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مقاله انگلیسی با ترجمه
Testing two water bodies for pollution
Introduction
Two water bodies of the same water catchment are going to be investigated, to look for and compare any pollution that may be present. They have to be in the same water catchment because this will ensure that they both get the same rainfall. If they didn't, it would affect the results, e.g. if slightly acidic rain fell into one of the two, and not in the other, this wouldn't be fair. So by using two in the same water basin, the results should be as accurate as possible.
Downs Banks Stream is a tributary to the River Trent, and is found within a national park, where the general public are not allowed to pollute it directly. This means that it shouldn't have any pollutants that would be present if the public were allowed access to drop litter, dump waste, etc, to pollute it. Also this stream is used by the local water authority to compare pollution levels around the area with, this is due to the fact that this stream is one of the most unpolluted water bodies around the area \ will provide accurate results to compare others to.
Yet it is believed that the river Trent at Stone, is significantly polluted. There are many factors which provoke this belief, one is that it is down stream from a major industrial town- Stone, this provides alot of sources of pollution: public dumping their wastes, rusty car parts have also been found in the spot to be investigated.
Also, because the river is down stream from an industrial town, this means that there will be the hot water spilling out from factories, etc, these would be point sources, which reduces O2 levels \ killing off aquatic life. Moreover, there is a sewage works up stream, which when there are bad storms, has overspills of untreated waste into the river. This means that aswell as raw sewage, there are also the effluents and chemicals that get into the sewage works, these will all contribute to the polluting of the river and aquatic life.
Also pollution from landfill sites in the area can get into ground water and filtrate into the surrounding rivers, river Trent included. Aswell as land fills; there are still the old mineshafts, which are on route to the spot to be investigated on the Trent. Some of these mineshafts have become flooded with ground water and if the water happens to be polluted by anything and it could seep into the rivers. These wouldn't be point sources because determining where the pollution originated would be difficult.
The Trent is also far down stream from farmland which could be treated with chemicals such as nitrates and phosphates. Overuse of these chemicals means excess, which when it rains, can get washed directly into the river, or into tributaries, and eutrophication can set in: These excess nitrates can then cause the aquatic plants to overgrow, become crowded and die off. Bacteria then thrives growing in population and using up all the oxygen, which then affects the other aquatic life which too die off.
Method
Apparatus:
Large white tray (white so show up the organisms)
specimen tray (to look closer at the different species)
pH testing kit
nitrate testing kit
dissolved oxygen testing kit
net
Trent biotic index
magnifying glasses
To investigate pollution levels of both the water bodies, four tests are going to be carried out: pH test- approx 10ml of the water that is to be tested in put in a small container and a tablet (that is crunched up) is added, this solution is put in a little box and looking through the box, the colour is compared to other colours on the box. Whichever one matches, that is the pH. The pH is going to be investigated to see if there are any impurities in the water, that may have an acidic or alkaline origin. Although, it is known that water found in rivers is naturally acidic because of the pollution in our atmosphere, some becomes dissolved in the rain clouds and rains down slightly acidic. Also when aquatic organisms die, the amino acids in their bodies disperse in the water too.
A nitrate test is going to be carried out to find out if there are too many nitrates- parts/million, if there is it could lead to eutrophication. Naturally, there are going to be some levels of nitrates in the water because of nitrogen from decaying organisms and nitrates in excretion that could get into water bodies, etc:
The tube will be rinsed with the water to be tested to dispose of any impurities. This will then be filled with 10ml of the water to be tested. Next add, using the clippers, the contents of the little sachet- Nitraver 5 nitrate reagent powder to the solution- BE VERY CAREFUL BECAUSE THE NITRATE SUBSTANCE IS CARCINOGENIC- and shake for one minute to mix it with the water. Take the solution and compare it with a resin block, which will show what levels of nitrates match up with which colour.
Also an oxygen test will be carried out to see how much dissolved oxygen there is in the water- parts/million. This will be done by carrying out the following process:
Rinse the glass stopper bottle 3 times and fill up to the neck with the water to be tested.
Add 5 drops of manganous sulphate and shake. CAREFUL CHEMICAL CAN BE HARMFUL.
Add 5 drops of sodium hydroxide, potassium iodide, and sodium aride solution and shake. CAREFUL CHEMICALS CAN BE TOXIC, IRRITANT AND CORROSIVE.
Place some of the sol into the plastic container up to 5ml.
Add 10 drops of 42% sulphuric acid and shake. CORROSIVE.
Add 1 drop of starch , salicylic acid solution till the colour turns dark. IRRITANT.
Add 1 drop of sodium thiosulphate till the solution turns back to the original colour and this will be taken as the end point. By counting how many drops it took to turn the colour back, use this figure, multiply it by 10 and this gives the dissolved oxygen content in mg/l (parts/million).
The Trent biotic index was also used to determine how polluted the two water bodies were. This contains different species of aquatic life, not including plants, which are found in certain conditions and levels of pollution because some can withstand a little pollution, yet some can't, etc. This test will be done by carrying out several kick tests per water body, these will be done by: taking a large tray and a specimen tray, and filling them with the water being tested
wash the net out first to get rid of anything that may still be on it from previous investigations placing a net in the opposite way to the direction that the water is flowing, stand facing the net and start to kick around the bottom side to side,
whilst doing this move up stream as to gather more of wha Color t is going into the net,
after approx 30 seconds stop and empty the contents of the net into the large tray making sure that everything has been taken out.The various organisms that have been collected can then be looked at closely. Afterwards, they will be put into the specimen trays (one of each species) and marked down, then they will be released back into the water. This will be carried out several times in different places, but around the same spot, on the water bodies to get as accurate results as possible. Also if a species is missed in one place it may be found in another but a little farther down stream.
Then by using a key (found on page A), which determines how polluted a water body is by what species it has in it, the pollution levels of the two water bodies being investigated can be determined.
Precautions and limitations
Ideally, each of these tests would be done every 4 hours or so to obtain max accurate results, because then the changes could be seen during the night aswell as the day, yet this isn't possible because of the time limit and limited facilities. So instead, the two water bodies are going to be investigated both on the same day, this is because if they weren't, it could be raining one day and not the other. This would affect the results considerably, e.g. if the rain that fell was acidic, it would cause the water bodies to be acidic also.
These tests to see how polluted the water was were chosen because it was thought that they were some of the most effective and would provide a good enough result for this investigation. Also, some of the chemicals used in the tests can be harmful if not used properly, so care must be taken when carrying out the tests.
Also, when investigating the stream, the kick test can be carried out in the middle or at the edges because it isn't very deep. Yet in the Trent, the middle part is extremely deep \ the kick test cannot directly be done there, only at the edges. This is a limitation because there might be organisms living in the middle of the river Trent that may never be seen in this investigation because they couldn't be reached. Yet in the stream almost all the possible organisms could be found because of the access all areas (apart from the parts where there are isolated pools; these could contain certain organisms that may not live in the actual water body being investigated).
Handling and analysing data
The Trent biotic index will be recorded in a table like the one below. This shows the type
This example would show that that Baetis mayfly was present in the Downs banks stream but the Rithrogena mayfly wasn't, and that neither of the two species was present in the river Trent.
Also to show the results of the other three tests a table will also be drawn as shown below. This shows the levels of nitrates, the pH and the dissolved oxygen content
This example would show that the pH is slightly alkaline which isn't the appropriate reading of natural water, which is slightly acidic, showing some slight pollution. Less than 5 parts/million in the nitrate test would show that there was hardly any pollution from nitrates which would be a good thing. The result of the oxygen test would be average showing that there wasn't any major change in the oxygen content.
Prediction
I think that the river Trent will be more polluted that the Downs banks stream will be. This is because the Trent is down stream from an industrial town and there are quite a few sources of pollution there (see above in the introduction for the reasons). E.g. rubbish dumped by public, hot water from industries getting pumped into the rivers and reducing the amount of dissolved O2 and killing off aquatic organisms, etc.
Yet the Downs banks stream is in a national park, which means that it is protected, \ won't be as polluted because there are no industries putting hot water into it, or any farmland nearby where nitrates and other chemicals can get into it. Or any sewage works discharging pollutants into the water. It is considered to be very clean because the local water authority use it to compare other polluted water bodies to. So I think that this will be the most unpolluted out of the two.
I also think that the most effective way of investigating how polluted the water bodies are, will be the Trent biotic index. I think this because most aquatic life forms are quite sensitive to any severe pollutions, there are the few species that are tolerant to a certain amount of pollution, yet the majority prefer cleaner waters \ the Trent index will show which of these organisms are present in both water bodies.
Conclusion
By looking at the Trent biotic index results, I can see straight away that the Downs Banks stream had the larger diversity of species compared to the River Trent. This already shows that the River Trent is perhaps more polluted than the other stream, because of the amount of different species.
By looking closer at the results, living within the Downs Banks stream there are several species that are quite sensitive to even the slightest pollution, e.g. mayflys and stoneflys, \ this immediately shows that this stream must be very clean to support these pollution sensitive organisms.
Yet in the River Trent there are aquatic organisms e.g. leeches, which can with stand some pollution and I can see that there aren't species that can't withstand pollution. Also, I can see that some of the species that were present in the Downs Banks stream, were not present in the River Trent. This shows that the River Trent is significantly more polluted than Downs Banks stream.
Also by using the Trent biotic key (see page 6) the pollution level of each of the two water bodies could be determined. This was done by looking at what species were present in the streams and putting this info to the table on the back of page 6 and working the number out:
Downs Banks stream-9-10- Diverse fauna including several sensitive species; no organic pollution.
River Trent-5-6- Low diversity, no sensitive species present; intermediate pollution.
Then by looking at the other test results I can also see that these show that the River Trent is more polluted than the Downs Banks stream. I can see this because in the pH test, the River Trent is slightly more acidic than the stream, therefore, there must be a source before the point that was investigated along the Trent, that is making the water slightly more acidic. Although, by looking at the readings- 7.8 and 7.6, these two are both quite neutral which isn't the natural pH of rain water which is 5.6 (quite acidic). This is probably so because of other natural sources in both water bodies that makes this water slightly more alkaline than natural rain water.
The results of the nitrate test didn't really give a difference between the two because both of the results were less than 5. This means that both streams weren't polluted by any nitrates and so identifying which of the two had the most pollution by the results of this nitrate test would prove to be difficult.
By looking at the dissolved oxygen test results, There is a difference in both of the water bodies. This difference backs up what was predicted, that the River Trent has the lowest oxygen content out of the two. This could be so because of the industrial town up stream which would use the water as a coolant in the industries, then pump it straight back into the stream again, and it would be at a slightly higher temp than before. This means that the oxygen would be less likely to stay in the water and would evaporate out, leaving less for the aquatic life. Which would have trouble respiring on less oxygen and would most probably die. This would occur more in the River Trent because its O2 content was the least out of the two.
Evaluation
Overall, I think that the whole experiment went quite well, the results obtained were generally what we expected; that the River Trent is more polluted than the Downs Banks stream. I think this is so because the Downs Banks stream is located in a national park therefore is protected from any sources of pollutants that aren't naturally there already. This includes litter, human waste, fertiliser run-off, etc, this is because the stream isn't near any farmland or any urban areas for the public to pollute it. Also, this stream is used by the local water authority to test and compare against other water bodies in the area, because it is one of the cleanest around this area. This means that pollution sensitive organisms can live in these waters because they are relatively fresh and that's why we found some.
Yet the River Trent is going to be more polluted because it is just down stream from a major industrial town which means that the public have access to throw their rubbish and waste into it. Also it is down stream from a sewage works, this means that sewage will go into the sewage works, be treated and the resulting water from the treated sewage will then be released back into the River Trent. The water will \ contain more pollutants and chemicals which will be harmful and kill pollution sensitive aquatic life. That is why in the River Trent there were no organisms like mayflys.
If the investigation were to be carried out again with more time and better facilities I think that a few improvements could be made. More accurate equipment would be used, e.g. the nitrate, pH and dissolved oxygen tests would be more accurate to obtain better results. Also, the net could have even smaller holes to catch even smaller organisms that probably fell through the other net. The pictures in the Trent biotic index were not as good as I think they could have been, so if it were to be carried out again an index with more detailed pictures would be more useful, because there was abit of trouble in identifying some of the species.
Also, the tests that were carried out were suffice for this investigation, but to obtain even more accurate results I think that different tests could be carried out, e.g. phosphate test to see if there was too much fertilisers in the water. Or a dissolved carbon dioxide test could be carried out.
Moreover, there wasn't enough time to carry out these tests more than once \ this meant that the results obtained may not be as accurate as they could be. They could all be a fluke from that day, perhaps because one of the two may have had a major pollution flow from a nearby pollution provider. Also, the temperature would be recorded to see any rises or decreases, or differences between the two. A temperature increase in water results in a decrease in oxygen content \ would support less life than if it were lower in temp.
The kick tests were carried out ten times in the same area but in different spots to obtain all possible mini beasts. I think that this was all right for what we wanted to know, but if it were to be carried out again more could be done just in case a species buried deeper under the rubble was overlooked last time. Also, the area could be widened a little to get a larger variety
The Trent Biotic Index
This index will give you a measure of the amount of organic polluion in the water. The index values range from 0 (no life, extreme pollution ) to 10 ( diverse life , no pollution).
To calculate the index, you first need to know how many indicator groups you have in your sample.
1) Compare your species list with Table 1. You score each time there is a match between your list and the groups in Table 1. Work down the table and each time an indicator group appears on your list add 1 to your tally.
TABLE 1
1 The swimming Mayfly (Baetis)
2 One for each other type species of Mayfly
3 One for each family of Caddis fly ( Trichoptera)
4 One for each species of Stonefly (Plecoptera)
5 One for each species of Alderfly (Neuroptera)
6 The Bloodworm (Chironomus riparious)
7 One for midge larvae other than the Bloodworm (Family Chironomidae)
8 The Blackfly (Simulium)
9 One for each other species of fly than those above (e.g. Diptera)
10 The Freshwater Shrimp (Gammarus pulex)
11 The Water Hoglouse (asellus)
12 One for each species of Leech (Hirudinea)
13 One for each species of Flatworm (Platyhelminthes)
14 One for each species of worm (Annelida)
15 One for each species of Snail (Mollusca)
16 One for each species of Beetle (Coleoptera)
17 One for each species of Water Mite (Hydrocarina)
2) The tally gives you the number of Indicator Groups in your sample
