Hydrocarbons Flashcards
(22 cards)
What are polyaromatic hydrocarbons?
naturally produced, fused aromatic rings
How many priority PAHs are there and which one is the most important?
19, benzo-a-pyrene
What are the two classifications of PAHs?
pyrogenic and petrogenic
How are pyrogenic PAHs produced?
combustion of organic material-bbq, forest fires, volcanic eruptions
How are petrogenic PAHs produced?
crude oil in petroleum-exhaust, rubber manufacturing and burning
What are differences between petrogenic and pyrogenic PAHs
petrogenic have side chains (substituted) which makes them more persistent and pyrogenic can be broken down by photodegradation
What happens to the properties of PAHs as the molecular weight increases?
lipophilicity increases and vapor pressure decreases (less volatile) so highly bioaccumulative
Which animals cannot metabolize PAHs?
crustaceans and bivalves
What is one troubling mode of transportation for PAHs?
can be transported in atmosphere
During what season are PAH levels increased in environment?
Summer, due to snow run off
What is the major cause of PAH levels in the ocean?
oil spills
What are the two structures of polychlorinated biphenyls and which one is more toxic?
coplanar and non co planar- coplanar because it can activate aryl hydrocarbon receptors
What is the meaning of coplanar?
there are no or 1 chlorine at the ortho position
How many congeners of PCBs are there and how many of them are threatening?
209, 36
Where are PCBs found?
electrical insulants, coolants, lubricants, paint additives, plasticizers, and hard plastic materials
Why are PCBs so dangerous?
They are POPs
What happens as the number of chlorine atoms increase in a PCB?
lipophilicity increases
What are the sources of PCDDs and PCDFs?
by product of chlorination and bleaching, burning of plastics, chorlophenol herbicide and fungicide production
What is the most toxic dioxin?
2,3,7,8 tetrachloro-dibenzo-p-dioxin
What is the accepted safe dose of dioxins/difurans?
0, no safe level
What are the chemical properties of these compounds that make them so dangerous
lipophilic and highly stable due to polychlorination
What are the routes of exposure of PCDDs
atmospheric
