L6 & 7 - Glacier Hydrochemistry

Question 1

Give 5 reasons why chemistry is necessary

Answer 1

1. Solute Sources
2. Chemical Weathering Basics
3. Chemical Weathering Reactions
4. Simple Models
5. Solute Acquisition Scheme

Question 2

Why is studying the chemical weathering environment important?

Answer 2

For determining drainage system evolution

Question 3

What has recently been discovered?

Answer 3

That glaciers can export as much solute as some of the worlds major rivers

Question 4

What 2 things are needed for dissolution?

Answer 4

Rock and Water Sources

Question 5

What is chemical weathering?

Answer 5

A process by which rocks and minerals undergo changes in their composition

Question 6

Give 5 characteristics of glacial meltwater

Answer 6

1. Low Temperatures
2. Low Ionic Strength
3. Dilute
4. Freeze-Thaw Processes Occur
5. High Suspended Sediment

Question 7

Why are glaciers good at grinding up rock?

Answer 7

1. Exposed Mineral Facies

2. High Surface Areas

Question 8

What gives the potential for long rock:water contact times?

Answer 8

Bimodal Flow

Question 9

What is used as a proxy for total dissolved solids ?

Answer 9

EC

Question 10

What 5 things can chemistry tell you that EC cannot?

Answer 10

1. What minerals are present
2. Reaction kinetics
3. Atmospheric contact
4. Bed contact
5. Any other processes?

Question 11

Water splits into what 2 ions?

Answer 11

H+ and OH-

Question 12

Rock splits into what?

Answer 12

Cations and anions

Question 13

Chemical equations must what?

Answer 13

BALANCE!

Question 14

Reaction speeds are controlled by what?

Answer 14

Physical conditions (wet and warm is favourable)

Question 15

What are favourable reaction kinetics ?

Answer 15

Those that easily dissolve go into solution first

Question 16

Which mineral is the easiest to dissolve?

Answer 16

Calcium Carbonate

Question 17

No matter, which minerals are the most common in the bedrock which is always the major ion in the run off?

Answer 17

Bicarbonate

Question 18

What is chemical balance and coupling of reactions?

Answer 18

One reaction changes the chemical conditions of water, which helps other reactions to proceed

Question 19

Give 2 examples of coupling of reactions

Answer 19

1. 2:1 ratios of Ca2+ + Mg2+ and SO4

2. Carbonate dissolution and Sulphide oxidation

Question 20

What is hydrolysis?

Answer 20

The interaction between water and the mineral surface and almost always produces alkaline solutions

Question 21

What is acid hydrolysis?

Answer 21

Similar to hydrolysis, but water interacts with another compound to produce an acid, whose H+ ions interact with the mineral surface

Question 22

How does acid hydrolysis change the water conditions?

Answer 22

1. pH increases
2. PCO2 decreases
3. Increased potential for CO2 adsorption

Question 23

What enables silicate hydrolysis?

Answer 23

Acidic conditions from carbonate hydrolysis

Question 24

What happens to water with regards to carbonate?

Answer 24

It becomes repaid saturated so that no more can dissolve

Question 25

Where does sulphide oxidation occur and what does this man for carbonate dissolution?

Answer 25

Debris-Rich environments which lowers pH and allows for further carbonate dissolution

Question 26

Why does silicate hydrolysis take longer than carbonate hydrolysis?

Answer 26

Requires longer rock contact time, solicit is more resistant to weathering and has slower reaction kinetics

Question 27

Where were boreholes drilled that revealed 3 glacier modes?

Answer 27

Haut Glacier, d'Arolla

Question 28

What does VPA show?

Answer 28

If there is water at the bed or if it has flowed out

Question 29

What 2 things are needed to determine the drainage structure of the glacier?

Answer 29

1. Borehole Data | 2. Ions in Meltwater

Question 30

What is the SO42- + HCO3-

Answer 30

Sulphate Mass Fraction - used to look at rock: water contact time

Question 31

Which mode is furthest from the channel?

Answer 31

Mode 3

Question 32

Which mode has low concentrations of all ions?

Answer 32

Mode 1

Question 33

Which mode has carbonation of carbonates?

Answer 33

Mode 2

Question 34

What is the most likely source of the excess sulphate?

Answer 34

Microbes!!!

Question 35

What do microbes act as?

Answer 35

Catalysts to speed up reactions including the coupled Fe (III) reaction and to produce products that are used in reactions

Question 36

What does microbial oxidation of organic carbon do?

Answer 36

Produces CO2 for carbonation of carbonates and silicates

Question 37

What can microbial processes drive the bed towards?

Answer 37

Anoxia

Question 38

What are psychrophiles?

Answer 38

Cold Specialists

Question 39

What are psychrotolerant?

Answer 39

Cold Tolerant

Question 40

What are autotrophs?

Answer 40

They make their own food/energy

Question 41

What are heterotrophs?

Answer 41

Organisms that eat other organisms

Question 42

What are chemolithoautotrophs?

Answer 42

Organisms that get their food from chemical reactions on the rocks

Question 43

What can investigation subglacial microbes tell you?

Answer 43

The composition of meltwater and the properties of the weathering environment

Question 44

Give 2 direct subglacial microbe measurements and how you can access this environment

Answer 44

1. Sediment & Water Phases 2. Genetic & Culturing Methods Accessed via subglacial seeps and exposed basal debris

Question 45

Give the 5 indirect indicators of microbes in the subglacial environment

Answer 45

1. Major Ions (Nitrate and Sulphate) 2. Gases (O2 and CH4) 3. Nutrients (N, P and Fe) and Trace Elements 4. Chemical Indicators (pH and CO2) 5. Carbon