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Toxicity 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

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Toxicity of Petroleum and PAHs

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  1. Toxicity of Petroleum and PAHs Sources, Ecotoxicology and Assessment

  2. 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?

  3. What is oil? (Sometimes called ohl, awl, oi-ul) • Chemistry • Chemically complex  difficult to predict potential toxic effects • Crude oil = thousands of different organic compounds (mostly hydrocarbons) • Major classes of HC • Alkanes (e.g. ethane, propane, butane) • Cyclohexanes (napthenes) • Aromatics (e.g. benzene, toluene, napthalene) • Oil from different sources has different composition • Can determine the “finger print” of an oil sample  use for forensic spill source matching

  4. What is Oil? • Refined Oil - essentially done by distillation • separates different fractions at different boiling points • Low temperatures (low boiling point)  gasoline • Medium temperatures  naptha  used in petrochemical industry • High temperatures  diesel oil > bunker oil (ships, electrical power plants) > tar is left (use on roads, roofs)

  5. Toxicity of Oil Generally, as increase refinement • Decrease toxicity to animals • Increase “ “ plants • Direct biological effects • Directly toxic compounds in petroleum include • Polycyclic aromatic hydrocarbons (PAHs) • Polychlorinated biphenyls (PCBs) • Metals (especially Pb) Note: b and c above are very persistent in the environment

  6. Polycyclic Aromatic Hydrocarbons (PAHs) • Most studied petroleum product • Defined as two or more fused benzene rings • Type/concentration determines biological effect

  7. Ring structures of representative PAHs Mostly aromatic Highly volatile High acute toxicity Low carcinogenicity Low volatility High chronic toxicity High carcinogenicity

  8. PAHs (continued) • Sensitivity crustaceans > insects > mollusks > algae > fish (can metabolize) Humans  mostly toxic as carcinogens

  9. Toxicity of Oil B. Direct Biological Effects • Microbes  stimulatory  creates BOD, COD • Algae  low sensitivity to oil but highly sensitive to 2° effects • Increase in primary production from • Death, decomposition, nutrient release of sensitive species • N-fixing species for certain oils • Nothing dying?  decrease in primary productivity • Higher plants  reduction in Ps rates • Changes cell permeability of cell membranes • Direct absorption of light required by chloroplasts (because oil is THICK and BLACK)

  10. Toxicity of Oil • Factors Determining Ecotoxicology of Oil • Dosage/duration of exposure • Size of spill, time to dispersal  lakes worse than rivers/streams • Type of oil (level of aromatics) • Refined more toxic but evaporates/breaks down faster • Geographic location • Oil breaks down more slowly in arctic than tropics • Season of year • Weather, adult vs. juvenile (more sensitive) • Effects of oil on competing biota • Competitive release • Ecosystem’s previous exposure to oil/other pollutants  tolerant organisms left (PICT)

  11. 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?

  12. 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

  13. 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

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