidified and again rendered harmless.

What's Due Next Week

There are plenty of things that need to be completed for next week.

1.  Your experiment proposal Due Monday 29/10).  I need to see the
     following:

• Aim
• Hypothesis
• Equipment
• Method
• Safety Precautions
• How you are going to record your results (desirable but not compulsory)

Please refer to your task notification, especially the section about best practice for writing reports.  Remember, the more criteria you fulfil, the better your mark. 

2.  Your dot points for the first 2 sections of the syllabus.  This is to do with:

• Australian soils (East vs West)
• Erosion (urban and rural)

This will be due in on Thursday 1/11.  On that day a quiz will be done on the class to see your level of understanding and if I need to change what I am doing.  There will be at least 1 past HSC question in this quiz.

Some more hints regarding the assessment task.

As discussed in class yesterday, there are a number of things you need to bear in mind. These include:

1. What is the variable that you are going to change?

2. What is the variable you are going to measure

• Time for water to enter the soil?
• Time it takes for water to leak out of the soil?
• Amount of water the soil can hold?

3.  What variables need to be controlled?

4.  What other pieces of information need to be collected and how are you going to present your results?

5.  What were the faults in your experiment?  Can these be improved?

Assessment task - Compaction of soils

Task 1 - The effects of compaction of soils

The task notification can be viewed/downloaded from here

The handout notes can also be viewed/downloaded from here

You will need to perform the experiment and write it up.  If you watch the movie that is on the network and note the key impacts it has on soil and its relationship with water, it should be fairly straightforward to design an experiment.  The task notification gives you hints on equipment and how to write this up.

Erosion in an Urban Setting

Building sites

Building sites are one region where erosion occurs in urban areas.  This is because the vegetation is removed.  As a result many building sites have to control the movement of sediments when rain washes the top layer of soil off.

note the sediment fences to stop soil entering the storm water system and keep water quality high in nearby creeks/rivers

Developed areas

In urban areas which are largely developed, the impermeable surfaces of roofs, paths and roads cause stormwater to be concentrated and fed into creeks and rivers.  This causes a pulses of high and then low water flows between rain.  During and immediately after rain when the water flows are high, they erode the sides of the creeks and rivers.  This in turn means that sediment is picked up and deposited elsewhere.


With this in mind, we began looking at the Lake Macquarie area as a place where erosion and sedimentation was taking place. Not only is there erosion taking place in the creeks due to development, but the sediments were filling the main lake area.  The council has been working with community groups to revegetate affected areas and constructing artificial wetlands.  As schematic diagram is below:

Apart from acting as a sediment trap and removing nutrients from the water, artificial wetlands slow the flow rate of water and in doing so, they reduce the amount of erosion from the path that they travel.  Various features of artificial  wetlands are discussed in your handouts.

Apart from these wetlands, community groups have been heavily involved in revegetating areas around creeks etc that have been eroded to try and stabilise the situation.  Once again the roots of the plants will hold the soil together and it should no longer wash away.  

Finally, the council has adopted codes of practice that must be adhered to by building site managers.  These include trapping sediment on site so that it is not washed away.

Erosion in a Rural Setting

Causes of Erosion and Possible Solutions in Rural Areas

The biggest cause of erosion is started by land clearing.  By removing vegetation, there are no roots to hold or stabilise the soil and so it can be removed by wind or water.  In the case of wind, the fine topsoil layer is lifted and carried away.  

In the case of water, the lack of vegetation means the soil cannot hold as much water and it begins to flow over the surface.  There are 3 main types of surface erosion:

1. Sheet erosion.  As the name implies water moves over the surface in a large area.  It removes the most productive layers of the soil (the A and O layers) and can remove seed from freshly planted fields.

2.  Rill erosion.  Once again, the upper layers of the soil are removed but now channels are starting to form. Rill erosion can lead to gully erosion.

3.  Gully erosion.  This is where channels over 0.5 m deep are dug out by the water.  The channels are too deep to allow vehicles or animals to safely cross and so they effectively reduce the amount of usable land.

4.  Streambank erosion.  This is where rising water can wash out the sides of creeks and rivers.  In our local area, the wash from boats can also contribute to this.



Erosion on rural land can be mitigated by:

1. Contour ploughing.  This is where the land is ploughed at right angles to the slopes of hills. This means that water flow is greatly slowed by the furrows in the land and so it reduces the potential damage it can cause.  Contour ploughing can only work on slight slopes and beyond that terracing may be required.

2. Seed drilling.  Rather than pulling out the old crop or reploughing the land seed drilling involves slashing the old plants and leaving the roots still in the ground and a mulch cover on top.  The mulch prevents drying and wind erosion while the roots stop water from carrying soil away.  The new seed is planted by drilling it into the soil next to the slashed plant.  As the new seed grows the old plant rots away adding organic material to the soil, and the growing plants roots begin to stabilise the soil  This type of farming is called no-till farming and is increasing in popularity in Australia and around the world.

12EES - Review of soils of Australia

Review of the soils of Australia.

In the first week of our new class format everyone should have completed the following:

1.  The survey
2.  The question sheets
3.  The "dot point" questions/summaries.


The key points to be aware of are as follows:

1.  Age
Western Australian soils come from rocks that are very old (over 2 billion years).  Over time the minerals form the soil get leached from it by rainfall (the minerals that are dissolvable/soluble in water are removed and sink further away from access by plants).  Eastern Australian soils have been formed from rocks that are only 10,000 to 30 million years old.  Because of this they are far richer in minerals, and unsurprisingly make some of the most productive soils in this country.  The reason the rock/soil in Eastern Australia is so young by comparison is due to the eastern region of Australia drifting over a hot spot which in turn led to a chain of volcanoes forming from QLD down to southern Victoria.

2.  Rainfall.
Easter Australia is far wetter than most of Central Australia and WA.  As a result vegetation is reduced.  Vegetation is required to contribute to the organic content of the soil.  In addition moist soil contains more micro-organisms which help break down the dead material into materials that can be absorbed by the soils and therefore accessible to plants planted by farmers.

3. Topography
You would notice that in the presented maps, that the only significant an rapid changes of height above sea level are on the Eastern coast.  This means that when moist air is pushed up over these areas the moisture is more likely to condense and fall as rain.  In Western Australia, the air passes over mostly flat terrain and so has less opportunity to form clouds and rain.  The consequences of this is reduced rainfall (See 2.)

4. Lack of Glaciation
In recent history Australia has had no significant glaciation over the continent.  When the last ice age ended 10000 years ago, the glaciers in Europe and North America had scoured away the old soils and replaced them with new ones made from the freshly ground rock that the glaciers had passed over.  Because these soils are much newer they have a much greater mineral content compared to most Australian soils.


Differences between Easter and Western soils.

Eastern soils - red to brown due to higher mineral and organic content.  Generally high in nitrates and phosphates.  Some trace elements such as magnesium may be a bit low, but the soils are suitable for agriculture without the need for large scale fertiliser addition.

Western soils - Yellow to red soils with high silica content.  This is a result of prolonged leaching causing minerals that are useful to plants being leached out.  These soils tend to be low in nitrate and phosphate and for successful farming, repeated applications of fertiliser may be required.

Survey Link

For all of you who have yet to do the survey, find the link below:

survey