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A river can be polluted in many different ways.

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A river can be polluted in many different ways. Farmer's slurry in the nearby fields could fall in and pollute the river. The slurry could cover any vegetation in the river, not allowing them photosynthesise. Bacteria can reproduce rapidly and can double once every 20 minutes. The fungi and bacteria can also break down the plant and they need oxygen to live, so they take it from the water. This then starves the other animals and plants in the water. There are two types of sewage: Foul Sewage and Storm sewage. Storm sewage is the water which washes up anything on the road's surface such as oil, dog faeces and food. This then goes down the storm drains. Further down the pipe it will join up with the foul sewage and if it has been raining heavily it will overflow and go into the river. Foul sewage is from the toilets and dirty dishwasher water. If there is a mine near the river, then it can have some bad effects on the river. If iron is present in the water then the river will look orange and murky. Iron cannot dissolve in water so the solid covers the riverbed. This stops the plants from photosynthesising. Indicators of poor river quality are the animals that live there. ...read more.


After we did the invertebrates count, Howard, our group leader, took several tests of the abiotic variables and samples of the river so further tests could be carried out later in the evening. SKETCH OF SITE ONE Site 2 The water at this site looked orange. This was because the riverbed was covered in ochre. This happens because the water runs through the Big Pit mine and picks up iron in the water. Then it runs over the limestone in the rocks and with help from the gushing water it turns into this orange compound, called ochre. This completely covers the riverbed making it hard for the plants to photosynthesise. This then starves the river from oxygen and can then affect the insects that depend on the plants. The Environmental Agency had discovered this and had made a reed bed just beside the river. The aim of this reed is to let the water trickle through hopefully dropping the iron as it goes around the reeds. Therefore purifying the water. This is a picture of the reed beds. Lime dosers Recently, the environmental Agency has installed a lime doser. The doser dispenses into the upper sections of the Afon Llwyd to ensure a better balance of the river's pH levels. Fish and invertebrate life have died in the past as they cannot tolerate the frequent increases of acidity of the river's water caused by the 'acid rain'. ...read more.


Total Site Score Site 1 94 Site 2 34 Site 3 38 Site 4 66 This shows that Site 1 is the cleanest followed by Site 4, Site 3 and Site 2. Conclusion Our results have been very interesting. It shows that having the large amount of ochre at site 2, does largely affect the water quality. We found a smaller range of species when we did the timed disturbance sampling and this site had the largest amount of total dissolved solution. The temperature of the water didn't vary too much so it suggests that there was no other interference with the water such as a factory disposing of warm water etc. Evaluation You could say there were many faults in this investigation. For instance, when we did the 'timed disturbance' sampling, we repeated it twice. So it could be possible that we were catching the same invertebrates twice. Another defect would have been that we didn't repeat the Abiotic Variables. And the Aesthetic Classes were based on personal judgement, so what one person might of counted as gross litter another person may say it is general litter. To improve this experiment we could have maybe visited more sites, than we did. And we could of repeated the Abiotic Variables to get a more reliable result. HOW AND WHY DOES THE WATER QUALITY VARY ALONG THE AFON LLWYD? By Stephanie Richards ...read more.

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