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To investigate the downstream changes of pollution in the river Cray.

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CONTENTS A Level Fieldwork Introduction The source of the River Cray begins in Priory Gardens in Orpington through Sidcup and into Crayford and then finally into the River Darent near the Dartford Marshes. The route of the river takes it through many urban areas which will most certainly add pollution to the water. The river is a low lying river and is also a first order stream. Aim To investigate the downstream changes of pollution in the river Cray. Hypothesis * Due to the surroundings of the river, I believe that there will be increased pollution downstream * The level of oxygen will decrease downstream * There will be a higher biotic index nearer the source Justification of Hypothesis * There are areas surrounding the river that are very urban and so have many cars fumes and other types of pollution which can be easily transferred into the river. As you can see from Map 1, the route of the river Cray follows closely to that of the A224 and A223. This would mean that there are many cars as well as general pollution form the public. Pedestrians walking along the river side into fields surrounding the river such as in five arches can drop litter into the river polluting it further. * When a river is polluted there will be more bacteria within it. ...read more.


This would enable the temperature of the water to take full effect on the thermometer. Velocity The velocity of the river is how fast the water travels downstream. I collected this data using a flow meter. I had to place the rod with the fan on it in the river and record how fast the propeller took to move down the rod. The propeller needed to be faced upstream as to have the full effect of the river flowing downstream. pH Measuring the pH levels tell me how alkaline or acidic the river is. The optimum level for the river would be if it had a pH of 7, this means that the river is neither alkaline nor acidic and so is neutral. I measured the pH level using a pH strip. This strip was dipped into the river for one second. The strip then changed colour and a colour chart was used to distinguish how acidic or alkaline the river is. Nitrates Nitrates are chemicals that enter the river either through farming practices or traffic along the roads in urban areas. To test the water for Nitrates, I needed to take a nitrate stick and place it in the water for one second. I then let this dry off for a minute or two. ...read more.


16 283 6 270 1 5 25 202 8 246 2 6 36 208 7 122 6 1 1 107 9 200 3 6 36 103 10 100 7 3 9 R = 1 - 6x?d� n�-n r = 1 - 6x216 1000-10 r = 1 - 1296 990 r = 1 - 1.3 r = -0.3 The way the rank spearman result is interpreted, is if the end value comes out as -1, this means that there is a strong negative relationship between the two sets of data and if the result is +1, there is a strong relationship. My end result was -0.3, this shows that there is a weak negative correlation. This means that it is not statistically significant that as oxygen is lower the biotic index is lower. Analysis of Photos The source - Priory Gardens This was my first site and was at the source of the River Cray. As you can see from the photo, there is very little pollution and the presence of wildlife also indicates this as they would feed on the other life in the water. There is only one piece of pollution in the picture and that was caused by humans. Priory Gardens is a small park area and is available for use by the public at all times so has the potential to become polluted, but careful management prevents this. Site 2 - ...read more.

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