Hydrology

Question 1

What is an AQUIFER

Answer 1

a permeable rock or deposit that stores groundwater. The water can be extracted from wells or springs. These can range in size from local to continent-size. It can also generally be referred to as groundwater.

Question 2

What is the VADOSE zone?

Answer 2

The zone at which pore spaces can be either water or air filled. Below this is the water table.

Question 3

What is a confined aquifer?

Answer 3

Surrounded by impermeable layers like clays. Unconfined aquifers are open to the surface.

Question 4

define POROSITY

Answer 4

Porosity is the fraction of a volume that is pore space. Effective porosity is the fraction of interconnected pore space (unconnected pores can’t allow flow). This is decided by grains, packing, cementation, fractures etc.

Question 5

what is HYDRAULIC HEAD

Answer 5

The mechanical energy per unit weight of water, equal to the potential energy from elevation and pressure on the water.

Question 6

What is Darcy’s Law?

Answer 6

Describes fluid flow through a porous medium
Q=−kA ∆h/∆l
Q is discharge
where k is hydraulic conductivity
A is the x-sectional area
∆h is the hydraulic head and
∆l is the length of cylinder

Q=Anv, relating to velocity and n being the effective porosity.

Question 7

What is ADSORPTION

Answer 7

solute held at mineral surface by either inner sphere or outer sphere mechanisms.

Question 8

What is ION EXCHANGE

Answer 8

ion sorbed at surface by changing places with a similarly charged ion.

Question 9

Why does surface complexation occur?

Answer 9

The solutes are charged, and so do the surfaces, for example when Al substitutes for Si.
OH groups can form on the surface, and depending on the pH, can become O- or OH2

Question 10

What are inner and outer sphere complexes?

Answer 10

Outer sphere complexes form from IM forces and exchange readily. Inner sphere complexes form direct and stronger bonds.

Question 11

What are Isotherms?

Answer 11

Isotherms show the ratio of concentrations of the cation that are solid vs in solution.

Question 12

What are Langmuir isotherms?

Answer 12

Langmuir assumes there are a maximum number of sites and one sorbate.
S = (S(max) KC)/(1+KC)

where K is a partition coefficient, S is solid and C is solution

Question 13

What are Freundlich isotherms?

Answer 13

Assumes some sites are more difficult to fill than others.
S = KC^n

where K is a partition coefficient, S is solid and C is solution. The graph changes with varying n.

Question 14

What are COLLOIDS

Answer 14

substances consisting of very tiny particles that are suspended (from 10k MW to 0.45 micrometres). Trace elements can partition onto colloids and so be transported by them.

Question 15

What is DISPERSION

Answer 15

When ions take different microflow paths through groundwater, hence arriving at slightly different times.

Question 16

How can estuaries mix?

Answer 16

From the marine section (seawater) to fluvial section (freshwater), mixing can occur as freshwater is less dense. This can be any angle between vertical and stratified.
Fluvial and marine sections also contain different ions and hence are graded in the amount of that ion though not necessarily linearly.
For example, iron only comes from sediment in colloids, but these settle quickly as they saltwater neutralises them and they settle.

Question 17

How do hydrothermal vents affect ocean chemistry?

Answer 17

Cold water flows into fissures and gets heated. It then rises out of a black smoker. This removes O2 Mg and SO4 from the ocean, and dissolves Fe Mn and K.

Question 18

Diffusive double layer model

Answer 18

Surfaces have 1 layer of fixed surface charge, and a diffuse layer of counter ions helping to balance surface charge.

Question 19

Retardation factor

Answer 19

Groundwater velocity/constituent velocity

S (1-n) ρr
————
C n ρw

S - conc in water
C - conc in rock
n - porosity