Transcript Toxicicity of Petroleum and PAHs

Toxicity of Petroleum and PAHs
Sources, Ecotoxicology
and
Assessment
Introduction
• Oil has been naturally released into the
environment for millennia
• Man-made spill is different  highly
concentrated in a relatively small area 
and often refined
• Typically there are 10 oil-consuming bacteria/L
of seawater  after a spill increases to 50
million bacteria/L
• Used motor oil is a huge problem
• CA alone “loses” 200,000 – 300,000 gallons of
used motor oil each years
• “down the drain”?
• Used on dogs for mange?
What is oil?
(Sometimes called ohl, awl, oi-ul)
A. Chemistry
Chemically complex  difficult to
predict potential toxic effects
2. Crude oil = thousands of different
organic compounds (mostly
hydrocarbons)
3. Major classes of HC
1.
a. Alkanes (e.g. ethane, propane, butane)
b. Cyclohexanes (napthenes)
c. Aromatics (e.g. benzene, toluene,
napthalene)
4. Oil from different sources has
different composition
a. Can determine the “finger print” of an
oil sample  use for forensic spill
source matching
What is Oil?
B. Refined Oil
- essentially done by
distillation
 separates different
fractions at different
boiling points
1. Low temperatures (low
boiling point)  gasoline
2. Medium temperatures 
naptha  used in
petrochemical industry
3. High temperatures  diesel
oil > bunker oil (ships,
electrical power plants) > tar
is left (use on roads, roofs)
Toxicity of Oil
Generally, as increase refinement
•
•
Decrease toxicity to animals
Increase “
“
plants
A. Direct biological effects
1. Directly toxic compounds in
petroleum include
a. Polycyclic aromatic hydrocarbons (PAHs)
b. Polychlorinated biphenyls (PCBs)
c. Metals (especially Pb)
Note: b and c above are very persistent in the
environment
Polycyclic Aromatic Hydrocarbons (PAHs)
• Most studied petroleum product
• Defined as two or more fused
benzene rings
• Type/concentration determines
biological effect
Ring structures of representative PAHs
Mostly aromatic
Highly volatile
High acute toxicity
Low carcinogenicity
Low volatility
High chronic toxicity
High carcinogenicity
PAHs (continued)
• Sensitivity
crustaceans > insects > mollusks >
algae > fish (can metabolize)
Humans  mostly toxic as
carcinogens
Toxicity of Oil
B. Direct Biological Effects
1. Microbes  stimulatory  creates BOD, COD
2. Algae  low sensitivity to oil but highly
sensitive to 2° effects
a. Increase in primary production from
1) Death, decomposition, nutrient release of sensitive
species
2) N-fixing species for certain oils
b. Nothing dying?  decrease in primary productivity
3. Higher plants  reduction in Ps rates
a. Changes cell permeability of cell membranes
b. Direct absorption of light required by chloroplasts
(because oil is THICK and BLACK)
Toxicity of Oil
C. Factors Determining Ecotoxicology of
Oil
1. Dosage/duration of exposure
•
Size of spill, time to dispersal  lakes worse than
rivers/streams
2. Type of oil (level of aromatics)
•
Refined more toxic but evaporates/breaks down
faster
3. Geographic location
•
Oil breaks down more slowly in arctic than tropics
4. Season of year
•
Weather, adult vs. juvenile (more sensitive)
5. Effects of oil on competing biota
•
Competitive release
6. Ecosystem’s previous exposure to oil/other
pollutants  tolerant organisms left (PICT)
Magnitude of problem
• Leaking Underground Storage Tanks
(LUST
• 25% of all underground tanks > 15 years
old are leaking (EPA estimate)
• 11 million gallons of gasoline seeps into
ground annually (EPA estimate)
• Note: 1 gallon gasoline can pollute
1,000,000 gal of drinking water
(undrinkable)
• Gas station in Thayer, MO was losing
100 gal./week (AR PC&E)  entering
Spring River?
Magnitude
• Accidental spills
• Big name spills relatively minor
• Trains, planes, automobiles
• Refineries, drilling platforms (Mexican
Ixtoc is worst spill in history)
• Boats
• Outboards very inefficient  discharge
up to 1/3 of fuel into water
Summary
• Big problem even with lots of laws to
prevent problem
• Why  we use so much of it!
• Next lecture  Exxon Valdez oil spill
case history