Water Quality B/C

[FlyingMonkey85]

Thanks gigaboo. As you can see, I am new to Scioly too. However, I did not find an answer to what kind of salt we use. Previous posts just say "NaCl". Is this the iodized salt or the non iodized? I would think non iodized as iodized salt contains minute amounts of iodine-containing salts, but the "Make a Simple Salinometer" on the Science Olympiad site shows a box of iodized salt in the first picture (I think?).

[quizbowl]

Thanks gigaboo. As you can see, I am new to Scioly too. However, I did not find an answer to what kind of salt we use. Previous posts just say "NaCl". Is this the iodized salt or the non iodized? I would think non iodized as iodized salt contains minute amounts of iodine-containing salts, but the "Make a Simple Salinometer" on the Science Olympiad site shows a box of iodized salt in the first picture (I think?).

To be honest, it does not matter at all. While there are some "iodine-containing salts", their presence is incredibly miniscule - they would not change the actual salinity of the water by an amount that would be detrimental to a salinometer. While yes, it is possible that it could create a slightly different salinity, but it would be affecting, at most, the hundredths digit of the percentage. Relax.

[FlyingMonkey85]

Thanks! That saved me from buying extra salt that I probably won't use in the future... That hundredths digit of the percent could easily change the tenths digit when rounded, and with only .5% lenience, it could be very significant.

[Patar Eyevan]

hey have you guys taken any of the practice tests on the test exchange? If so I was wondering if the answer key was right or wrong for a few questions... One of the question asked the water in which scenario has more dissolved oxygen and the answer on the key stated that high pressure and low temperature is correct. But I thought lower pressure and lower temperature meant higher DO?... and also another question asked what was the pH range of most aquatic organisms. The answer on the key was 7-9 but I thought many organisms can tolerate below pH of 7?

[Patar Eyevan]

Sorry for the double post... but also for the Macomb regionals test, one of the questions asks: what does the amount of oxygen in any body of water depend on? and the options were:

A: the amount of animals species diversity
B: the amount of plant species diversity
C: Water temperature, number of green plants, and sunlight
D: All of the above

I put C since the quality of water does not depend on species diversity, rather the species diversity represents the quality of the water. The answer on the answer key was D... can anyone clarify this?

[FlyingMonkey85]

Patar:
--I believe that high pressure too increases dissolved oxygen (http://www.elmhurst.edu/~chm/vchembook/174temppres.html)

--The ideal pH range for aquatic animals is around 6.5-8.5 (http://www.ncsu.edu/sciencejunction/dep ... fects.html). The answer varies online, but generally aquatic organisms prefer alkaline waters.

--I am not sure about this, but I would think that plant and animal diversity would affect the dissolved oxygen levels because of photosynthesis and respiration, respectively. In would be hesitant to pick "C" because it says "green plants" because I think plant of other colors also perform photosynthesis. (No Source Here...)

[quizbowl]

...One of the question asked the water in which scenario has more dissolved oxygen and the answer on the key stated that high pressure and low temperature is correct. But I thought lower pressure and lower temperature meant higher DO?... and also another question asked what was the pH range of most aquatic organisms. The answer on the key was 7-9 but I thought many organisms can tolerate below pH of 7?

You're right that low temperatures correlate to higher Dissolved Oxygen levels. However, it is true that as one increases the pressure of a liquid, the amount of gas that can be dissolved will increase. That's why lakes at high elevations often have surprisingly low DO levels - the decrease in atmospheric pressure is to blame for that. As for the pH range, I've always remembered that the true range for most aquatic organisms is 6.5 to 8.2. I'd understand a pH of 7 being the minimum for the answer (rounded up and such) but 9 does seem a bit high - I'm sure that the incredibly basic environment would be detrimental to some organisms.

...one of the questions asks: what does the amount of oxygen in any body of water depend on? and the options were:

A: the amount of animals species diversity
B: the amount of plant species diversity
C: Water temperature, number of green plants, and sunlight
D: All of the above

I put C since the quality of water does not depend on species diversity, rather the species diversity represents the quality of the water. The answer on the answer key was D... can anyone clarify this?

Well, think of it this way - high species diversity means high water quality, right? And usually with high water quality, one sees a strong correlation with DO levels. I know the question sounds poorly worded, but it is clear that species diversity plays an important role in establishing these levels.

[hpfananu]

We took our state test today and it had mostly Dynamic Planet stuff with Base Levels, flow rate, stream gradients and sediment patterns etc.
Has anyone found this on any other test or was it just this weird test? The events are slightly related but I think it's slightly wild to expect us to know all about Dynamic Planet and general Water Quality...

[Infinity Flat]

...One of the question asked the water in which scenario has more dissolved oxygen and the answer on the key stated that high pressure and low temperature is correct. But I thought lower pressure and lower temperature meant higher DO?... and also another question asked what was the pH range of most aquatic organisms. The answer on the key was 7-9 but I thought many organisms can tolerate below pH of 7?

You're right that low temperatures correlate to higher Dissolved Oxygen levels. However, it is true that as one increases the pressure of a liquid, the amount of gas that can be dissolved will increase. That's why lakes at high elevations often have surprisingly low DO levels - the decrease in atmospheric pressure is to blame for that. As for the pH range, I've always remembered that the true range for most aquatic organisms is 6.5 to 8.2. I'd understand a pH of 7 being the minimum for the answer (rounded up and such) but 9 does seem a bit high - I'm sure that the incredibly basic environment would be detrimental to some organisms.

...one of the questions asks: what does the amount of oxygen in any body of water depend on? and the options were:

A: the amount of animals species diversity
B: the amount of plant species diversity
C: Water temperature, number of green plants, and sunlight
D: All of the above

I put C since the quality of water does not depend on species diversity, rather the species diversity represents the quality of the water. The answer on the answer key was D... can anyone clarify this?

Well, think of it this way - high species diversity means high water quality, right? And usually with high water quality, one sees a strong correlation with DO levels. I know the question sounds poorly worded, but it is clear that species diversity plays an important role in establishing these levels.

Well, the plant species diversification at least can affect DO levels - eutrophication and algal blooms are pretty good examples of this.

[mnstrviola]

Okay I was thrown into this event at states 5 min. into the competition. There were 6 stations I believe. 2 were Dynamic Planet material, 1 was species ID, 1 was interpreting graphs based on pollution, 1 was random stuff I didn't understand and I forgot what happened on the last one. It seemed like an easy event, but we did pretty bad on the salinometer thing.

The test heavily emphasized on water treatment methods, also on coliform bacteria...

CORRECTION: it wasn't stations, but different colored papers that are part of the test. It should be *sections