Fate of Contaminants Flashcards
How to contaminant tend to migrate in the environment?
From high to low concentration
Point source
Toxicant come from a direct source
- industrial waste
- sewage discharge
- spills
Non-point source discharge
Toxicant comes from an indirect source
- agricultural and urban runoff
Exxon Valez
Accidental Spill
- 2-butoxyethanol used as surfactant
- elevated PAH still detected on beaches
BP Oil disaster
Accidental spill
- large quantity of gaseous hydrocarbons
- high levels of PAH
- burn events leading to production of dioxins/furans (and PAHs)
East Palestine Ohio
Accidental train derailment
- 2-butoxyethanol
- vinyl chloride (PVC)
- controlled burns released phosgene and HCl
Chernobyl
Nuclear accident
- Iodine-131 (HL 8 days), caesium-137 (HL 30 yr) released in atmosphere and soil
Alpha radiation
239-Plutonium, too big to enter skin, but can be ingested or breathed in
Beta radiation
137-Caesium and 90-Strontium, limited range
What does radiation cause
leads to break in DNA followed by incorrect DNA repair leading to mutation/cancer
Times Beach
-Company making agent orange hired company which hired some guy to dispose of hit
- he mixed it with oil and spread it to control dust in fields
- spread it over dirt roads all over town
- river flooding, spreading dioxins, town evacuated
Deliberate application
- fertilizers or pesticides directly applied to the land
- urban water or run off
- aerosols or gases
- combustion or incineration
Volatile organic compounds (VOCs)
ex. paint
Groundwater
Landfill - contaminants can leach into the soils/groundwater
-Pesticides, fertilizers, settle and adsorb to the land
- storage tanks leak
Kow
measure of hte behaviour of a chemical between water and an organic solvent
Kow depends on:
- water solubility
- hydophobility
- vapour pressure
- environmental half life
Determining Kow:
- take equal vol water and octanol
- add chemical, mix well
- measure the concentration of chemical in water & octanol
Kow =
concentration of chemical in octanol/concetration of chemical in water
High Kow indicates:
Lipophilic/hydrophobic
Low Kow indicates:
Lipophobic/hydrophilic
Vapour pressure
ratio between vapour pressure to water solubility is the Henry’s law (H) coefficent
H =
concentration of chemical in air/concentration of chemical in water
Factors that affect persistence
- double bonds or oxygen containing functional groups - makes organics more susceptible to attack,
- break down by enzymes and light (less persistent) - replacement of hydrogen by halogens
- protects organic compounds (more persistent)
