lec 13 Flashcards
how do oxygen profiles look for eutrophic and oligotrophic lakes? what are the subsequent dominating factors in each ecosystem?
we been gone over eutrophic (high in epi, low in hypo)
for oligotrophic, there are less organisms so photosynth prod has less of an impact –> temp is prevailing factor
as u get deeper, instead of O2 trailing off, O2 conc actually incr since O2 is more soluble in colder water
what is the relationship between organic carbon and DO with respect to changes in the epilimnion:hypolimnion?
in general, organic carbon sinks from epilimnion to hypolimnion
when epi is greater, [more likely to experience winterkill/anoxia]
when epi is smaller, hypo gets more O2 cycled –> less likely to undergo anoxia
what is a [+] heterograde? [-] heterograde?
[+] heterograde is when DO max occurs in metalimnion; [-] heterograde is when DO min occurs in metalimnion
[WHY DA FUCK??]
how do redox reactions generally work?
in one reaction, an electron is lost; in another reaction, that same electron is moved and gained
what makes O2 such a great electron accepter? what happens when it’s no longer available?
O2 is highly electronegative so it readily accepts electrons. when it is not available, we enter into the redox staircase, where other ions are used to accept electrons. specialized bacteria are needed to engage in the redox staircase
looking at a gibbs free energy diagram, how do we know if a reaction will occur or not?
go from top to bottom idk
what is the order of the redox staircase? u made a way to remember this. what is it?
O2 –> H2O (3190 kJ/mol)
NO3- –> N2 (2080 kJ/mol)
MnO2 –> Mn2+ (3030 kJmol)
Fe(OH)3 –> Fe2+ (1330 kJ/mol)
(SO4)2- –> H2S (380 kJ/mol)
CO2 –> CH4 (350 kJ/mol)
notice how the bonus energy yield gets smaller and smaller
Oh No Mine Feet So Cold!
if anoxic conditions return to oxic conditions, what happens? alternatively, what occurs when reducing conditions return to oxidizing conditions?
oxidized species (lost electrons) regain their electrons and become reduced
what is the colorimetry equation? what does it tell us?
colorimetric equation is used to determine a concentration of ions, with certain concentrations coupled with certain wavelengths on the colour spectrum
A = C*I where
A: absorbance
C: conc of chem that absorbs light
I: distance light travels through a solution
what is a low value redox potential (Eh)? high value?
redox value potential (also called Eh) illustrates when reactions occur naturally and when reactions require an input of energy
low value indicates high transferability of electrons (reaction occurs); high value is opposite
what is O2’s redox value? what about this is important?
O2 redox value is high [+], so it readily accepts electrons (prevents other dudes from accepting electrons –> their reactions cant occur)
what do microbes do that may affect redox values?
microbes do enzyme shit that lowers activation energy –> might be able to lower reaction energy enough that it can occur even when it shouldnt
(ex. photosynth)
