Analysis Of Brisbane River Biology Essay

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The Brisbane River is located in Queenslands South East, from its ending at Moreton Bay it extends inland for 300 kilometers to its origin at the foothills of the Great Dividing Range.

The explorer John Oxley was surveying the coast for a new penal settlement when he discovered the River that was later to be named after the Governor of New South Wales, Sir Thomas Brisbane in 1823. European explorers Captain James Cook and Matthew Flinders explored the region of Moreton Bay but they both failed to discover the Brisbane River. Oxley entered what he described as a clean and unpolluted river and sailed upstream on December 3, noting an abundance of fish and tall pine trees overwhelmed by the sheer natural beauty he witnessed while travelling up the rivers reaches.

The city of Brisbane was established in 1825 and the first exports were shipments of timber during the early days of European settlement. Lumbar was taken down the river by boat or raft to Dunwich on North Stradbroke Island. There sailing ships would load the timer and set sail for Sydney.

Brisbane emerged as the commercial centre in the colony between 1850 and 1885. The net tonnage of timber and goods through the port grew from 8,128 tonnes in 1850 to 690,883 tonnes in 1885. In the same period the area's population grew from under 8,000 people to over 100,000. (History of Brisbane Marine Industry)

As there were no forms of road transport other than horseback during this time the river and water was the only form of transport to Sydney and Ipswich. Ships carried coal and rural products to Sydney for export and also transported imported manufactured goods between Brisbane and Ipswich.

The Brisbane River has been dredged from 1862 for the purposes of navigation with large quantities of gravel and sand being extracted from the river. The rate of materials being removed from the river is far higher than what was being deposited so the river has been a type of underwater mine.

Boral Sands was the main contractor responsible for the dredging of the Brisbane River and over time this dredging caused significant impact to the overall health of the rivers waters. The determining factors from dredging for decreased water quality include increased turbidity (muddy or cloudy water), river bed and bank erosion and changes in tidal flows. The nature of the tides within the river and the general muddy nature of the sand removed by dredging created brown clay sediment in the river which has not cleared. In October 1996 a meeting was held by Local Government and Councilors regarding the dredging of sand and gravel from the river. It was agreed that by September 30, 1997 all dredging would cease. A new surge of development began later in the decade, engineering and consumable products were dominant consisting of meat, oil, sugar and minerals from mining.

The Brisbane River is in a very poor condition environmentally and has been this way for many years. Major causes of contaminants and pollution in the river include excess nutrients, pesticides, hydrocarbons and bacteria which after flowing off surrounding lands become concentrated in the river and its sediment. The areas surrounding the Brisbane River have provided grazing lands for cattle and fertile ground for agriculture. Suitable catchment sites for damming were quickly realised and the Wivenhoe dam was formed for the potable supply of water to Brisbane. The river presented advantages to industry such as easy and cheap disposal of waste and this was carelessly exploited throughout the past century. The Brisbane River gained extensive public awareness and support through environmental groups and the public. Queensland Parliament now has control over the water quality in the river and as a result passed two acts designed to protect the river from waste products and pollutants:

The Pollution of Waters by Oil Act of 1973

The Clean Waters Act of 1971.

 The purpose of this report is to analyse the water quality in the Brisbane River from April 2000 to January 2010 and provide an estimate for water quality in the future. Samples of Nitrogen and Phosphorus have been taken over the past 10 years. From the results collected recommendations can be made to reduce pollution in and along the river.

Past and Current Pollution Levels

The Brisbane River supports farming, land clearing, agriculture and current urbanisation. The following are just a few of the Brisbane River's current and future attributes and concerns.

Water for Industry

 

Rivers & Catchments

Mining

Agriculture - crops

Manufacturing

Development

Transportation

Sport and Recreation

Flood Mitigation

Droughts

Community

Policy & Regulations

Water supply

Indigenous considerations

Urban design

Environmental Policy

Sewage and Storm water

Traffic and Transport Policy

Dredging

Water Sources

 

Climate Change

Storages - dams and barrages

Groundwater

Ecosystem impacts

New technology

Future impacts

Tidal Flows

Marine Life

The Brisbane Rivers major source of pollutants comes from discharge from waste water treatment plants that process raw sewage. At present sewage is treated and released into the Brisbane River as waste water and although 99% of bacteria and solids have been removed during the treatment process there are detrimental chemicals released into the river as a direct result. The sewage discharge contributes to excess Nitrogen (N), Phosphorus (P) and Chlorine (Ch) in the River and an increased demand for oxygen in the water, this leads to the contamination of fish and other marine organisms. Another major input of contaminants into the river is stormwater such as run-off from industrial and urban land, farmlands located in the upper regions of the River can release significant quantities of toxic pollutants such as pesticides and fertilizer into the river.

Algal blooms are the result of an excess of nutrients, particularly Nitrogen and Phosphorus. The excess of nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes, these nutrients can then enter watersheds through water runoff. When phosphates are introduced into water systems, higher concentrations can cause increased growth of algae and plants. Algae tend to grow very quickly under high nutrient availability, but each alga is short-lived, and the result is a high concentration of dead organic matter which starts to decay. The decay process consumes dissolved oxygen in the water, resulting in hypoxic conditions. Without sufficient dissolved oxygen in the water, animals and plants may die in large numbers. (Wikipedia)

Soluble Nitrogen (Nitrate) is an important limiting factor in the growth of certain bacteria in ocean waters. Artificial fertilizers applied to crop-lands to increase yields result in run-off delivery of soluble nitrogen to oceans at river mouths. This process can result in eutrophication of the water, as nitrogen-driven bacterial growth depletes water oxygen to the point that all higher organisms die. (Wikipedia)

Data Samples

To recommend possible improvements towards the safe management of the Brisbane River we will assess the current and past quality of the water over a period of Ten years. The following tests were conducted on water samples at the Story Bridge (EHMP) site 703 at a depth of 0.2 metres.

Date Surveyed

Nitrogen (N) total as (mg/L)

Phosphorus (P) total as (mg/L)

Date Surveyed

Nitrogen (N) total as (mg/L)

Phosphorus (P) total as (mg/L)

3/04/2000

1.47

0.075

10/12/2001

1.9

0.42

19/05/2000

3.16

0.16

8/01/2002

2

0.51

15/06/2000

2.5

0.13

6/02/2002

1.3

0.4

17/07/2000

3.22

0.16

11/03/2002

0.8

0.21

9/08/2000

2.1

0.48

8/04/2002

1

0.29

11/09/2000

1.5

0.34

13/05/2002

0.97

0.26

9/10/2000

1.9

0.44

24/06/2002

1.3

0.33

6/11/2000

2.2

0.49

22/07/2002

1.3

0.32

6/12/2000

1.9

0.46

19/08/2002

1.4

0.35

8/01/2001

1.3

0.32

16/09/2002

2

0.47

5/02/2001

1.9

0.45

16/10/2002

1.6

0.35

5/03/2001

0.84

0.2

14/11/2002

1.1

0.28

2/04/2001

1.1

0.24

16/12/2002

1.1

0.27

21/05/2001

1.3

0.32

13/01/2003

1

0.26

19/06/2001

1.1

0.24

11/02/2003

1.2

0.33

16/07/2001

1.6

0.35

12/03/2003

1.1

0.3

20/08/2001

1

0.24

15/04/2003

0.86

0.22

17/09/2001

1.4

0.32

12/05/2003

1

0.27

15/10/2001

1.3

0.29

10/06/2003

1.1

0.31

12/11/2001

1.6

0.3

10/07/2003

0.93

0.26

8/08/2003

1.1

0.26

15/12/2006

0.51

0.2

8/09/2003

1.1

0.28

16/01/2007

0.46

0.2

6/10/2003

1.4

0.29

14/02/2007

0.48

0.2

3/11/2003

1.7

0.3

16/03/2007

0.47

0.19

3/12/2003

1.4

0.28

17/04/2007

0.43

0.2

19/01/2004

1.3

0.29

15/05/2007

0.51

0.25

16/02/2004

0.7

0.21

14/06/2007

0.66

0.28

15/03/2004

0.72

0.15

12/07/2007

0.56

0.25

14/04/2004

0.63

0.16

10/08/2007

0.41

0.25

Date Surveyed

Nitrogen (N) total as (mg/L)

Phosphorus (P) total as (mg/L)

Date Surveyed

Nitrogen (N) total as (mg/L)

Phosphorus (P) total as (mg/L)

13/05/2004

0.74

0.2

10/09/2007

0.5

0.24

11/06/2004

1.1

0.26

9/10/2007

0.49

0.23

12/07/2004

1.2

0.24

7/11/2007

0.55

0.25

12/08/2004

1.1

0.22

5/12/2007

0.48

0.25

9/09/2004

1.4

0.29

8/01/2008

0.7

0.31

11/10/2004

0.95

0.24

5/02/2008

0.57

0.19

8/11/2004

1.7

0.37

5/03/2008

0.35

0.098

7/12/2004

1

0.25

4/04/2008

0.37

0.14

6/01/2005

0.83

0.22

15/05/2008

0.44

0.17

4/02/2005

0.57

0.2

17/06/2008

0.57

0.16

7/03/2005

0.89

0.24

16/07/2008

0.57

0.17

5/04/2005

0.54

0.21

15/08/2008

0.45

0.14

4/05/2005

0.63

0.26

11/09/2008

0.38

0.13

2/06/2005

0.65

0.25

13/10/2008

0.43

0.15

4/07/2005

1.2

0.38

12/11/2008

0.46

0.15

2/08/2005

1

0.34

10/12/2008

0.71

0.14

1/09/2005

0.81

0.26

8/01/2009

0.58

0.1

14/10/2005

0.89

0.28

9/02/2009

0.42

0.11

14/11/2005

0.61

0.2

10/03/2009

0.59

0.17

13/12/2005

0.81

0.24

8/04/2009

0.68

0.18

10/01/2006

0.86

0.28

7/05/2009

0.48

0.13

8/02/2006

0.64

0.24

5/06/2009

0.55

0.1

10/03/2006

0.7

0.27

6/07/2009

0.71

0.095

10/04/2006

0.6

0.24

5/08/2009

0.42

0.084

10/05/2006

0.55

0.23

3/09/2009

0.5

0.12

7/06/2006

0.56

0.25

5/10/2009

0.46

0.12

7/07/2006

0.67

0.31

4/11/2009

0.3

0.088

8/08/2006

0.57

0.24

3/12/2009

1.9

0.16

6/09/2006

0.63

0.25

13/01/2010

0.51

0.11

4/10/2006

0.54

0.24

15/11/2006

0.52

0.23

Statistical Results

From the above results the following conclusions can be determined:

Nitrogen Phosphorus

Mean (average) ----- 0.98 ----- 0.25

Median (Middle Value) ----- 0.82 ----- 0.24

Mode (Most Frequent) ----- 1.1 ----- 0.24

Range (Low to High) ----- 0.3 - 3.22 ----- 0.075 - 0.51

Standard Deviation ----- 0.56 ----- 0.09

Pearson's r Coefficient ----- 0.54

Where:

Mean is the sample mean or Average

Median is the middle sample value

Mode is the most frequent sample

Range is the lowest sample to the highest

Standard Deviation is how the sample differs from the Mean

Pearson's r is the correlation between the two samples

Nitrogen Levels from 2000 to 2010 in mg/L

From the graph we can see the levels of Nitrogen spiked in November or thereabouts from 2000 to 2004. This may be due to the seasonal crops such as sugar cane and other agriculture. The wet season would also wash water off the land and into the river. Nitrogen levels also have been on the decline since higher levels were recorded in 2000. A major spike in the readings was recorded in December 09 which may be the result of an individual event occurring in the river. The average is 0.98mg/L which is on the high side of the acceptable Nitrite/nitrogen levels. Nitrogen levels below 90 mg/L are more acceptable and seem to have no affect on warm water fish. (Nitrogen and water quality) A relatively high standard deviation indicates that the data is spread out over a large range of values. This tells us that the Nitrogen levels are not close to a constant and have been changing on a large scale.

Phosphorus Levels from 2000 to 2010 in mg/L

From the graph we can see the levels of Phosphorous were quite low in April 2004 then increased substantially in November 2004. Each year in around the same time the readings were high. This may be due to the seasonal crops of sugar cane or other agriculture. The wet season would also wash water off the land and into the river. The average is 0.25mg/L which is very high from acceptable Phosphorous levels. Phosphorous levels over 0.1 mg/L will cause accelerated growth and consequent problems. A low standard deviation indicates that the data is close to the mean or average. This tells us that the Phosphate levels are close to a constant and have not been changing on a large scale.

Future Predictions on Nitrogen and Phosphorus Levels

From both the Nitrogen and Phosphorous graphs and the value of Pearson's r, the correlation between these two variables is 0.54. This indicates a positive correlation coefficient of a medium to high level. We can determine from this that with an increase in Nitrogen there will be a likely increase in Phosphorous. From the graph above we can see that the Nitrogen and Phosphate levels during the past 10 years have been on a steady decline. This tells us that it is quite possible this trend will continue into the future with Nitrogen and Phosphate becoming a minor problem in the next 10 years.

Solution

Nitrogen and Phosphorus entering the River by water runoff can be negated by farmers implementing nutrient management plans that help maintain high yields and save money on fertilizers. Ensuring soils are nutrient rich by applying a soluble organic fertilizer instead of a synthetic inorganic fertilizer. Organic fertilizers include natural organic materials, such as Manure, worms, seaweed and compost. As well as fertilizing plants directly and increasing yield, organic fertilizers can improve the long-term productivity of soil. Organic nutrients will increase the amount of organisms within the soil by providing organic matter and micronutrients. This aids plants in absorbing nutrients and can drastically reduce external inputs of pesticides, energy and fertilizer.

Water from wastewater treatment plants can be directed to wetlands where the Nitrogen and Phosphorus can be broken down or transformed into gas. In wetlands, conversion to nitrogen gas by micro-organisms is the main process of removal, where the nitrogen is released into the atmosphere.

New technologies are currently available for the removal of Nitrogen and Phosphates from treated water using ion exchange and reverse osmosis. Although both of these options generate a significant amount of waste as they remove all contaminants this waste can be used as fertilizer in farms and agriculture.

Conclusion

Although Nitrogen and Phosphorus levels currently experienced in the Brisbane River are higher than acceptable the continuous efforts of Government and Lobby Groups are having a detrimental effect on the water quality. Over the past 10 years levels have reduced considerably and if this trend continues the River will be in great shape for the future. Although the levels are reducing an effective surface water protection plan must be implemented. These should include land management practices designed to reduce the movement of nutrients and waste water control to limit the amount of chemicals dumped into the river by sewage treatment.

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