Oil Spills. Petroleum Petroleum (or crude oil) is a non-renewable resource that is used as a source of energy and to manufacture petrochemicals, asphalt,

Oil Spills

Petroleum

Petroleum (or crude oil) is a non-renewable resource that is used as a source of energy and to manufacture petrochemicals, asphalt, and other products

petroleum is mined in huge quantities, but this happens far from the places where most consumption occurs

this is the reason why petroleum and its refined products are transported widely by pipelines, ships, trains, and trucks

there is always a risk of accidental (or rarely, deliberate) spillage, causing severe environmental damage

Canada produces considerably more petroleum than it consumes, while the U.S. imports 2/3 of its consumption

~ 95% of Canadian production occurs in sparsely populated areas of Alberta and Saskatchewan, while most consumption is in densely populated areas

western Canada exports much petroleum and refined products to the U.S. and Asia, while eastern Canada imports from the Middle East and Latin America

therefore, petroleum moves within, out of, and into Canada and its regions

Petroleum & Refined Products

Petroleum is a natural mixture of liquid & gaseous organic compounds, most of which are hydrocarbons

petroleum is a fossil fuel, as are coal, oil-sand, oil-shale, and natural gas

fossil fuels are derived from ancient biomass that:

became buried in deep sedimentary formations

and were subjected over geological time to high pressure, high temperature, and anoxia

the resulting chemical reactions eventually produced a mixture of gaseous, liquid, and solid hydrocarbons and other organic compounds

Hydrocarbons

Hydrocarbon molecules are entirely composed of H and C atoms

Naturally occurring hydrocarbons range in complexity from:

gaseous methane (CH4) weighing 16 g/mole

through liquids such as octane (C8H18) to solid substances with molecular

weight exceeding 20,000 g/mole a "mole" is a standard quantity,

equivalent to the weight of 6.02 x 1023 atoms or molecules of a substance

Hydrocarbons can be classified into groups: aliphatics have their C atoms in an open chain saturated aliphatics (or paraffins or alkanes)

have a single bond between adjacent C atoms unsaturated aliphatics have >1 double or triple

bonds illustrated by these two‑C, aliphatic hydrocarbons:

ethane, H3C‑CH3 ethylene, H2C=CH2 acetylene, HC=CH

unsaturated aliphatics are relatively unstable and do not occur naturally in petroleum

they are produced during refining and also by photochemical reactions after crude oil is spilled

alicyclic hydrocarbons have some or all C atoms arranged as a ring structure (may be saturated or unsaturated)

aromatic hydrocarbons contain one or more 5-C or 6-C rings in their molecular structure

benzene is the simplest C6H6 ring

Crude Oil

Petroleums vary greatly in chemical composition, but typically consist of about: 98% liquid hydrocarbons <1-2% S <1% N V and Ni up to 0.15%

petroleum also contains dissolved gaseous hydrocarbons

the refining process separates hydrocarbon fractions by distillation at various temperatures

refining produces such products as: natural gas, gasoline, jet fuel, kerosene, heating oil, lubricating oils, waxes, and residual fuel oil (or bunker fuel)

in addition, a process known as “catalytic cracking” converts some heavier fractions into lighter, more valuable ones, e.g., those in gasoline

Oil Spills

The largest spills involve accidents in which petroleum or bunker fuel are discharged: to the ocean from a disabled tanker or

drilling platform to an inland waterway from a barge or

ship to land or freshwater from a well blowout

or broken pipeline some enormous oil spills have also

resulted from warfare

In Canada, there are ~ 35 x 103 km of pipeline for transporting petroleum, and 227 x 103 km of natural-gas pipeline in the 1990s there were ~2,300 reported oil

spills per year in Canada 42% were in the vicinity of production wells 29% were from pipelines 16% from tanker trucks

the Canadian network of pipelines has spill sensors and other technology to allow sections of pipeline to be rapidly closed

this allows accidents to be kept relatively small and confined

some other countries do not utilize these technologies as much as in Canada, and they may suffer huge petroleum spills from overland pipelines

e.g., such accidents occur commonly in northern Russia and other former Soviet republics

Oil spilled on land affects relatively localized areas of terrain, because soil is absorbent of petroleum

Much larger areas are affected if spilled petroleum reaches a watercourse oil spilled onto water affects an extensive area

because wind & currents cause slicks to spread and disperse widely

During the 1970s and early 1980s, petroleum spills into the oceans were about 3-6 x 106 tonnes/year more recently (1989), spillage was reduced to 0.6

x 106 t/yr

Massive spills from wrecked supertankers or well-platforms attract a great deal of attention — and deservedly so however, much smaller but frequent discharges

from urban runoff, oil refineries, and other coastal sources amount to a globally larger quantity of spillage than do rare massive spills

Natural Emissions

There are large natural emissions of non-petroleum hydrocarbons to the oceans mostly chemicals synthesized by plankton, at a

global rate of about 26 x 106 t/yr contributes to the background concentration of

hydrocarbons in seawater of about 1 ppb (1 µg/l) biogenic emissions represent “natural

contamination”

There are also natural emissions of petroleum from oil seeps 0.2-0.6 x 106 t/y, sometimes causing local damage these emissions also contribute to the

background concentration in seawater of 1 ppb

Tanker bilge washings

Discharge of oily residues from tanker storage-tanks are an important cause of marine spills after a tanker delivers a load of petroleum

to a refinery, its storage tanks are filled with seawater as a stabilizing ballast while the ship travels to get its next load of crude oil

as a tanker approaches its destination the ballast may be (illegally) discharged to the ocean, saving time & money at the port

the dumped wastewater may contain hydrocarbon residues equivalent to 1.5% of the tanker's capacity in the case of bunker-C fuel, but <1% for petroleum, and 0.1% for light products such as gasoline

illegal dumping of oily bilge water has been decreasing since the 1970s, due to widespread use of a procedure called load-on-top (LOT)

LOT is a process to separate and contain most oily residues before ballast water is discharged at port or to the marine environment (the residual oil is then combined with the next load)

if used in calm seas, LOT can recover 99% of oily residues, but only <90% if a ship has had a turbulent passage

although LOT is now widely used, some tankers still illegally discharge oily waste at sea — this pollution causes intensive and needless seabird mortality off the coasts of Canada and other countries

Infamous Oil Spills

Wrecked Tankers: the Torrey Canyon in 1967 off southern England,

which spilled 117 x 103 t of petroleum Metula in the Strait of Magellan in 1973 (53 x 103 t) Amoco Cadiz in 1978 in English Channel (230 x 103

t) Exxon Valdez in 1989 in southern Alaska (35 x 103

t) Braer in 1993 off Shetland Islands (84 x 103 t)

Offshore platforms: blowout of IXTOC-I exploration well in Gulf of

Mexico in 1979 (500 x 103 t) the world’s largest-ever accidental spill

blowout in 1969 off coast of Santa Barbara in s California (10 x 103 t)

Ekofisk blowout in 1977 in North Sea off Norway (30 x 103 t)

Notable Canadian spills involving tankers: the Arrow in 1970 in Chedabucto Bay, NS,

spilling 11 x 103 t bunker-C

the Kurdistan in 1979, in Cabot Strait between NF and NS, spilling 7.5 x 103 t bunker-C

the Nestucca in 1988 off Washington State, which polluted shorelines on western Vancouver Island, BC; the spill volume was 875 tonnes of bunker-C

A beach on

Chedabucto Bay, NS,

affected by bunker-C

residue from the

Arrow spill in 1970

Spills during Warfare

during WWII, German submarines sank 42 tankers off eastern North America, spilling ~417 x 103 t

during the Iran-Iraq War of 1981-1987, there were 314 attacks on tankers, 70% by Iraqi forces in 1983, Iraq damaged 5 tankers and 3

production wells at the Iranian Nowruz ship-loading facility, causing >260 x 103 t of petroleum to spill into the Gulf of Arabia

During the brief Gulf War of 1991: the largest-ever marine spill occurred

when Iraqi forces released 0.8-2.0 x 106 t of petroleum into the Gulf of Arabia from a Kuwaiti offshore loading facility

this was partly an act of war, intended to impede an amphibious landing by Allied forces

the largest-ever land spill occurred when Iraqis sabotaged & ignited all of the >700 wells in Kuwait – emissions of petroleum were 2-6 x 106 t/day

it took 11 months to cap the blowouts 42-126 x 106 t petroleum had spilled 5-21 x 106 t accumulated as crude-oil

“lakes” in the desert; most of the rest burned in the atmosphere or evaporated

Fate of Spilled Oil

Depending on chemical and physical characteristics of the spilled oil, various hydrocarbon fractions can selectively:

evaporate spread dissolve into water accumulate as persistent residues be degraded by microorganisms

Evaporation dissipates almost 100% of gasoline spilled at sea, 30‑50% of crude oil, and 10% of bunker fuel

relatively light and volatile hydrocarbons are selectively evaporated, leaving heavier residues behind

evaporation is increased by warm temperatures and by vigorous wind

Spreading is movement of a slick over the surface of water or land it may occur over a very large area on

water, but much less on land because of the absorptive capacity of soil

slicks on water are moved about by currents and wind, and may eventually wash onto a shore

an experimental spill of 1 m3 of petroleum onto calm seawater created a 0.1-mm-thick slick with a 100-m-diameter after 100 minutes

a slick <0.3 µm thick can be visually detected as an iridescent sheen on calm water

Dissolution causes pollution of water beneath a slick

lighter hydrocarbon fractions are more soluble in water than heavier ones, while aromatics are much more soluble than alkanes

after a petroleum spill at sea, the hydrocarbon concentration in water several m beneath the slick is up to 4-5 ppm

the background concentration is 1 ppb

Residual materials remain after lighter fractions of spilled petroleum have evaporated or dissolved

at sea, residual materials form a gelatinous, water‑in‑oil emulsion, known as "mousse"

mousse stranded on shore may weather to a persistent residue on rocks, or it may combine with particles of sediment to form sticky, tar-like patties

mousse that does not wash ashore weathers into a dense, semi-solid, floating asphaltic residue known as “tar balls”

sticky, asphaltic materials

are the most persistent

residues of petroleum spills

Degradation is the slow decomposition of spilled materials by biological oxidation and photo-oxidation

many bacteria, fungi, and other microorganisms can utilize hydrocarbons as a metabolic substrate

the biodegradation rate depends on the availability of key nutrients such as N & P, ambient temperature, and availability of O2

these can be “limiting factors” to the degradation rate

lighter fractions are relatively easily decomposed by biological and inorganic oxidations, while heavier fractions resist degradation and may be persistent in the environment

Toxicity

Acute toxicity caused by petroleum, its refined products, or pure hydrocarbons is often associated with: the destruction of cellular membranes

pathology caused to key organs of detoxification and excretion, such as liver and kidneys

bioaccumulation of lipid-soluble, water-insoluble hydrocarbons and organics

increased production of detoxification enzymes, known as mixed-function oxidase enzymes (MFOs)

Toxic effects are influenced by environmental and biological factors, especially: chemical composition of the spilled material intensity of exposure (amount or concentration) frequency of exposure events (chronic or

episodic) timing of exposure (e.g., during critical time for

a species or ecosystem) thickness of the slick, nature of the emulsion,

degree of weathering, & persistence of residues environmental influences on exposure and

toxicity, including weather conditions, O2 status, and the presence of other pollutants

toxicity of dispersants used during a clean-up sensitivity of exposed species to toxic effects

Ecosystem-level damage may be influenced by: physical disturbance associated with the

clean-up

effects of the use of dispersants and emulsifiers, hot-water washing, substrate removal, burning, and tilling to improve aeration

damage may also be influenced by effects on “keystone" species within ecological communities

Effects on Seabirds

Seabirds are extremely vulnerable to oil spills: cormorants and shags sea ducks: eiders, goldeneye, mergansers, scaup,

scoters alcids: auklets, guillemots, murres, puffins, razorbills penguins

An ill-timed oil spill can cause enormous mortality to seabirds – most species congregate in large, seasonal populations most seabirds have slow reproduction, so it

takes a long time to recover from mass mortality

e.g., murres breed after 5-yr old, lay a 1-egg clutch, and fledge only ~1 young/4 breeding adults/yr

Most seabird mortality is caused by feathers being fouled with oil this causes loss of critical insulation and

buoyancy – animals die from heat loss leading to hypothermia, or by drowning

oil ingested while preening is also toxic eggs may be killed by only light oiling from

feathers of an adult

The size of a spill does not necessarily relate to its potential for causing damage to bird populations even a small spill in critical a habitat, such

as a staging or wintering area, can be devastating to seabird populations

Oiled birds are tragic victims of oil spills

These murres were cleaned of oil

residues and later released to the wild

The Torrey Canyon

The Torrey Canyon was a supertanker that went aground in 1967 off Wales, spilling 117 x 103 t of crude oil hundreds of kilometres of coast were polluted

with petroleum residues 30-thousand seabirds were killed

~ 8-thousand were captured and cleaned, but only 6% survived to be released, and post-release survival was likely very low

an intensive clean-up used large amounts of detergent & dispersant to create emulsions of oil‑in‑water that were rinsed to the ocean using pressurized water from hoses

but the emulsifiers were highly toxic to marine organisms, and exacerbated the damage caused to beaches, intertidal, and subtidal habitats

where emulsifiers were not used, seaweed was damaged by oil but regenerative tissues often survived so regrowth was quick

some intertidal invertebrates were rather tolerant of oiling (but not to the dispersants used)

intertidal recovery was almost complete by 10 years

ecological damage was always much worse wher detergent or dispersant has been used

this was a critical lesson of the clean-up, and it resulted in the development of less toxic dispersants for use in oil-spill emergencies

also a more judicous usage, mostly to clean high-value sites for industrial or recreational uses, or at offshore locations

The Amoco Cadiz

A supertanker that lost steerage and went aground in 1978 between southern England and France, spilling 233 x 103 t of petroleum 360 km of shore were fouled (140 km heavily oiled) many polluted beaches were intensively cleaned

mostly by removing oily sand, sediment, & residues detergent and low-toxicity dispersant were only used

to remove fouling residues in harbours, and in offshore habitats to disperse floating mousse

ecological damage caused by oil and the cleanup was less severe than with the Torrey Canyon

recovery was rapid and substantially complete within several years

but some effects on invertebrates lasted 10 yr there was lingering damage to local alcid colonies

Rocky intertidal habitat affected by

petroleum spilled from the Amoco Cadiz

Use of pressurized water streams to

clean rocky intertidal habitat affected by

petroleum from the Amoco Cadiz

The Exxon Valdez

This 1989 tanker accident is the most damaging ever in North America

36 x 103 t of petroleum were spilled into Prince William Sound, s Alaska (the load was 176 x 103 t)

40% washed onto shoreline habitat, 25% carried out of the Sound by currents, 35% evaporated, <10% was recovered or burned

the grounding of the Exxon Valdez was a reckless accident

the damage was compounded by a stunning lack of preparedness by industry and government for dealing with an oil-spill emergency out of Valdez

essential equipment was not immediately available, and it took too long to mobilize trained staff

sea otters (Enhydra lutris) were the hardest-hit marine mammals, with >1,000 killed out of a population of 5-10 thousand in the Sound

357 oiled otters were captured and treated; 223 survived to be released or placed in zoos

about 36-thousand dead birds were tallied, but total mortality was likely 375-435 thousand

>153 bald eagles (Haliaeetus leucocephalus) were killed

400 people, 140 boats, & 5 aircraft were hired to capture and treat oiled birds (they handled 1600 birds of 71 species)

1/2 of the captured birds died – the rest were treated and released, but few likely survived because of lingering effects of hydrocarbon poisoning & stress

Clean up of a shore polluted

by the Exxon Valdez spill

Exxon Valdez clean-up

a recently oiled beach the same beach: 3 years

of clean-up by humans

and by natural forces

Terrestrial Oil Spills

Oiled plants suffer a rapid defoliation

the oil acts like a contact herbicide

trees and shrubs may survive but then suffer winter mortality

after initial post-oiling damage, many species begin to recover

some by regeneration of surviving plants

others by invasion of the oiled site

a wide range of soil-dwelling microorganisms can utilize petroleum residues as a metabolic substrate

they increase rapidly when soil is polluted by an oil spill

microbial activity can be enhanced by: fertilizing with P and N (use oleophilic P) tilling the soil to enhance O2 availability

oil spills cause severe damage to terrestrial vegetation, but relatively local areas are affected

soil has a large absorptive capacity for petroleum

much of the spilled oil accumulates in low spots

damage in aquatic habitats is much more widespread

contamination of groundwater is extremely persistent

boreal forest new Norman Wells where

experimental oil spills were made

The petroleum spill was devastating to the

ground vegetation, and recovery was slow

Shrub tundra –

reference habitat

First growing season

after oiling

Regeneration issuing from

unkilled willow shoots

10 years of post-spill

recovery

Experimental Spills in Aquatic Habitats