Environmental Forensics: Principles and Applications - Chapter 1 docx

Chapters 1 through 6 1 An Overview of the History, Chemistry, and Transport of Chlorinated Solvents 1.3.2 Chemical Structure and Properties 1.3.3 Henry’s Law Constant KH 1.3.4 Liquid De

Library of Congress Cataloging-in-Publication Data

Morrison, Robert D.

Environmental forensics : principles and applications / by Robert

D Morrison

p cm.

Includes bibliographical references and index.

ISBN 0-8493-2058-5 (alk paper)

1 Environmental forensics 2 Solvents — Environmental aspects.

3 Organochlorine compounds — Environmental aspects 4 Petroleum

chemicals — Environmental aspects 5 Hydrocarbons — Environmental

aspects 6 Groundwater flow I Title.

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Printed in the United States of America 1 2 3 4 5 6 7 8 9 0

Printed on acid-free paper

Environmental forensics is the systematic examination of environmental information

used in litigation The purpose of this book is to provide a working reference for the

practicing environmental attorney or environmental consultant As a working ence, the topics and examples selected are common denominator issues encountered

refer-in environmental litigation; as such, this book is not refer-intended to be a treatise on aparticular subject but rather to present information that you will likely encounter.Whenever possible, expanded mathematical or chemical discussions were relegated

to the Appendices

Chapters 1 and 2 provide a working overview of information about chlorinatedsolvents and petroleum hydrocarbons The foundational information in Chapters 1and 2 was selected to assist you in deciding which forensic tools described in Chapter

4 are applicable to your case Recognize that the forensic tools described in Chapter

4 are rapidly evolving Whenever possible, contact the proponents of these gies directly to ascertain their current capabilities relative to your case Chapters 3and 5 provide information on how to identify biased environmental data and sugges-tions in regard to the applications and review of biased environmental data, as well

technolo-as suggestions concerning the evaluation of contaminant transport models Chapter

6 describes techniques for forensically evaluating settlement and trial exhibits andanimations

The information in this book is intended to allow you to distinguish betweenevidence and opinions based on scientific methods vs junk science Regardless ofyour position on an allegation, everyone is well served if valid technical informationand interpretations form the basis for an expert witness opinion

Best wishes for a successful and informed environmental career

Robert D Morrison

San Diego, CA

The Author

Robert Daniel Morrison has a B.S in Geology, an

M.S in Environmental Studies, an M.S in mental Engineering, and a Ph.D in Soil Physics fromthe University of Wisconsin at Madison Dr Morrisonhas been working for 27 years in the environmentalfield on issues related to soil and groundwater con-tamination He specializes in the forensic review andinterpretation of scientific data used in support oflitigation involving soil and groundwater contamina-tion Dr Morrison has published articles and books

Environ-on soil and groundwater cEnviron-ontaminatiEnviron-on topics and hasshared this information via lectures throughout theworld He is active in reviewing technical papers on forensics techniques and has

served on the editorial boards of Ground Water and Groundwater Monitoring Review and Remediation and currently serves on the editorial board of The Interna- tional Journal of Environmental Forensics Dr Morrison has worked as an expert

witness and consultant for the U.S Department of Justice, the EnvironmentalProtection Agency (EPA), and numerous law firms on cases where environmentalforensics were used to allocate responsibility In the capacity as an expert witnessand confidential consultant, Dr Morrison has provided testimony in numerouscases, some with claims ranging from tens of thousands of dollars to as much as fivebillion dollars

Scientists who directly assisted in the preparation of this book include Sherri Komelyan,Kathleen Calsbeck, Jamie Campos, Kevin Vaughn, and Christian Benitez of R.Morrison & Associates, Inc Numerous colleagues and researchers provided assis-tance in the form of communication and information Special thanks to Dr JimBruya, of Friedman & Bruya in Seattle, WA; Dr James Szecsody, of BattelleNorthwest Laboratories in Hanford, WA; Dr Blayne Hartman, of TEG in SolanoBeach, CA; David Kaminski, of QED in Ann Arbor, MI; Kevin Beneteau, of GolderAssociates, Calgary, Alberta, Canada; Dr Barbara Sherwood Lollar, Department ofGeology, University of Toronto, Canada; Dawn Zemo, of Geomatrix in San Fran-cisco, CA; and Dr Ramona Aravena, University of Waterloo, Waterloo, Ontario,Canada

Special thanks to the wonderful group at CRC Press, especially BeckyMcEldowney, who provided creative insight and inspiration, and Debrah Goldfarb.who provided marketing direction Special thanks, too, to Sarah Nicely Fortener ofNicely Creative Services in Geneva, IL, for her wonderful editing of this book.Special acknowledgement to my wife, Donna, who tolerated my night stalkingand the use of her computer during this effort

Chapters 1 through 6

1 An Overview of the History, Chemistry,

and Transport of Chlorinated Solvents

1.3.2 Chemical Structure and Properties

1.3.3 Henry’s Law Constant (KH)

1.3.4 Liquid Density

1.3.5 Solubility

1.3.6 Viscosity

1.3.7 Vapor Pressure and Density

1.3.8 Boiling Point and Latent Heat of Vaporization1.3.9 Octanol/Water Partition Coefficient (Kow)1.3.10 Hydrolysis

1.3.11 Sorption

1.3.12 Biodegradation

1.3.12.1 Anaerobic Degradation1.3.12.2 Aerobic Degradation1.4 Transport of Chlorinated Solvents through Soil

1.5 Impact of Cosolvency on Transport through Soil

1.6 Transport of Vapors in Soil

1.7 Transport through the Capillary Fringe

1.8.6 Free Phase Solvent Transport in Groundwater1.8.7 Transport in Fractures

1.8.8 Transport in Fractured Porous Media

References

2 Chemistry and Transport of Petroleum Hydrocarbons

2.1 Introduction

2.2 Chemistry of Crude Oil

2.3 Chemistry of Refined Products

2.3.1 Gasoline

2.3.2 Diesel

2.4 Chemical Reactions in the Vadose Zone

2.4.1 Henry’s Law Constant (KH)

2.5.4 Vapor Phase Transport

2.6 Hydrocarbon Interactions at the Capillary Fringe

2.6.1 Hydrocarbon Solubilization from the

Capillary Fringe into Groundwater2.7 Transport in Groundwater

2.7.1 Rate of Transport

2.7.2 MTBE Transport in Groundwater

2.7.3 Length of a Petroleum Hydrocarbon Plume

3.2.1 Boring Log Terminology

3.3 Interpretation of Geologic Information

3.4 Soil Collection for Chemical Analyses

3.4.1 Soil Sampling Equipment

3.4.2 Subsampling and Sample Transfer

3.4.3 Soil Compositing

3.5 Groundwater Characterization

3.5.1 Monitoring Well Location

3.5.2 Installation of Groundwater Monitoring Wells3.5.3 Sampling Plan

3.5.11 Field Quality Control Samples

3.6 Soil Vapor Surveys

3.6.1 Interpretation of Soil Vapor Data

3.7 Analytical Methods

3.7.1 Misidentification of Analytes

3.7.2 Laboratory Documentation

3.7.2.1 Chain of Custody3.7.2.2 Document Control/Control Log 3.7.2.3 Signature List

3.7.2.4 Logbook Cover Sheet3.7.2.5 Sample Kit Preparation Log3.7.2.6 Field Logs

3.7.2.7 Sample Receipt Checklist and/or Log3.7.2.8 Sample Preparation Logbook3.7.2.9 Sample Analysis Log3.7.2.10 Instrument Run Log3.7.2.11 Instrument Maintenance Log3.7.2.12 Certificates of Analysis3.7.2.13 Laboratory Certification3.7.3 Laboratory Quality Control Samples

4.5 Commercial Availability of a Chemical

4.6 Chemicals and Formulations Unique

to a Manufacturing Process or Activity

4.6.1 Polychlorinated Biphenyls

4.7 Petroleum Refinery Throughput Analysis

4.8 Chemical Identification of Petroleum Hydrocarbons

4.9 Radioactive Isotope Dating

4.9.1 Dating Groundwater with Isotopes

4.9.2 Isotopic Analysis for Petroleum Hydrocarbons4.9.3 Lead Isotope Analysis

4.9.4 Lead Isotope Analysis for Gasoline Fingerprinting4.9.5 Isotope Analysis of Crude Oil and BTEX

4.9.6 Isotope Analysis of Gas Samples

4.9.7 Isotopic Analysis of Chlorinated Solvents

4.10 Chemical and Biological Degradation Models:

4.10.5 Challenges to BTEX Ratio Methods

4.11 Chemical Degradation Models: Chlorinated Solvents

4.12 Rapid Optical Screening Tool™ Testing

References

5 Contaminant Transport Modeling

5.1 Introduction

5.2 Liquid Transport through Pavement

5.3 Vapor Transport through Pavement

5.4 Contaminant Transport in Soil

5.4.1 Challenges to Contaminant Transport Models for Soil5.4.2 Colloidal Transport

5.4.3 Preferential Pathways

5.4.4 Cosolvent Transport

5.5 Contaminant Transport in Groundwater

5.5.1 Types of Groundwater Models

5.5.2 Selection of Boundary Conditions,

Grids, and Mass Loading Rates5.5.3 Software Applicability

5.6 Application of Groundwater Modeling

in Environmental Litigation

5.6.1 Confirmation Models

5.6.2 Reverse Models

5.6.3 Hydrogeologic Variables

5.6.4 Contaminant Properties

5.6.5 Challenges to Reverse Models

5.6.6 Challenges to Phase-Separate Reverse ModelsReferences

6 Forensic Review of Environmental Trial Exhibits

6.1 Introduction

6.2 Exaggerated Vertical and Horizontal Scales

6.3 Selective Data Presentation

References

Appendices

A Sample Calculation for the Transport of

PCE Vapor through Concrete Pavement

A.1 Introduction

A.2 Sample Calculation

References

B Sample Calculation for the Transport of

PCE Liquid through Concrete via Diffusion

B.1 Introduction

B.2 Sample Calculation

References

C Properties of Alcohol Oxygenates and Ether Oxygenates

D Advective and Partitioning Transport Equations

of Radon for Detecting Diesel in Groundwater

D.1 Introduction

D.2 Derivation

D.3 Conclusions

References

E Chemical and Commercial Synonyms for Selected Chlorinated Solvents and Aromatic Hydrocarbons

References

F Laboratory Terms and Definitions

Chapters 1 through 6

1.2 CHRONOLOGY AND USE OF

CHLORINATED SOLVENTS

The global production and use of chlorinated solvents began after World War II, withvolumes gradually increasing through the 1950s and 1960s In the early years ofsolvent use, the military was the primary consumer From 1978 through 1988, thetotal production of chlorinated solvents in the United States declined modestly, byabout 11% After 1988, the decline was more substantial, amounting to about 45%between 1978 and 1985 The decrease in the demand of chlorinated solvents during

1978 to 1985 reflects the production ban on 1,1,1-trichloroethane (1,1,1-TCA, orTCA) and Freon-113 (1,1,2-trichloro-1,2,2-trifluoroethane) Another factor in thisdecrease was the increased regulations on TCA, tetrachloroethylene (PCE), and

methylene chloride (MC) The total global capacity for chlorinated solvents in 1994was about 1.7 million metric tons, with the U.S accounting for about 36% of thetotal, followed by Western Europe and Japan at 40% and 23%, respectively Table1.1 summarizes the consumption of chlorinated solvent use in the U.S in 1988 forvarious industries and applications (IRTA, 1994).

The primary use of chlorinated solvents is vapor degreasing In vapor degreasing,solvents are boiled (150 to 250∞F), thereby producing a heated vapor zone within thedegreaser A single-chamber vapor degreaser contains heating coils at the bottom toboil the liquid solvent, and cooling coils surround the top to contain the vapor (seeFigure 1.1) Metal parts are lowered into the solvent vapor zone for cleaning, usually

in a metal basket The warm solvent condenses on the colder parts, dissolving thecontaminants or oil into the solvent In some instances, a spray wand is manuallyused to spray the solvent vapor on the parts in the basket The vapor zone height islimited by the cooling coils that condense the solvents and return them to the liquid

at the bottom of the degreaser The mixture drains to a water/solvent separator, wherethe heavier solvent sinks to the bottom and the condensed water and dissolved solventare disposed While many vapor degreasers are more sophisticated, with vacuum

TABLE 1.1

Chlorinated Solvent Uses in the U.S in 1988

systems, multiple chambers, attached distillation units for removing the soils fromthe solvent, ultrasonics, and mechanized basket trays, the general operating principle

Equipment related to vapor degreasers includes distillation or evaporation stillsused to recover solvents The two types of stills are batch and continuous In a batchstill (also differential, Raleigh, or pot distillation), a fixed amount of spent solvent isplaced inside a heated evaporation chamber from which the condensed vapor iswithdrawn Continuous, multistage distillation (also fractional distillation) is usedwhen there is a need for a high degree of distillation purity, if the amount of spentsolvent to be recovered is large, or when differences in solvent volatility are small.Continuous distillation is accomplished in a column equipped with trays or packingmaterials to facilitate contact between the liquid and vapor phases Liquid is intro-duced continuously into the column at the top while the vapor moves upward,becoming more enriched with the more volatile compounds The high boiling com-pounds thereby become concentrated in the liquid

FIGURE 1.1 Single-stage vapor degreaser.

Knowledge of the vapor degreaser or solvent still manufacturer is useful inidentifying what solvents are compatible with the equipment Obtaining the originaloperating manual from the manufacturer will provide this information Table 1.2summarizes the boiling range and types of solvents that can be recycled for severaldistillation stills (California Department of Health Services, 1988).

Chlorinated solvents are used in the electronics manufacturing industry, cially in the production of semiconductors Applications include:

espe-• Semiconductor wafer fabrication and assembly

• Printed circuit board fabrication and assembly

• In situ generation of etchants

• Miscellaneous critical electronic applications

Chlorinated solvents used in the semiconductor industry include 1,2,2-trifluoroethane (Freon-113); 1,1,1-trichloroethane (TCA); methylene chloride(MC); trichloroethene (TCE); and tetrachloroethylene (PCE) Freon-113 and TCAapplications include removal of flux from printed circuit boards after the variouselectronic components are soldered to the board TCA is frequently combined withalcohol because alcohol is an effective flux remover TCA and methylene chlorideare also used in the photoresist process In the early 1990s, all photoresist solutionswere solvent, aqueous, or semi-aqueous solutions In the photoresist process, dry-film photoresist is applied to the copper substrate of the electronic board and thedesired circuitry is imprinted by shining a high-intensity light through a photomask

1,1,2-trichloro-If a negative photoresist is used, the areas of the film exposed to the light polymerize,whereas the unexposed areas do not After the developer carries away theunpolymerized material, the photoresist is then developed with a solvent such asTCA, which is followed by the etching step The remaining photoresist is thenstripped, often with methylene chloride Table 1.3 lists the composition of formulations

TABLE 1.2

Solvent Compatibility with Distillation Stills

Boiling Range Distillation Model/Manufacturer (∞F) Solvents Recycled

SD-15 Acra Electric; Schiller Park, IL N/A TCE, 1,1,1-TCA, PCE LS-JR Finish Engineering; Erie, PA 100–320 Alcohols, aromatics, chlorinated

solvents, aliphatics, ketones

RS-20 Recyclene Products; San Francisco, CA <400 Methylene chloride, acetone,

methanol, 1,1,1-TCA,

n-butyl-acetate, xylene,

mineral spirits, isopropyl alcohol, Stoddard solvents

associated with the photoresist process (California Department of Health Services,1988).

Wafer fabrication is an integral process of semiconductor manufacturing

Poten-tial contaminants associated with this process include xylene, n-butyl acetate,

ammo-nium fluoride, hydrofluoric acid, sulfuric acid, arsenic, antimony, copper, zinc,phosphorus, boron, nitric acid, acetic acid, chromic acid, and phosphoric acid.Dopants used to change the electrical properties of the silicon wafer include anti-mony, arsenic, boron, and aluminum In some cases, the chronological use of dopantsprovides a means of determining the earliest date that contaminants with thesecompounds were introduced into the environment A diagram of a wafer fabricationprocess used since 1986 is shown in Figure 1.2

While the use and application of chlorinated solvents for semiconductor facturing has evolved with time, the manufacturing processes remains similar Thevolume of solvents for different electronic applications in the U.S for 1987 and 1989

manu-is shown on Table 1.4 (California Department of Toxic Substance Control, 1991) Asshown in Table 1.4, about 72,000 metric tons of chlorinated solvents were used in

1987 Freon-113 was widely used in 1987, followed by TCA and methylene chloride.The use of TCA and PCE during this time frame is believed to be associated withdegreasing applications Of the electronic board manufacturing activities, solvent usewas highest for board assembly

In environmental litigation, the most commonly encountered solvents are TCE,PCE, 1,1,1-TCA, and methylene chloride Information about the specific applica-tions and historical production of these solvents is summarized in the followingsections

TABLE 1.3

Compounds Associated with the Photoresist Process in Wafer Fabrication

Proprietary Compound Composition

Waycoat photoresist 85% xylene

Microresist developer 95–100% Stoddard solvent

Photoresist developer I 10–30% aromatic hydrocarbons; >60% aliphatic hydrocarbons Photoresist developer II Mixture of petroleum solvents

Negative photoresist 48% 2-ethoxyethylacetate; 5% n-butyl acetate; 5% xylene.

Positive photoresist 52% 2-ethoxyethylacetate; 6% n-butyl acetate; 6% xylene.

Ultrasonic degreaser Perfluoroisobutylene

Stripper 712D Dodecyl benzene sulfonic acid; 1,2,4-trichlorobenzene, phenols;

pH = 2.4–2.6 Negative photoresist stripper 63% methylene chloride and chlorobenzenes; 23% phenyl sulfonic J100 (Kodak) acid; 14% phenols and derivatives.

Microstrip 75% chlorinated solvents; orthocresol, dodecylbenzosulfonic acid,

PCE, and dichlorobenzene Burmar <25% phenol; <25% sulfonic acid; <25% aromatic solvents;

<50% chlorobenzenes

1.2.1 T RICHLOROETHYLENE (TCE)

Trichloroethylene is used as a metal degreaser and has been available worldwide forabout 50 years Trichloroethylene was first prepared by Fisher in 1864 duringexperiments on the reduction of hexachloroethane with hydrogen (Hardie, 1964)

FIGURE 1.2 Description of processes for semiconductor wafer fabrication, post-1986.

Trichloroethylene production began in Austria and the United Kingdom in 1908;Germany, in 1910; the U.S., 1925; and Japan, 1935 Trichloroethylene is manufac-tured by the catalytic oxidation of 1,1,2,2-tetrachloroethane (U.S patent number2,951,103) and the catalytic chlorination of acetylene (U.S patent number 2,938,931).

In the U.S., the Vietnam War accelerated the use of trichloroethylene for aircraftparts and engine maintenance and production, cleaning rocket hardware, and spaceapplications and in the automotive industries The demand for trichloroethylene inthe U.S peaked in 1968 at about 261,000 metric tons In 1970, trichloroethyleneaccounted for 82% of all of the chlorinated solvents used in vapor degreasing; in

1976, its share had declined to 42% By 1975, numerous federal, state, and localregulations in the U.S existed that restricted the use of TCE due to its being asuspected carcinogen In 1975, the National Cancer Institute reported to the NationalInstitute of Occupational Safety and Health (NIOSH) that PCE and TCE were

“suspect human carcinogens” and that exposure should be minimized NIOSH mended that TCA be handled with caution due to its chemical similarity to PCE andTCE In 1976, the U.S exported about 16 million kg, primarily to the FederalRepublic of Germany (3.8 million kg), France (3.4 million kg), Mexico (2.1 millionkg), and Brazil (2 million kg) (U.S Department of Commerce, 1977)

recom-The demand for trichloroethylene in the U.S in 1995 was about 128 millionpounds, of which about 16.5 million pounds were imported and about 40 millionpounds exported (Halogenated Solvents Industry Alliance, 1996) While trichloro-ethylene is an excellent vapor degreaser due to its ability to degrease faster and morethoroughly than alkaline cleaners, its suspected carcogenicity resulted in many usersswitching to TCA and PCE in the 1970s and 1980s TCA gradually replaced TCEfrom 1963 through 1988; as the demand for trichloroethylene decreased, the use ofTCA increased In February of 1995, the International Agency for Research onCancer (IARC) concluded that there was sufficient epidemiological and animal

Defluxing boards 25.6 (23.0) 6.6 (8.0) 0.7 (0.6) 0.5 (0.6) 0.5 (0.6)

Note: Figures are in units of thousands of metric tons.

testing data to classify PCE and TCE as “probable human carcinogens” The IARCdid not classify 1,1,1-TCA as a human carcinogen In 1996, the applications of TCE

in the U.S was about 55% for metal cleaning and degreasing, 41% as a chemicalintermediate, and 4% for miscellaneous applications Water-based products and

compounds such as n-propyl bromide (EnviroChem) became more common as a

replacement for TCE In the U.S., trichloroethylene is produced by Dow ChemicalCompany and PPG Industries

Global consumption of trichloroethylene decreased from 224,000 metric tons in

1990 to 214,000 in 1993, but there is expected to be an increase in TCE consumption

as a precursor for HFC-134a production The annual trichloroethylene consumption

in the U.S and Japan from 1993 to 1998 was expected to increase about 16% and 6%,respectively TCE consumption is expected to decrease in Western Europe by about2% annually, as decreases in the use of TCE in metal degreasing will offset increases

in HFC-134a precursor consumption

In Western Europe, trichloroethylene is produced by Elf Atochem (France), DowEurope/Switzerland (Germany), EniChem (Spain), ICI Chemicals and Polymers(United Kingdom) and Solvay/Belgium (France and Italy) In Western Europe,according to the European Chlorinated Solvent Association (1998), TCE productionfrom 1993 to 1997 was as follows: 1993 and 1994 (94,000 metric tons), 1995(103,000 metric tons), 1996 (99,000 metric tons), and 1997 (92,000 metric tons) Theincrease in TCE production in 1995 and 1996 is due to the replacement of 1,1,1-trichloroethane with TCE for vapor degreasing

1.2.2 T ETRACHLOROETHYLENE

(PCE, OR P ERCHLOROETHYLENE )

Tetrachloroethylene was first formulated in 1821 (Izzo, 1992) Global demand ofPCE decreased from 513,000 metric tons in 1990 to 338,000 metric tons in 1993 Theuse of PCE as a precursor in the production of chlorofluorocarbon-113 (CFC-113)ceased in 1996 due to its association with ozone depletion In some countries, PCEconsumption is expected to increase due to its use in manufacturing hydrochloro-fluorocarbon-123 (HCFC-123) and hydrofluorocarbon-134a (HFC-134a) From 1993

to 1998, PCE consumption in the U.S and Japan increased about 3% but decreasedabout 12% annually in Western Europe

Tetrachloroethylene has been the chlorinated solvent of choice in the drycleaningindustry since the late 1930s By the late 1940s or early 1950s, PCE replacedsynthetic solvents such as carbon tetrachloride in the drycleaning industry Prior tothe 1960s, however, petroleum derivatives were still the dominant solvents in thedrycleaning industry in the U.S., where the demand for PCE increased steadily from

1972 to 1981 PCE usage peaked in 1975 at about 348,000 metric tons After 1975,

a decline in demand continued until 1994, when the demand for tetrachloroethylenewas about 113,000 metric tons In the late 1980s, drycleaners consumed 56% of thePCE in the U.S In 1990, PCE production in the U.S was about 383 million pounds,

of which 55 million pounds were exported In 1990, about 72.1 million pounds were

imported into the U.S (Halogenated Solvents Industry Alliance, 1994) In the U.S.,PCE is produced by Dow Chemical USA, PPG Industries, and Vulcan MaterialsCompany Figure 1.3 summarizes PCE usage in the U.S by drycleaners from 1985

to 1997 (Halogenated Solvents Industry Alliance, 1998a) In 1990, ene use in the U.S was 50% for drycleaning/textile processing, 25% as a chemicalintermediate, and 15% in metal cleaning and degreasing, with miscellaneous usesaccounting for about 10% (Halogenated Solvents Industry Alliance, 1998a)

tetrachloroethyl-In 1992, there were approximately 34,000 drycleaning businesses in the U.S.,with about 28,000 facilities using PCE In 1992, the typical commercial drycleanerprocessed about 75,000 pounds of clothing annually, which represented about 90%

of the industry Approximately 25,000 of these commercial drycleaners used PCE(about 120,000 metric tons annually) (Wolf, 1992)

The three categories of drycleaning machines that use tetrachloroethylene are

• A transfer machine, in which the clothing is washed in one unit and physically transferred to a dryer for drying Emissions from the washer and dryer can be uncontrolled or they can be routed to a control device Approximately 30% of all drycleaning machines are transfer units.

• A dry-to-dry vented unit, in which the clothing is washed and dried in the same cylinder The PCE emitted from the unit can be uncontrolled or vented to a control device Approximately 70% of the retail drycleaners in the U.S have dry-to-dry units.

• A dry-to-dry closed loop unit, in which the wash and dry cycles occur in the same unit Tetrachloroethylene emissions are controlled within the unit with a refriger- ated condenser.

FIGURE 1.3 PCE demand by the drycleaning industry in the U.S from 1985 to 1997.

Most drycleaners (about 90%) remove soil, dust, hair, and lint from the solventwith cartridges of activated carbon Distillation units are used to remove oils andfats from the solvent After filtration through the activated carbon or tubular filters,the solvent is heated to between 190 and 250∞F The PCE is condensed andrecovered, and the remaining sludge can contain up to 50% PCE Some drycleanersreclaim the PCE in the sludge in a muck cooker or a cooker/still combination.

In Western Europe, tetrachloroethylene production declined about 4.8% between

1993 and 1997, from 84,000 tons in 1993 to 68,000 tons in 1997, due to thereplacement of obsolete open drycleaning machines with closed systems From 1988

to 1998, PCE use in the drycleaning industry in Western Europe declined by abouttwo thirds due to replacement of older equipment with machines with refrigerationtechnology that reduced the volume required for operation (Halogenated SolventsIndustry Alliance, 1998) In Western Europe, TCE is produced by Elf Atochem(France), Dow Europe/Switzerland (Germany), EniChem (Spain), ICI Chemicalsand Polymers (United Kingdom), and Solvay/Belgium (France and Italy) (EuropeanChlorinated Solvent Association, 1996)

1.2.3 1,1,1-T RICHLOROETHANE (1,1,1-TCA,

OR M ETHYLCHLOROFORM )

1,Trichloroethane was created in 1840 by the reaction of chlorine with dichloroethane TCA was first reported in the U.S in 1946 (U.S Tariff Commis-sion, 1947) In the U.S., it is produced via the chlorination of vinyl chloride derivedfrom 1,2-dichloroethane, via hydrochlorination of vinylidene chloride derived from1,2-dichloroethane, or through the thermal chlorination of ethane In Japan, 1,1,1-TCA is produced by the chlorination of vinyl chloride

1,1-TCA production and consumption have decreased dramatically due to its ozonedepletion potential in the upper atmosphere Global consumption from 1990 to 1993decreased from 665,000 to 349,000 metric tons On a worldwide basis, productionwas reduced to 50% of its 1989 levels throughout 1994 and 1995 Since 1995, TCA

in Europe has been used only as a precursor chemical Except for its use as aprecursor, worldwide production essentially ceased in 1996

TCA is the historical solvent of choice in cold cleaning The demand forTCA increased substantially over about three decades (1967 to 1994) in the U.S

In the late 1960s, when the use of TCE came under scrutiny due to its cation as an animal carcinogen, TCA was often used as its replacement Thehistorical demand for TCA in the U.S between 1967 and 1994 peaked in 1988 whenabout 298,000 metric tons were consumed TCA usage declined in 1991 due to anamendment to the Montreal Protocol that called for a complete phase-out ofTCA by 1996 due to its contribution to ozone depletion In Western Europe,most manufacturers ceased production by the end of 1995 with the exception ofits use as a chemical intermediate and for some permitted uses for virginsolvents By 1994, the U.S demand for TCA had decreased to about 159,000metric tons

identifi-1.2.4 M ETHYLENE C HLORIDE (D ICHLOROMETHANE )

Methylene chloride was introduced as a replacement for more flammable solventsover 60 years ago Total demand in the U.S in 1996 was about 285 million pounds,

of which about 20 million pounds were imported and about 130 million poundsexported (Halogenated Solvents Industry Alliance, 1998b) Globally, methylenechloride is produced by the following manufacturers:

• Aragonesas and Erkimia (Spain)

• Elf Atochem (France)

• Dow Chemical and Vulcan Materials (U.S.)

• Dow Europe/Switzerland (Germany)

• LIL Europe (Germany)

• ICI Chemical and Polymers (United Kingdom)

• Solvay/Belgium (France and Italy)

Methylene chloride consumption in Western Europe decreased from about 190,000

to 135,000 metric tons from 1985 to 1994 (European Chlorinated Solvent tion, 1997)

Associa-Methylene chloride is the active ingredient in many paint removers, includingcommercial and furniture strippers and home paint removers It is also used in aircraftmaintenance due to its ability to penetrate, blister, and remove a variety of paintcoatings In the maintenance of military and commercial aircraft, a methylenechloride-based product is often specified for surface inspection for damage Since themid-1990s, methylene chloride has replaced 1,1,1-TCA in nonflammable adhesiveformulations, including the fabrication of upholstery foam TCA is currently theleading auxiliary blowing agent used to produce slabstock flexible polyurethanefoams in the furniture and bedding industries In the pharmaceutical industry, meth-ylene chloride is used as a reaction and recrystallization solvent for extraction, aswell as a carrier for pharmaceutical tablet coatings In the chemical processingindustry, it is used in the production of cellulose triacetate, which serves as a base forphotographic film The uses of methylene chloride in the U.S in 1996 and WesternEurope in 1994 as a percentage of the total consumption are shown on Table 1.5(European Chlorinated Solvent Association, 1997)

1.3 CHEMISTRY AND PROPERTIES

OF CHLORINATED SOLVENTS

1.3.1 T ERMINOLOGY AND C LASSIFICATION

Chlorinated solvents include a wide range of compounds As such, a commonterminology for describing these compounds is useful Acronyms used in environ-mental reports to characterize chlorinated solvents and non-chlorinated compounds

as a function of their specific density include the following terms (Lizette et al.,1997):

• NAPL (non-aqueous phase liquid)

• DNAPL (dense non-aqueous phase liquid)

• LNAPL (light non-aqueous phase liquid)

A NAPL is generally immiscible with water The term “free phase liquid” is used todescribe a NAPL or DNAPL/LNAPL mixture (U.S EPA, 1992) A DNAPL describes

a chemical with a fluid density greater than 1.01 g/cm3 and a vapor pressure less than

300 torr (a torr is equal to 1/760th of a standard atmosphere or about 1 mmHg).Examples of DNAPLs include acetic acid, phenol, dichloroethylene, carbon disulfide,naphthalene, polychlorinated biphenyls, ethylene dichloride, sulfuric acid, parathion,tetrachloroethylene, trichloroethylene, and methyl bromide LNAPLs are compoundswith a fluid density less than water (about 1.01 g/cm3) and include mineral spirits #10,hexane, gasoline, benzene, butyl acetate, turpentine, ether, crude oil, and diethyl sulfide.Another classification scheme is based on the degree of halogenation and whetherthe compound is volatile or semi-volatile Classes of chlorinated hydrocarbons based

on this scheme are summarized in Table 1.6 Properties of chlorinated solventsaffecting their fate and transport through the subsurface include their chemicalstructure, their Henry’s Law constant, liquid density, water solubility, viscosity,vapor pressure and density, boiling point, latent heat of vaporization, and the octanolpartition coefficient Reactions that impact the movement and transformation ofsolvents in the subsurface and are interrelated with these chemical and physicalproperties include hydrolysis, sorption, and biodegradation

1.3.2 C HEMICAL S TRUCTURE AND P ROPERTIES

The major chlorinated solvents used in industry are TCE, PCE, 1,1,1-TCA, theFreons (primarily chlorofluorocarbon-113, or CFC-113), and methylene chloride.The chemical structures of these solvents are shown on Figure 1.4 Trichloroethylene(TCE) and perchloroethylene (PCE) have an ethylene or double-bonded carbon

TABLE 1.5

Use of Methylene Chloride in the U.S and Western Europe

United States Western Europe

structure with three and four chlorines, respectively Methylene chloride is a ylene chlorideane structure containing two chlorine atoms Trichloroethane (TCA)and CFC-113 are ethane derivatives 1,1,1-TCA has three chlorines, all on onecarbon CFC-113 is fully halogenated with three chlorines and three fluorine atoms.Freon is a chlorofluorocarbon because it contains a fluorine atom.

meth-TABLE 1.6

Classification of Chlorinated Solvents Based on Degree of

Halogenation and Volatility

Halogenated Volatiles

Chlorobenzene, 1,2-dichloropropane; 1,1-dichloroethylene; 1,2-dichloroethane;

trans-1,2-dichloroethylene; cis-1,2-dichloroethylene; 1,1,1-trichloroethane;

methylene chloride; 1,1,2-trichloroethane; trichloroethylene (TCE); chloroform;

carbon tetrachloride; 1,1,2,2-tetrachloroethane; tetrachloroethylene (PCE);

ethylene dibromide

Halogenated Semi-Volatiles

1,1-dichlorobenzene; 1,2-dichlorobenzene; Aroclor-1242; Aroclor-1254;

Aroclor-1260; chlordane; dieldrin; 2,3,4,6-tetrachlorophenol; pentachlorophenol

Non-Halogenated Semi-Volatiles

2-methyl naphthalene; o-cresol; p-cresol; 2,3-dimethylphenol; m-cresol; phenol;

naphthalene; benzo(a)anthracene; fluorene; acenaphthene; anthracene;

dibenzo(a,h)anthracene; fluoranthene; pyrene; chrysene; 2,4-dinitrophenol

Miscellaneous

Coal tar, creosote

FIGURE 1.4 Chemical structure of PCE, TCE, TCA, Freon-113, and methylene chloride.

1.3.3 H ENRY ’ S L AW C ONSTANT (K H )

The Henry’s Law constant (KH) (also known as the air-water partition coefficient) isthe ratio of the partial pressure of a compound in air to the concentration of thatcompound in water at a given temperature The Henry’s Law constant is, therefore,

a measure of the propensity of a compound to volatilize when moving through thesoil As the Henry’s Law value increases, the concentration of the contaminant in thesoil vapor phase increases Compounds with high Henry’s Law constants (PCE,Freon-11, Freon-113, and vinyl chloride) are more amenable to soil gas surveys andremediation via vapor extraction than compounds with low values Values forHenry’s Law constants are usually expressed in units of moles per cubic meter forair to moles per cubic meter for water (atm-m3/mol) As a rule of thumb, compoundswith a Henry’s Law constant greater than 10–3 atm-m3/mol and a molecular weightless than 200 g/mol are considered volatile (U.S EPA, 1996) A compound with aHenry’s Law constant less than about 5 ¥ 10–5 atm-m3/mol is considered soluble andtends to remain in water (Olson and Davis, 1990)

The Henry’s Law constants for TCE and PCE are 0.00937 and 0.0174 atm-m3/mol, respectively, and Table 1.7 lists the Henry’s Law constants for selected chlori-nated solvents (Montgomery, 1992; Pankow and Cherry, 1996)

Values for Henry’s Law constants can also be expressed in dimensionless form as:

where

KH ¢ = dimensionless Henry’s Law constant.

KH = Henry’s Law constant (atm-m 3 /mol).

R = ideal gas constant (8.20575 ¥ 10 –5 atm-m 3 /mol – K).

K = temperature of water (degrees K).

TABLE 1.7

Henry’s Law Constant for Selected Chlorinated Solvents

Henry’s Law Constant

1.3.4 L IQUID D ENSITY

The density (also called specific gravity) of a substance is the ratio of its densityrelative to distilled water (a mass-to-volume ratio) The density of distilled water atstandard temperature and pressure is about 1.0 g/mL The density of a substance isdependent on the temperature at the time of measurement Most chlorinated solventshave fluid densities greater than 1 g/cm3

Compounds with densities greater than 1.0 relative to water (e.g., ylene, trichloroethylene, polychlorinated biphenyls, bromoform) have a greater prob-ability of “sinking” into the groundwater Chlorinated solvents with fluid densitiesgreater than water are transported vertically in the vadose zone due to gravity andcapillary forces Upon entering the groundwater, these DNAPLs are transported as

perchloroeth-a function of specific grperchloroeth-avity perchloroeth-and less by perchloroeth-advection (the mperchloroeth-ass trperchloroeth-ansport of groundwperchloroeth-a-ter) through groundwater Liquids with densities less than 1.0 (methyl ethyl ketone,gasoline, diesel, Stoddard solvent, mineral oils) tend to “float” and spread along thecapillary fringe Table 1.8 lists selected chlorinated solvents, their formulas, andliquid densities (Montgomery, 1992; Pankow and Cherry, 1996; Ramamoorthy andRamamoorthy, 1998)

a Also known as ethylene bromide and ethylene dibromide.

b Also known as trichloromethane.

c Also known as tetrachloromethane.

d At 20 ∞C.

e At 15 ∞C.

The density of a mixture of free phase chlorinated solvents varies as a result ofthe selective dissolution (i.e., effective diffusion coefficient) of individual solventsinto soil or rock Individual compounds of a DNAPL mixture such as a spent solventmigrating through a fractured clay will selectively dissolve with time into the clay.The dissolution of the chlorinated solvent into the clay results in a change in thecomposition and physical properties of the solvent, including liquid density (Parker

et al., 1994a) In most cases, the specific density of the mixture increases as the higherdensity solvents persist longer in the immiscible phase

1.3.5 S OLUBILITY

The solubility of a compound is the saturated concentration of the compound in water

at a known temperature and pressure In general, the higher the water solubility, themore likely it is that the compound will be mobile in the subsurface while being lessaccumulative, bioaccumulative, volatile, and persistent The lower the water solubil-ity, the greater the probability that it will be immobilized via adsorption and will bemore accumulative or bioaccumulative in organisms The solubility of many chlori-nated solvents is high

The terms “slightly soluble” or “very soluble” are used in environmental reports

or by expert witnesses These generic categories of solubility at room temperature (20

to 30∞C) are described in Table 1.9 (Kamrin, 1997) Calculated and literature bilities of selected pure phase chlorinated solvents in water at 25∞C are shown inTable 1.10 (Huling and Weaver, 1991; Pankow and Cherry, 1996; Ramamoorthy andRamamoorthy, 1998)

solu-The effective solubility of a multi-component solvent in water depends on thecomposition of the mixture and the respective breakdown products A constituent’ssolubility within this multi-component mixture may be orders of magnitude lowerthan the aqueous solubility of the pure chemical in water (Odencrantz et al., 1992).The concentration of a dissolved phase solvent at a threshold concentration isused as evidence of the presence of a DNAPL In the 1980s, the rule of thumb wasthat, if a dissolved concentration of 10% of the saturation for the chlorinated solventwas detected, the presence of a DNAPL was inferred (Feenstra and Cherry, 1988)

In the early 1990s, research indicated that concentrations 1% or more of a compound’s

TABLE 1.9 Generic Categories of Solubility

Generic Category Solubility (mg/L)

Insoluble Less than 1 Slightly soluble 1–100

Very soluble Greater than 10,000

solubility constitute a high likelihood of the presence of a DNAPL (Cohen et al.,1993; U.S EPA, 1992, 1993) The most recent convention is consistent with this “1%rule” (Newell and Ross, 1991; Pankow and Cherry, 1996).

1.3.6 V ISCOSITY

Viscosity is the property of a substance to offer internal resistance to flow Kinematicviscosity is the absolute viscosity of the substance divided by its density Forexample, the absolute viscosity of TCE is 0.57 cSt and its specific density is 1.46, soits kinematic viscosity is 0.39 cSt A high-density liquid with a low viscosity has alow kinematic viscosity; such a fluid flows quickly through a porous medium vs aliquid with a higher kinematic viscosity

Viscosity units encountered in environmental reports include the poise and stoke The poise is a measure of absolute viscosity and is equal to gm/sec ¥ cm.Kinematic viscosity is expressed in stokes, which are equal to gm/sec ¥ cm ¥ density

at a given temperature A centipoise (cP) and centistoke (cSt) are each equal to0.01 stoke

Fluid velocity through porous media is often approximated as a proportionalinverse to the kinematic viscosity In the vadose zone, TCE may move 2.5 timesfaster than water through the same soil (Dragun, 1988) A decrease in viscosity,therefore, increases the flow rate of a chlorinated solvent through a porous media.The kinematic viscosities of selected chlorinated solvents are summarized in Table1.11 (Huling and Weaver, 1991; Montgomery, 1992)

TABLE 1.10

Calculated and Literature Solubilities of Chlorinated Solvents

Calculated Solubility Literature Solubility

constant) (Pankow and Cherry, 1996).

1.3.7 V APOR P RESSURE AND D ENSITY

Volatilization is the phase change of a compound from a liquid or solid to a gas Anexample is the partition of TCE from a shallow or highly fluctuating groundwaterinto the soil vapor in the unsaturated zone Volatilization is not a form of degradation.Factors affecting the volatility of a compound include:

• Vapor pressure

• Water solubility

• Soil moisture content

• Adsorption

• Wind speed, exposure to sunlight, air temperature, and turbulence (if the product

is released at the ground surface)

• Soil temperature

• Depth below the land surface and time available for volatilization to occur

In general, compounds with vapor pressures exceeding 0.5 to 1 mmHg can exist inappreciable concentrations in the vapor phase near a free phase solvent The vaporpressures and densities of selected chlorinated solvents are summarized in Table 1.12(Montgomery1992: Pankow and Cherry, 1996; Ramamoorthy and Ramamoorthy, 1998)

1.3.8 B OILING P OINT AND L ATENT

H EAT OF V APORIZATION

The boiling point of a chlorinated solvent is important due to its application in vapordegreasing Table 1.13 lists the boiling point and latent heat of vaporization forseveral common chlorinated solvents (Montgomery, 1992: Ramamoorthy andRamamoorthy, 1998) The boiling point of PCE is high, while methylene chlorideand CFC-113 are low The latent heat of vaporization is one measure of the energynecessary to maintain the solvent at its boiling point The higher the latent heat ofvaporization, the higher the energy needed to keep the solvent at its boiling point

TABLE 1.11 Kinematic Viscosity of Selected Solvents

(cSt)

Trichloroethylene (TCE) 0.39 Tetrachloroethylene (PCE) 0.54 1,2-Dibromomethane (EDB) 0.79