exam 3 soils practice Flashcards
(17 cards)
CO2+H2O–>H2CO3
What type of reaction is this?
Dissolution
-most often in an aqueous solution.
-pure solid seperated
Cr^+6 + 3e- —> Cr3+
What type of reaction is this?
Reduction
- reactant and products is reduced
Ca2+ +MgX –> CaX + Mg2+
What type of reaction is this?
Cation exchange
-charge is exchanged to different product or reactant
Ca2+(aq) + SO4^2- (aq) –> CaSO4(s)
Precipitation
-substances will dissolve turn into solid product
How to identify a hydrolysis reaction
Hydrolysis (“hydro” = water and “lysis” = break) involves adding water to one large molecule to break it into multiple smaller molecules.
-AB + HOH ⇌ AH + BOH.
How to identify a denitrification reaction
Denitrification is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere
-NO3^- –> NO2^- –> NO+N2O –> N2
How to identify a oxidation reaction
When a change in oxidation number occurs in a reaction, with both an increase in number and a decrease in number, then the reaction is classified as redox. If this does not occur, then the reaction is non-redox.
-oxidation loses
2 major pools of decomposing OM in soils
-labile carbon: OM such as plant matter which is never and not very decomposed. decomposes quickly.
- humus: OM that is much older and has been decomposing for many years.
Which compounds in OM is most resistant to decomposition?
Lignin
3 benefits to the soil of increasing OM
- increased microbiome
-better drainage - increase in plant available nutrients
soil pH has a strong correlation with which environmental factor?
Rainfall. The more rainfall causes the soil to have a lower pH making it more acidic.
What is buffering capacity? What causes it?
buffering capacity is the ability for a soil to replace contents that attach to the molecules with H+. This is caused by changing pH levels.
how do you calculate CEC of soil?
add all cmolc/kg numbers
how to calculate %base saturation
add all bases and divide by total CEC then multiply by 100 to get percentage
2 soil properties that promote metal adsorption
- amount of clay and drainage capacity
-clay molecules attract metals for adsorption.
-soils with bad drainage are more likely to promote metal adsorption because less leaching will take place.
Ex-situ & In-situ examples and definition of both terms
ex situ- excavating all contaminated soil and taking it to a place where it can be treated
in situ- using plants for phytoremediation to treat the contaminated soil on site.
Benchmark properties for mobility and persistence
Kd or KOC
-persistence is half life
-the lowest KD value is most mobile and able to travel to the water table and contaminate it
-the higher the half life days, the most persistent it is
