5. Organics Flashcards
What are organic contaminants?
Chemicals that contain carbon and more than one C-H covalent bond
What is the “origin” of organic contaminants
Absent from the Earth’s crust; number without limit and increasing
Background concentration approaches 0.
What is a hydrocarbon?
A molecule consisting of hydrogen and carbon.
What is an aromatic hydrocarbon?
Includes an aromatic group (ring structure)
What are PAHs?
Polycyclic Aromatic Hydrocarbons
Characteristics of PAHs (5)
- Two or more fused benzene rings
- Exists as complex mixtures
○ 100s of congeners
○ Additive, synergistic, antagonistic effects - Persistent (years to decades to break down)
- Natural and anthropogenic sources
○ Natural: burning of organic matter (forest fire, volcanoes)
○ Anthropogenic: oil spills, charring your meat on the BBQ - Environmentally significant PAHs range from 2 rings (naphthalene) to 7 rings (coronene)
What are congeners
Different forms within a class
(dioxins, furans, PAHs, PCBs, all have each some congeners)
Characteristics of low molecular weight (LMW) PAHs? (3)
- water soluble
- not likely to bioaccumualte
- can be acutely toxic
Characteristics of high molecular weight (HMW) PAHs? (5)
- Hydrophobic
- More resistant to oxidation, reduction, and vaporization
- Can accumulate in sediments and organisms
○ Particularly in invertebrates (lack of metabolizing enzymes) - Carcinogens
- More harmful to birds because they bioaccumulate (hazard less, exposure higher, so risk higher)
What are HAHs?
Halogenated Aromatic Hydrocarbons
Characteristics of HAHs (2)
- Many congeners, all occur as complex mixtures
○ Always these → number of rings - Very potent and very persistent
○ Very potent → only need a little bit to have an effect
○ Longer half life (more than PAHs)
Effects of PAHs (4)
- Development Abnormalities
- Carcinogenic
- Endocrine disruption
- Immune effects
Examples of HAHs (4)
- dioxins
- furans
- PCBs
- some pesticides e.g. DDT
What is the structure of dioxins
2 halogenated benzene rings linked together by 2 oxygens
What is the structure of furans?
2 halogenated bezene rings linked together with 1 oxygen