Application of environmental aquatic chemistry

Application of environmental aquatic chemistry

CRC Press is an imprint of the

Taylor & Francis Group, an informa business

Boca Raton London New York

Eugene R Weiner

Second Edition

Applications of

Environmental Aquatic

Chemistry

A Practical Guide

CRC Press

Taylor & Francis Group

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Library of Congress Cataloging-in-Publication Data

Weiner, Eugene R.

Applications of environmental aquatic chemistry : a practical guide / Eugene R Weiner 2nd ed.

p cm.

Rev ed of: Applications of environmental chemistry / Eugene R Weiner 2000.

Includes bibliographical references and index.

ISBN 978-0-8493-9066-1 (alk paper)

1 Environmental chemistry 2 Water quality I Weiner, Eugene R

Applications of environmental chemistry II Title

Preface to the Second Edition

Preface to the First Edition

Author

Chapter 1

Water Quality

1.1 Defining Environmental Water Quality

1.1.1 Water-Use Classifications and Water Quality Standards1.1.2 Water Quality Classifications and Standards

for Natural Waters

1.1.3 Setting Numerical Water Quality Standards

1.1.4 Typical Water-Use Classifications

1.3.1 What Impurities Are Present?

1.3.2 How Much of Each Impurity Is Present?

1.3.3 Working with Concentrations

1.3.4 Moles and Equivalents

1.3.4.1 Working with Equivalent Weights

1.3.5 Case History Example

1.3.6 How Do Impurities Influence Water Quality?

Exercises

Chapter 2

Contaminant Behavior in the Environment: Basic Principles

2.1 Behavior of Contaminants in Natural Waters

2.1.1 Important Properties of Pollutants

2.1.2 Important Properties of Water and Soil

2.2 What Are the Fates of Different Pollutants?

2.3 Processes That Remove Pollutants from Water

2.3.1 Natural Attenuation

2.4.5 Inorganic Nonmetal Species

2.5 Chemical and Physical Reactions in the Water Environment2.6 Partitioning Behavior of Pollutants

2.6.1 Partitioning from a Diesel Oil Spill

2.7 Intermolecular Forces

2.7.1 Temperature Dependent Phase Changes

2.7.2 Volatility, Solubility, and Sorption

2.7.3 Predicting Relative Attractive Forces

2.8 Origins of Intermolecular Forces: Electronegativities,Chemical Bonds, and Molecular Geometry

2.8.1 Chemical Bonds

2.8.2 Chemical Bond Dipole Moments

2.8.3 Molecular Geometry and Molecular Polarity2.8.4 Examples of Nonpolar Molecules

2.8.5 Examples of Polar Molecules

2.8.6 The Nature of Intermolecular Attractions

2.8.7 Comparative Strengths of Intermolecular Attractions2.9 Solubility and Intermolecular Attractions

Exercises

Chapter 3

Major Water Quality Parameters and Applications

3.1 Interactions among Water Quality Parameters

3.5 Acidit y and Alka linity

3.9.4 Water Quality Criteria and Standards for Ammonia3.9.5 Nitrite and Nitrate

3.9.6 Water Quality Criteria and Standards for Nitrate

3.9.7 Methods for Removing Nitrogen from Wastewater

for H2S3.10.2 Case Study

3.10.2.1 Odors of Biological Origin in Water (Mostly

Hydrogen Sulfide and Ammonia)3.10.2.2 Environmental Chemistry of Hydrogen Sulfide3.10.2.3 Chemical Control of Odors

3.10.2.4 pH control

3.10.2.5 Oxidation

3.10.2.6 Eliminate Reducing Conditions Caused

by Decomposing Organic Matter3.10.2.7 Sorption to Activated Charcoal

3.11.6 Removal of Dissolved Phosphate

3.12 Solids (Total, Suspended, and Dissolved)

3.12.1 Background

3.12.2 TDS and Salinity

3.12.3 Specific Conductivity and TDS

3.12.4 TDS Test for Analytical Reliability

4.1.2 Mobility of Metals in the Water Environment

4.1.3 General Behavior of Dissolved Metals in Water

4.1.3.1 Hydrolysis Reactions

4.1.3.2 Hydrated Metals as Acids

4.1.4 Influence of pH on the Solubility of Metals

4.1.5 Influence of Redox Potential on the Solubility of Metals

4.1.5.1 Redox-Sensitive Metals: Cr, Cu, Hg, Fe, Mn4.1.5.2 Redox-Insensitive Metals: Al, Ba, Cd, Pb, Ni, Zn4.1.5.3 Redox-Sensitive Metalloids: As, Se

4.2 Metal Water Quality Standards

4.4.1.1 Summary of Acid Formation in Acid

Rock Drainage4.4.1.2 Non-iron Metal Sulfides Do Not Generate Acidity4.4.1.3 Acid-Base Potential of Soil

4.4.1.4 Determining the Acid-Base Potential

5.1.1.3 Secondary Mineral Formation

5.1.1.4 Roles of Plants and Soil Organisms

5.2 Soil Profiles

5.3.2 Some Properties of Humic Materials

5.3.2.1 Binding to Dissolved Species

5.6 Partition Coefficients

5.6.1 Air–Water Partition Coefficient (Henry’s Law)

5.6.2 Soil–Water Partition Coefficient

5.6.3 Determining KdExperimentally

5.6.4 Role of Soil Organic Matter

5.6.5 Octanol–Water Partition Coefficient, Kow

5.6.6 Estimating KdUsing Measured Solubility or Kow

5.7 Mobility of Contaminants in the Subsurface

5.7.1 Retardation Factor

5.7.2 Effect of Biodegradation on Effective Retardation Factor5.7.3 A Model for Sorption and Retardation

5.7.4 Soil Properties

5.8 Particulate Transport in Groundwater: Colloids

5.8.1 Colloid Particle Size and Surface Area

5.8.2 Particle Transport Properties

5.8.3 Electrical Charges on Colloids and Soil Surfaces

5.8.3.1 Electrical Double Layer

5.8.3.2 Adsorption and Coagulation

5.9 Case Study: Clearing Muddy Ponds

5.9.1 Pilot Jar Tests

5.9.1.1 Jar Test Procedure with Alum Coagulant

5.9.1.2 Jar Test Procedure with Gypsum Coagulant

6.1 Types and Properties of Nonaqueous Phase Liquids

6.2 General Characteristics of Petroleum Liquids, the Most

Common LNAPL

6.2.1 Types of Petroleum Products

6.2.2 Gasoline

6.2.3 Middle Distillates

6.2.4 Heavier Fuel Oils and Lubricating Oils

6.3 Behavior of Petroleum Hydrocarbons in the Subsurface

6.3.1 Soil Zones and Pore Space

6.3.2 Partitioning of Light Nonaqueous Phase Liquids

in the Subsurface

6.3.3 Processes of Subsurface Migration

6.3.4 Petroleum Mobility Through Soils

6.3.5 Behavior of LNAPL in Soils and Groundwater

6.3.6 Summary: Behavior of Spilled LNAPL

6.3.7 Weathering of Subsurface Contaminants

6.3.8 Petroleum Mobility and Solubility

6.4 Formation of Petroleum Contamination Plumes

6.4.1 Dissolved Contaminant Plume

6.4.2 Vapor Contaminant Plume

6.5 Estimating the Amount of LNAPL Free Product in the Subsurface6.5.1 How LNAPL Layer Thickness in the Subsurface AffectsLNAPL Layer Thickness in a Well

6.5.1.1 Effect of Soil Texture on LNAPL in the Subsurface

and in Wells6.5.1.2 Effect of Water Table Fluctuations on LNAPL

in the Subsurface and in Wells6.5.1.3 Effect of Water Table Fluctuations on LNAPL

Measurements in Wells6.6 Estimating the Amount of Residual LNAPL Immobilized

in the Subsurface

6.6.1 Subsurface Partitioning Loci of LNAPL Fuels

6.7 Chemical Fingerprinting of LNAPLs

6.7.1 First Steps in Chemical Fingerprinting of Fuel Hydrocarbons6.7.2 Identifying Fuel Types

6.7.3 Age-Dating Fuel Spills

7.2 DNAPL Free Product Mobility

7.2.1 DNAPL in the Vadose Zone

7.2.2 DNAPL at the Water Table

7.2.3 DNAPL in the Saturated Zone

7.3 Testing for the Presence of DNAPL

7.3.1 Contaminant Concentrations in Groundwater and Soil

That Indicate the Proximity of DNAPL

7.3.2 Calculation Method for Assessing Residual DNAPL in Soil7.4 Polychlorinated Biphenyls

Biodegradation and Bioremediation of LNAPLs and DNAPLs

8.1 Biodegradation and Bioremediation

8.2 Basic Requirements for Biodegradation

8.3 Biodegradation Processes

8.3.1 Case Study

8.3.1.1 Passive (Intrinsic) Bioremediation of Fuel LNAPLs:

California Survey8.4 Natural Aerobic Biodegradation of NAPL Hydrocarbons

8.5 Determining the Extent of Bioremediation of LNAPL

8.5.1 Using Chemical Indicators of the Rate of Intrinsic

Bioremediation

8.5.2 Hydrocarbon Contaminant Indicator

8.5.3 Electron Acceptor Indicators

8.5.4 Dissolved Oxygen Indicator

8.5.5 Nitrate Plus Nitrite Denitrification Indicator

8.5.6 Metal Reduction Indicators: Manganese (IV) to Manganese (II)and Iron (III) to Iron (II)

8.5.7 Sulfate Reduction Indicator

8.5.8 Methanogenesis (Methane Formation) Indicator

8.5.9 Redox Potential and Alkalinity as Biodegradation Indicators

8.5.9.1 Using Redox Potentials to Locate Anaerobic

Biodegradation within the Plume8.5.9.2 Using Alkalinity to Locate Anaerobic Biodegradation

within the Plume8.6 Bioremediation of Chlorinated DNAPLs

8.6.1 Reductive Dechlorination of Chlorinated Ethenes

8.6.2 Reductive Dechlorination of Chlorinated Ethanes

8.6.3 Case Study: Using Biodegradation Pathways

for Source Identification

9.2.1 A Few Basic Principles of Chemistry

9.2.1.1 Matter and Atoms

9.2.7 Balancing Nuclear Equations

9.2.8 Rates of Radioactive Decay

9.2.8.1 Half-Life

9.2.9 Radioactive Decay Series

9.2.10 Naturally Occurring Radionuclides

9.3 Emissions and Their Properties

9.4 Units of Radioactivity and Absorbed Radiation

9.4.1 Activity

9.4.3 Dose Equivalent

9.4.4 Unit Conversion Tables

9.4.4.1 Converting between Units of Dose Equivalent

and Units of Activity (Rems to Picocuries)9.5 Naturally Occurring Radioisotopes in the Environment

9.5.1 Case Study: Radionuclides in Public Water Supplies

9.5.2.1 Uranium Geology

9.5.2.2 Uranium in Water

Selected Topics in Environmental Chemistry

10.1 Agricultural Water Quality

10.2 Sodium Adsorption Ratio

10.2.1 What SAR Values Are Acceptable?

10.3 Deicing and Sanding of Roads: Controlling

10.3.4 Environmental Concerns of Chemical Deicers

10.3.5 Deicer Components and Their Potential

10.4.6.1 Hypochlorite

10.4.6.2 Definitions

10.4.7 Drawbacks to Use of Chlorine: Disinfection

By-Products

10.4.7.1 Trihalomethanes10.4.7.2 Chlorinated Phenols

10.4.9 Chlorine Dioxide Disinfection Treatment

10.4.10 Ozone Disinfection Treatment

10.5.3 Exchangeable Bases: Percent Base Saturation

10.5.4 CEC in Clays and Organic Matter

10.5.4.1 CEC in Clays10.5.4.2 CEC in Organic Matter10.5.5 Rates of Cation Exchange

10.6 Indicators of Fecal Contamination: Coliform

and Streptococci Bacteria

10.7.1 Pathogens in Treated Wastewater

10.7.2 Transport and Inactivation of Viruses in Soils

and Groundwater10.8 Oil and Grease

10.8.1 Oil and Grease Analysis

10.8.2 Silica Gel Treatment

10.9 Quality Assurance and Quality Control in Environmental Sampling10.9.1 QA/QC Has Different Field and Laboratory Components10.9.2 Essential Components of Field QA/QC

10.9.2.1 Sample Collection10.9.3 Field Sample Set

10.9.3.1 Quality Control Samples10.9.3.2 Blank Sample Requirements10.9.3.3 Field Duplicates and Spikes10.9.3.4 Understanding Laboratory Reported Results10.10 Case Study: Water Quality Profile of Groundwater

in Coal-Bed Methane Formations

10.10.1 Geochemical Explanation for the Stiff Patterns

10.10.1.1 Bicarbonate Anion Increase10.10.1.2 Calcium and Magnesium Cation Decrease10.10.1.3 Sodium Cation May Increase

10.10.1.4 Sulfate Anion DecreaseReferences

Parameters and Pollutants

Answers to Selected Chapter Exercises

Preface to the Second EditionMuch new material has been added to this second edition Besides a totally newchapter on radionuclides, the text has been reorganized and updated with separatechapters on metals, light nonaqueous phase liquids (LNAPLs), dense nonaqueousphase liquids (DNAPLs), and biodegradation Also, some end-of-chapter exerciseshave been added The dictionary of inorganic pollutants has been enlarged andsome important organic pollutants added The former appendices listing drinkingwater standards, water quality criteria, and sample collection protocols have beenomitted because these data are continually changing and are readily available on the

environmental professionals and students work with chemical information in theirwork and studies

Preface to the First Edition

By sensible definition, any by-product of a chemical operation for which there is noprofitable use is a waste The most convenient, least expensive way of disposing of saidwaste– up the chimney or down the river – is the best

From American Chemical Industry– A History, by W Haynes,

Van Nostrand Publishers, 1954The quote above describes the usual approach to waste disposal as it was practiced in

correcting problems caused by such misguided advice and go further toward trying

to maintain a non-degrading environment Regulations such as federal and stateClean Water Acts have set in motion a great effort to identify the chemical com-

contaminants regulated by the United States Government has increased from aboutfive in 1940 to over 150 in 1999

There are two distinct spheres of interest for an environmental professional,the ever-changing, constructed sphere of regulations and the comparativelystable sphere of the natural environment Much of the regulatory sphere is bounded

envir-onmental sphere is bounded by the innate behavior of chemicals of concern.While this book focuses on the environmental sphere, it makes an excursion into asmall part of the regulatory sphere in Chapter 1, where the rationale for stream

discussed

This book is intended to be a guide and reference for professionals and students

It is structured to be especially useful for those who must use the concepts of

inclination to learn all the relevant background material Chemistry topics that aremost important in environmental applications are succinctly summarized, with agenuine effort to walk the middle ground between too much and too little informa-tion Frequently used reference materials are also included, such as water solubilities,

conveniently offer ways to quickly estimate important aspects of the topic beingdiscussed

choice of inclusions and omissions, I have based my choices on the most frequently

asked questions from my colleagues and the material Ifind myself looking-up overand over again The main goal of this book is to offer non-chemist readers enoughchemical insight to help them contend with those environmental chemistry problemsthat seem to arise most frequently in the work of an environmental professional.

the book valuable as a general-purpose reference

to 1992, he was a consultant with the U.S Geological Survey, Water ResourcesDivision in Denver, and has consulted on environmental issues for many otherprivate, state, and federal entities After 27 years of research and teaching environ-mental and physical chemistry, he joined Wright Water Engineers Inc., an environ-

He received a BS in mathematics from Ohio University, an MS in physics fromthe University of Illinois, and a PhD in chemistry from Johns Hopkins University

He has authored and coauthored more than 400 research articles, books, and nical reports In recent years, he has conducted 16 short courses, dealing with themovement and fate of contaminants in the environment, in major cities around theUnited States for the continuing education program of the American Society of CivilEngineers

tech-1 Water Quality

1.1 DEFINING ENVIRONMENTAL WATER QUALITY

Water quality means different things to different people, depending on their goals forthe water A chemist in the laboratory will regard high-quality laboratory water aswater free from chemical impurities or suspended solids High-quality environmentalwater has different criteria The same chemist on a wilderness backpack trip mightidentify high-quality water as water in a pristine environment unaltered by human

substances that have to be removed or treated to produce safe and palatable drinkingwater A broad view of high-quality water will take into consideration its suitabilityfor particular uses

The U.S Congress recognized this when they enacted the Federal Water tion Control Act Amendments of 1972 (Public Law 92500, also known as the Clean

quality is a measure of its suitability for particular designated uses Implementing thelaw entails identifying these uses, setting standards that are protective of the desig-nated uses, and providing enforcement procedures that require compliance with thestandards

1.1.1 WATER-USECLASSIFICATIONS ANDWATERQUALITYSTANDARDS

In most parts of the world, the days are long gone when rivers, lakes, springs, andwells from which one can directly drink could readily meet almost all needs for high-quality water Where such water remains, mostly in high mountain regionsuntouched by mining, grazing, or industrial fallout, it must be protected by strictregulations In the United States, many states seek to preserve high-quality waterswith antidegradation policies But most of the water that is used for drinking watersupplies, irrigation, and industry, not to mention supplying a supporting habitat for

acceptable

Whenever it is recognized that water treatment is required, new issues ariseconcerning the degree of water quality sought, the costs involved, and, perhaps,restrictions imposed on the uses of the water Since it is economically impossible tomake all waters suitable for all purposes, it becomes necessary to designate for whichuses various waters are suitable

In this context, a practical evaluation of water quality depends on how the water

is used, as well as its chemical makeup The quality of water in a stream might beconsidered good if the water is used for irrigation but poor if it is used as a drinking

the water will be used and only then determine appropriate numerical standardsfor important water quality parameters that will support and protect the designatedwater uses

Strictly speaking, a water impurity is any substance in the water that is not a part

of a water molecule, and absolutely pure water is unattainable in any realistic watersample High-quality water is not pure; it just contains amounts of impurities too

acid rain and acid mine drainage; hardness and alkalinity decrease the solubility and

water generally is not desirable Water with very low concentrations of dissolvedimpurities is more corrosive (aggressive) to metal pipes than water containing ameasure of hardness, it cannot sustain aquatic life, and it certainly does not taste asgood as natural water saturated with dissolved oxygen and containing a healthy mix

of minerals

or neutral to the intended uses of the water

derived from a water molecule only, and is considered, when present in

For most purposes, the quality of water is not judged by its purity but rather by its

3)illustrates this point In drinking water supplies, nitrate concentrations greater than

used for potable water but may be of good quality for agricultural use

be established to protect each use

There are three different types of water quality standards set by state and federalregulations:

* The species Hþ, OH
, H 3 Oþ, H 5 Oþ2 can all be derived from water molecules only Species such as Cl
,

Naþ, MnO
4, Ca(OH) 2 , etc., clearly cannot.

1 Surface and groundwater standards, for the ambient quality of naturalwaters (rivers, lakes, reservoirs, wetlands, and groundwater) These stand-ards are chosen to protect the current and intended uses of natural waters, asdiscussed later.

chosen so that wastewaters discharging into natural waters do not cause the

flu-ent standards are affected by the ambiflu-ent standards for the receiving water,the assimilation capacity of the receiving water, the total pollutant loadcontributed by all dischargers into that water, etc

3 Drinking water standards, which apply both to groundwater used as a publicwater supply and to water delivered to the public from drinking watertreatment plants Drinking water standards are chosen to protect the publichealth

1.1.2 WATERQUALITY CLASSIFICATIONS ANDSTANDARDS

FORNATURAL WATERS

The following preliminary steps, taken by a state or federal agency, are a commonapproach to evaluating water quality in natural waters:

poten-tially be used (water supply, aquatic life, recreation, agriculture, etc.) Thesewill be the categories used for classifying uses for existing bodies of water

2 Set numerical water quality standards for physical and chemical istics that will support and protect the different water-use categories

bodies according to whether their present or potential quality is suitable forthe assigned water uses

para-meter, the more stringent standard will apply

It is clear that measuring the chemical composition of a water sample collected in

compared with the standards assigned to that water body If no standards are

information is collected about environmental and health effects of individual waterconstituents, it may be necessary to revise the standards for different water uses.Federal and state regulations require that water quality standards be reviewed

In addition to the review process for existing standards, the Safe Drinking WaterAct requires the Environmental Protection Agency (EPA) to periodically publish a

Dri nking Wa ter Con taminant Candidat e List (C CL), a lis t of contam inants that , ‘‘atthe time of publicati on, are not subje ct to any propos ed or promulgat ed nationalprim ary drinking wat er regulatio ns, are known or anti cipated to occur in publi c water

app ropriate regul atio ns or conclu de that no acti on is curren tly necess ary

1.1.3 S ETTING NUMERICAL WATER QUALITY S TANDARDS

Num erical water quali ty stand ards are chosen to protect the curren t an d intended uses

stand ards may b e estab lished wher e special condit ions exist, such as where aqua ticlif e has becom e acclimat ed to high levels of dissolved metals Each state has tables of

env ironment al wat ers, there are separate human health-bas ed stand ards for wat er used for public drinking water suppl ies, and for treated drinking wat er asdeli vered from a water treatmen t plant or, for some param eters such as lead andcop per, as delivered at the tap

ground-The states, not the U.S EPA, have the primary respon sibility for setting water

fica-tion s that serve as minim um requi reme nts for the state stand ards In addifica-tion, EPAissu es guidan ce and model regul ations regard ing stand ards, and EPA approva l isrequi red before stand ards can be adopte d or changed by states

ch lorine, nitrates, amm onia, phospho rus, sulfate, etc

co nductivity, p H, diss olved oxygen , hardness, tota l diss olved solids(T DS), chemi cal oxygen deman d, etc

gross beta emissions, etc

1.1.4 TYPICALWATER-USECLASSIFICATIONS

All states classify surface waters and groundwater according to their current and

1.1.4.1 Recreational

suitable for recreational activities in or on the water when the ingestion of small

* More information may be found at: www.epa.gov =safewater=ccl=index.html

quantities of water is likely to occur and prolonged and intimate contact with the

water-skiing, etc The Clean Water Act requires that waters shall be presumed, by default,

to be suitable or potentially suitable for class 1 uses, unless a use attainabilityanalysis demonstrates that there is not a reasonable potential for primary contactuses to occur in the water segments in question within the next 20 year period Forwaters that are not currently suitable for class 1 status but could be restored within 20

and class 1b:

primary contact uses have been documented or are presumed to be present.Waters for which no use attainability analysis has been performed demon-

failed to identify any existing class 1 uses of the water segment

water segments for which no use attainability analysis has been performed

reasonable level of inquiry has failed to identify any existing class 1 uses ofthe water segment

in or around the water, which are not included in the primary contact categories,

activities

1.1.4.2 Aquatic Life

Surface waters that presently support aquatic life uses as described below, or mayreasonably be expected to do so in the future due to the suitability of present

become suitable for such uses as a goal Separate standards should be applied toprotect:

sustaining a wide variety of cold water biota (considered to be the inhabitants ofwater in which temperatures normally do not exceed 208C), including sensitivespecies or (2) could sustain such biota but for correctable water quality conditions.Waters shall be considered capable of sustaining such biota where physical habitat,

impair-ment of the abundance and diversity of species

of sustaining a wide variety of warm water biota (considered to be the inhabitants

of water in which temperatures normally exceed 208C), including sensitive species

or (2) could sustain such biota but for correctable water quality conditions Watersshall be considered capable of sustaining such biota where physical habitat, waterflows or levels, and water quality conditions result in no substantial impairment of theabundance and diversity of species.

capable of sustaining a wide variety of cold or warm water biota, including sensitive

uncorrect-able water quality, which result in substantial impairment of the abundance anddiversity of species

1.1.4.3 Agriculture

Surface waters that are suitable or intended to become suitable for irrigation of cropsand that are not hazardous as drinking water for livestock

1.1.4.4 Domestic Water Supply

Surface waters that are suitable or intended to become suitable for potable water

waters will meet federal and state drinking water standards

1.1.4.5 Wetlands

circumstances do support, a prevalence of vegetation and organisms typicallyadapted for life under saturated soil conditions Surface water and groundwaterthat supply wetlands may be subject to the same standards applied to wetlands

stabi-lization, sediment or other pollutant retention, nutrient removal or transformation,biological diversity or uniqueness, wildlife diversity or abundance, aquatic lifediversity or abundance, and recreation

1.1.4.6 Groundwater

Subsurface waters in a zone of saturation that are at the ground surface or can

be brought to the ground surface or brought to surface waters through wells,springs, seeps, or other discharge areas Separate standards are applied to ground-water used for

Domestic use: Groundwaters that are used or are suitable for a potable watersupply

Agricultural use: Groundwaters that are used or are suitable for irrigating cropsand livestock water supply

Surface wat er quality prote ction : This classi ficati on is used for groundw atersthat feed surfa ce waters It places restrict ions on propos ed or existingactivities that could imp act groundw aters in a way that water quality

Potent ially usabl e : Gro undwaters that are not used for domesti c or agricu lturalpurposes, where backgro und level s are not known or do n ot meet humanhealth an d agric ultural stand ards, where TDS level s are less than 10,000

in the futur e

Limite d use : Gro undwaters where TDS levels are equal to or great er than

-cations are not met

1.1.5 STAYING UP -TO-DATE WITH S TANDARDS AND OTHER R EGULATIONSThis is a daunting challenge and, in the op inion of some, an imp ossible one Not onlyare the federal regul ations conti nually ch anging b ut also indiv idual states maypromulgat e different rules because of local needs The usual approac h is to obtainthe latest regul atory infor mation as the need aris es, always recognizing that yourcurren t know ledge may be outdated Part of the problem is that few envir onmen tal

first publi shes all propos ed and final regul ations

Fortun ately, most trade magaz ines and profes siona l journ als highlight importan tchanges in stand ards and regul ations that are of interest to their readers If you stayabreas t of this literat ure, you will be awar e of the regul atory chang es and theirimplic ations Fo r the great est level of securi ty, one has to often con tact stat e andfederal infor mation centers to ensure you are working with the regul ations that arecurren tly being enforc ed Amon g the most useful source s for stayi ng abreas t of the

has link s to infor mation hotlines , law s and regulatio ns, databa ses and soft ware,available publications, and other information sources Each state environmentalagency also has its own Web site

1.2 SOURCES OF WATER IMPURITIES

RULE OF THUMB

Generally, the most stringent standards are for drinking water and aquatic life

Thus, calcium carbonate (CaCO3) is a water impurity even though it is not ered hazardous and is not regulated Impurities can be divided into three classes: (1)regulated impurities (pollutants) considered harmful or aesthetically objectionable,(2) unregulated impurities not considered harmful, and (3) unregulated impurities notyet evaluated for their potential health risks.*

consid-In water quality analysis, unregulated as well as regulated impurities are ured For example, hardness is a water quality parameter that results mainly from thepresence of dissolved calcium and magnesium ions, which are unregulated impur-ities However, high hardness levels can partially mitigate the toxicity of manydissolved metals to aquatic life Hence, it is important to measure water hardness

meas-in order to evaluate the hazards of dissolved metals

Data concerning unregulated water impurities are also helpful for anticipatingcertain non-health-related potential problems, such as a tendency for the water to formdeposits in pipes and boilers, to cause metal corrosion, and for irrigation water to causesoils to swell and diminish their permeability Unregulated impurities can also help toidentify the recharge sources of wells and springs, identify the mineral formationsthrough which surface water or groundwater passes, and age-date water samples

1.2.1 NATURAL SOURCES

Snow and rainwater contain dissolved and particulate minerals collected fromatmospheric particulate matter, and small amounts of gases dissolved from atmos-pheric gases Snow and rainwater have virtually no bacterial content until they reachthe surface of the earth

the soil, there are innumerable opportunities for introduction into the water ofmineral, organic, and biological substances Water can dissolve at least a little ofnearly anything it contacts Because of its relatively high density, water can alsocarry suspended solids Even under pristine conditions, surface and groundwater willusually contain various dissolved and suspended chemical substances

1.2.2 HUMAN-CAUSEDSOURCES

Many human activities cause additional possibilities for water contamination Someimportant sources are

* The 1996 Amendments to the Safe Drinking Water Act created a Contaminant Candidate List and a process to determine if new regulations are needed to protect drinking water safety EPA is required to periodically publish a list of potential contaminants that, ‘‘at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation, which are known or antici- pated to occur in public water systems, and which may require regulation ’’

. Urban storm water runoff, which may contact all the debris of a city,

including spilled fuels, animal feces, dissolved metals, organic scraps,road salt, tire and brake particles, construction rubble, etc

Environmental professionals must remain alert to the possibility that natural impurity

of human-caused sources Whenever possible, one should obtain background surements that demonstrate what impurities are present in the absence of known human-caused contaminant sources For instance, groundwater in an area impacted by miningoften contains relatively high concentrations of dissolved metals Before any remedia-tion programs are initiated, it is important to determine what the groundwater quality

ground-water encounters subsurface mineral structures similar to those in the mined area

1.3 MEASURING IMPURITIES

There are four characteristics of water impurities that are important for an initialassessment of water quality:

1 What kinds of impurities are present? Are they regulated compounds?

2 How much of each impurity is present? Are any standards exceeded for thewater body being sampled?

Bene-ficial? Unaesthetic? Corrosive?

4 What is the fate of the impurities? How will their location, quantity, andchemical form change with time?

1.3.1 WHATIMPURITIESAREPRESENT?

The chemical content of a water sample is found by qualitative chemical analysis of

present but not the quantity (although qualitative and quantitative analyses are oftencombined in a single measurement) Some of the analytical methods used are gas andion chromatography, mass spectroscopy, optical emission and absorption spectros-copy, electrochemical probes, and immunoassay testing

1.3.2 HOWMUCH OFEACHIMPURITYISPRESENT?

The amount of impurity is found by quantitative chemical analysis of the water

interest for predicting the effect of an impurity on the environment It is used for

addition to concentration standards, an additional limit of total mass may be applied

to some rivers in the form of total maximum daily loads (TMDLs) of certainpollutants Total maximum daily loads are used in setting standards for waste

1.3.3 WORKING WITHCONCENTRATIONS

Unfortunately, there is not one all-purpose method for expressing concentration Thebest choice of concentration units depends in part on the medium (liquid, solid, orgas), and in part on the purpose of the measurement The example problems in thisand the following sections illustrate some applications of concentration calculations.For regulatory compliance purposes, concentration is usually expressed as mass

of impurity per unit volume or unit mass of sample

milli-grams (mg), micromilli-grams (mg), or nanomilli-grams (ng) of impurity per liter (L)

of water sample Although this is actually comparing a weight to a volume,

it is generally assumed that the liter of water sample weighs exactly 1000

of impurity in 1 million grams of water, or one part per million (1 ppm).*

milli-grams, micromilli-grams, or nanograms of impurity per kilogram of soil sample

as simply as in water or soils, because gas volumes and densities arestrongly dependent on temperature and pressure In addition, the amount

of some air pollutants (such as carbon monoxide or organic vapors) can be

as large or as greater than the oxygen and nitrogen levels in severelypolluted air; thus, the approximation of the footnote below, used for waterconcentrations, may not apply to air concentrations

For these reasons, parts per million for gases is different from parts per millionfor liquids and solids For liquids and solids, ppm is a ratio of two masses

* Note that the actual mass of the water sample includes the mass of the water plus the mass of the impurity Since 1 L of pure water at 48C and 1 atm pressure weigh 1000 g, there is an inherent assumption when equating 1 mg =L to 1 ppm, that the mass of the impurity in the sample is negligible compared to the mass of water and that the density of the sample does not change signi ficantly over the temperature and pressure ranges encountered in environmental sampling.

(sometimes written as ppm (w=w)), whereas for gases, ppm means a ratio of two

There is no consensus regarding the appropriate units by which to express trations of substances in air Air pollution standards are usually promulgated as ppm,whereas air pollutant concentrations in reports and other literature may be expressed as

be able to convert gas concentrations from one set of units to another The rules ofthumb box below illustrate the principles for converting between the two different

RULES OF THUMB

1.3.4 MOLES ANDEQUIVALENTS

For chemical calculations (as opposed to regulatory compliance calculations), centrations in any phase are usually expressed either as moles* of impurity per liter

sample Moles per liter are related to the number of impurity molecules, ratherthan the mass of impurity Because chemical reactions involve one-on-one molecularinteractions, regardless of the mass of the reacting molecules, moles are best forchemical calculations, such as balancing chemical reactions and calculating reaction

EXAMPLE 1

CALCULATING A CONCENTRATION IN WATER

A 45.6 mL water sample was found to contain 0.173 mg of sodium What is theconcentration in mg=L of sodium in the sample?

or 3.79 3 10
3g (3.79 mg) of sodium in 103g (1 L) of solution, or 3.79 3 10
6g (3.79 mg)

of sodium per gram of solution.)

* Operationally, 1 mole of any pure element or compound is that quantity of the substance that has a mass equal to the atomic or molecular weight, in grams, of that substance Thus, 1 mole of pure sodium (Na) metal is the amount that weighs 23.00 g; 1 mole of sodium chloride (NaCl) is the amount that weighs 58.45 g This arises from the definition of a mole (abbreviated mol in chemical notation, as in mol=L): the term mole indicates a particular number of things, just as a dozen indicates 12 things and a pair indicates 2 things The number of things indicated by a mole is defined to be the number of carbon atoms found in exactly 12 g of the 12 C isotope The number of atoms present in 12 g of 12 C has been determined experimentally to be 6.022 3 10 23 atoms (given here to 4 signi ficant figures) This large number is called Avogadro ’s number, after the first scientist to deduce its value.

The molecular (or atomic) weight of any molecule (or atom), expressed in grams, contains one mole, or 6.022 3 10 23 molecules or atoms.

Thus, 1 mole of pure calcium metal (weighing 40.08 grams) contains 6.022 3 10 23 calcium atoms As

an example of a molecule, 1 mole of pure calcium chloride (CaCl 2 ; weighing 40.08 þ

2 3 35.45 ¼ 110.98 g) contains 6.022 3 10 23

calcium chloride molecules When 1 mole of calcium chloride dissolves, it dissociates into 1 mole of Ca2þions and 2 moles of Cl
ions.

EXAMPLE 2

CALCULATING A CONCENTRATION IN AIR

The equations used in these calculations are based on the ideal gas laws, which arediscussed in introductory general chemistry textbooks The equations are used herewithout derivation

The ozone (O3) level in the Denver, Colorado, atmosphere was reported to be 2.50 ppmv(2.50 mL=L) Express this in mg=m3at ambient conditions of 378C and 722 mm Hg.Answer:

CO 3(mg=m3)¼ 2500 ppbv 48 g=mol  0:950 atm

310 K

10:08205

Answer:

The chemical formula for benzene is C6H6(meaning that one molecule of benzenecontains six atoms of carbon and six atoms of hydrogen) Therefore, its molecularweight is (6312þ 631) ¼ 78 g=mol The concentration of benzene in the sample can

be expressed as

Cbenzene¼(1000 mg=g)(78 g=mol)0:017 mg=L ¼ 2:18  10
7 mol=L

EXAMPLE 4

USING MOLES,PPM,AND MG/L TOGETHER

The federal primary drinking water standard for nitrate is 10 mg of nitrate–nitrogen perliter of water (written as: 10 mg NO3–N=L) It is defined in terms of the nitrogen content

of the nitrate ion present in the sample, neglecting the mass of the oxygen atoms in themolecule.

If a laboratory analysis includes the mass of the oxygen atoms and reports the nitrateconcentration in a water sample as 33 ppm NO3=L (not NO3–N=L), does the analysisindicate that the water source is in compliance with the federal drinking water standard?Answer:

33 ppm¼ 33 mg=L ¼ 33  10
3g=LMoles of NO3in 1 L of sample¼weight of NO3in 1 L of sample

is in compliance

EXAMPLE 5

USING MOLES,PPM,AND MG/L TOGETHER

2.00 g of the disinfectant calcium hypochlorite, Ca(OCl)2, is added to a hot tubcontaining 1050 L of water Ca(OCl)2dissociates in water by the reaction

Ca(OCl)2þ 2H2O! 2HOCl þ Ca2 þþ 2OH
(1:3)HOCl partially dissociates further by

a What would be the concentration of Ca(OCl)2in the hot tub water if Ca(OCl)2didnot dissociate? In other words, what concentration of Ca(OCl)2is initially added to thehot tub water?

in water completely, and that the available free chlorine is 50% HOCl and 50% OCl
(in terms of number of molecules, or moles, not by weight), as is the case at pH ¼ 7.5.Procedure: (Use the periodic table for atomic weights.)

(1) Determine the number of moles in 2.00 g of Ca(OCl)2

(2) Determine the moles of HOCl formed by 2.00 g of Ca(OCl)2, if no furtherdissociation occurred

(3) Determine the moles of HOCl and OCl
in the water after complete dissociation(Equation 1.4)

(4) Determine the weight of HOCl and OCl
in the water

(5) Calculate the ppm of HOCl þ OCl
in 1050 L of water

Answer :

(1) MW of Ca(OCl)2 ¼ 40.1 þ 23 16.0 þ 2335.4 ¼ 142.9 g=mol

Moles of Ca(OCl)2 in 2 :00 g ¼142: 9 g=mol 2: 00 g ¼ 0: 014 mol

(2) Equation 1.3 indicates that 2 moles of HOCl are formed from 1 mole of Ca(OCl)2.Therefore

2 3 0.014 mol ¼ 0.028 moles of HOCl are formed from 2.00 g of Ca(OCl)2.(3) Half of the HOCl dissociates to OCl
, resulting in 0.014 moles of HOCl and 0.014moles of OCl

(4) MW of HOCl ¼ 1.0 þ 16.0 þ 35.4 ¼ 52.4 g=mol

MW of OCl
¼ 16.0 þ 35.4 ¼ 51.4 g=mol

Weight of HOCl in the water ¼ 0.014 mol 3 52.4 g=mol ¼ 0.73 g

Weight of OCl
in the water ¼ 0.014 mol 3 51.4 g=mol ¼ 0.72 g

Total weight of HOCl þ OCl
¼ weight of free chlorine ¼ 1.45 g

(5) Concentration of free chlorine in hot tub ¼ 1:45 g

1050 L ¼ 0: 0014 g=L ¼ 1: 4 ppm

EXAMPLE 6

USING CONCE NTRATION CALCUL ATIONS TO PREDICT A PRECIPITAT E

In this example, the result of a chemical reaction must be determined and it is necessary

to use concentration units of moles=L (molarity)

A mole is the amount of a compound that has a weight in grams equal to itsmolecular weight Molecular weight is the sum of the atomic weights of all theatoms in the molecule (See periodic table inside front cover for atomic weights.)For example, the atomic weight of oxygen is 16 An oxygen molecule (O2) contains twooxygen atoms and, thus, has a molecular weight of 32 A mole of O2is the amount, ornumber of molecules, that weighs 32 g Another example: the atomic weights of carbonand calcium are 12 and 40, respectively The molecular weight of CaCO3is

40þ 12 þ 3  16 ¼ 100 gOne mole of CaCO3is the quantity that weighs 100 g

A water sample is taken from a stream that passes through soils containing gypsum(CaSO4), some of which dissolves The stream already carries some Ca2þand SO2
4dissolved from other mineral sources Laboratory analysis of the water shows

4 will precipitate when the system is atequilibrium The quantity [Ca2þ][SO2
4 ], using experimental concentrations, is calledthe reaction quotient

1.3.4.1 Working with Equivalent Weights

This is useful for chemical calculations involving ions, because ionic reactions mustalways balance electrically, i.e., with respect to ionic charge Since environmentalwaters normally contain many ionic species, equivalent weights are often useful inwater quality calculations

The equivalent weight of an ion is its molecular weight (for molecular ions such

magnitude of charge (without regard for the sign of the charge) For nonionic species

molecules were dissolved (also called the oxidation number)

weight that would carry 1 mole of charge Thus,

atomic weight, because 1 mole of the ions carries 1 mole of charge

molecular or atomic weight, because 1 mole of the ions carries 2 moles ofcharge

. One equivalent weight of a triply charged ion is equal to one-third of its

molecular or atomic weight, because 1 mole of the ions carries 3 moles ofcharge

positive charge:

4 CaSO4 ƒƒƒ!H2 O

4

Since each ion formed carries a charge of magnitude 2, the equivalent weight of

Equivalents per liter of an impurity are equal to the moles per liter multiplied by the

moles of charge (or two equivalents of charge) That this is consistent with the factthat the equivalent weight of a substance is its molecular weight divided by the

EXAMPLE 7

EQUIVALENT WEIGHT OF AN ION

What is the equivalent weight of Cr3þ?

Answer:

The equivalent weight of Cr3þis the mass that contains 1 mole of charge Since eachion of Cr3þcontains 3 units of charge, the moles of charge in a given amount ofchromium are 3 times the moles of ions Thus, 1 mole of Cr3þ, or 52 grams, contains 3moles of charge, or 3 equivalent weights Therefore,

of eitherþ2 or
2

EXAMPLE 8

EQUIVALENT WEIGHT OF A COMPOUND

Alkalinity in a water sample is reported as 450 mg=L of CaCO3 Using Table 1.1,convert this result to eq=L of CaCO3 Alkalinity is a water quality parameter that resultsfrom more than one constituent It is expressed as the amount of CaCO3 that wouldproduce the same analytical result as the actual sample (see Chapter 2)

450 mg=L ¼(100 g=mol)(1000 mg=g)450 mg=L ¼ 4:5  10
3mol=L or 4:5 mmol=L

4:5  10
3mol=L  2 eq=mol ¼ 9:0  10
3eq=L or 9:0 meq=L

EXAMPLE 9

USING EQUIVALENT WEIGHT

Chromium(III) in a water sample is reported as 0.15 mg=L Express the concentration

as eq=L (The Roman numeral III indicates that the oxidation number of chromium

Equivalent Weight Species

Atomic Weight

Absolute Charge

Equivalent Weight

in the sample isþ3 It also indicates that the dissolved ionic form would have acharge ofþ3.)

Answer:

The atomic weight of chromium is 52.0 g=mol Chromium(III) ionizes as Cr3þ, so its

concentration in mol=L is multiplied by 3 to obtain its equivalent weight

USING MG/L,MOLES/L,AND EQUIVALENTS TOGETHER

Using the dissolution reaction CaCl2! Ca2þþ 2Cl

a Calculate how many moles=L of CaCl2are needed to produce a solution with 500mg=L of Ca2þ, with 500 mg=L of Cl
.

b Show that dissolving in water one equivalent weight of calcium chloride (CaCl2),results in an electrically neutral solution containing 1 mole of positive ions and 1mole of negative ions

Answer:

a Calculate how many moles=L of Ca are in 500 mg=L of Ca2 þ.

500 10
3 g=L

40:1 g=mol ¼ 0:0125 mol=LThe dissolution reaction shows that the moles of Ca2þproduced are equal to themoles of CaCl2dissolved Therefore, 0.0125 mol=L of CaCl2are needed

Calculate how many moles=L of Cl are in 500 mg=L of Cl

500 10
3 g=L35:5 g=mol ¼ 0:0141 mol=LThe dissolution reaction shows that the moles of Cl
produced are two times the moles

of CaCl2dissolved Therefore, 0.0141=2 ¼ 0.00704 mol=L of CaCl2are needed

b The exact amount of CaCl2 dissolved is irrelevant However, many moles orequivalents are dissolved in any amount of water, the concentration of Cl
produced

is always twice the concentration of Ca2þproduced and the total negative charge isalways equivalent to the total positive charge

Given that

. The total negative charge in the solution is 1 3 [Cl
]

. The total positive charge in the solution is 2 3 [Ca2 þ]

. Total negative charge must equal total positive charge: [Cl
]¼ 2 3 [Ca2þ]

Then, negative charge¼ 1 3 [Cl
]¼ 1 3 (2 3 [Ca2 þ])¼ positive charge

This result is general Dissolving electrically neutral compounds in water alwaysresults in an electrically neutral solution

1.3.5 CASEHISTORY EXAMPLE

A shallow aquifer below an industrial park was contaminated with toxic halogenatedhydrocarbons (in this case, hydrocarbons containing chlorine and bromine).Although other pollutants were present, only the halogenated hydrocarbons werefound to threaten a municipal drinking water supply The state environmentalauthorities mandated a remediation program to be paid for by the responsible parties,which were several industrial facilities in the park In order to allocate an appropriateshare of the cleanup expenses to each responsible party, it was necessary to estimatewhat percentage of the total pollution was caused by each party

An automobile rental agency was cited as one of the responsible parties, eventhough they did not use halogenated chemicals in their business, because they hadhad a leaking underground gasoline storage tank that released approximately 2500gal of leaded gasoline to the subsurface above the aquifer The gasoline containedadditives with chlorine and bromine compounds

During the time period between the late 1920s and the early 1990s, leadcompounds, particularly tetraethyl lead (also called TEL), were added to automotiveand aviation gasoline as an octane enhancer During that time, it was commonpractice to also add halogenated organic compounds, particularly 1,2-dichloroethane(also called ethylene dichloride* or EDC) and 1,2-dibromoethane (also called ethyl-

prevent lead deposits from accumulating in gasoline engines

a Use the data below to calculate the mass in grams of EDC and EDB thatwas potentially added to the aquifer from the spill of 2500 gal of leadedgasoline

b Measurements of the contaminant plume indicated that the gasoline spill

volume was occupied by water in the soil pore space and calculate thepotential average concentrations of EDC and EDB in the aquifer water(ignoring biodegradation, evaporation, and other loss mechanisms)

*,y The use of these common trade names may be confusing because the name ethylene normally means that there is a double bond between two carbons, whereas the compounds 1,2-dichloroethane and 1,2-dibromoethane contain only single bonds The use of ethylene dichloride and ethylene dibromide

as trade names arose because 1,2-dichloroethane and 1,2-dibromoethane were often manufactured from ethylene with chlorine or bromine.