L6 - Adsorption at the mineral-water interface Flashcards
What is surface topography?
The quantitative physical features and texture of a surface.
How is surface structure different from surface topography?
Surface structure refers to the atomic and molecular composition and arrangement of atoms in space
How does the surface of a crystal differ from its bulk?
The surface is fundamentally different in structure and chemistry compared to the bulk.
What are the two main types of strand breaks in nucleic acids?
Abiotic and enzymatic strand breaks.
What causes abiotic strand breaks?
Hydrolysis, depurination, and deamination.
What enzymes are involved in enzymatic strand breaks?
DNase and RNase
What are examples of chemical damage to nucleic acids?
Radiation damage, pyrimidine dimers, and oxidative damage by free radicals like *OH
What is the significance of a 2-million-year-old ecosystem discovered in Greenland?
It was reconstructed using environmental DNA
What is the difference between basal and edge mineral surfaces?
Basal surfaces undergo permanent changes, while edge surfaces have variable charges depending on pH
What is an outer-sphere complex?
Adsorption via only electrostatic interactions.
What is an inner-sphere complex?
A coordinate bond formed between DNA and a mineral atom like Fe
How do mineral surfaces affect DNA survival?
They can protect DNA, but adsorption at variable surface charge sites (edges) is crucial.
What happens to DNA preservation at the point of zero charge (PZC)?
There is a sharp fall in DNA adsorption due to loss of surface charge
Why are mineral surfaces important in the environment?
They influence biogeochemical cycles, nutrient mobility, and contaminant transport.
Why is RNA interference being explored as a biopesticide?
It offers a sustainable alternative to chemical pesticides.
What are the sustainability goals for pesticide use?
To reduce chemical pesticide use by 50% by 2030.
Why is food security a pressing issue?
Food production needs to increase by 50–70% by 2050 to meet demand
List applications of environmental nucleic acid research
Wastewater epidemiology, paleogenomics, microbial evolution, biofilm formation, and conservation modeling
How do mineral surfaces influence nucleic acid stability?
They can protect DNA but may enhance RNA degradation
What are the two common oxidation states of arsenic in natural systems?
Arsenite (As³⁺) and arsenate (As⁵⁺)
Which form of arsenic is more toxic?
Arsenite (As³⁺) is 25–60 times more toxic than arsenate (As⁵⁺)
How does pH affect arsenic speciation and mobility?
Arsenite is neutral at low pH, while arsenate is negatively charged and repelled by mineral surfaces at higher pH.
What happens to arsenate in the presence of iron oxides?
It binds strongly, forming stable complexes
What is managed aquifer recharge (MAR)?
The subsurface storage of water in depleted aquifers to balance supply and demand during extreme weather events.
What are some methods used in MAR?
Infiltration basins, riverbank filtration (RBF), and aquifer storage and recovery (ASR)
How does MAR improve water quality?
Through natural filtration and adsorption processes during subsurface transport
Why is arsenic mobilization a challenge in MAR?
Changes in geochemical conditions can release adsorbed arsenic, rendering water unusable.
What geochemical reactions occur at the plume front during MAR?
Mineral precipitation/dissolution, adsorption/desorption, and cation exchange.
How do divalent cations like Ca²⁺ and Mg²⁺ affect arsenic mobility?
They form cation bridges, enhancing arsenic adsorption and retention
What happens when recharge water is low in Ca²⁺ or Mg²⁺?
It reduces cation bridging and promotes arsenic desorption
How do mineral surface charges affect environmental processes?
They influence contaminant mobility, biomolecule preservation, and pesticide effectiveness
What causes contaminants like arsenic to be released from mineral surfaces?
Changes in geochemical conditions such as pH and cation concentrations.
