PROCESSES AFFECTING

FATE AND TRANSPORT

OF CONTAMINANTS

PART 1

Chapter 1 The Extent of Global Pollution

Chapter 2 Physical-Chemical Characteristicsof Soils and the Subsurface

Chapter 3 Physical-Chemical Characteristicsof Water

Chapter 4 Physical-Chemical Characteristicsof the Atmosphere

Chapter 5 Biotic Characteristics of theEnvironment

Chapter 6 Physical Processes AffectingContaminant Transport and Fate

Chapter 7 Chemical Processes AffectingContaminant Transport and Fate

Chapter 8 Biological Processes AffectingContaminant Transport and Fate

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CHAPTER 1

THE EXTENT OF GLOBALPOLLUTION

I.L. Pepper, C.P. Gerba, and M.L. Brusseau

Pollution is ubiquitous, and can even cause beautiful sunsets. Photo courtesy Ian Pepper.

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4 Chapter 1 • The Extent of Global Pollution

1.1 SCIENCE AND POLLUTION

Pollution is ubiquitous and takes many forms and shapes.For example, the beautiful sunsets that we may see in theevening are often due to the interaction of light and atmo-spheric contaminants, as illustrated above.

Pollution can be defined as the accumulation and adverseaffects of contaminants or pollutants on human health andwelfare, and/or the environment. But in order to truly under-stand pollution, we must define the identity and nature of po-tential contaminants. Contaminants can result from waste ma-terials produced from the activity of living organisms,

INFORMATION BOX 1.1

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5I.L. Pepper, C.P. Gerba, and M.L. Brusseau

especially humans. However, contamination can also occurfrom natural processes such as arsenic dissolution frombedrock into groundwater, or air pollution from smoke that re-sults from natural fires. Pollutants are also ubiquitous in thatthey can be in the solid, liquid, or gaseous state. InformationBox 1.1 presents the major categories of pollutants and theirpredominant routes of human exposure. Clearly, many of theagents identified in Information Box 1.1 occur directlythrough activities such as mining or agriculture. But in addi-tion, pollution is also produced as an indirect result of humanactivity. For example, fossil fuel burning increases atmo-spheric carbon dioxide levels and increases global warming.Other classes of pollutants can occur due to poor waste man-agement or disposal, which can lead to the presence ofpathogenic microorganisms in water. Some examples of mi-crobial pathogens and associated diseases are shown in Table1.1. Another example of pollution due to human activity isaccidental spillage of organics that can be toxic, such as chlo-rinated solvents or petroleum hydrocarbons that contaminate

groundwater. Some common contaminants that find their wayinto the environment, with the potential to adversely affect hu-man health and welfare, are shown in Table 1.2.

In this textbook, we will discuss these major sources ofpollution in a science-based context, hence the name: Envi-ronmental and Pollution Science (Information Box 1.2).

The focus of the text will be to identify the basic scien-tific processes that control the transport and fate of pollutantsin the environment. We will also try to define the potentialfor adverse effects to human health and welfare, and theenvironment using a risk-based approach. Finally, we willpresent real world “case studies.” The diverse nature of thescientific disciplines needed to study pollution science areshown in Information Box 1.3. It is the holistic integration ofthese diverse and complex entities that presents the majorchallenge to understanding both “Environmental andPollution Science.”

1.2 GLOBAL PERSPECTIVE OFTHE ENVIRONMENT

The environment plays a key role in the ultimate fate of pollu-tants. The environment consists of land, water, and theatmosphere. All sources of pollution are initially released ordumped into one of these phases of the environment. Aspollutants interact with the environment, they undergo physi-cal and chemical changes, and are ultimately incorporated intothe environment. The environment thus acts as a continuuminto which all waste materials are placed. The pollutants, in

TABLE 1.1 Recently discovered microbes that have had a significant impact on human health.

AGENT MODE OF TRANSMISSION DISEASE / SYMPTOMS

Rotavirus Waterborne DiarrheaLegionella Waterborne Legionnaire’s diseaseEscherichia coli O157:H7 Foodborne Enterohemorrhagic fever,

Waterborne kidney failureHepatitis E virus Waterborne HepatitisCryptosporidium Waterborne Diarrhea

FoodborneCalicivirus Waterborne Diarrhea

FoodborneHelicobacter pylori Foodborne Stomach ulcers

WaterborneCyclospora Foodborne Diarrhea

Waterborne

TABLE 1.2 Common organic and inorganic contaminantsfound in the environment.

CHEMICAL CLASS FREQUENCY OF OCCURRENCE

Gasoline, fuel oil Very frequentPolycyclic aromatic Common

hydrocarbonsCreosote InfrequentAlcohols, ketones, esters CommonEthers CommonChlorinated organics Very frequentPolybrominated diphenyl

ethers (PBDEs)Polychlorinated biphenyls Infrequent

(PCBs)Nitroaromatics (TNT) CommonMetals (Cd, Cr, Cu, Hg, Ni, Common

Pb, Zn)Nitrate Common

From Environmental Microbiology © 2000, Academic Press,San Diego, CA.

Environmental and Pollution Science is the study of thephysical, chemical, and biological processesfundamental to the transport, fate, and mitigation ofcontaminants that arise from human activities as well asnatural processes.

INFORMATION BOX 1.2

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turn, obey the second law of thermodynamics: matter cannotbe destroyed; it is merely converted from one form to another.Thus, taken together, the way in which substances are addedto the environment, the rate at which these wastes are added,and the subsequent changes that occur determine the impact ofthe waste on the environment. It is important to recognize theconcept of the environment as a continuum, because manyphysical, chemical, and biological processes occur not withinone of these phases, such as the air alone, but rather at the in-terface between two phases such as the soil/water interface.

The concept of the continuum relies on the premise thatresources are utilized at a rate at which they can be replacedor renewed, and that wastes are added to the environment ata rate at which they can be assimilated without disturbing theenvironment. Historically, natural wastes were generated thatcould easily be broken down or transformed into beneficial,or at least benign, compounds. However, post-industrial con-tamination has resulted in the formation of xenobioticwaste—compounds that are foreign to natural ecosystemsand that are less subject to degradation. In some cases, naturalprocesses can actually enhance the toxicity of the pollutants.For example, organic compounds that are not themselves car-cinogenic can be microbially converted into carcinogenicsubstances. Other compounds, even those not normally con-sidered pollutants, can cause pollution if they are added to the

environment in quantities that result in high concentrations ofthese substances. An excellent example here is nitrate fertil-izer, which is often added to soil at high levels. Such nitratescan end up in drinking water supplies and cause methe-moglobinemia (blue baby disease) in newborn infants (seeChapter 16).

Some pollutants, such as microbial pathogens, are en-tirely natural and may be present in the environment at verylow concentrations. Even so, they are still capable of caus-ing pathogenic diseases in humans or animals. Such naturalmicroorganisms are also classified as pollutants, and theiroccurrence within the environment needs to be carefullycontrolled.

1.3 POLLUTION AND POPULATIONPRESSURES

To understand the relationship between population and pol-lution, let us examine a typical curve for the growth of a pureculture of bacteria in a liquid medium (Figure 1.1). Early on,the bacteria growing in the medium do not increase signifi-cantly in number, due to low population densities, which re-sults in organisms operating as separate entities. This initiallow-growth phase is known as the lag period. Next, the

6 Chapter 1 • The Extent of Global Pollution

INFORMATION BOX 1.3

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7I.L. Pepper, C.P. Gerba, and M.L. Brusseau

number of organisms increases exponentially for a finiteperiod of time. This phase of growth is known as the expo-nential phase or log phase. After this exponential phase ofgrowth, a stationary phase occurs, during which the totalnumber of organisms remains constant as new organisms areconstantly being produced while other organisms are dying.Finally, we observe the death phase, in which the totalnumber of organisms decreases. We know that bacteria re-produce by binary fission, so it is easy to see how a doublingof bacteria occurs during exponential growth. But whatcauses the stationary and death phases of growth?

Two mechanisms prevent the number of organismsfrom increasing ad infinitum: first, the organisms begin torun out of nutrients; and second, waste products build upwithin the growth medium and become toxic to the organ-isms. An analogous situation exists for humans. Initially, in

prehistoric times, population densities were low and popu-lation numbers did not increase significantly or rapidly(Figure 1.2.). During this time resources were plentiful;thus, the environment could easily accommodate theamount of wastes produced. Later, populations began to in-crease very rapidly. Although not exponential, this phase ofgrowth was comparable to the log phase of microbialgrowth. During this period then, large amounts of resourceswere utilized, and wastes were produced in ever-greaterquantities. This period of growth is still under way. How-ever, we seem to be approaching a period in which lack ofresources or buildup of wastes (i.e., pollution) will limitcontinued growth—hence the renewed interest in recyclingmaterials as well as in controlling, managing, and cleaningup waste materials. To do this, we must arrive at an under-standing of the predominant biotic and abiotic characteris-tics of the environment.

Currently the world population is 6.3 billion and in-creasing rapidly. This population pressure has caused intenseindustrial and agricultural activities that produce hazardouscontaminants in their own right. In addition, increased pop-ulations result in the production of wastes that at lowconcentrations are not hazardous, but which at high concen-trations become hazardous. Hence, concentrated animalfeedlot operations (CAFOs), where large numbers of ani-mals are kept in close proximity, require special attention tominimize potential pollution (see Chapter 27). Finally, notethat as the world population increases, people tend to relo-cate from sparsely populated rural areas to more congestedurban centers or “mega-cities.” Typically, urbanized areasconsume more natural resources and produce more waste per

Figure 1.1 Typical growth curve for a pure culture of bacteria.A � lag period, B � exponential phase, C � stationary phase,D � death phase. From Pollution Science © 1996, Academic Press,San Diego, CA.

Figure 1.2 World population increases from the inception of the human species. FromPopulation Reference Bureau, Inc., 1990. Adapted from Pollution Science © 1996, Academic Press,San Diego, CA.

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capita than rural areas. The trend towards mega-cities willintensify this problem.

1.4 OVERVIEW OF ENVIRONMENTALCHARACTERIZATION

In order to ascertain the potential or actual extent of pollu-tion that has occurred, it is necessary to undertake environ-mental monitoring of the polluted site (see Chapter 12; alsoArtiola et al., 2004). This frequently involves site charac-terization, which involves identifying the area and/or vol-ume of the environment which has been polluted. It canalso involve comparisons with nonpolluted control sites toevaluate normal background levels of contaminants. In or-der to undertake site characterization, it is important toestablish proper sampling regimens for the particular envi-ronmental sample, be it soil, water, or air. Here we providean overview of the basic strategies for environmentalsampling. Because so many choices are available, it is im-portant to ensure that quality assurance is addressed by de-veloping a quality assurance project plan (QAPP), asshown in Table 1.3.

1.4.1 Soil and the Subsurface

Physically, surface soil samples are easy to obtain usinginexpensive equipment such as a shovel or a soil auger(Figure 1.3).

Augers are useful in that they allow samples to betaken at exactly the same depth on every occasion. Augersare available that can take soil cores to a depth of 2 me-ters, in 1-foot increments. Typically a soil sample consistsof about 2 kilograms. Because soils are heterogeneous, itis frequently better to collect multiple cores that aremixed together to give a composite sample. Soil samplesthat are collected for microbial analysis should be kept onice while transported to the laboratory. Microbial analysesshould be performed as soon as possible to minimize theeffects of storage on microbial populations and should notbe air dried prior to analyses. Soils sampled for chemicalanalyses should be air dried and can then be kept indefi-nitely pending analysis.

For subsurface sampling, mechanical drill rigs, suchas rotary mud drilling (Figure 1.4) or hollow-stem augers(Figure 1.5), are necessary. Subsurface sampling is morecomplex and more expensive than surface soil sampling,particularly when deep subsurface sampling is attempted.

1.4.2 Water

Collecting water samples tends to be somewhat easier thansampling soils. First of all, water at a given site tends to bemore homogenous than soils, with less site-to-site variabilitybetween two samples collected within the same vicinity.Secondly, it is often physically easier to collect water sam-

Chapter 1 • The Extent of Global Pollution

TABLE 1.3 Collection and storage specifications for a QualityAssurance Project Plan (QAPP). a

Sampling strategies: Number and type of samples, locations,depths, times, intervals

Sampling methods: Specific techniques and equipment to be usedSample storage: Types of containers, preservation methods,

maximum holding times

aThe QAPP normally also includes details of the proposed microbialanalysis to be conducted on the soil samples.

From Environmental Microbiology © 2000, Academic Press,San Diego, CA.

Figure 1.3 Hand auger. From Environmental Microbiology © 2000,Academic Press, San Diego, CA.

Figure 1.4 Rotary mud drilling. With rotary drilling themechanical rotation of a drilling tool is used to create aborehole. Either air (air rotary drilling) or a fluid often called adrilling mud (mud rotary drilling) is forced down the drill stemto displace the borehole cuttings to the outside of the drill andupward to the surface. From Environmental Microbiology © 2000,Academic Press, San Diego, CA.

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9I.L. Pepper, C.P. Gerba, and M.L. Brusseau

impaction is the forced deposition of airborne particleson a solid surface. Two of the most commonly used de-vices for microbial air sampling are the SKC biosamplers(SKC-West Incorporated, Fullerton, CA) (Figure 1.6) andthe Andersen Six Stage Impaction Sampler (AndersonInstruments Incorporated, Atlanta, GA) (Figure 1.7) (seealso Chapter 27).

Figure 1.5 Diagram of a hollow-stem auger. Note the reverse threading on the outside of theauger. This is used to displace the borehole cuttings upward to the surface. A subcore of eachcore collected is taken using a split spoon sampler or a push tube. In either case, the outside ofthe core must be regarded as contaminated. Therefore, the outside of the core is shaved off witha sterile spatula or a subcore can be taken using a sterile plastic syringe. Alternatively, as shownin this figure, intact cores are automatically pared to remove the outer contaminated material,leaving an inner sterile core. From Environmental Microbiology © 2000, Academic Press, San Diego, CA.

ples. Surface water samples can be collected in wide-mouthpolyethylene jars or with a bucket. Subsurface water samplescan be collected through the use of bailers or garden hoselines submerged to specific depths and attached to a pump.The amount of water collected can be a few milliliters, suchas when routine analyses such as pH are to be done. In othercases, large volumes need to be collected (1000 liters), as inthe case of determining the presence of enteric viruses in ma-rine waters. Normally water samples are kept as cool as pos-sible in sealed containers to prevent microbial and chemicalactivity and preclude evaporation.

1.4.3 Air

The collection of air samples for analysis can be done in avariety of ways. In some cases samples of air are diverted au-tomatically into instruments for continuous measurementof pollutant concentrations. In yet other applications, airsamples are collected in sample bags for later laboratorychemical analysis.

Aerosolized biological particles including microor-ganisms are known as bioaerosols. Many devices havebeen designed for the collection of bioaerosols, includingimpingement and impaction devices. Impingement is thetrapping of airborne particles in a liquid matrix. In contrast, Figure 1.6 SKC Biosamplers. Photo courtesy J. Brooks.

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level of milligrams per liter. A newer improved flamelessAA technique using a graphite furnace improved detectionlimits to the level of micrograms per liter. The latest tech-nology utilizes inductively coupled plasma (ICP) spec-troscopy, which has detection limits of nanograms per liter.

Advanced methods have been developed that allow in-vestigation of physical, chemical, and microbial processesat the molecular scale. For example, atomic force mi-croscopy is being used to examine the distribution of atomsand molecules at solid surfaces. X-ray absorption finestructure spectroscopy is being used to determine the ge-ometry, composition, and mode of attachment of ions atmineral-water interfaces. Nuclear magnetic resonancemethods are being used to study the interaction of contam-inants with soil organic matter. Recent advances in imag-ing methods, such as synchrotron x-ray microtomography,have allowed us to begin to directly measure the pore-scaledistribution of fluids in porous media. This will provide abetter understanding of how water and organic liquidsmove through the subsurface.

1.5.2 Advances in Biological Analysis

Great progress has been made towards new innovative tech-nology for characterizing microbial properties and activities.State-of-the-art approaches are shown in Table 1.4.

The use of molecular technology in particular has revo-lutionized biological detection capabilities. The polymerasechain reaction based technique allows for detection of anorganism’s DNA at the nanogram level (Figure 1.8). Se-quence analysis using PCR and computer searches allows forenhanced identification of new microbes.

Overall, the advent of these new supersensitive tech-nologies allows us to reexamine the question of “How cleanis clean?” Environmental samples that were analyzeddecades ago and found to contain no detectable heavy metalswere considered pristine. Using today’s technology allowsfor quantification of metal concentrations, albeit at ex-tremely low levels. Perhaps the real question is not “Are thesamples pristine,” but “Are they pristine enough?”

1.6 THE RISK BASED APPROACH TOPOLLUTION SCIENCE

Risk assessment is an integral part of pollution science andis covered in detail in Chapter 14. Its importance lies in thefact that it provides a quantifiable answer to the question “Isthis polluted site safe?” Throughout this text whereappropriate, we evaluate two types of risk assessment:health-based risks and ecological risks. The former focuseson human health, whereas the latter focuses on potentialdetrimental effects to parts of the environment or the entireenvironment.

Regardless of the focus, the risk assessment processconsists of four basic steps (Information Box 1.4).

10 Chapter 1 • The Extent of Global Pollution

Figure 1.7 Schematic representation of the Andersen six-stageimpaction air sampler. Air enters through the top of thesampler and larger particles are impacted upon the surface ofthe petri dish on stage 1. Smaller particles, which lack sufficientimpaction potential, follow the air stream to the subsequentlevels. As the air stream passes through each stage, the air ve-locity increases, thus increasing the impaction potential, so thatparticles are trapped on each level based upon their size.Therefore, larger particles are trapped efficiently on stage 1 andslightly smaller particles on stage 2 and so on until even verysmall particles are trapped on stage 6. The Andersen six-stagesampler thus separates particles based upon their size. FromEnvironmental Microbiology © 2000, Academic Press, San Diego, CA.

1.5 ADVANCES IN ANALYTICALDETECTION TECHNOLOGY

When evaluating environmental quality, the question is fre-quently asked, “How clean is clean?” The answer to thequestion depends on the technologies available for analyticaldetection of contaminants. As our technologies improve,they are continually redefining our understanding of the term“clean.” Using new instruments and innovative techniques,we are increasingly capable of measuring environmentalparameters with greater sensitivity and accuracy.

1.5.1 Advances in Chemical Analysis

An example of enhanced chemical detection technology isillustrated by the determination of heavy metal concentra-tions in water. Thirty years ago, atomic absorption (AA)spectroscopy was utilized, which gave measurements at the

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11I.L. Pepper, C.P. Gerba, and M.L. Brusseau

TABLE 1.4 State-of-the-art approaches to the monitoring of microbial propertiesand activities.

TECHNIQUE FUNCTION

I. MicrobialEpifluorescent microscopy Detection of specific microbesElectron microscopy Magnification up to 106

Confocal scanning microscopy 3-D images

II. PhysiologicalCarbon respiration Heterotrophic activityRadiolabeled tracers Degradation of specific compoundsEnzyme assays Specific microbial transformations

III. ImmunologicalImmunoassays Detection of specific microbesImmunocytochemical assays Location of specific antigensImmunoprecipitation assays Semi-quantitative determination of antigens

IV. Nucleic Acid BasedPolymerase chain reaction (PCR) Detection of genes or specific microbesReverse transcriptase (RT-PCR) Detection of mRNA or virusesGene probes Detection of genesDenaturing gradient gel electrophoresis Microbial diversity changesPlasmid profile analysis Unique microbial functions

From Environmental Monitoring and Characterization © 2004. Elsevier Academic Press, San Diego.

Figure 1.8 (a) An automated PCR thermalcycler that is usedto amplify target DNA. (b) A gel stained with ethidium bro-mide. From Pollution Science © 1996, Academic Press, San Diego, CA.

The Risk Assessment Process

Hazard identification—Defining the hazard and natureof the harm; for example, identifying a chemicalcontaminant, such as lead or carbon tetrachloride, anddocumenting its toxic effects on humans.Exposure assessment—Determining the concentrationof a contaminating agent in the environment andestimating its rate of intake in target organisms; forexample, finding the concentration of aflatoxin in peanutbutter and determining the dose an “average” personwould receive.Dose-response assessment—Quantifying the adverseeffects arising from exposure to a hazardous agent basedon the degree of exposure. This assessment is usuallyexpressed mathematically as a plot showing the responsein living organisms to increasing doses of the agent.Risk characterization—Estimating the potential impactof a hazard based on the severity of its effects and theamount of exposure.

INFORMATION BOX 1.4

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ity since the advent of Superfund in 1980, a federalprogram designed to support such activities. The numerousmethods available for remediation of hazardous waste siteswill be reviewed in Chapter 19. Over the past two decadeswe have learned that once contaminated, sites can not becompletely cleaned up, and also that site remediation is of-ten very expensive. This leads to the axiom of pollutionprevention: that preventing pollution from occurring in thefirst place is much preferred to the alternative. This in turnleads back to the use of best management practices for pol-lution control.

Ecosystems damaged through human activity or naturalprocesses may lose productivity or sustainability. Examplesof this issue include the loss of native vegetation via defor-estation and loss of soil fertility due to salinization, thebuildup of salts in soil. These damaged ecosystems need to berestored through a process analogous to hazardous-waste siteremediation. The basis of, and methods used for ecosystemrestoration are discussed in Chapter 20.

12 Chapter 1 • The Extent of Global Pollution

REFERENCES AND ADDITIONAL READING

Artiola J.F., Brusseau M.L., and Pepper I.L. (2004)Environmental Monitoring and Characterization. AcademicPress, San Diego, California.

Maier R.M., Pepper I.L., and Gerba C.P. (2000) A Textbook of Environmental Microbiology. Academic Press, San Diego, California.

Pepper I.L., Gerba C.P., and Brusseau M.L. (1996) PollutionScience. Academic Press, San Diego, California.

Once a given risk has been calculated, informed deci-sions can be made with respect to the severity of the pollution,and what should be done about it.

1.7 WASTE MANAGEMENT, SITEREMEDIATION, AND ECOSYSTEMRESTORATION

As noted above, human activities produce enormous volumesof waste, much of which ends up in the environment and hasthe potential to cause pollution. Improper management of thiswaste exacerbates the pollution problem. Thus, significant re-sources are expended to control and treat this waste. Thesemethods will be discussed in Part 5 of the book.

Once a site becomes contaminated with hazardouspollutants and is judged to pose a risk to human health orthe environment, it must be cleaned up or remediated. Re-mediation of contaminated sites has become a major activ-

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