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Flashcards in Dissolved Oxygen Deck (14):

What is the concentration of dissolved oxygen in water at 20oC?

9 ppm or 9 mg/dm3


What is Biological Oxygen Demand (BOD)?

A measure of the amount of oxygen used by microbes to oxidize organic matter in a particular body of water


How is BOD calculated?

The difference of the oxygen concentrations before and after 5 days of incubation at C


Define the method of a Winkler Titration

MnSO4 is oxidized to Mn(IV) by water, producing MnO(SO4)2. This is further oxidized in acidic solution to Mn(SO4)2. I- reacts with Mn(IV) to produce Mn(II) and I2. I2 can be titrated with (S2O3)2-.


What is the relationship between oxygen at the beginning and thiosulfate at the end of a Winker Titration?

Oxygen represents 1/4 the number of moles as thiosulfate.


What is the correlation between oxidation number and the type of decay organic matter undergoes (i.e. anaerobic or aerobic)?

Aerobic decay produces CO2, (NO3)-, (SO4)2-, and (PO4)3-.Anaerobic decay produces CH4, NH3, H2S, PH3 (phosphine).Aerobic decay results in more highly oxidized compounds.


To what form are carbon compounds oxidized in aerobic and anaerobic respiration?

Aerobic: CO2Anaerobic: CH4


To what form are nitrogen containing carbon compounds oxidized? In which type of respiration does this occur?

NH3; Both.


How is NH3 further oxidized under aerobic conditions?

Via reaction with oxygen as (NH4)+. (NO3)-, H2O and H+ are produced.


How is H2S further oxidized by aerobes to produce (SO4)2-?

H2S reacts with O2, forming S and H2O. S reacts with O2 and H2O to form (SO4)2- and H+


What are the main nutrients and associated human processes involved with eutrophication?

Nitrates and phosphates from runoff of agricultural fertilizers


Describe Eutrophication

Algae blooms result from excess nutrients from fertilizer runoff. When these die, they are oxidized by decomposers in the water, and oxygen becomes less available. At lower oxygen levels, invertebrates and fish begin to die.


What are the two main effects of Eutrophication?

Reduction of dissolved oxygen in the water and production of toxic substances.


What is the relationship between dissolved gas in water and temperature?

Inverse relationship. As temperature increases, dissolved gas decreases.