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

This content is available online at .

Available for free at Connexions 71 72

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-

Available for free at Connexions 73

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.

Available for free at Connexions 74

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

Available for free at Connexions 75

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

Available for free at Connexions 76

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.

Available for free at Connexions