Lecture 21 Flashcards
Define sorption
fixation / capture of a gas or vapor from a substance in a condensed state like a solid or liquid.
Define volatilization
The conversion of a liquid chemical into a vapor which can then escape into the atmosphere
What is the relationship between aromatic rings and solubility in water (mg/L)?
It is inversely related with
What is natural attenuation? What physical processes can give the appearance of attenuation but without any net loss in mass?
Remediation strategy that relies on natural processes to achieve site-specific clean-up objectives.
- dilution
- volatilization
- sorption
What is MNA?
Monitored Natural Attenuation aka intrinsic bioremediation.
Provides evidence for biodegradation and loss of contaminants, especially the BTEX compounds
What are some advantages of MNA?
- low cost
- minimal site disturbance
- little cross-contamination between multiple sites
- can use when excavation is impossible or very difficult.
- little waste generated
- reduced human exposure to contaminant
- complete destruction of contaminant (sometimes)
What are some disadvantages of MNA?
- Not suitable for treating free product (in water table)
- when contaminant is close to or already impacting a receptor.
- relies on anaerobic processes so takes a long time to clean up.
- Ongoing monitoring is essential
- Rates of biodegradation or attenuation may change over time.
What are three active/ engineered methods or bioremediation?
- bioaugmentation/ biostimulation (in-situ addition of selected microbes to speed up degradation)
- bioventing/ biosparging (in-situ venting of CO2 and O2)
- biopiles/ landfarming (ex-situ high aeration)
What are three criteria needed to prove that intrinsic bioremediation is occuring?
- Demonstrating Mass Loss of hydrocarbons in soil (GC-MS)
- Demonstrate biodegradation potential
- Demonstrating biodegradation in situ.
What are some tools to demonstrate in situ hydrocarbon biodegradation?
- Biogeochemical indicators
- Microbial communities
- Hydrocarbon metabolites
- Biodegradation genes
- Determine rates of biodegradation
- Stable isotopic fractionation of hydrocarbons
What are limitations of biogeochemical indicators?
- No information about current activity status
- No information about hydrocarbon biodegradation
What are limitations of enumeration of microbial communities in determining MNA?
- Relies on growth in defined medium
- Rely on culturable organisms (~1% of microbial world)
What are limitations of molecular analysis of microbial communities in determining MNA, specifically based on the 16S rRNA gene?
- No information about which species are actively biodegrading hydrocarbons.
-pimer bias
What are some limitations of Hydrocarbon metabolites?
- need to identify metabolites first
- Doesn’t identify which organisms are carrying out the biodegradation reactions
- doesn’t give information about the in situ rates of hydrocarbon degradation.
What are characteristics of signature metabolites?
- Stable intermediates which don’t accumulate.
- Singular relationship to a specific compound.
- No commercial or industrial use/origin.
- Produced exclusively via anaerobic organisms.
