Material characterisation

Question 1

What is leaching?

Answer 1

a proces by which inorganic or organic contaminants are released from the solid phase inte the water phase

affected by:
- pH
- L/S ratio
- redox
- temperature
- shaking/stiring intensity
- particle properties

Question 2

For what is leaching used?

Answer 2

• the environmental acceptability of materials used in construction
• remediation of contaminated soils
• disposal options for industrial, hazardous and nuclear wastes

Question 3

what is ASE?

Answer 3

accelerated solvent extraction

• used for organic contaminents
• technique for extracting solid and semisolid samples with liquid solvents
• elevated temperature (up to 200 grader)
• high pressure (upp to 200 atm)

Question 4

What are some of the limitations to leaching tests?

Answer 4

• a simplified system
• time aspect
• mainly performed at room temperature
• dificult to control (microbial activity, redox)
• poor correlation with bioavalability

Question 5

What is bioavailability?

Answer 5

the degree to which a contaminant or nutrient in an environment media can be absorbed, transported and utilized physiologically

a process of physical, chemical and biological interaction

• if a nutrient or contaminant can be taken up by a organism it is “bioavailable”

Question 6

How can bioavailible fraction of contaminants be assessed?

Answer 6

chemical methods: assessment outside a cell, contaminanat release

bioassays: determination inside a cell, uptake across a physiological membrane

Question 7

When does chemical methods work?

Answer 7

• weak extractions
• reductive extractants
• weak acids
• strong complexing agents
• combination of salt-acid extractants
• diluted strong acids
• concentrated strong acids

Question 8

When does bioassays work?

Answer 8

Main groups of tests:
- whole -cell bacterial biosensors
- microbial
- plant
- invertebrate