Omg!! Help me gottta hsc assesment so lost!!! (1 Viewer)

[aero135]

Q) Describe the possible source of contamination in a catchment area?

is one of those sources dead animal bodies and excrements ( faeces and urine)

the next question states!

Q) For the identified sources of contamination describe a chemical test available to determine the contamination levels.

Am i testing for OD or BOD and is this through Winklers method!?


cheers

 

[macbeth]

I am doing that same assessment now, for the possible sources of contamination you'd talk about human activities in the vicinity and yeah faeces haha

For the second part, testing for OD is different to testing for BOD, OD is adding iodine and then starch or winkler's method, and then the whole microorganism oxidation wait for 5 days method is BOD

 

[aero135]

but which one am i testing for BOD or OD?

 

[macbeth]

both, you know that it's dissolved oxygen and biological oxygen demand right, read your textbook... BOD is effectively for the amount of organic wastes in the water

 

[Fortify]

Q) Describe the possible source of contamination in a catchment area?
Agricultural, Industrial or Urban Sources - fertilizers, pesticides, animal faeces, microbes, sewage run-offs.

Q) For the identified sources of contamination describe a chemical test available to determine the contamination levels.
AAS, gravimetric analysis, winkler titration.

 

[aero135]

a lil bit more detail please on how to test for these coontamination one para mate?

 

[Fortify]

I'm not going to do your assessment for you. I gave you main points for you to research.

 

[aero135]

sorry but what i meant was that i tried that. But im stuck on the WINKLER EXPLANATION!

 

[Fortify]

The Winkler method involves the reaction of sodium thiosulfate and oxygen gas with manganese and iodide ions as intermediate reactants.
3 Main Steps:

Step 1: Oxygen oxidises Mn[2+]; 2Mn2+ + O2 + 4OH- => 2MnO(OH)2

Step 2: The resulting solution is then acidified and iodide ions are added; MnO(OH)2 + 2I[-] + 4H[+] => I2 + Mn2+ + 3H2O (Iodide is oxidized to iodine)

Step 3: The iodine is then titrated with sodium thiosulfate solution;
I2 + 2S2O3[2-] => 2I[-] + S4O6[2-]

Starch is used as an indicator as it forms a deep blue colour with iodine. The formation of a colourless solution indicated the endpoint of the titration.

 

[aero135]

sorry to sound stupid but i still dont get it! ARRRHGHH is it the winkler method that dermines DO that shows whether the contaminaton exists? ( faecal and urine)