Study Guide 5
Chapter 16
AIR, WATER AND SOIL 1
16.1 AIR, WATER AND SOIL
16.1.1 INTRODUCTION
Human activities release a variety of substances into the biosphere, many of which negatively aect the
environment. Pollutants discharged into the environment can accumulate in the air, water, or soil. Chemicals
discharged into the air that have a direct impact on the environment are called primary pollutants. These
primary pollutants sometimes react with other chemicals in the air to produce secondary pollutants.
A wide variety of chemicals and organisms are discharged into lakes, rivers and oceans daily. Left
untreated, this sewage and industrial waste has a serious impact on the water quality, not only in the
immediate area, but also downstream.
16.1.2 AIR POLLUTANTS
The eight classes of air pollutants are: oxides of carbon, sulfur and nitrogen, volatile organic compounds,
suspended particulate matter, photochemical oxidants, radioactive substances and hazardous air pollutants.
Oxides of carbon includecarbon monoxide (CO) andcarbon dioxide (CO2). Carbon monoxide,
a primary pollutant, is mainly produced by the incomplete combustion of fossil fuels. It is also present in
cigarette smoke. The colorless, odorless gas is poisonous to air-breathing animals. Carbon monoxide binds to
hemoglobin, impeding delivery of oxygen to cells. This causes dizziness, nausea, drowsiness, and headaches;
at high concentrations it can cause death. Carbon monoxide pollution from automobiles can be reduced
through the use of catalytic converters and oxygenated fuels. Carbon dioxide is produced by the complete combustion of fossil fuels. It is considered a greenhouse
gas because it heats up the atmosphere by absorbing infrared radiation. As a result of this characteristic,
excess amounts of carbon dioxide in the atmosphere may contribute to global warming. Carbon dioxide can
also react with water in the atmosphere and produce slightly acidic rain. Carbon dioxide emissions can be
reduced by limiting the amount of fossil fuels burned. Oxides of sulfur includesulfur dioxide (SO2) andsulfur trioxide (SO3). Sulfur oxides are primarily
produced by the combustion of coal and oil. Oxides of sulfur have a characteristic rotten egg odor, and
inhalation of them can lead to respiratory system damage. They react with atmospheric water to produce
sulfuric acid, which precipitates as acid rain or acid fog. Acid rain is a secondary pollutant that acidies
lakes and streams, rendering the water unt for aquatic life. It also corrodes metals, and dissolves limestone
and marble structures. Oxides of sulfur can be removed from industrial smokestack gases by "scrubbing"
the emissions, by electrostatically precipitating the sulfur, by ltration, or by combining them with water,
thereby producing sulfuric acid which can be used commercially. 1
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CHAPTER 16. AIR, WATER AND SOIL
Oxides of nitrogen include:nitric oxide (NO),nitrogen dioxide (NO2), andnitrous oxide (N2O).
Nitric oxide is a clear, colorless gas formed during the combustion of fossil fuels. Nitrogen dioxide forms when
nitric oxide reacts with atmospheric oxygen; the reddish-brown pungent gas is considered to be a secondary
pollutant. Exposure to oxides of nitrogen can cause lung damage, aggravate asthma and bronchitis, and
increase susceptibility to the u and colds. Nitrogen dioxide can combine with atmospheric water to form
nitric acid, which is precipitated as acid rain. Nitrogen dioxide is also a key ingredient in the formation of
photochemical smog, and nitrous oxide is a greenhouse gas. Automobile emissions of these pollutants can
be reduced by catalytic converters which convert them to molecular nitrogen and oxygen. Volatile organic compounds (VOCs) includehydrocarbons such as methane (CH4), propane
(C3H8), and octane (C8H18), and chlorouorocarbons (CFCs)such as dichlorodiuoromethane
(CCl2F2). Hydrocarbons are released into the atmosphere in automobile exhaust and from the evaporation of
gasoline. They contribute to the formation of photochemical smog. Chlorouorocarbons were used as
propellants for aerosols and as refrigerants until it was discovered they can cause depletion of the protective
ozone layer. Volatile organic compound emissions can be reduced by using vapor-recovery gasoline nozzles
at service stations and by burning oxygenated gasoline in automobile engines.
Suspended particulate matter consists of tiny particles of dust, soot, asbestos, and salts, and of
microscopic droplets of liquids such as sulfuric acid and pesticides. Sources of these pollutants include the
combustion of fossil fuel (e.g. diesel engines) and road and building construction activity. Exposure to these
particles can lead to respiratory irritation, reduction of lung capacity, lung cancer, and emphysema. Photochemical oxidants are primarily produced during the formation of photochemical smog. Ozone
(O3) is a highly reactive, irritating gas that causes breathing problems, as well as eye, nose, and throat
irritation. It also aggravates asthma, bronchitis, and heart disease. Ozone and other photochemical oxidants
can damage or kill plants, reduce visibility, and degrade rubber, paint, and clothes. Photochemical oxidants
are secondary pollutants, and can be controlled by reducing the amount of nitrogen dioxide in the atmosphere. Radioactive substances include radon-222, iodine-131, and strontium-90. Radonis gas produced during
the decay of uranium that is naturally present in rocks and building materials made with these rocks. It
is known to cause lung cancer in humans. The other radioisotopes are produced by nuclear power plants
(iodine-131) or are contained in the fallout from atmospheric nuclear testing (strontium-90). They can be
introduced into the food chain through plants and become incorporated in the tissues of humans and other
animals. Their ionizing radiation can produce cancers, especially those related to the thyroid and bone. Hazardous air pollutants include benzene(C6H6) and carbon tetrachloride (CCl4). Benzene is a
common organic solvent with numerous industrial uses. Carbon tetrachloride was formerly used as a solvent
in the dry cleaning business. It is still used in industrial processes. Exposure to these compounds can cause
cancer, birth defects and central nervous system problems.
16.1.3 WATER POLLUTANTS
The eight classes of water pollutants are: infectious agents, oxygen-depleting wastes, inorganic chemicals,
organic chemicals, plant nutrient pollutants, sediments, radioactive materials and thermal pollution. Infec-
tious agents such as bacteria, viruses, and parasitic worms enter water from human and animal waste, and
cause diseases such as typhoid fever, cholera, hepatitis, amoebic dysentery, and schistosomiasis, a condition
marked by blood loss and tissue damage. Oxygen-depleting wastes include animal manure in feedlot and farm runo, plant debris, industrial
discharge, and urban sewage. They are consumed by aerobic bacteria. Excessive growth of these organisms
can deplete water of dissolved oxygen which leads to eutrophication and the eventual death of oxygen-
consuming aquatic life. Inorganic chemical pollutants include mineral acids, toxic metals such as lead, cadmium, mercury,
and hexavalent chromium, and mineral salts. They are found in industrial discharge, chemicals in household
wastewater, and seepage from municipal dumps and landlls. The presence of inorganic chemical pollutants
in water can render it undrinkable, as well as cause cancer and birth defects. In addition, sucient concen-
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trations of these chemicals in water can kill sh and other aquatic life, cause lower crop yields due to plant
damage, and corrode metals. Organic chemical pollutants encompass a wide variety of compounds including oil, gasoline, pesticides,
and organic solvents. They all degrade the quality of the water into which they are discharged. Sources
of these pollutants include industrial discharge and runo from farms and urban areas. Sometimes these
chemicals enter aquatic ecosystems directly when sprayed on lakes and ponds (e.g. for mosquito control).
These types of chemicals can cause cancer, damage the central nervous system and cause birth defects in
humans. Plant nutrient pollutants are found mainly in urban sewage, runo from farms and gardens, and house-
hold wastewater. These chemicals include nitrates (NO3-), phosphates (PO43-) and ammonium (NH4+) salts
commonly found in fertilizers and detergents. Too much plant nutrients in the water can cause excessive
algae growth in lakes or ponds. This, in turn, results in the production of large amounts of oxygen-depleting
wastes. The subsequent loss of dissolved oxygen causes eutrophication of the lakes or ponds. Erosion of soils is the main process contributing sediments, orsilts , to water bodies. Sediments can cloud
the water of streams and rivers, reducing the amount of available sunlight to aquatic plants. The concurrent
reduction in photosynthesis can disrupt the local ecosystem. Soil from croplands deposited in lakes and
streams can carry pesticides, bacteria, and other substances that are harmful to aquatic life. Sediments can
also ll up or clog lakes, reservoirs, and waterways limiting human use and disrupting habitats. Radioactive materials such as iodine-131 and strontium-90 are found in nuclear power plant euents and
fallout from atmospheric nuclear testing. They can be introduced into the food chain through plants and
become incorporated in body tissues of humans and animals. Their ionizing radiation can produce cancers,
especially in the thyroid and bone where they tend to concentrate.
A power generating plant commonly discharges water used for cooling into a nearby river, lake, or ocean.
Because the discharged water can be signicantly warmer than the ambient environment, it represents a
source of thermal pollution . Industrial discharges are also sources of thermal pollution. The increased
temperature of the water may locally deplete dissolved oxygen and exceed the range of tolerance of some
aquatic species, thus disrupting the local ecosystem. Processing water in treatment plants can reduce the amounts of infectious agents, oxygen-depleting
wastes, inorganic chemicals, organic chemicals and plant nutrients. Bans and restrictions on the use of certain
chemicals, such as those on DDT and hexavalent chromium compounds, are also very helpful in reducing
the amounts of these chemicals in the environment. By limiting exposure to these harmful substances, their
negative eects on humans and local ecosystems can be greatly reduced.
16.1.4 SOIL POLLUTANTS
The persistence of pesticides in the soil is related to how quickly these chemicals degrade in the environment.
There are three ways pesticides are degraded in the soil: biodegradation,chemical degradation , and
photochemical degradation . Microorganism activity plays the predominant role in the biodegradation of
pesticides. Water plays an important role in the chemical degradation of pesticides (e.g. some pesticides are
hydrolyzed on the surfaces of minerals by water). Exposure to sunlight can also degrade some pesticides. A variety of pesticides are used to control insects, weeds, fungi, and mildew in agricultural, garden, and
household environments. There are three classes of pesticides: insecticides, which kill insects; herbicides,
which kill plants; and fungicides, which kill fungi. Each of these classes includes dierent types of chemicals.
These chemicals dier in chemical composition, chemical action, toxicity, and persistence (residence time)
in the environment. Some of these pesticides can bioaccumulate (e.g. they concentrate in specic plant and
animal tissues and organs). Pesticides can accumulate in the soil if their structures are not easily broken
down in the environment. Besides rendering the soil toxic to other living organisms, these pesticides may
leach out into the groundwater, polluting water supplies. The ve classes of insecticides are: chlorinated hydrocarbons, organophosphates, carbamates, botanicals
and synthetic botanicals. Chlorinated hydrocarbons such as DDT, are highly toxic in birds and shes,
but have relatively low toxicity in mammals. They persist in the environment, lasting for many months
or years. Because of their toxicity and persistence, their use as insecticides has been somewhat restricted.
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CHAPTER 16. AIR, WATER AND SOIL
Organophosphates , such asMalathion , are more poisonous than other types of insecticides, but have
much shorter residence times in the environment. Thus, they do not persist in the environment and cannot
bioaccumulate. Carbamates, such asSevin, are generally less toxic to mammals than are organophos-
phates. They also have a relatively low persistence in the environment and usually do not bioaccumulate.
Botanicals , such ascamphor, are derived from plant sources. Many of these compounds are toxic to
mammals, birds, and aquatic life. Their persistence in the environment is relatively low, and as a result
bioaccumulation is not a problem. Synthetic botanicals, such asAllethrin , generally have a low toxicity
for mammals, birds, and aquatic life, but it is unclear how persistent they are and whether or not they
bioaccumulate. The three classes of herbicides are: contact chemicals, systemic chemicals and soil sterilants. Most
herbicides do not persist in the soil for very long. Contact chemicalsare applied directly to plants, and
cause rapid cell membrane deterioration. One such herbicide, Paraquat, received notoriety when it was used
as a defoliant on marijuana elds. Paraquat is toxic to humans, but does not bioaccumulate. Systemic
chemicals , such as Alar, are taken up by the roots and foliage of plants, and are of low to moderate toxicity
to mammals and birds; some systemic herbicides are highly toxic to shes. These compounds do not have a
tendency to bioaccumulate. Soil sterilantssuch asDiphenamid , render the soil in which the plants lives
toxic. These chemicals have a low toxicity in animals, and do not bioaccumulate. Fungicides are used to kill or inhibit the growth of fungi. They can be separated into two categories:
protectants and systemics. Protectant fungicides, such as Captan, protect the plant against infection at the
site of application, but do not penetrate into the plant. System fungicides, such as Sovran, are absorbed
through the plant's roots and leaves and prevent disease from developing on parts of the plant away from
the site of application. Fungicides are not very toxic and are moderately persistent in the environment.
Soil can absorb vast amount of pollutants besides pesticides every year. Sulfuric acid rain is converted in
soil to sulfates and nitric acid rain produces nitrates in the soil. Both of these can function as plant nutrient
pollutants. Suspended particulate matter from the atmosphere can accumulate in the soil, bringing with it
other pollutants such as toxic metals and radioactive materials.
16.1.5 Point and Non-point Pollution Sources
Environmental regulations are designed to control the amounts and eects of pollutants released by agricul-
tural, industrial, and domestic activities. These laws recognize two categories of pollution and polluters
point source and non-point source. Point Source Pollution
Point sources are single, discrete locations or facilities that emit pollution, like a factory, smokestack,
pipe, tunnel, ditch, container, automobile engine, or well.
Because point sources can be precisely located, the discharge of pollutants from them is relatively easy to
monitor and control. The United States Environmental Protection Agency, or EPA, sets emission standards
for particular chemicals and compounds. Then, outow from the point source is sampled, and the pollutants
in it are measured precisely to ensure that discharge levels are in compliance with regulations. New techniques to reduce emissions from point sources are more likely to be developed because their
eectiveness can be evaluated quickly and directly and because point source polluters have an obvious
nancial incentive to reduce waste and avoid regulatory nes. Non-point Source Pollution
Non-point sources are diuse and widespread. Contaminants are swept into waterways by rainfall and
snowmelt or blown into the air by the wind. They come from multiple sources, such as vehicles dripping
oil onto roads and parking lots, pesticides used on lawns and parks and elds, wastes deposited by livestock
and pets, or soil disturbed by construction or plowing.
Non-point source pollution is more dicult to regulate than point source emissions. Contamination is
measured not at the source, but at the destination. Samples are collected from the air, soil, and water, or
from the blood and tissues of organisms in polluted areas. The contribution of various non-point sources
to these pollution levels can only be estimated. EPA regulations cannot be directed at specic individuals
or businesses and are instead generally directed at municipalities. For example, federal standards are set
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for allowable levels of chemicals in drinking water, and communities are responsible for treating their water
until it meets those standards. It can be dicult to reduce many types of non-point source pollution because most of the people who
contribute to it are not directly faced with legal or nancial consequences. Individuals must be persuaded
that their activities are causing ecological harm and that they should alter their behavior or spend their
money to remedy the situation. Once they do, they may have to wait a long time for noticeable environmental
results.
16.1.6 Parts per million (ppm) and Micrograms per milliliter (ug/mL)
Very small quantities of some chemicals can have a large impact on organisms. Because of this, substances
that are present in trace amounts, such as nutrients and contaminants, are usually measured and recorded
using very small units. Two of the most common measures are parts per million and micrograms per milliliter. Micrograms per milliliter (ug/mL)
Micrograms per milliliter, or ug/mL, measures mass per volume. It is generally used to measure the
concentration of a substance dissolved or suspended in a liquid. One microgram is one millionth of a gram
(1 ug = 0.0000001 g), and one milliliter is one thousandth of a liter. Parts per million (ppm)
Parts per million, abbreviated as ppm, is a unitless measure of proportion. It is obtained by dividing
the amount of a substance in a sample by the amount of the entire sample, and then multiplying by 106. In
other words, if some quantity of gas, liquid, or solid is divided into one million parts, the number of those
parts made up of any specic substance is the ppm of that substance. For example, if 1 mL of gasoline is
mixed with 999,999 mL of water, the water contains 1 ppm of gas. Concentration Equivalents
Since a microgram is one millionth of a gram, and a milliliter of water equals one gram of water, ug/mL is
equivalent to parts per million. Ppm is also equivalent to many other proportional measurements, including
milligrams per liter (mg/L), milligrams per kilogram (mg/Kg), and pounds per acre (lb/acre). But parts per
million is often more useful in describing and comparing trace amounts of chemicals because it eliminates
specic units and is applicable to liquids, solids, and gases. Examples
Both ppm and ug/mL can be used to describe the amount of particulate dust in a sample of air:
If the total particulate dust in a one liter volume of air is 5 mg, there is 5 ppm of particulate dust in the
air that was sampled, since mg/L (milligrams per liter) = ppm. How much dye should you add to one gallon of water to achieve a nal 500 ppm mixture?
Concentration Measurements and Environmental Regulations
Because many toxins begin to have negative environmental eects at very low levels, their abundance in
ppm or ug/mL are used to set the limits of pollutants that are legally permitted in stack smoke, discharge
water, soil contamination, and so on. For example, coal red power plants may be limited to a discharge
of 0.5 ppm of SO2 in the stack smoke. If a plant's emissions exceed that amount, it may be in violation of
local or federal air quality standards and could be sub ject to a ne.
16.1.7 Pollution Eects on Wildlife
Not unreasonably, we tend to be most concerned by the impact of pollution on human health and interests.
However, there is growing documentation of the harm pollution is inicting on wildlife. The following are
just a small sample. Pesticides
The pesticide DDT was banned in the U.S. in 1972 because it caused raptor eggs to thin and break. But
residual DDT and other persistent organochlorine pesticides continue to impact wildlife today. Additionally,
DDT is still used in many other countries as the most eective control of malaria-bearing mosquitoes. Prescription Drugs
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CHAPTER 16. AIR, WATER AND SOIL
Prescription drugs, caeine, and other medications can pass through both the human body and sewage
treatment facilities, and are now present in many waterways. Some of these may be toxic to aquatic life.
Others, especially steroids, estrogen, testosterone and similar regulatory hormones, are likely to interfere
with the development of organisms. Heavy Metals
When hunters shoot animals with lead shot, but do not recover the dead or injured animals, the shot is
eventually ingested by other wildlife. The lead is concentrated as it passes up the food chain, and the top
predators, especially raptors, get lead poisoning. Many states now require the use of steel shot. Mining wastes also release toxic levels of substances like lead and mercury into waterways.
Water Acidication
Acid rain and snow is produced from the burning of high-sulfur coals in electrical power plants. Acid
mine run-o is caused by the reaction of rainwater with mine tailings. Acidication can sterilize water
bodies, killing o all aquatic ora and fauna. When wildfowl and other wildlife ingest this water, they can
be poisoned by heavy metals. Dioxin
Dioxin is generated by burning wastes and in the production of some papers and plastics. It accumulates
in animal fats and concentrates up the food chain, and has been linked to cancers and reproductive issues
in a number of species. Oil Spills
Oil spills have immediate devastating eects marine mammals and waterfowl coated with oil drown, are
poisoned, or die of hypothermia. Balls of oil that sink to the seaoor can smother organisms. Less obvious
eects include tumors and reproductive damage in shes and crustaceans caused by oil byproducts.
Noise Pollution
Chronic noise pollution from low-ying aircraft, snowmobiles, motorcycles, and trac can cause wildlife
to abandon habitats, lose reproductive function, and become more vulnerable to predation due to loss of
hearing. Light Pollution
Light pollution at night disorients bats, insects, and migratory birds.
Eutrophication
Eutrophication results from the addition of enriching agents detergents, fertilizers, and organic wastes
to water bodies. Explosive growth and subsequent decay of algae use up available oxygen, which in turn
suocates aquatic animals and plants. The change in water chemistry can also drive out native species. Sedimentation
Sediments eroded during construction or agricultural practices are washed into waterways, damaging sh
spawning grounds and smothering bottom dwelling organisms.
16.1.8 Summary
Studies of the eects of pollution on wildlife are of more than academic interest. Like the proverbial canary
in the coal mine, disease and damage in the natural world is often a harbinger of similar danger to ourselves.
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