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Chemistry > L6 - Adsorption at the mineral-water interface > Flashcards

L6 - Adsorption at the mineral-water interface Flashcards

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1
Q

What is surface topography?

A

The quantitative physical features and texture of a surface.

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2
Q

How is surface structure different from surface topography?

A

Surface structure refers to the atomic and molecular composition and arrangement of atoms in space

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3
Q

How does the surface of a crystal differ from its bulk?

A

The surface is fundamentally different in structure and chemistry compared to the bulk.

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4
Q

What are the two main types of strand breaks in nucleic acids?

A

Abiotic and enzymatic strand breaks.

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5
Q

What causes abiotic strand breaks?

A

Hydrolysis, depurination, and deamination.

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6
Q

What enzymes are involved in enzymatic strand breaks?

A

DNase and RNase

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7
Q

What are examples of chemical damage to nucleic acids?

A

Radiation damage, pyrimidine dimers, and oxidative damage by free radicals like *OH

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8
Q

What is the significance of a 2-million-year-old ecosystem discovered in Greenland?

A

It was reconstructed using environmental DNA

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9
Q

What is the difference between basal and edge mineral surfaces?

A

Basal surfaces undergo permanent changes, while edge surfaces have variable charges depending on pH

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10
Q

What is an outer-sphere complex?

A

Adsorption via only electrostatic interactions.

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11
Q

What is an inner-sphere complex?

A

A coordinate bond formed between DNA and a mineral atom like Fe

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12
Q

How do mineral surfaces affect DNA survival?

A

They can protect DNA, but adsorption at variable surface charge sites (edges) is crucial.

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13
Q

What happens to DNA preservation at the point of zero charge (PZC)?

A

There is a sharp fall in DNA adsorption due to loss of surface charge

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14
Q

Why are mineral surfaces important in the environment?

A

They influence biogeochemical cycles, nutrient mobility, and contaminant transport.

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15
Q

Why is RNA interference being explored as a biopesticide?

A

It offers a sustainable alternative to chemical pesticides.

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16
Q

What are the sustainability goals for pesticide use?

A

To reduce chemical pesticide use by 50% by 2030.

17
Q

Why is food security a pressing issue?

A

Food production needs to increase by 50–70% by 2050 to meet demand

18
Q

List applications of environmental nucleic acid research

A

Wastewater epidemiology, paleogenomics, microbial evolution, biofilm formation, and conservation modeling

19
Q

How do mineral surfaces influence nucleic acid stability?

A

They can protect DNA but may enhance RNA degradation

20
Q

What are the two common oxidation states of arsenic in natural systems?

A

Arsenite (As³⁺) and arsenate (As⁵⁺)

21
Q

Which form of arsenic is more toxic?

A

Arsenite (As³⁺) is 25–60 times more toxic than arsenate (As⁵⁺)

22
Q

How does pH affect arsenic speciation and mobility?

A

Arsenite is neutral at low pH, while arsenate is negatively charged and repelled by mineral surfaces at higher pH.

23
Q

What happens to arsenate in the presence of iron oxides?

A

It binds strongly, forming stable complexes

24
Q

What is managed aquifer recharge (MAR)?

A

The subsurface storage of water in depleted aquifers to balance supply and demand during extreme weather events.

25
Q

What are some methods used in MAR?

A

Infiltration basins, riverbank filtration (RBF), and aquifer storage and recovery (ASR)

26
Q

How does MAR improve water quality?

A

Through natural filtration and adsorption processes during subsurface transport

27
Q

Why is arsenic mobilization a challenge in MAR?

A

Changes in geochemical conditions can release adsorbed arsenic, rendering water unusable.

28
Q

What geochemical reactions occur at the plume front during MAR?

A

Mineral precipitation/dissolution, adsorption/desorption, and cation exchange.

29
Q

How do divalent cations like Ca²⁺ and Mg²⁺ affect arsenic mobility?

A

They form cation bridges, enhancing arsenic adsorption and retention

30
Q

What happens when recharge water is low in Ca²⁺ or Mg²⁺?

A

It reduces cation bridging and promotes arsenic desorption

31
Q

How do mineral surface charges affect environmental processes?

A

They influence contaminant mobility, biomolecule preservation, and pesticide effectiveness

32
Q

What causes contaminants like arsenic to be released from mineral surfaces?

A

Changes in geochemical conditions such as pH and cation concentrations.

Chemistry (9 decks)

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