lec 11 Flashcards
if O2 is not polar, how does it get into water?
- photosynth
- mixing at air/water interface
what is the effect of temperature on DO? air pressure? salinity?
- colder water holds more DO
- higher pressure holds more DO (lower elevation has higher pressure –> more DO, higher elevation has lower pressure etc)
- less salinity holds more DO
what is saturation? subsaturation? supersaturation?
saturation is the amount of O2 that can be held in a body of water. subsaturation occurs when water can still hold more DO; supersaturation can occur when there is more O2 than the water can hold, resulting in bubbles etc
at the air/water interface, what are the main factors that determine diffusion?
- degree of saturation in the water (more saturation = less diffusion)
- turbulence of water (higher turbulence = more mixing = more diffusion)
what is the equation for turbulence?
F = -k(Cw - Ca) where
F: flux rate
Cw/Ca: conc of O2 in water/air
k: gas transfer velocity
how do DO and oxygen saturation compare in winter and summer? in other words, what is the difference between DO and DO saturation
winter: DO is high, saturation is low (water is colder = able to hold more absolute amts)
summer: DO is low, saturation is high
how does DO look in oligo- and eutrophic lakes?
oligo: DO is relatively stable (no one is using it)
eu: DO fluctuates depending on stratification and other factors
in littoral or pelagic regions is DO higher?
littoral (plants in lakebed)
define dissolved, colloidal, and gravitoidal
dissolved: fully disappeared
colloidal: not dissolved but just kinda floating around
gravitoidal: not dissolved, big enough to be acted upon by gravity
how is microbe biomass related to runoff?
inversely related (higher runoff = less time to dissolve; lower runoff = more time to dissolve)
if silicate is the most abundant mineral in the earth’s crust, why is it not the most abundant ion in water?
silicate does not dissolve in water, so it cannot float around
what does hardness of water refer?
indicates ability of water to precipitate soap (bad bc buildup of minerals etc)
what is the saturation conc with respect to the air?
saturation concentration is when pure water is well mixed, resulting in equilibrium with the atmosphere
why do deeper lakes have trouble with uniform DO?
metalimnion prevents lots of diffusion of DO, so it separates into epilimnion that has DO and hypolimnion that doesn’t have
how can supersaturation and anoxic conditions exist together?
supersaturation can exist in epilimnion while anoxic conditions can exist in hypolimnion, all in the same lake
