Environmental Encyclopedia

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Environmental Encyclopedia 3

Pet trade

to identify data gaps and assessment needs. The amendments

mandate that after this generic review, the EPA is to establish

as “registration standard” for the active ingredient basis.

Then, the EPA must wait for additional data in order to

establish specific requirements for each substance’s specific

use on differing crops. (The EPA does not specifically ad-

dress inert ingredients, although inert ingredients have been

found to be just as potentially toxic as the active ingredients.)

The 1988 amendments extended the deadline for re-

registration until 1997. To date, however, the EPA only has

complete residue data on less than 25% of pesticides used

on foods, and less than ten products, as yet, have been

registered. Thus, the backlog of substances awaiting re-regis-

tration is on the order of some 16,000 to 20,000 compounds,

including, according to the General Accounting Office, over

650 active ingredients. As a consequence, most of these

untested chemicals temporarily retain their registration sta-

tus under the former testing requirements.

Once tested in accordance with contemporary stan-

dards, many of the older pesticides are likely to be identified

as carcinogenic. In fact, the

National Academy of Sciences

estimates that 25–33% of the pesticides to undergo re-regis-

tration procedures are likely to be found to be oncogenic.

An oncogen causes tumors in laboratory animals and is con-

sidered potentially cancerous to humans. In general, such

older pesticides, registered prior to 1972, have not been

tested adequately for oncogenicity. For a substance to be

used on a new crop, however, current data must be submitted

in order to obtain a tolerance.

One way pesticide companies are able to completely

skirt EPA regulations is to send pesticides that are suspended

or banned in the United States to

Third World

countries.

At least 25% of American pesticide exports are products that

are banned, heavily restricted or have never been registered

for use in the United States. Hazardous pesticide exports

are a major source of

pollution

in Third World countries

where lack of regulation, illiteracy, and repressive working

conditions can turn even a “safe” pesticide into a deadly

weapon for the field workers. These pesticides are returned

to the United States, unexamined, as residues in the imported

food American consumers eat.

[Liane Clorfene Casten]

ESOURCES

OOKS

Briggs, S. A. Basic Guide to Pesticides: Their Characteristics and Hazards.

Washington, DC: Hemisphere, 1992.

Dinham, B. Pesticide Hazard: Global Health and Environmental Audit. High-

lands, NJ: Humanities Press International, 1993.

Somerville, L. Pesticide Effects on Terrestrial Wildlife. London: Taylor and

Francis, 1990.

1077

ERIODICALS

Raloff, J., and D. Pendick. “Pesticides in Produce May Threaten Kids.”

Science News 144 (July 3, 1993): 4–5.

Pet trade

Pets are part of human cultures all around the world. We

keep animals to admire their beauty or to enjoy their com-

panionship or devotion. The pet trade is big business

throughout the world but with its positive aspects, there

are distinct negative ones as well. As with any commodity,

economics dictates that the rarer an item is, the more valuable

it becomes in the market place. Many

rare species

thus

become quite valuable to wealthy collectors, who are willing

to pay exorbitant prices to black market dealers for certain

species—even though they are protected by international

treaties and laws.

Because these illegal pets must be smuggled into the

market arenas, concealment almost always requires physical

abuse of the animals. This may be in the form of constrictive

bindings, overcrowded or confined spaces, exposure to ex-

treme heat, or lack of oxygen due to these restrictions. Such

treatment results in the death of many individuals during

transit, with

mortality

that often approaches 80–90%.

Therefore, collectors and smugglers must over-collect speci-

mens in order to ensure the delivery of a sufficient quantity

to realize a profit. Two groups, monkeys and

parrots

, have

been the recipients of the bulk of this treatment. Due to

their popularity as pets, there is a lucrative business in their

illegal trade, and because the rarer

species

bring a higher

price, these practices further threaten

extinction

of certain

species.

This problem extends beyond the black market trade

in birds and mammals. Other animal groups, as well as the

legal pet trade, are also involved. Exotic reptiles, snakes and

lizards in particular, are a target group. Legitimate pet dealers

get involved in this problem when they, often unknowingly,

purchase pets that were illegally caught or smuggled.

The

aquarium trade

has also faced illegal collecting.

Over-collecting and poor handling of specimens during ship-

ment have been problems in the freshwater segment of this

business, but recent years have produced rampant abuses in

the marine aquarium trade. Advances in technology over the

past twenty years have made marine aquaria more accessible

to the general public, and the sheer beauty of the brilliant,

often neon-like, colors of many of the

coral reef

fish has

fascinated a new breed of aquarists.

The main problems here still include the removal of

large numbers of specimens of localized populations of rare

or low density species and their illegal trade. Now, new

and profound problems exist in the capture of these marine

Environmental Encyclopedia 3

Roger Tory Peterson

creatures: the total destruction of their

habitat

and the

killing of unwanted, non-commercial species. Although le-

gitimate collecting of marine fish is done with nets, it is

estimated that during the 1980s about 80% of specimens

for the marine aquarium trade were collected by using poison.

Since most of the

target species

use coral reefs as hiding

places, collectors use a squeeze bottle filled with sodium

cyanide to force the fish out into the open water. The

stunned, gasping fish are thus more easily caught, but the

section of coral reef sprayed with poison, and the animals

that did not escape, are now dead. Lingering effects of the

poison and abusive shipping practices lead to mortality rates

of 60–80% for these pets.

Public awareness and some governmental regulations

have eased some of the abuses of these animals, but the

illegal pet trade is still a profitable business. As long as people

are willing to purchase rare species, the illegal pet trade will

threaten the very species the collectors hold in high esteem.

See also Endangered Species Act; Overhunting; Parrots and

parakeets; Poaching; Wildlife management

[Eugene C. Beckham]

ESOURCES

OOKS

Forshaw, J., and W. Cooper. Parrots of the World. Melbourne, Australia:

Lansdowne Press, 1973.

ERIODICALS

Bergman, C. “The Bust!” Audubon 93 (1991): 66–77.

Derr, M. “Raiders of the Reef.” Audubon 94 (1992): 48–56.

McLarney, W. “Still a Dark Side to the Aquarium Trade.” International

Wildlife 18 (1988): 46–51.

Speart, J. “What’s Wildlife Worth?” Wildlife Conservation 95 (1992): 44–47.

PETA

see

People for the Ethical Treatment of

Animals

Roger Tory Peterson (1908 – 1996)

American ornithologist

A small book, tucked away in innumerable back-packs and

car pockets, ever ready to hand for perhaps the majority of

birders in the United States, is quite likely to be Roger Tory

Peterson’s A Field Guide to the Birds, first published in 1934,

revised and reissued several times, and still a must-have for

many bird-watchers, serious or otherwise. In 1941 it was

joined by a companion volume, A Field Guide to Western

Birds. Together, the two guides (the first rejected by four

publishers before Houghton Mifflin finally accepted it) have

1078

sold on the order of seven million copies by 1997. The critic

William Zinser suggested that Peterson’s Field Guide was

“the single most revolutionary development in American

birding.” He was the first to introduce simplified, compara-

tive drawings and to point out key field marks (distinguishing

characteristics) that help identification in the field. Later

critics judged Peterson harshly for his last revision of the

Guide as “not knowing much about contemporary identifica-

tion skills.” But the revolutionary importance of the Guides

lies in the number of people they have “turned on” to birds

and to birding; they still sell, and are still used by birders at

every level.

The man who has been called the modern successor

to John James Audubon was born in Jamestown, New York,

of a Swedish immigrant father and a German immigrant

mother. Reportedly a loner, a boy considered strange by

other children, Peterson came out of his shell when one of

his teachers started a Junior Audubon Club. Birds became

a passion for the eleven-year old, and he sought a job as a

newspaper delivery boy so that he could buy a camera to

photograph birds. Some seven decades later, he was still

making pictures of birds. The prescient caption under his

photograph in his high school yearbook read “Woods! Birds!

Flowers! Here are the makings of a great naturalist.”

Peterson studied art rather than ornithology, and he

considered himself first a painter, then a writer, and only

third a naturalist. Yet such was his reputation and standing

among people interested in natural history that the New

York Times could announce his death as that of “the best-

known ornithologist of the twentieth century.” Because his

work reached so many people, because it helped them be-

come involved in knowing more about the world around

them, and because it inspired them to actually get out in

the field and get involved, Peterson might even deserve Sports

Afield’s label of “the twentieth century’s most influential nat-

uralist.” Academically trained or not, he spent his lifetime

doing ornithology, i.e., studying birds, and in getting other

people to join in that passion. His guides provided clear

access to bird identification, even for the most rank amateur.

Along with his many awards for art, he was also honored

as a Fellow in the American Association for the Advance-

ment of Science, and was bestowed with the Linne

gold

medal of the Royal Swedish Academy of Sciences.

After art school, he taught at a boys’ school in Massa-

chusetts. The success of the first field guide allowed him to

return to New York to a position as an educational specialist

and art editor for Audubon Magazine. He remained associ-

ated with the

National Audubon Society

for the rest of

his professional life, serving in various capacities as artist,

writer, secretary, and two different terms as director.

His passion for

nature

centered on birds, certainly,

but he also was enthusiastic for all of the natural world,

Environmental Encyclopedia 3

Petroleum

worked on many fronts to protect its diversity, and became an

advocate for and teacher about managing the

environment

wisely. For example, he and his wife shared a love of flowers,

and created and maintained butterfly gardens; one of his best

known field guides is for wildflowers. All told, he published

almost 50 books, including his edition of Audubon’s Birds of

America, and wrote many articles on birds as well as on other

topics in

conservation

and management of gardens and

wildlands.

As stated in a New York Times editorial, Peterson did

indeed become “a great naturalist and more. He was one of

the pioneers in teaching twentieth-century Americans to

walk more gently on their land.”

[Gerald L. Young Ph.D.]

ESOURCES

OOKS

Devlin, J. C., and G. Naismith. The World of Roger Tory Peterson: an

Authorized Biography. New York: New York Times Books, 1977.

Peterson, R. T., and R. Hoglund, eds. Roger Tory Peterson; Art and Photogra-

phy from the World’s Foremost Birder. New York: Rizzoli, 1994.

Petrochemical

Petroleum

is probably best known as a source for many

important fuels, such as

gasoline

, kerosene, acetylene, and

natural gas

. However, many of the organic compounds

that make up the complex mixture known as petroleum have

another use. They are raw materials used in the production

of a host synthetic products. These

chemicals

are known

as petrochemicals. To a large extent, these petrochemicals

are

hydrocarbons

. Some of these petrochemicals and the

products into which they are made include ethylene (

plas-

tics

, synthetic fibers, and anti-freeze),

benzene

(synthetic

rubber

, latex paints and paper coatings), propylene (drugs

and

detergents

), and phenol (adhesives, perfumes, flavor-

ings, and pesticides). See also Fossil fuels; Synthetic fuels;

Volatile organic compound

Petroleum

Petroleum is a complex mixture of solid, liquid, and gaseous

hydrocarbons

normally found a few miles beneath the

earth’s surface. It, along with

coal

and

natural gas

,isone

of the

fossil fuels

. That name comes from the most common

scientific theory that these three materials were formed be-

tween 10 and 20 million years ago as a product of the decay

of plants and animals. Petroleum is sometimes called crude

oil or, simply, oil, although some authorities give slightly

different means to these terms.

1079

Most commonly, petroleum and natural gas occur to-

gether under dome-shaped layers of rock. When

wells

are

drilled into such domes, gas pressure forces petroleum up

into the well, producing the “gushers” that are typical of

successful new wells.

Petroleum has been known to and used by humans

for thousands of years. Collecting the liquid that seeped to

the surface, the Egyptians, Babylonians, and Native Ameri-

can Indians used petroleum for waterproofing, embalming,

caulking ships, warpaint, and medicine. The first successful

oil well in the United States was drilled in 1859 by “Colonel”

Edwin Drake.

The number and variety of compounds found in petro-

leum are large, and its composition varies significantly from

location to location. Petroleum from Pennsylvania tends to

have a high proportion of aliphatic (open-chain) hydrocar-

bons, those from the West contain more aromatic (benzene-

based) hydrocarbons, and those from the Midwest contain

a more even mix of the two.

The most common impurities (non-hydrocarbon com-

pounds) in petroleum are compounds of sulfur and

nitrogen

The percentage of sulfur in a sample of petroleum determines

its status as “sweet” (low-sulfur) or “sour” (high-sulfur) crude

oil. The emphasis on sulfur derives from the fact that one

of the most undesirable products of the

combustion

petroleum is

sulfur dioxide

. Oil with low sulfur is, therefore,

more desirable than that with high sulfur.

The complex mix of compounds that make up petro-

leum results in its having relatively few important uses in

its natural state. It becomes an important product only when

some method is used to separate the native liquid into its

component parts. The fractional distillation of petroleum

results in the production of portions known as petroleum

ether,

gasoline

, kerosene, heating oil, lubricating oil, and

a semi-solid residue that includes paraffin, pitch, and tar.

Each of these fractions can then be utilized directly or subdi-

vided even further.

Few naturally occurring materials have as many envi-

ronmental effects as does petroleum. During its removal

from the earth, it may escape from wells and contaminate

groundwater

. The combustion of some of its most impor-

tant components, gasoline, kerosene and fuel oil results in

the release of

carbon dioxide

carbon monoxide

carbon

sulfur dioxide, and

nitrogen oxides

, all compounds that

contribute to

air pollution

, global warming, or other envi-

ronmental problems.

In recent decades, petroleum has found another major

use: in the production of petrochemicals. The compounds

found in oil are now important starting materials in the

manufacturing of a nearly limitless number of synthetic prod-

ucts. The manufacture, use and disposal of these

petrochem-

ical

products contributes to additional environmental prob-

Environmental Encyclopedia 3

Pfiesteria

Natural gas and oil deposits in the United States. (Council on Environmental Quality.)

lems such as

hazardous waste

disposal and

solid waste

accumulation. See also Alternative fuels; Decomposition;

Emission standards; Greenhouse effect; Groundwater pollu-

tion; Oil drilling; Oil spills

[David E. Newton]

ESOURCES

OOKS

Fesharaki, F., and R. Reed, eds. The Petroleum Market in the 1990s. Boulder,

CO: Westview Press, 1989.

Kupchella, C. E. Environmental Science: Living within the System of Nature.

3rd ed. Boston: Allyn and Bacon, 1993.

Metzger, N. “Getting More Oil.” In Energy and the Way We Live, edited

by M. Kranzberg and T. A. Hall. San Francisco: Boyd & Fraser, 1980.

Petroleum Exploration: Continuing Need. Washington, DC: American Petro-

leum Institute, 1986.

Petulla, J. M. American Environmental History. 2nd ed. San Francisco:

Boyd & Fraser, 1988.

THER

Flavin, C. “World Oil: Coping With the Dangers of Success.” Worldwatch

Paper #66. Washington, DC: Worldwatch Institute, 1985.

1080

Pfiesteria

Pfiesteria piscicida (fee-STEER-ee-uh pis-kuh-SEED-uh)

is a microscopic, polymorphic organism that belongs to a

group of single-celled, free-swimming

phytoplankton

called dinoflagellates. Although many phytoplankton photo-

synthesize to generate the energy they need to survive, Pfiest-

eria does not—it is more animal-like in that it consumes

other organisms such as bacteria and algae. It can transform

in and out of the following stages within a matter of minutes:

flagellated, amoeboid, and cyst. In the flagellated stage

Pfiesteria is powered by two tiny flagella that resemble tails.

The cyst stage lies dormant in the bottom sediments of

estuaries and rivers.

Two

species

are known to release

toxins

that are

harmful to aquatic and human life: Pfiesteria piscicida and

Pfiesteria shumwayae.

When it was discovered in 1988, Pfiesteria was declared

to be a new family (Pfiesteriaceae), genus (Pfiesteria), and

species (piscicida), in the order Dinamoebales. It was named

in honor of Dr. Lois Pfiester, an internationally respected

Environmental Encyclopedia 3

Pfiesteria

researcher of dinoflagellates. Since its discovery, it has been

identified in mud cores from the bottom of

Chesapeake

Bay

that are at least 3,000 years old.

Depending on its stage, Pfiesteria piscicida, the most

studied Pfiesteria species, ranges in size from about 5–450

microns in diameter. It is typically found in the bottom

sediments and water of

brackish

tidal rivers and estuaries,

primarily along the eastern seaboard of the United States.

Pfiesteria is a remarkably hardy organism that can sur-

vive over a wide range of temperatures and water salinities.

For most of its life cycle Pfiesteria is a nontoxic predator,

feeding on bacteria, algae, and other small organisms. When

schools of fish are present, Pfiesteria occasionally responds

with a quick release of

biotoxins

into the water. These

chemicals

stun or kill the fish, which allow the Pfiesteria

to feed on the injured skin, blood, and dying tissue.

These toxic episodes last for several hours before dissi-

pating, sometimes resulting in large-scale

fish kills

, many

of which plagued the Atlantic coastline in the late 1980s

and 1990s. Fish kills attributed to Pfiesteria occurred in

estuaries in the Albemarle–Pamlico estuarine system in

North Carolina, Chesapeake Bay tributaries in Virginia, the

Chicamacomico, Pokomoke, and Manokin Rivers and

King’s Creek in Maryland, and Indian River in Delaware.

Pfiesteria has been identified as far north as Long Island,

New York, and as far west as the southern tip of Texas. It may

also occur in Pacific waters along the California–Oregon–

Washington coastline, but has not yet been identified be-

cause these waters have not been sampled.

Although Pfiesteria is technically not an algae, it’s fish

kills are usually included under the category of harmful algal

blooms (HABs). This is because Pfiesteria shares many phys-

iological and toxicological characteristics with the various

algae species that cause algal blooms (red or brown tides),

some of which are toxic to aquatic life.

Toxic strains of Pfisteria have been identified along

European, Scandinavian, New Zealand, and

Australia

coastlines. It likely occurs in other international waters that

have not been tested for its presence. As the technology of

detection improves, it is highly probable the global distribu-

tion of Pfiesteria will become better defined. However, the

United States is the only country in the world that has

experienced the serious deleterious effects of its toxins on

aquatic life and human health.

When Pfiesteria detects fish oils or excretions in the

water from a large school of fish, a biological toxic response

may be triggered. The organisms change from the cyst stage

(excystment) into the predator flagellate or ameoboid stages,

which then release potent toxins into the water.

The toxins penetrate the skin of the fish, creating

bleeding ulcers. The fish become lethargic or die. The skin

becomes so damaged that the fish cannot maintain their

1081

internal salt balance. The Pfiesteria organisms feed on the

dead skin tissue, blood, and other fish fluids leaking into

the water. Within several hours Pfiesteria transforms back

to the cyst stage (encystment) and lays dormant in the bottom

sediments. Fish kills usually occur in warmest times of the

year and when the

dissolved oxygen

content of the water

is low.

There has been a global increase in toxic and harmful

algae blooms in the late twentieth century, including Pfiest-

eria. Modern technology increasingly allows for the rapid

identification of the species causing the bloom or the fish

kill. Pfiesteria attacks are becoming a growing problem be-

cause they have a negative impact on

commercial fishing

recreation

, and human health along the eastern seaboard.

Toxins can be present in the water or aerosolize into

the air. Toxic episodes and fish kills close down sections of

coastline, which impact the fish and shellfish industries. If

fish aren’t killed directly by Pfiesteria, they are seriously

weakened, which makes them susceptible to other predators

or bacterial and fungal infections. Humans can suffer serious

health problems from coming into contact with, or inhaling,

these biotoxins. Effects to humans and aquatic life persist

for six to eight weeks after the bloom disappears.

Two kinds of toxins have been discovered to date: a

fat-soluble toxin that blisters skin and a water-soluble toxin

that affects the nervous system. Injection of Pfiesteria toxin

has induced significant learning problems in laboratory rats.

Symptoms in humans consist of lethargy, sores and rashes,

eye sensitivity, headaches, blurred vision, gastrointestinal

distress, nausea, memory loss, kidney and liver problems,

shortness of breath, and fibromyalgia-like symptoms. Symp-

toms can recur for up to eight years after exposure. This

condition, sometimes referred to as possible estuary-associ-

ated syndrome (PEAS) can be developed from exposure to

Pfiesteria biotoxins, even if there is no evidence of fish kills

or fish disease in the water.

Identifying a fish kill as being Pfiesteria-related (and

taking subsequent actions, such as closing shorelines and

issuing fish consumption warnings) can be difficult because

Pfiesteria has 24 recognized morphological shapes at differ-

ent growth stages. Scientists use light microscopes, bioassays,

scanning electron microscopes, or polymerase

chain reac-

tion

(PCR) methods to establish positive identifications.

An unanswered question remains: Are fish from areas

that have experienced Pfiesteria outbreaks safe to consume?

This may have significant impact to the fishing industry. So

far research indicates that no person has become ill from

eating fish or shellfish that have been exposed to Pfiesteria—

the data, however, are limited. Most experts recommend to

err on the side of caution: If an area has been closed because

of a Pfiesteria outbreak, do not catch or consume fish from

Environmental Encyclopedia 3

that area or swim or waterski in those waters for at least

eight weeks after the outbreak.

Data suggest that Pfiesteria has a fairly wide global

distribution, but only creates health problems under certain

conditions, which seem to be best demonstrated in the

coastal estuaries of the eastern and southern United States.

Research at North Carolina State University’s Center

of Applied Aquatic Ecology shows that Pfiesteria is stimu-

lated by organic or inorganic

nitrogen

and

phosphorus

the water—two key components of

fertilizer

Carbon

may

also be a trigger substance. It has been documented that

Pfiesteria outbreaks occur in areas that are downstream from

septic tanks, sewage-plant discharges, agricultural waste such

as excrement from cattle, swine, and poultry, and agricultural

or landscaping chemical

runoff

. When these nutrients accu-

mulate in slow-moving or stagnant sections of estuaries and

mix with the incoming tidal water, Pfiesteria can become

more active and toxic. Other stimulators may be airborne

pollutants that settle in the water. An abundance of fish is

also required. As yet it has not been determined if the

nutrient loading

stimulates the growth of the algae on

which Pfiesteria feeds, or if directly stimulates Pfiesteria.

Federal organizations such as the U.S.

Environmental

Protection Agency

(EPA), U.S.Department of Agriculture,

U.S. Department of the Interior

National Oceanic and

Atmospheric Administration

, Centers for Disease Control

and Prevention(CDC), and the

National Institute of Envi-

ronmental Health Sciences

, state departments of health or

natural resources

, and several prominent university re-

search centers are continuing research into the life cycles of

Pfiesteria and other Pfiesteria-like organisms, their nutri-

tional ecologies, and the trigger mechanisms that result in

toxic episodes.

One major areas of study focuses on integrating man-

agement approaches with new emerging technologies. This

collaborative effort between risk managers, universities, fed-

eral agencies, and users—commercial and recreational fish-

ermen, Native peoples, and other water users—will lead

toward a systematic approach to managing the risk for expo-

sure to Pfiesteria biotoxins. The ultimate goal is to develop

an accurate model of prediction—what conditions will result

in toxic Pfiesteria/algal blooms? Knowing these factors may

reduce or eliminate the need to close down sections of coast-

line and interrupt commercial fishing operations.

Researchers are also attempting to purify and study

Pfiesteria biotoxins. When the actual toxin can be identified,

it will be much easier to determine if fish kill/disease episodes

are related to Pfiesteria attacks. Once the chemical signature

of the toxin is identified, methods can be developed to test

humans for exposure. Antitoxins or related drugs may also

be developed. It is also possible that, when consumed or

injected in prescribed dosages under certain conditions,

1082

Pfiesteria toxins may be useful medicines that reduce or

alleviate other health conditions in humans.

[Mark J. Crawford ]

ESOURCES

ERIODICALS

Burkholder, J. M. “Overview and Present Status of the Toxic Pfiesteria

Complex.” Phycologia.

Burkholder, J. M., et al. “New ’Phantom’ Dinoflagellate Is the Causative

Agent of Major Estuarine Fish Kills.” Nature 358 (1992): 407–410.

Burkholder, J. M. and H. B. Glasgow. “Pfiesteria piscicida and Other Toxic

Pfiesteria-like Dinoflagellates: Behavior, Impacts, and Environmental Con-

trols.” Limnology & Oceanography. 42 (1997):1052–1075.

THER

Pfiesteria and Related Harmful Blooms: Natural Resources and Human Health

Concerns. Pamphlet. U.S. Environmental Protection Agency, 1998.

What You Should Know about Pfiesteria piscicida. Document EPA 842-F-

98-011. U.S. Environmental Protection Agency, 2002.

U.S. Department of Public Heath and Human Services.ldquo;Pfiesteria:

From Biology to Public Health.rdquo; Environmental Health Perspectives

109 (2001): Supplement 5.

RGANIZATIONS

Aquatic Pathobiology Center, University of Maryland, 8075 Greenmead

Dr., College Park, MD USA 20742 (301)314-6808, Fax: (301)314-6855

Maryland Sea Grant, University of Maryland, 0112 Skinner Hall, College

Park, MD USA 20742 (301)405-6371, Fax: (301)314-9581

North Carolina State University Center for Applied Aquatic Ecology, 620

Hutton Street, Suite 104, Raleigh, NC USA 27608 (919)515-3421, Fax:

(919)513-3194

U.S. Environmental Protection Agency, 1200 Pennsylvania Avenue NW,

Washington, DC USA 20460 (202)260-2090

Virginia Institute of Marine Science, Route 1208 Greate Road, Gloucester

Point, VA USA 23062 (804)684-7000, Fax: (804)685-7097

PFOS

see

Perfluorooctane sulfonate

A measure of the acidity or alkalinity of a solution based on

its

hydrogen ion

) concentration. The pH of a solution

is the negative logarithm (base 10) of its H

concentration.

Since the scale is logarithmic, there is a tenfold difference

in hydrogen ion concentration for each pH unit. The pH

scale ranges from 0 to 14 with 7 indicating neutrality ((H

(OH

)). Values above 7 indicate progressively greater alka-

linity, while values below 7 indicate progressively increasing

acidity. See also Acid and base; Buffer

Environmental Encyclopedia 3

Phosphates

pH scale. (McGraw-Hill Inc. Reproduced by permission.)

Phosphates

Phosphorus

is essential to the growth of biological organ-

isms, including both their metabolic and photosynthetic pro-

cesses. Phosphorus occurs naturally in bodies of water mainly

in the form of phosphate (i.e., a compound of phosphorus

and oxygen). Addition of phosphates through the activities

1083

of humans can accelerate the eutrophication process of

nutri-

ent

enrichment that results in accelerated ecological aging

of lakes and streams. Phosphorus, especially in inland waters,

is often the nutrient that limits growth of aquatic plants.

Thus when it is added to a body of water, it may result in

increased plant growth that gradually fills in the lake. Critical

levels of phosphorus in water, above which eutrophication

is likely to be triggered, are approximately 0.03 mg/l of

dissolved phosphorus and 0.1 mg/l of total phosphorus. The

discharge

of raw or treated

wastewater

, agricultural

drainage

, or certain industrial wastes that contain phos-

phates to a surface water body may result in a highly eutro-

phic state, in which the growth of photosynthetic aquatic

micro- and macroorganisms are stimulated to nuisance lev-

els. Aquatic plants and mats of algal scum may cover the

surface of the water. As these algal mats and aquatic plants

die, they sink to the bottom, where their

decomposition

microorganisms

uses most of the oxygen dissolved in the

water. The decrease in oxygen severely inhibits the growth of

many aquatic organisms, especially more desirable fish (e.g.,

recreational catch fish such as trout) and in extreme cases

may lead to massive

fish kills

. Excessive input of phosphorus

can change clear, oxygen-rich, good-tasting water into

cloudy, oxygen-poor, foul smelling, and possibly toxic water.

Therefore, control of the amount of phosphates entering

surface waters from domestic and industrial waste discharges,

natural

runoff

, and

erosion

may be required to prevent

eutrophication.

Rocks may contain phosphates; those with calcium

phosphate upon heat treatment with sulfuric

acid

serve as

a source of fertilizers. Phosphates, in addition to those found

in fertilizers, are also present in such consumer products as

detergent, baking powders, toothpastes, cured meats, evapo-

rated milk, soft drinks, processed cheeses, pharmaceuticals,

and water softeners. Phosphates are classified as orthophos-

phates (PO

-3

, HPO

-2

, and H

); condensed

phosphates, or polyphosphates, which are molecules with

two or more phosphorus atoms, oxygen atoms and in some

cases,

hydrogen

atoms, combined in a complex molecule;

and organically-bound phosphates.

Orthophosphates in an aqueous solution can be used

for biological

metabolism

without further breakdown. Or-

thophosphates applied to agricultural or residential culti-

vated land as fertilizers may be carried into surface waters

with

storm runoff

and melting snow.

Polyphosphates can be added to water when it is used

for laundering or cleaning, for polyphosphates are present

as builders of some commercial cleaning preparations for

the public health sector. Massive algal blooms in lakes and

floating foam on rivers aroused alarm in the United States

in the 1970s. After it was shown that phosphates from

detergents

were a key factor, legislation banning the use

Environmental Encyclopedia 3

Phosphates

of phosphates in home laundry detergents was passed in

many areas. Phosphate legislation usually includes exemp-

tions for products such as hard-surface cleaner and automatic

dishwashing detergents used in the public health sector.

Polyphosphates may also be added to water supplies during

culinary

water treatment

and during treatment of boiler

water. Polyphosphates slowly undergo hydrolysis in aqueous

solutions and are converted to the orthophosphate forms.

Organic phosphates are formed primarily by biological

processes. They enter sewage water through body wastes

and food residues. They may also be formed from orthophos-

phates in biological treatment processes and by receiving

water organisms. Like polyphosphates, they are biologically

transformed back to orthophosphates.

One means of surface water protection from phospho-

rus addition in both domestic and industrial wastewaters is

the use of

phosphorus removal

processes in wastewater

treatment. Phosphates are typically present in raw waste-

waters at concentrations near 10 mg/l as P. During waste-

water treatment, about 10-30% of the phosphates in raw

wastewater is utilized during secondary biological treatment

for microbial cell synthesis and energy transport. Additional

removal is required to achieve low

effluent

concentration

levels from the wastewater treatment process. Effluent limits

usually range from 0.1-2 mg/l as P, with many established

at 1.0 mg/l. Removal processes for phosphates from waste-

waters utilize incorporation into suspended solids and the

subsequent removal of those solids. Phosphates can be incor-

porated into chemical precipitates that are insoluble or of

low solubility or into biological solids, (e.g, microorganisms).

Chemical precipitation is accomplished by the addi-

tion of metal salts or lime, with polymers often used as

flocculant aids. The precipitation of phosphates from waste-

water can occur during different phases within the waste-

water treatment process. Pre-precipitation, where the

chem-

icals

are added to raw wastewater in primary

sedimentation

facilities, removes the precipitated phosphates with the pri-

mary

sludge

. In co-precipitation, the chemicals are added

during secondary treatment to the effluent from the primary

sedimentation facilities; to the mixed liquor in the activated-

sludge process; or to the effluent from a biological treatment

process before secondary sedimentation. They are removed

with the waste biological sludge. In post-precipitation, the

chemicals are added to the effluent from secondary sedimen-

tation facilities and are removed in separate sedimentation

facilities or in effluent

filters

The most commonly used metal salts are ferric chloride

and

aluminum

sulfate (alum), which combine with phos-

phate to form the precipitates aluminum phosphate and iron

phosphate, with one mole of iron or aluminum precipitating

one mole of phosphate. However, because of competing

reactions and the effects of alkalinity,

, trace elements,

1084

and ligands found in wastewater, appropriate dosages are

established on the basis of bench-scale or full-scale testing.

Less commonly used metal salts are ferrous sulfate and fer-

rous chloride, which are available as by-products of steel

production operations. Because polyphosphates and organic

phosphorus are less easily removed than orthophosphates,

adding metal salts after secondary treatment, where organic

phosphorus and polyphosphates are transformed into ortho-

phosphates, usually results in the best control.

Lime (CaOH)

is used less frequently because of the

larger amounts of sludge produced as compared with the

use of metal salts. Also, operating and maintenance problems

are associated with the handling, storage, and feeding of

lime. As lime is added to water, it reacts with natural bicar-

bonate alkalinity to precipitate CaCO

. As the pH of the

wastewater increases beyond about 10, excess calcium ions

react with phosphates to precipitate hydroxylapatite, Ca

)

(OH)

. The amount of lime required will be indepen-

dent of the amount of phosphate present and will depend

primarily on the alkalinity of the wastewater and the degree

of phosphate removal required. The pH of the wastewater

must be adjusted by recarbonation with

carbon dioxide

(CO

) before subsequent treatment or disposal. Lime can be

added to primary sedimentation tanks or following secondary

treatment.

Biological phosphate removal is accomplished by se-

quencing and producing appropriate environmental condi-

tions in a reactor system in which microorganisms absorb

and store phosphorus. The Acinetobacter bacteria are one

of the primary microorganisms responsible for phosphorus

uptake. The sludge containing the microorganisms with the

excess phosphorus can either be wasted or removed and

treated in a side stream to release the excess phosphate, which

can then be treated with chemical precipitation processes.

Wasted sludge, if it has a relatively high phosphorus content

(3-5%), may have

fertilizer

value.

In natural treatment systems for wastewater, which

include managed land-farms, landscape

irrigation

sites,

groundwater

recharge sites, and constructed

wetlands

phosphates are removed by

sorption

with

clay minerals

in the

soil

matrix and by chemical precipitation. Sorbed

phosphates are held tightly and are generally resistant to

leaching

until the soil sorptive capacity for phosphates be-

comes saturated. Chemical precipitation with calcium (in

soils with neutral or alkaline pH) or with iron or aluminum

(at acid pH) occurs at a slower rate than sorption, but is also

an important removal mechanism. The degree of phosphorus

removal in a natural treatment system depends on the degree

of wastewater contact with the soil matrix.

Transport of phosphates into surface waters from non-

point sources is controlled by practices that minimize soil

erosion and runoff water. Phosphate losses from a

water-

Environmental Encyclopedia 3

Phosphorus removal

shed

can be increased by a number of human activities,

including timber harvest, intensive livestock grazing, soil

tillage, and soil application of animal manures and phos-

phate-containing fertilizers. Since most soils, except for very

sandy soils or soils with high levels of organic matter, retain

phosphates through sorption and precipitation, techniques

that prevent soil transport will also prevent transport of

phosphates. Control of runoff water is required to prevent

dissolved phosphates from entering rivers and lakes.

[Judith L. Sims]

ESOURCES

OOKS

Metcalf & Eddy. Wastewater Engineering: Treatment, Disposal, and Reuse.

3rd ed. New York: McGraw-Hill, 1991.

Phosphorus

An important chemical element, which has the atomic num-

ber 15 and atomic weight 30.9738. Phosphorus forms the

basis of a large number of compounds, by far the most

environmentally important of which are

phosphates

. All

plants and animals need phosphates for growth and function,

and in many natural waters the production of algae and

higher plants is limited by the low natural levels of phospho-

rus. As the amount of available phosphorus in an aquatic

environment

increases, plant and algal growth can increase

dramatically leading to eutrophication. In the past, one of the

major contributors to phosphorus

pollution

was household

detergents

containing phosphates. These substances have

now been banned from these products. Other contributors

to phosphorus pollution are

sewage treatment

plants and

runoff

from cattle

feedlots

. (Animal feces contain signifi-

cant amounts of phosphorus.)

Erosion

of farmland treated

with phosphorus fertilizers or animal manure also contri-

butes to eutrophication and

water pollution

. See also Cul-

tural eutrophication

Phosphorus removal

Phosphorus

(usually in the form of phosphate, PO

)isa

normal part of the

environment

. It occurs in the form of

phosphate-containing rocks and as the excretory and decay

products of plants and animals. Human contributions to the

phosphorus cycle result primarily from the use of phospho-

rus-containing

detergents

and fertilizers.

1085

The increased load of phosphorus in the environment

as a result of human activities has been a matter of concern

for more than four decades. The primary issue has been to

what extent additional phosphorus has contributed to the

eutrophication of lakes, ponds, and other bodies of water.

Scientists have long recognized that increasing levels of

phosphorus are associated with eutrophication. But the evi-

dence for a direct cause and effect relationship is not entirely

clear. Eutrophication is a complex process involving

nitro-

gen

and

carbon

, as well as phosphorus. The role of each

nutrient

and the interaction among them is still not en-

tirely clear.

In any case, environmental engineers have long ex-

plored methods for the removal of phosphorus from

waste-

water

in order to reduce possible eutrophication effects.

Primary and secondary treatment techniques are relatively

inefficient in removing phosphorus with only about ten per-

cent extracted from raw wastewater in each step. Thus, spe-

cial procedures during the tertiary treatment stage are needed

to remove the remaining phosphorus.

Two methods are generally available: biological and

chemical. Bacteria formed in the

activated sludge

produced

during secondary treatment have an unusually high tendency

to adsorb phosphorus. If these bacteria are used in a tertiary

treatment stage, therefore, they are very efficient in removing

phosphorus from wastewater. The

sludge

produced by this

bacterial action is rich in phosphorus and can be separated

from the wastewater leaving water with a concentration of

phosphorus only about five percent that of its original level.

The more popular method of phosphorus removal is

chemical. A compound is selected that will react with phos-

phate in wastewater, forming an insoluble product that can

then be filtered off. The two most common substances used

for this process are alum,

aluminum

sulfate [Al

(SO

)

] and

lime, or calcium hydroxide [Ca(OH)

]. An alum treatment

works in two different ways. Some aluminum sulfate reacts

directly with phosphate in the waste water to form insoluble

aluminum phosphate. At the same time, the aluminum

ion

hydrolyzes in water to form a thick, gelatinous precipitate

of aluminum hydroxide that carries phosphate with it as it

settles out of solution.

The addition of lime to wastewater results in the for-

mation of another insoluble product, calcium hydroxyapatite,

which also settles out of solution.

By determining the concentration of phosphorus in

wastewater, these chemical treatments can be used very pre-

cisely. Exactly enough alum or lime can be added to precipi-

tate out the phosphate in the water. Such treatments are

normally effective in removing about 95 percent of all phos-

phorus originally present in a sample of wastewater.

[David E. Newton]

Environmental Encyclopedia 3

Photic zone

ESOURCES

OOKS

Phosphorus Management Strategies Task Force. Phosphorus Management

for the Great Lakes. Windsor, Ont.: International Joint Commission, 1980.

Retrofitting POTWs for Phosphorus Removal in the Chesapeake Bay Drainage

Basin: A Handbook. Cincinnati: U.S. Environmental Protection Agency,

1987.

Symposium on the Economy and Chemistry of Phosphorus. Phosphorus in

the Environment: Its Chemistry and Biochemistry. New York: Elsevier, 1978.

Photic zone

The surface waters of an ocean or lake that receive sufficient

solar radiation to support

photosynthesis

, (i.e. the growth

of vascular plants and

phytoplankton

). When sunlight falls

on the surface of a lake or ocean, a large part of the light

is reflected, scattered, or absorbed. Some light penetrates

the water, but its intensity decreases quite rapidly with depth.

The photic zone can be up to 328 ft (100 m) deep, and,

typically, its limit is reached when the light intensity falls

below one percent of the incident radiation.

Photochemical reaction

Photochemical reactions are driven by light or near-visible

electromagnetic radiation. In general, incoming units of en-

ergy, known as photons, excite effected molecules, raising

their energy to a point where they can undergo reactions

that would normally be exceedingly difficult. The process is

distinguished from thermal reactions, which take place with

molecules in their normal energy states. Under sunlit condi-

tions, photochemical processes can generate small amounts

of extremely reactive molecules which initiate important

chemical reaction sequences.

To initiate a photochemical reaction, two require-

ments need to be met. First, the photon must have enough

energy to initiate the photochemical reaction in the molecule.

Second, the compound must be colored, in order to be able

to react with visible or near-visible photon radiation.

environmental chemistry

, photochemical reac-

tions are of considerable importance to the trace chemistry of

the

atmosphere

. The Los Angeles

photochemical smog

an example of a system of photochemical reactions. Perhaps

one of the most important reactions in this system is the

photochemically driven conversion of

nitrogen

dioxide, a

major component of

automobile

exhaust, to nitric oxide

and an atom of oxygen, which usually occurs in pairs in the

air. The oxygen atom subsequently attaches to an oxygen

molecule to form the secondary pollutant,

ozone

. Photo-

chemically initiated reactions are also responsible for gener-

ating the all important hydroxyl radical, a key intermediate

in the trace chemistry of the lower atmosphere.

1086

Photochemical reactions are also important in natural

waters. Here they may be responsible for enhancing the

reaction rate of organic compounds or changing the oxida-

tion state of metallic ions in solution. However, some of

these compounds are not colored, and are unable to absorb

light. In such cases reactions may be mediated by photosensi-

tizers, compounds capable of being energized by absorbed

light which then pass the energy onto other molecules. Sea-

water appears to contain natural photosensitizers, perhaps

in the form of fulvic

acid

or chlorophyll derivatives. Photo-

sensitizers activated by sunlight can react with organic com-

pounds or

dissolved oxygen

to produce the reactive sin-

glet-oxygen, which can react rapidly with many seawater

compounds.

Photochemical reactions also occur in solids. Since

solids often lack the transparency required for the light to

penetrate the surface, reactions are usually limited to the

surface, where incoming photons initiate reactions in the

top-most molecules. There is also some evidence that, under

extremely bright

desert

sunlight, traces of nitrogen and

water absorbed on titanium and zinc oxides can be photo-

chemically converted to ammonia. Such processes are no

doubt also important on planetary surfaces. See also Air pollu-

tion; Air quality; Emission; Los Angeles Basin

[Peter Brimblecombe]

ESOURCES

OOKS

Findlayson-Pitts, B. J., and J. N. Pitts. Atmospheric Chemistry. New York:

Wiley, 1986.

Photochemical smog

A form of

smog

that characterizes polluted atmospheres

where high concentrations of

nitrogen oxides

and volatile

organic compounds--often from gas-driven automobiles--

mixed with sunlight promote a series of photochemical reac-

tions that lead to the formation of

ozone

and a range of

oxidized and nitrated organic compounds. The smog turns

brownish in color and lowers

visibility

towards the middle

of the day as sunlight becomes intense. The smog also causes

eye irritation and a range of less distinct short- and long-

term health effects. Photochemical smog, though typified by

the

atmosphere

of the

Los Angeles Basin

, is increasingly

found in cities all over the world where volatile fuels are used.

Photodegradable plastic

Plastics

are clearly one of the great chemical inventions of

all time. It would probably be impossible to list all the ways