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Glaciology > L6 & 7 - Glacier Hydrochemistry > Flashcards

L6 & 7 - Glacier Hydrochemistry Flashcards

1
Q

Give 5 reasons why chemistry is necessary

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

Why is studying the chemical weathering environment important?

A

For determining drainage system evolution

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3
Q

What has recently been discovered?

A

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

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4
Q

What 2 things are needed for dissolution?

A

Rock and Water Sources

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5
Q

What is chemical weathering?

A

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

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6
Q

Give 5 characteristics of glacial meltwater

A
  1. Low Temperatures
  2. Low Ionic Strength
  3. Dilute
  4. Freeze-Thaw Processes Occur
  5. High Suspended Sediment
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7
Q

Why are glaciers good at grinding up rock?

A
  1. Exposed Mineral Facies

2. High Surface Areas

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8
Q

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

A

Bimodal Flow

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9
Q

What is used as a proxy for total dissolved solids ?

A

EC

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10
Q

What 5 things can chemistry tell you that EC cannot?

A
  1. What minerals are present
  2. Reaction kinetics
  3. Atmospheric contact
  4. Bed contact
  5. Any other processes?
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11
Q

Water splits into what 2 ions?

A

H+ and OH-

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12
Q

Rock splits into what?

A

Cations and anions

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13
Q

Chemical equations must what?

A

BALANCE!

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14
Q

Reaction speeds are controlled by what?

A

Physical conditions (wet and warm is favourable)

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15
Q

What are favourable reaction kinetics ?

A

Those that easily dissolve go into solution first

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16
Q

Which mineral is the easiest to dissolve?

A

Calcium Carbonate

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17
Q

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

A

Bicarbonate

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18
Q

What is chemical balance and coupling of reactions?

A

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

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19
Q

Give 2 examples of coupling of reactions

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

2. Carbonate dissolution and Sulphide oxidation

20
Q

What is hydrolysis?

A

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

21
Q

What is acid hydrolysis?

A

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

22
Q

How does acid hydrolysis change the water conditions?

A
  1. pH increases
  2. PCO2 decreases
  3. Increased potential for CO2 adsorption
23
Q

What enables silicate hydrolysis?

A

Acidic conditions from carbonate hydrolysis

24
Q

What happens to water with regards to carbonate?

A

It becomes repaid saturated so that no more can dissolve

25
Q

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

A

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

26
Q

Why does silicate hydrolysis take longer than carbonate hydrolysis?

A

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

27
Q

Where were boreholes drilled that revealed 3 glacier modes?

A

Haut Glacier, d’Arolla

28
Q

What does VPA show?

A

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

29
Q

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

A
  1. Borehole Data

2. Ions in Meltwater

30
Q

What is the SO42- + HCO3-

A

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

31
Q

Which mode is furthest from the channel?

A

Mode 3

32
Q

Which mode has low concentrations of all ions?

A

Mode 1

33
Q

Which mode has carbonation of carbonates?

A

Mode 2

34
Q

What is the most likely source of the excess sulphate?

A

Microbes!!!

35
Q

What do microbes act as?

A

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

36
Q

What does microbial oxidation of organic carbon do?

A

Produces CO2 for carbonation of carbonates and silicates

37
Q

What can microbial processes drive the bed towards?

A

Anoxia

38
Q

What are psychrophiles?

A

Cold Specialists

39
Q

What are psychrotolerant?

A

Cold Tolerant

40
Q

What are autotrophs?

A

They make their own food/energy

41
Q

What are heterotrophs?

A

Organisms that eat other organisms

42
Q

What are chemolithoautotrophs?

A

Organisms that get their food from chemical reactions on the rocks

43
Q

What can investigation subglacial microbes tell you?

A

The composition of meltwater and the properties of the weathering environment

44
Q

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

A
  1. Sediment & Water Phases
  2. Genetic & Culturing Methods

Accessed via subglacial seeps and exposed basal debris

45
Q

Give the 5 indirect indicators of microbes in the subglacial environment

A
  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

Glaciology (8 decks)

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