MONITORING TECHNOLOGIES FOR WELLHEAD PROTECTION
Contract Numbers (68-03-3249 and 68-CO-0049)
Work Assignment Manager
S. P. Gardner
Environmental Monitoring Systems Laboratory
Advanced Monitoring Systems Divisions
U.S. Environmental Protection Agency
P.O. Box 93478
Las Vegas, NV 89193-3478
U.S. ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
LAS VEGAS, NEVADA 89193-3478
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Task Lead
E. Eschner’
Contributing Authors
R. M. Bochicchio 2
w. H. Cole, III ’
D. Eastwood 1
W. H. Englem nn
R.LLidberg’
EL Miller 1
B. A. Moore 1
E. J. Poziomek’
S. R. Schroedel’
R. 3. White 1
S. M. H. Klainer 1
E Eschner’
‘Lockheed Engineering & Sciences Company
2 Desert Research Institute, University of Nevada, Las Vegas
U. S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory
‘Environmental Research Center, University of Nevada, Las Vegas
FiberChem, Inc.
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NOTICE
The information in this document has been funded wholly or in part by the
Environmental Protection Agency under Contract Nos. 68-03-3249 and 68-CO -0049 to
Lockheed Engineering & Sciences Company. It has been subject to the Agency’s peer
and administrative review, and it has been approved for publication as an EPA
document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
‘U
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ABS1RAC
The s pe of this document is bifocal, highlighting potential wellhead protection field
technologies, as well as recent, applicable literature. The technologies are classified into four groups:
in mi and in-line monitoring technologies, portable monitoring technologies, mobile monitoring
technologies, and teihnologies airrendy under development in .ri& and in-line t chnnlogies monitor
general physical and chemical parameters at a site, such as electrical conductivity, oxidation reduction
potential, turbidity, temperature, water level, dissolved osygen, pH, and lh ity. Portable monitormg
technologies are those which can be h2nd-carrini into the field, such as gcophysica, imniunoassays,
soil-analysis, test kits, X-ray fluorescence, and gas analysis equipment. Mobile monitoring
technologies use equipment that h transported to the field in a trailer or a mobile laboratory. Mobile
monitoring technologies include gas chromatography, mass spectroscopy, analytical x-ray fluorescence,
and atomic absorption. Innovative monitoring technologies presently in the laboratory-development
stage indude ion Mobility Spectromctry, Molecular Optical Spectrometry, extraction membranes,
surface acoustic wave probes and quartz-crystal inicrobalances, spectroelectrochenustry, and
biosensors.
The document also contains case studies of water agencies that employ innovative monitormg
technologies for ground-water and surface water quality monitonng as early-warning contaminant
detection. The case studies describe technology applications of the Orange County Water District.
California and the State of Florida.
iv
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TABLE OF CONTENTS
NOTICE ui
ABSTRACT. iv
FIGURES .
TABLES .
ABBREVIATIONS AND ACRONYMS . xiii
ACKNOWLEDGEMENTS xv
1 INTRODUCTION
1.1 References 1-3
2 WELLHEAD PROTECtION MONITORING DESIGN CONSIDERATIONS
2.1 Hydrogeologic Assessment 2-1
2.2 Source Assessment 2- i
2.3 Selection of Monitoring Parameters 2-3
2.3.1 General Water Quality Parameters 2-3
2.3.2 Site-Specific Monitoring Parameters . .. 2-4
2.4 Selection of Monitoring Technologies 2-5
2.5 References 2-6
3 AVAILABLE IN SITU AND IN-LINE MONITORING TECHNOLOG1ES
3.]. Introduction 3-I
3.2 Theory of Operation
3.2.1 In Situ, Monitoring, Multiparameter Probes
3.2.2 In-line, Monitoring, Multiparameter, Flow-Through Cells
3.2.3 Ion-Specific Electrodes
3.2.4 Water-Level Monitoring
3.3 Methodology
3.11 In Sini, Monitonng, Multiparameter Probes
3.3.2 In-line, Monitoring, Multiparameter, Flow-Through Cells
33.3 Ion-Specific Electrodes
3.14 Water-Level Monitoring
3.4 Application to WHPA Monitoring
3.4.1 In Situ, Monitoring, Multiparameter Probes
3.4.2 In-line, Monitoring, Multiparameter, Flow-Through Cells
343 Ion-Selective Electrodes
144 Water-Level Monitoring
33 Limitations/Performance
3.5.1 In Situ, Monitoring, Multiparameter Probes
33.2 In-line, Monitoring, Multiparameter, flow-Through Cells
3-2
3-2
3-2
3-3
3-6
3-6
3-6
3-8
3-8
3-8
3-8
3-8
3-9
3-9
3-9
3-9
3-9
3-13
V
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TABLE OF CONTENTS (eonthued)
3.5.3 Ion-Specific Electrodes . 3-13
3.5.4 Water-Level Monitoring 3-15
3.6 Summ2ry 3-15
3.7 References 3-16
4 PORTABLE MONITORING METhODS
4.1 Geophysies 4-1
4.1.1 Introduction 4-1
4.1.2 Theory of Operation 4-2
4.1.3 Methodology 4-3
4.1.4 Application to WHPA Monitoring 4-9
4.1.5 UfionsiPerformance 4-10
4.1.6 Summary 4-11
4.1.7 References 4-13
4.2 Immunoassays 4-15
4.2.1 Introduction 4-15
4.2.2 Theory of Operation 4-15
4.2.3 Methodology 446
4.2.4 Application to WHPA Monitoring 4-16
42.5 Limitations/Performance 4-20
4.2.6 Summary 4-24
4.2.7 References 4-25
4.3 Soil-Gas Sampling and Analysis 4-27
4.3.1 Introduction 4-27
4.3.2 Theory of Operation 4-27
4.3.3 Methodology 4-31
4.3.4 Application to WHPA Monitoring 4-32
4.3.5 Limitations/Performance 4-32
4.3.6 Summary 4-33
4.3.7 References 4-33
4.4 Test Kits 4-34
4.4.1 Introduction 4-34
4.4.2 Theory of Operation 4-35
4.4.3 Methodology 4-39
4.4.4 Application to WHPA Monitoring 4-39
4.4.5 Limitations/Performance 4-39
4.4.6 Summary 4-39
4.4.7 References 4-40
vi
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4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4.5.7
TABLE OF CONTEN1 (arnunued)
4-42
4-42
4-42
4-44
4-45
4-45
4-47
4-47
4.6 Gas Analysis Equipment
4.6.1 Introduction
4.6.2 Theoty of Operation
4.6.3 Methodology
4.6.4 Application to WHPA Monitoring
4.6.5 Limitations/Performance
4.6.6 Summary
46.7 References
5 MOBILE MONITORING METhODS
5.1 Introduction
5.2 Theory of Operation
5.2.1 Chromatographic Techniques
5.2.2 Spectrometric Techniques
5.3 Methodology
5.4 Application to WHPA Monitoring
5.5 LimitationsiPerformance
5.6 Summary
5.7 References
6 MONITORING TECHNOLOGIES UNDER DEVELOPMENT
6.1 Ion Mobility Spectrometiy
6.1.1 Introduction
6.1.2 Theory of Operation
6.1.3 Methodology
6.1.4 Application to WHPA Monitoring
6.1.5 Limitations/Performance
6.1.6 Summary
6.1.7 Referen
4.5 X-Ray fluorescence Spectroseopy
4.5.1 Introduction
Theory of Operation
Methodology
Application to WHPA Monitoring
Limitations/Performance
Simmary
References
4-49
4-49
4-49
4-49
4-50
4-50
4-51
4-51
5-1
5-1
5-4
5-4
5-5
5-5
5-5
5.6
5-6
6-1
6-1
6-2
6-2
6-3
6-3
6-3
6-4
vu
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TABLE OF CONThN1S (antmued)
6.2
Molecular Optical Spectroscopy
6.2.1 Introduction
.
.
6.2.2 Theory of Operation
.
6.2.3 Methodology
6.2.4 Application to WHPA Monitoring
6.2.5 Limitations/Performance
6-9
6-10
6-12
6.2.6 Sumn 2ry
6-14
6.2.7 Rcfe vnces
645
6.3
Extraction Membranes
6-19
6.3.1 Introduction
6-19
6.3.2 Theory of Operation
6-20
6.3.3 Methodology
6.3.4 Application to WHPA Monitoring
6.3.5 Limitations4’edormance
6-21
6-22
6-22
6.3.6 Summary
6-23
6.3.7 Referen
6-23
6.4
Surface Aurnstic Wave Probes and Quartz-crystal
Microbalances
6-24
6.4.1 Introduction
6-24
6.4.2 Theory of Operation
6-24
6.4.3 Methodology
6.4.4 Application to WHPA Monitoring
6.4.5 Umitations/Perfonnance
6-24
6-25
6-25
6.4.6 Sumn 2ty
6-25
6.4.7 References
Spectroclectrochemistry
6.5.1 Introduction
6-25
6-26
6-26
6.5
6.5.2 Theory of Operation
6.5.3 Methodology
6.5.4 Application to WHPA Monitoring
6.5.5 LimitationslPerformance
6-27
6-27
6-28
6-28
6.5.6 Summary
6-28
6.5.7 References
6-28
6.6
Biosensors
6-29
6.6.1 Introduction
6-29
6.6.2 Theory of Operation
6.6.3 Methodology
6.6.4 Application to WHPA Monitoring
6.6.5 Limitations/Performance
6-29
6-30
6-31
6-31
vru
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TABLE OF CONTEN1 ( nunued)
6.6.6 Summary . 6-31
6.6.7 References . 6-31
7 CASE STUDIES
7.1 Orange County (California) Water District: Innovative Approach to Ground-Water
Monitoring Using an In-Sini, Multi-Level, Continuous Ground-Water
Data Acquisition System 7-1
7.2 Florida’s Ground-Water Quality Monitoring Network 7-10
i x
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FIGURES
NUMBER ___
1-1 Schematic drawing of a wellhead protection area
2-1 Monitoring technologies and geneTal dass c of monitoring parameters.
3-la pH electrode which requires an external reference electrode
3-lb “Combination” pH electrode with internal reference electrode
3-2a Gas-sensing electrode
3-2b Enzyme electrode
3-2c fluoride electrode
3.3 Acxnstic device installed in a well and linked to a data logger
3-4 Conceptual drawing of a well monitoring system using
ion-selective electrodes
4-1 Diagram showing basic ncept of resistivity measurement
4-2 Illustration showing EM principle of operations
4-3 Illustration of ground penetrating radar system. Radar waves are
reflected from soil/rock interface
4-4 Enzyme Iinmunoassay
4-5 A typical field analysis kit
4-6 Field portable spectrophotometer
4-7 Contaminant volatilization and detection by soil-gas sampling and analysis
4-8 Various active soil-gas sampling probe designs
4-9 Passive soil-gas sampling using a sorbent badge and an inverted can
4-10 Typical test kit equipment
4-11 Schematic drawing of a detector tube
4-12 The field-portable, X-ray fluorescence system (FPXRF)
4-13 Bohr model atomic exatation
4-14 WdHh protection screening with FPXRF
4-15 Hand-held sampling probe
5-1 Modular mobile analysis laboratory arranged to accommodate a variety
of analytical equipment
6-1 Major regions of the electromagnetic spectra
6-2 Fiber optic chemical analysis system
6-3 Schematic diagram showing extraction disk concentrating
the analyte of interest
6-4 Schematic diagram of a biocatalytic-based biosensor
(after Arnold and Meyerhoff 1988)
7-la Location map
7-lb Idealized hydrogeologic cross section
7-2 Comparison of methods for monitoring ten levels between 0 and 1,500 ft
1-2
2-5
3-4
3-4
3-5
3-5
3-6
3-7
3-10
4-2
4-4
4-5
4- r i
4-18
4-18
4-28
4-30
4-31
4-34
4-38
4-43
4-44
4-46
4-50
5-2
6-7
6-9
6-20
6-30
7-2
7-2
7-3
x
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FIGURES (continued)
NUMBER
7-3 Schematic diagram showing various mnitiport t1I construction
techniques used for site-specific applications 7-4
7-4 Schematic illustration of MOSDAX System Monitoring fluid pressure
atmuLtiple leve lsinanMPSystemwe ll 7-5
7-5 Cartoon schematic showing idealized pound-water monitoring system 7-7
7-6 ldeslfred cross-section showing aquifers and confining beda of Florida 7-10
7-7 Principal aquifers within florida 7-11
7-8 The five water management districts in florida (from Leach, 1978) 7-12
7-9 Schematic i l lustration showing generalized SCADA concepts
(from Sierra-Misco, Inc.) 7-18
xi
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TABLES
NUMBER __
2-1 Common Sourees of Ground-Water Contamination . 2-2
2-2 Monitoring Parameters for Vanous Sourees within a WHPA 2-4
3-1 E mplcs of in iiw Probe Specifications 3-il
3-2 Example of Commercially Available Flow-Through Cell Specifications 3-13
3-3 Practjcaj Limits of Detection for Several Ion-Selective and
Gas Sensing Electrodes 3-14
4-1 Sumrnaiy of Log Applications 4-6
4-2 Summaiy of Conditions Affecting Well Logging Devices 4-12
4-3 Application of Immunoassays to WHPA Monitoring 4-19
4-4 Commercially Available Immunoassays for Environmental
Contaminant Measurements 4-21
4-5 Some Immunoassays for Environmental Contaminant Measurements
(Not Yet Commercially Available) 4-23
4-6 Advantages and Limitations of Immunoassays 4-23
4-7 Most Frequently Identlfieci Contaminants at 546 Superfund Sites
and the Compounds Amenable to Detection by Soil-Gas Sampling and Analysis .... 4-29
4-8 Commercially Available Wet-Qietnistry Kits, Badges,
and Water-Test Kits and Respective Target Analytes 4-36
4-9 The Inorganic Target Analyte List (TAL) 4-45
5-1 Degree of Laboratory Independence of Instrumentation
Used for Chemical Analyses 5-3
6-1 Application of Various Spectroscopic Methods to Major Chemical Groups 6-11
6-2 Advantages and Disadvantages of Various Spectroscopic Methods 6-13
7-1 Background Network Monitoring Parameters 7-14
7-2 Predominant Land Use Categories-VISA Network 7-16
x l i
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ABBREVIATIONS AND ACRONYMS
ABBREVIATIONS
AA atomic absorption
AC alternating current
ASTM Ametican Society for Testing and Materials
bp below ground surface
BOD biochemical oxygen demand
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
COD chemical oxygen demand
CV coefficient of variation
DC direct current
DO dissolved oxygen
DOOs data quality objectives
EC electrical xnductance
ELISA enzyme-linked immunosorbent immunoassay
EM electromagnetic
FID flame ionization detector
FOCs fiber optic chemical sensors
FPXRF field-portable, X-ray fluorescence
ETIR Founer Transform IR Spectrophotometer
GC gas chromatography
GC/MS gas chromatography/mass spectroscopy
gpm gallons per minute
GPR ground penetrating radar
HPLC high performance liquid chromatography
ICP/AES inductively aupled plasma discharge/atomic emission spectrosapy
IMS ion mobility spectrometer
IR infrared
LC-MS liquid chromatography-mass spectroscopy
OCWD Orange County Water Distnct
OVAs organic vapor analyzers
OVMs organic vapor meters
PAHs polyaroinatic hydrocarbons
PC personal computer
PCBs polychiorinated biphenyls
PID photoionization detector
ppb parts per billion
pph parts per hundred
ppm parts per million
ppt parts per trillion
x lii
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ABBREVIATIONS AND ACRONYMS (continued)
ppth pars per thousand
QA/OC quality assuranadquality control
QCM quartz-crystal inicrobalana
redox oxidation Suction
RCRA Resource Conservation and Recovery Act
RIA radloimmunoassay
SAW surface acoustic wan
SCADA Supervisor Control and Data Acxiuisition
SERS surface-enhanced Raman spectrvscopy
SITE Superfund Innovative TechnoLogy Evaluation
5M G! surface memory and control unit
SP spontaneous potential
SSC site specific calibration standards
TCE trich loroethylene
TDS total dissolved solids
TOC total organic carbon
TSS total suspended solids
UV-vis ultraviolet-visible
VISA very intense study area
VOC volatile organic compound
WHPA wellhead protection area
WHPP welihead protection program
WRMS Water Resources Management Sjstem
XRF X-ray fluorescence
x lv
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ACKNOWLEDGEMEN1S
The preparation of this doaiment required the servi of numerous anmbuting authors from
the U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory, Lockheed
Engineering & Sciences Company, the Desert Research Institute, the Environmental Research Center.
and FiberChem, Inc. The names of these individuals and the organizations they represent are
included in the list of authors on page ii.
The preparation of the case studies also required the support of numerous individuals.
Portions of the Orange County Water District (OCWD) case study are reprinted with permission of
the Association of Ground Water Scientists and Engineers, a division of the 4ational Water Well
Association. Individuals at OCWD who provided assistance on this case study are K L BnuI.
R. L Herndon, M. D. West, and 3. A 000dIiCIL 0. Florence and 0. H. Kinsman (Southwest Flonda
Water Management District), R. Copeland (Florida Department of Environmental Regulation), K
Rohrer (Sarasota Ecological Monitoring District) and 3. Kite (Saint John’s River Water Management
District) were instrumental in preparing the Florida case study.
The authors also acknowledge the technical editing services of J. M. 4ichoIson and word
processing skills of A. A. Viray (Lockheed Engineering & Sciences Company).
xv
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SEC 1ON I
INTRODUC T iON
The increasing threat of chemical contamination to public water supply wells has created a
new political and technical awareness of ground-water protecuon programs. Management of both
contaminant sour and public water supplies is necacazy to prevent and minimize ground-water
quality degradation. En 1986. the Safe Drinking Water Act was amended to include Section 1428.
This amendment called for the creation of a wel lhead protection program (WHPP), thus establishing
a legal framework to protect public water supply wells, welifields, and springs from contamination.
Elements of a WHPP include, at a minimum (EPA, 1989a):
• Specifying the roles and duties of cooperating agencies.
• Delineating the wellhead protection area (WHPA) for each wellhead or spring.
• Identifying sources of contamination within and in proximity to each welihead or spring.
• Developing management approaches to protect the water supply within WHPAs from
contaminants.
• Developing contingency plans in response to wellhead or spnng contamination.
• Siting new wells properly to maximize yield and to minimize contamination.
• Ensuring public participation.
An important technical and management element of WHPP implementation is the
rnonitorrng of chemical and physical parameters in WHPA& A WHPA is defined as the surface and
subsurface areas surrounding a well, welifield, or spring, through which contaminants could pass and
reach that portion of the ground water which is contributing to the water supply. Figure 1-1 depicts a
simplified WMPA with it’s potential source (landfill) and the water well to be protected.
A monitoring strategy for a WHPA is generally designed to perform three functions - source
release detection, ambient trend monitoring, and early warning detection (Caner et al, 1987). The
function that a monitoring device performs depends, in part, on its position along the flow path from
the potential source to the wellhead.
The source release detection function determines if contamination has begun migrating from
the source material. Monitoring devices would be situated below or immediately down-gradient of the
potential source area. The ambient trend monitoring function assesses the temporal and spatial trends
in ground-water quality in the bulk of the WHPA between the source area and the wellhead. A
dispersed array of monitoring devices situated along flow paths is required for this purpose. The early
warning detection function provides advance notice of the need to enact contingency response plans to
prevent public exposure to contaminants. This function is performed by monitoring devices a
relatively short distance up-gradient of the welihead.
1- 1
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This document focuses on field analytical techniques which may be incorporated into the
WHPA monitoring strate r to perform one or more of the monitoring functions described.
Numerous field technologies that measure chemical and physical parameters in soil and water have
been evaluated, but to date, an examination of the relationship of these technologies to WHPA
monitoring has not been compiled. This document is intended to fill that gap, presenting methods
that complement traditional laboratory analyses and that are especially useful for rapid field screening
of ground-water, soil, and soil-gas samples. As such, many of the technologies described are useful
tools in the characterization and monitoring of WHPAs.
As monitoring techniques, field methods have several advantages over conventional, analytical
laboratory analyses. For example, they can provide timely, on-site information that can be used
immediately to make decisions about additional sampling needs. This eliminates the frustration of
waiting several weeks for laboratory results. Field technologies are also more portable and less
expensive than laboratory methods.
There are, however, several drawbacks to field methods. The detection limits and accuracy of
field methods (especially methods currently under development) are not always as reliable as
laboratory methods. This is especially critical, for example, if the detection limit of the field method
does not meet water quality criteria or regulatory requirements. Nevertheless, even less accurate field
methods might be useful to screen samples prior to confirmatory laboratory analyses.
MONITORING
WELL
Figure 14. Schematic drawing of a welihead protection area.
1-2
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The s pe of this document is bifocal, highlighting potential WHPP applications of field
technologies, as well as reant, applicable literature It is written for technical personnel (engineers,
geologists, and chema) from local water departments and utility companies who are responsible for
the implementation of WHPP monitoring and the protection of public water supplies. The document
includes a description of WHPA monitoring design considerations (Section 2) and discussions of a
variety of field measurement technologies. These indude in sin. and in-tine monitoring technologies
for general chemical and physical parameters (Section 3), portable monitoring technologies
(Section 4), technologies that can be used in field laboratories (Section 5), and technologies currently
under development (Section 6). Section 7 contains descriptions of applications of monitonng
technologies by local water districts.
1.1 REFERENCES
U.S. Environmental Protection Agencyc 1989a. Wewzead &osecSn Programs: TooLc for Local
Govenimenu. EPA-440i6-89R)OZ U.S. EPA, Office of Ground-Water Protection, Washington, D.C
1 -3
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SECIION 2
WELLHEAD PROTECIION MONiTORING DESIGN CONSIDERATIONS
Ground water can become contaminated by numerous hazardous materials such as fertilizers,
pesticides, septic tank effluent, and organic and inorganic industrial waste. Ground-water systems can
vary greatly in the nature of their flow and assimilative characteristies. It is clear that a monitoring
strategy that effectively addresses the physical, chemical, and microbial threats to an adequately
characterized ground-water system is essential to protect against the danger of well contamination.
In this section, the considerations in the design of a WHPA monitoring strategy are briefly
discussecL Those considerations include the hydrogeologic assessment, the source assessment, the
selection of monitoring parameters, and the selection of monitoring technologies. It is not the intent
to reproduce information which is provided in other existing or developing WHPP guidance
documents, but to develop the framework for the discussion of field analytical techniques in
subsequent sections.
2.1 HYDROGEOLOGIC ASSESSMENT
Characterization of the WHPA hydrogeologic system is a prerequisite to the development of
the contaminant transport conceptual model and the design of an effective monitoring system.
Elements of the conceptual model include the sources, migration pathways, and receptors. In a
WHPP, the receptor is the public water supply well, welifield, or spring. During the initial stages of
program implementation, potential contaminant sources are identified, characterized, and prioritized.
Concurrently, WHPAs arc delineated based on a site-specific, ground-water flow and contaminant
transport - ment
2.2 SOURCE ASSESSMENT
A critical first step in the design of an effective monitoring system is the assessment of
potential sour of aquifer contamination. A wide variety of anthropogenic contaminant sources may
threaten ground-water supplies. A list of common sources of ground-water contamination is provided
in Table 2-1. General guidance for inventorying, prioritizing, and characterizing potential
contamination sour for welihead protection is in the following U.S. EPA documents:
• Tools for Local Governments (1989a).
• Practical Guide for Assessing and Remediating Contaminated Ground Water (198 %).
• Guide to Water-Supply Contingency Planning for Local and State Governments (1990a).
2-1
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TABLE 2-1. COMMON SOURCES OF GROUND-WATER CONTAMINATION
AGRICULTURAL
Animal burial areas
Animal leedlots
Che mical application
leg. pessiddes. lungicides, and (ertihzcrsl
Chemical slonge areas
Ii option
Maniac spreading ptts
COMMERCIAL
Airporis
A i.to repair shops
Burnt yards
Cons lruction areas
Car washes
Cernetenes
Dry cleaning establishments
Educalional Insfi lutlons leg, tabs, lawns, and
chemical siorage areas)
Gas siations
Coil onunes (che mical application)
Jewelry and metal plating
laundromats
Medical Institutions
rains shops
Photography establishments! pnnters
Itaitroad tracks and yards/maintenance
Research laboratories
ltoadektdngoperaiions leg. road sail)
Road ma intenance depots
Scrap and rink yards
Storage iaiiks and pipes tic • above ground
betuw graunit. unjngmnundl
IN IMISTR IA I.
Asphalt plants
Chemical mnanulacture, warehousing, and
iJ ,stnbution activities
Electrical and electronic products and
manu fa cturing
Electroplaters and metal labncaioms
Forir idar its
Machine and metalworking shops
Manufacturing and d istribution sites for
cleaning supplies
Mining (surface and underground) and
mine drainage
l’etzoleum prod uc ls production. storage.
and distribution centers
I’ipelines I c g . 0 4, gas, coal slurry)
Scptagc tagoons and sludge
Storage tanks lie e.. above-ground.
beluw-giound, underground)
losic and hazardous spiiis
Wells- operating and abandonS
Ce g . oil, gas, water supply. injection.
monitoring and caploration)
Wood l’reserwlng fadhitics
l(ESIl)IiNTJA I.
Fact siiuagc sy aems
trimliure and wood slippers and retinitis
I iuusthold hazardous products
1 lousehotd lawns (chemical application)
Septic systems. cesspoots. water solteners
Sewer tines
Swimming pocis leg . c hloonc)
WASTE MANAGEMENT
Fire training facilities
I lazardous wasie management anus
Ic g. landfills, land treatment areas. surface
tmpoundments. waste piles. iaclnerators,
treatment tanks)
Municipal incinerators
Municipal landfills
Municipal wastewaler and sewer lines
Open buniing sites
Recycling and rcduction laciliiics
Stonnwatcr drains, retention basins.
translcr stations
ha
it)
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• A Review of Sources of Ground-Water Contamination from Light-Industry (199(b).
• The Risk Ranking and Screening System (RRSS), Volumes 1,1 1, and III (In Review).
2.3 SELECI1ON OF MONiTORING PARAMETERS
After the contaminant sources are identified, optimal monitoring sites are determined based
on the prioritization of sources. Next; monitoring parameters for early-warning detection and source
assessment can be selected from a comprehensive list of known and suspectsd contaminants associated
with specific sour . Tailoring the monitoring objectives based on the source assessment and
choosing the appropriate monitoring parameters enhances protection and characterization, improves
efficiency, and reduces the cost of the program.
It is important to choose chemical parameters for WHPP ground-water monitoring based on
the potential contaminants from sources identified as the most serious threat to specific WHPAs.
However, if a wide variety of potential sources are within a WHPA, the number of monitoring
parameters ultimately must be balanced against the number of samples analyzed and the cost of the
analyses. Therefore, when possible, indicator parameters are sought that will be effective for detecting
the presence of ground-water contamination and signaling when more comprehensive laboratory
analysis is needed
2.3.1 General Water Quality Parameters
Ground water contains natural chemical constituents; the type and quantity nf these
constituents depends on the geochemical environment, migration, and source of the ground water
(Todd et at 1976). The most common inorganic chemical constituents, which are usually analyzed as
part of the broad category of general water quality parameters, include the major canons (calcium,
magnesium, potassium, and sodium) and major anions (bicarbonate, chloride, nitrate, and sulfate).
Analyses of environmental isotopes, such as Tritium, can be a valuable aid in a WHIt. These
data may allow the investigator to distinguish age zones within the system and to estimate the average
linear velocity of ground-water flow.
Other general indicators of water quality include temperature, electrical conductivities, ph,
dissolved oxygen (DO), biochemical oxygen demand (ROD), chemical oxygen demand (COD), total
organic carbon (TOC), specific conductance, oxidation reduction (redox) potential. total suspended
solids (flS), and turbidity.
By analyzing and graphing the inorganic chemical composition of ground water,
interpretations are made concerning the classification, age, origin, source of the water, ground-water
flow paths, and interconnections between aquifers. These geochemical interpretations are used to
refine the hydrogeologic conceptual model of the study area Data visualization methods, such as Stiff
diagrams, Piper diagrams, and other graphical techniques are commonly used for interpreting water
chemistry data (Davis and DeWeist; 1964 Freeze and Cherry, 1979; Hem, 19 O).
2-3
-------
2.3.2 Site-Specific Monitoring Parameters
Approaches for choosing indicator monitoring parameters were developed for characterizing
hazardous waste sites. The Resource Conservation and Recoveiy Act (RCRA) interim status
regulations identified four indicator parameters for usc in detection monitoring for ground-water
contamination: specific conductance, pH, total organic carbon, and total organic halides (EPA,
1989c). Numb (1985, 1987) and Plumb and Pitchford (1985) showed that volatile organic compounds
(VOC.s) were the single most abundant class of organic contaminants detected in ground water due to
releases from hazardous waste sites. They proposed using a VOC scan as a cost-effective monitoring
approach to detect ground-water contamination and suggested more comprehensive laboratory
analyses at both RCRA and Superfund sites. Rosenfeld (199( b) documented ground-water
contamination at hazardous waste disposal sites and other industries and proposed using site-specific
monitoring parameters that are customized for different source industries.
The chemical parameters in Table 2-2 are suggested as an approach for monitoring the broad
categories of sources typically found within or in proximity to WHPAs. This list is only a general
guideline, and it is extremely important to choose appropriate monitoring parameters on the basis of
site-specific conditions.
TABLE 2-2. MONITORING PARAMETERS FOR VARIOUS SOURCES WIThIN A WHPA
Source Monitoring Parameters
Agricultural General water-quality (canons, anions, TDS, pH, specitic
conductance, temperature, DO, redox)
Nutrients (nitrate, nitrite, ammonia, phosphate)
Pesticides, insecticides, herbicides VOC scan (optional)
Commercial and Industrial Facilities General water-quality
Trace metals
voc
Other Priority pollutants (optional)
Gross alpha and beta (optional)
Residential General waler-quality
Nutrients
VOC scan (optional)
Trace Metals (optional)
Waste Management General water-quality
VOC scan
Trace metals
Other priority pollutants (optional)
Gross alpha and beta (optional)
TDS = total dissolved solid
DO = dissolved oxygen
VOC = volatile organic compound
2-4
-------
The suggested approach L5 based primarily on using the VOC scan as an indicator of leakage
events at amrn rciaJ, industrial, and waste management sites. Trace metals should also be monitored
for those sources to check for inorganic contamination; organic priority pollutants (other than VOCs)
and radioactivity screening may also be ne s ary, depending on site-specific conditions. Nutrient and
pesticide analyses are suggested monitoring parameters for agricultural source and residential septic
system identification. Additionally, general water quality parameters can potentially be useful for all
types of sources, not only for source assessment, but also for refinement of the hydrogeologic
conceptual modeL
2.4 SELEC11ON OF MONiTORING TECHNOLOGIES
The field monitoring technologies presented in this document can be used for measurements
of many of the suggested monitoring parameters. Figure 2-1 lists the monitoring technologies
described in this document and sho the general dass s of monitoring parameters that can be
detected by each technology. Many of the technologies are used primarily for analyzing water
samples, but some of the technologies are more useful for source assessment activities because of
their applications for measurements of soil and soil-gas properties. Figure 2-1 can be used as a
reference index to the remaining sections of this document to find information on either a specific
type of instrumentation or class of monitoring parameter.
m ==- - - -
Q Owc.&tu
NONTD S
S *TLIOaGAI
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a
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11
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i
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Figure 2-1. Monitoring technologies and general classes of monitoring parameters.
I.SI I
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2-5
-------
2.5 REFERENCES
Canter, L W., R. C Knox, and D. K Fairchild. 1987. Ground Water Quality Protection. Lewis
Publishers, Inc.; Chelsea, Michigan.
Davis, S. N. and it 3. It DeWiest 1%& !t,vfrogeologst. Wiley; New York, New York
Freeze, It A and 1. A Cherry. 1979. Groundwater. Prentice-Hail, Inc.; Englewood Clif&, New
Jersey.
Hem,]. D. 1970. Study and lrnei’pretanon of the Chemical Characteristics of Natural Water. Geological
Survey Water-Supply Paper 1473, U.S. Geological Survey. U.S. Government Printing Office,
Washington, D.C
Plumb, 0.. H., Jr. 1985. “Disposal Site Monitoring Data: Observations and Strategy Iniplkaflonc
In: Proceedings of the Second Canadian/American Conference on Hydrogeo logy, Hazardous Wastes
in Ground Water A Soluble Dilemma. Banff, Alberta, Canada; National Water Well Association.
Dublin, Ohio. 69-77.
Plumb, R. H., Jr. 1987. ‘A Comparison of Ground Water Monitoring Data from CERCLA and
RCRA Sites.” Ground Water Monitonng Review. 7(4): 94-100.
Plumb, R. H., Jr. and A M. Pitchford. 1985. ‘Volatile Organic Scans: Implications for Ground-
water Monitoring.” Ig: Proceedings of the Conference on Petroleum Hydrocarbons and Organic
Chemicals in Ground Water - Prevention, Detection, and Restoration. Houston, Texas; National
Water Well Association. Dublin, Ohio. pp. 207-222.
RosenfeLd, J. K 1990a, “Ground-Water Contamination at Hazardous Waste Disposal Facilities.” In:
Ground Water Management. 1: 237-250. Proceedings of the 1990 Custer of Conferences, Kansas City,
Missouri; National Water Well Association. Dublin, Ohio.
Rosenfeld, ]. K 1990b. “Industry-Specific Ground-Water Contamination.” j : Proceedings of the
Conference on Minimizing Risk to the Hydrologic Environment Las Vegas, Nevada; American
Institute of Hydrology Minneapolis, Minnesota pp. 93-111.
Todd, D. K, It M. Tinlin, K. D. Schmidt, and L. D. Everett 1976. Montronng Groundwater Quality:
Mon:tonng Methodolog,’. EPA-60014-7&026. U.S. Environmental Protection Agency, Environmental
Monitonng Systems Laboratory, Las Vegas, Nevada
U.S. Environmental Protection Agency. 1987. An Annotated Bibliography on WeWsead Protection
Program. EPA-440th-87-014. U.S. EPA, Office of Ground-Water Protection. Washington, D.C
U.S. Environmental Protection Agency. 1989b. Practical Guide for Assessing and Remediating
Contaminated Ground Water (Unpublished Draft). U.S. EPA, Office of Solid Waste. Washington, D.C
2-6
-------
U.S. Environmental Protection Agency. 198k. Trwtç rT and Fate of Contaminant, LI the Subsurface
( Semm r Publiestion). Center fix Environmental Research Inflrmation and R. S. Kerr
Environmental Research Laboratory. EPA-625/4-89i019. R S. Kerr Environmental Research
Laboi tory Ada, Oklahoma.
U.S. Environrn ntal Protection Agency. 199( . Guide to Grcwid-Wate &q v Conthig y Planning/or
Local and State GovernmenL?. EPA-44O -9O-OO3. U.S. EPA, Office of Ground-Water Protection.
Washington, D.C.
U.S. Environmental Protection Agency. 1990b. A F view of Sources of Ground-Water
enntamination horn Light Industry. EPA-44OE J -005. U.S. EPA, Office of Ground-Water
Protection. Washington, DC.
U.S. Environmental Protection Agency. In Review. The Rick Ranking and Screening System (RRSS),
Vo4unes L Ii . and 11!. U.S. EPA. Washington, DC
2-7
-------
SECTION 3
AVAILABLE IN SITU AND IN-LINE MONITORING TECHNOLOGIES
3.1 INTRODUCTION
Current water quality monitoring practices generally involve costly and time consuming
annual, biannual, or quarterly ground-water sample collection and analysis activities. The use of field
screening technologies to monitor selected parameters may indicate the need for ground-water
sampling in response to a baseline change rather than as a part of a predetermined sampling schedule.
This will provide a more timely detection of the changes in water quality.
General indicators of ground-water quality were provided in Section 2.3.1. Because these
indicator parameters are useful for dictating when sampling should occur, it is imperative to establish
a data base containing baseline values of clean (uncontaminated) or ambient ground water.
These indicator parameters are sensitive to changes in pressure, temperature, agitation, and
exposure Lu atmospheric gases (Gillham Ct aL, 1983); therefore, it is advantageous to obtain in mu
sample readings (Garner 1988; EPA 1986). in situ monitoring devices possess some form of sensor or
probe which is designed to be placed in the medium to be monitored (i.e., ground water or soil). This
sensor reacts to certain chemical or physical parameters in the medium and transmits information
regarding the magnitude of that reaction by means of an electrical current (etc.) to a meter or a
recorder. Several companies produce in situ, multiparameter probes and data transmitter packages for
continuous water quality monitoring (e.g., Hydrolab Corporation; Martek Instruments, Incorporated).
The use of in sins monitoring devices in wells, however, is limited to certain conditions. The
rate of aquifer flow through the well screen must be adequate enough so that the well is self-flushing
and no purging procedure is nece -cary. This flow-through rate is controlled by the aquifer properties
and the design of the well. An adequate flow-through rate would be analyte -specific and would not
have been quantified.
When in situ monitoring is infeasible or impractical, measurements from in-line, flow-through
cells at the wellhead can be used to reduce the effects of atmospheric gaseous contamination (Walton-
Day et aL, 1990; Garner, 1988; Torstensson and Petsonk,, 1988; Barcelona et al., 1985; Nacht, 1983;
Gibb et al., 1981). In utilizing such a device, ground water is pumped to the surface in a closed
system. The ground water is directed to flow through a device (cell) which is designed to react to
certain chemical or physical parameters. The magnitude of these reactions are transmitted to a meter
or a recorder. Multiparameter, in-line, flow-through cells can be fabricated with commercially
available materials (Walton-Day et al., 1990), or purchased from commercial vendors (e.g., YSI
Incorporated; Hydrolab Corporation). Additionally, a variety of manufacturers provide standard water
quality instruments for measuring temperature, electrical conductivity, pH, and turbidity.
3-i
-------
Ion-specific electrodes, available from various vendors, are capable of measuring specific
analytes of interest and are commonly used in the waste-water industries. However, many ion-specific
electrodes are sensitive to various environmental factors and are not easily use.able in continuous
monitoring applications for wdfihead protection.
Water level monitonng technologies are also useful in WHPA applications. Water level
monitoring devices are classified into three main categories: float recorders, acoustic devices, and
pressure transducers. By using these methods, a)ntinuous water level measurements can be made.
3.2 THEORY OF OPERATION
3.2.1 In Situ. Monitoring. Multipararneter Probes
Commercially available probes are equipped with a sensor for measuring temperature and a
six electrode duster for measuring specific conductance, salinity, pH, DO, oxygen, and redox potential.
Additionally, the probes are equipped with a pressure transducer for measuring depth or water level.
Three types of sensors can be used for measuring temperature; these include thermistors,
thermocouples, and resistance temperature detectors (Ritchey, 1986). Specific conductance, or
conductivity, is measured with a multi-electrode cell that is calibrated with standard potassium chloride
or seawater solutions, and the measurement is automatically temperature-compensated because
conductivity varies with temperature. Salinity is automatically calculated from the conductivity
measurement. The pH is generally determined with a glass membrane etectrod celL The pH
electrode is calibrated using standard pH buffer solutions and is automatically temperature-
compensated. Dissolved oxygen is measured with an ion-specific electrode and a membrane cell
calibrated using saturated air, saturated water, or the Winkler titration method. The measurement is
automaticaUy temperature- and salinity-calibrated. The redox potential is measured using a platinum
electrode. Water level or depth is measured using a pressure sensitive, strain-gauge transducer that is
automatically compensated for specific conductance. The sensors must be calibrated before the probe
is submerged in the water well to the desired depth of the screened interval of interest.
3.2.2 In-Line Monitoring. Mwnparameter. flow-Through Cells
Flow-through cells can be purchased from several manufacturers to monitor temperature,
temperature-compensated conductivity, temperature-compensated pH, and redox potential. One
manufacturer supplies an attachable flow cup for the multiparameter probe that allows in-line
measurement of salinity, DO, and pressure.
Water extracted front the desired depth in the well is pumped through the inlet port of the cell
chamber where the measuring sensors are located. The chamber is generally constructed of durable.
clear acrylic so the water flow and turbidity conditions are observable. Electronically, the water
flowing through the chamber is continuously monitored by the sensors, and the values can be stored
using a data logger or a computer.
3-2
-------
3.2.3 Ion-Specific Electrodes
Electrodes are constructed of a metal wire coated with an insoluble salt of the metaL If the
electrode is dipped into a liquid solution containing a low concentration of the metal ion or a high
concentration of the negative ion of the insoluble salt, the metal wire will tend to react to form the
insoluble salt. Conversely, if the water solution contains a high concentration of the metal ion, or a
low concentration of the negative ion, the insoluble salt will tend to form the metal. In these
reactions, electrons are added to or removed from the metal wire, changing the electrical charge on
the wire. By measuring the voltage of a calibrated electrode, the concentration of the metal ion or
negative ion in the solution can be calculated.
The silver chloride and the silver sulfide electrodes are the most common electrodes used in
the manufacture of ion-selective electrodes. The silver chloride electrode consists of a silver wire
coated with insoluble silver chloride, which is immersed in a solution containing chloride ions. The
silver chloride electrode can be used to measure the concentration of silver ions or chloride ions
dissolved in water. The principle of operation of the silver sulfide electrode is identical to that of the
silver chloride electrode, but the construction of the silver sulfide electrode is simpler because it is not
immersed in a solution containing the negative ion of the insoluble salt (sulfide, in this case). If
another metal sulfide is dispersed in the silver sulfide matrix, the electrode can be used to measure the
concentration of that metal dissolved in water. For example, by mixing lead sulfide with the silver
sulfide, the electrode can be used to determine lead dissolved in water. If an insoluble silver salt is
dispersed in the silver sulfide, the electrode can be used to measure the concentration of the negative
ion of the silver salt dissolved in water. A cyanide-sensing electrode can be made by mixing silver
cyanide with the silver sulfide (Willa d ct al., 1974).
Perhaps the most familiar type of ion-selective electrode is the glass membrane electrode,
which is used for measuring the pH of water samples (Figure 3-la). The pH electrode uses a silver
chloride internal reference electrode immersed in a chloride internal filling solution surrounded by a
thin glass membrane (Figure 3-ib). When immersed in an alkaline solution, positive hydrogen ions
are removed from the outer surface of the bulb, leaving the bulb with a negative charge. The negative
charge on the bulb repels negatively charged chloride ions dissolved in the solution within the bulb.
The chloride ions duster around the silver wire, increasing the local chloride concentration, thus
making the electrode voltage more negative. When immersed in an acidic solution, hydrogen ions are
added to the surface of the glass bulb, giving it a positive charge. The positively charged bulb attracts
chloride ions and decreases their concentration around the silver wire. The electrode voltage is
charged according to the pH.
The pH electrode forms the basis of other electrodes which can be used to measure the
concentration of certain gases dissolved in water. In the ammonia electrode, for example, the glass
sensing element of a pH electrode is surrounded by an internal filling solution contained by a porous
membrane (Figure 3-2a). The membrane repels liquid water but permits the free passage of gases.
When this electrode is dipped into water that contains ammonia, the ammonia passes through the
electrode membrane and is dissolved in the solution surrounding the glass bulb. The ammonia
changes the pH of the solution; this, in turn, changes the voltage of the electrode. In addition to
ammonia, electrodes can be used to measure the concentration of other gases dissolved in water,
including carbon dioxide, oxides of nitrogen, and oxygen.
3-3
-------
Figure 3-la. pH electrode which
requires an external
reference electrode.
Figure 3-lb. “Combination” pH
electrode with internal
reference electrode.
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3-4
-------
Figure 3-2a. Gas-sensing electrode.
Modified gas-sensing electrodes n be used to measure the concentration of numerous
organic compounds dissolved in water. This is accomplished by coating the gas-sensing electrode
membrane with an enzyme or talyst which converts a specific organic compound to the gas that is
measured by the electrode (Figure 3-2b). The most common example is the urea electrode in which
the enzyme urease is applied to an ammonia electrode membrane. The urease converts urea to
ammonia, which is then detected by the ammonia electrode.
Figure 3-2b. Enzyme electrode.
The fluoride ion electrode is similar in construction to the pH electrode. Instead of a glass
membrane, however, the fluoride electrode uses a crystal of the insoluble solid-state ionic conductor
lanthanum fluoride, and the internal filling solution contains fluoride as well as chloride ions
(Figure 3-2c). When dipped into a solution more concentrated in fluoride than the internal solution,
negative fluoride ions enter the ciystal, giving it a negative charge As in the se of the pH electrode,
the negatively charged crystal increases the chloride concentration in the vicinity of the silver wire and
makes its voltage more negative. When dipped into a more dilute solution, fluoride ions leave the
crystal, giving it a positive charge. The chloride concentration in the vicinity of the silver wire is
decreased, and the voltage of the wire becomes more positive. Other ion-selective electrodes are based
on the silver sulfide electrode instead of the silver chloride electrode.
tI..w.
( =.
3-5
-------
3.2.4 Water-Level Monitoring
Several different types of devices can be used to monitor water-level measurements. These
indude float and weight systems, acoustic devi , or pressure transducers that can be connected to a
chart recorder, digital encoder and data loggers, or a modem.
Float systems installed in the well require a float that is connected to a weight by a beaded
cable or a graduated tape that rests on a pulley. The changing water level in the well causes the float
to rise or fail with the water in the well. The change in the position of the float causes the pulley to
rotate proportionally, and if the pulley is linked to a clock-controlled chart recorder, a pen records the
water level change on a scaled chart. Alternatively, a digital encoder may be linked to the puUey so
that the water level change produ a digital signal that is recorded using a data logging device, or the
logger may be linked to a modern and the data relayed to a centralized location for analysis and
computer storage and use.
Acoustic devices installed in the welihead produce short pulses of sound waves that reflect off
the water surface. The acoustic device receives the reflected sound wave, and the elapsed time between
pulse transmission and the reception of the reflected wave is convened to a distance measurement
The water level in the well is periodically monitored by the device, which is linked to a data logger or
modem (Figure 3.3).
Transducers, installed in the well beneath the water surface, use pressure/strain relationships to
create an electrical signal to measure water level or depth. The electrical signal is transmitted from the
transducer and is relayed up a coaxial cable to the weUhead.
3.3 METHODOLOGY
3.3.1 In Situ. Monitorine. Multiparameter Probes
The probe is calibrated at the welihead using the appropriate standard solutions that include
the ranges of values anticipated for the temperatures expected in the well water to be monitored.
Next, the probe is lowered into the well using a cable that mounts to a bracket attached to the probe.
Figure 3 .2c, fluoride electrode.
3-6
-------
Figure 3-3. Acoustic device installed in a well and linked to a data logger.
3-7
Casing
Water Level
-------
Parameter values are manually queried at the weithead with a rotating switch on the display unit; or
the data may be stored on a digital, field data, legging device for manual or unattended data storage.
Another device, called a data nnnngement unit, is needed to transfer the data from the logging device
to any RS-232-C compatible printer, data terminal, or computer. Therefore, unattended monitoring
can be performed, and the data can be stored at the monitoring site and retrieved by a site visit, or the
data may be tranimitted to the centralized data base via modem or telemetry.
3.3.2 In-Line. Monitoring. Multiparaineter. flow-Through Cells
flow-through cells are calibrated at the wel lhead using the appropriate standard solutions
tailored to the ambient water conditions. The in-line, multiparameter, flow-through cell is then
connectedwithinerttubingtoadevicesuchasabladderpump. Waterispurnpedfromthewellata
flow rate that ninimiiac agitation of the water. The sensors should be allowed several minutes to
adjust to the change in temperature and parameter va iues (Gamer, 1988). Also, the stagnant casing
water should be purged from the well in order to allow fresh aquifer water to be drawn into the
pumping system and into the celL Purging should continue until temperature, pH, and electrical
conductivity measurements of the purged water have stabilized. These measurements can also be
conducted with the use of an appropriate in-line, flow-through cell.
3.3.3 Ion-Specific Electrodes
Electrodes are calibrated by measuring the response voltage to at least two solutions
containing different known concentrations of the analyte of interest This calibration pro ure
defines the response (voltage) of the electrode within that concentration range of the analyte of
interest. To measure the apparent concentration of the analyte of interest in any other solution, the
electrode is placed in an apparatus such as a down-hole probe or a flow-through cell and placed in
contact with the ground water to be monitored in the appropriate manner, and the electrode voltage is
measured using a metering device. The concentration which corresponds to that voltage can then be
determined from the calibration data (Kolthof et aL, 1971). However, interfering constituents present
in some ground water makes proper calibration a difficult task in some situations (Ritchey, 1986).
3.3.4 Water-Level Monitoring
The “Methodolo r” and the ‘Theory of Operation” of these water-level monitoring devices are
essentially inseperable. Refer to Section 3.2.4 for this information.
3.4 APPLICATION TO WHPA MONITORING
3.4.1 In S i tu. Monitoring. Multiparanieter Probes
The hi sin g probe can be installed in two-inch or larger diameter monitoring wells to
continuously monitor indicator parameters. if the pound water in the monitoring well is
ui intaminateci and the water remains uncontaminated for several years. then valuable information
can be obtaine md used to model the na -at, temporal, and spatial variation of the ambient water
conditions. Such a record of ambient water quality conditions can be used for recognizing when
additional chemical analyses of water samples may be needed. As a result, the early-detection of
34
-------
contamination may be accomplished, Leading to early corrective action thus protecting valuable water
rcsour , expensive water extraction systems, and the consumer.
3.4.2 In.Tine Monitoring. Multipararneter. Flow-Through Cells
The flow-through cell technology is also used for monitoring ambient water conditions to
establish an historical data base to be used for the early.detection of ground-water conramination.
The flow-through cell concept can feasibly be implemented through a manual, monthly, monitoring
schedule. Additionally, the cells can be used to obtain the basic physical and chemical condition of
water collected for routine analysis or to determine when well-development procedures are effective.
3.4.3 Ion-Selective Electrodes
Ion-selective electrodes are available for the measurement of a large number of parameters of
interest in WHPPS, including ammonia, bromide, cadmium, calaum, carbon dioxide, chloride, copper,
cyanide, fluoride, hardness, lead, nitrate, nitrite, oxygen, pH, sodium, and sulfide (Baxter Healthcare
Corp., 1989). Ion selective electrodes could be installed in a flow-through cell or a probe
(Figure 3-4).
The silver sulfide-based electrodes (cadmium, copper, cyanide, Lead, chloride, and sulfide) are
solid, so they may be placed at depths of thousands of feet without being adversely affected by high
water pressures. The silver chloride-based electrodes contain liquid reservoirs; they must be
manufactured of flexible materials which can be slightly compressed without damage, in order to
equalize pressures inside and outside the electrode body. Some electrodes are constructed to withstand
high pressures and can be installed at almost any desired depth within a well. Of course, water
samples can be pumped from any depth and anaLyzed at the surface. However, this may compromise
the accuracy of the measurements of dissolved gases such as oxygen and carbon dioxide (Lammer,
1982).
3.4.4 Water-Level Monitoring
Many manufacturers produce equipment for continuous water level monitoring using floats.
acoustic devi , or pressure transducers linked to data loggers or telemeny equipment. The
information obtained from these systems is valuable for mapping apparent flow direction, seasonal
water-level fluctuation, and long-term, water-level changes.
3.5 LIMITATIONS/PERFORMANCE
3.5.1 in Siw. Monitoring.. Multiparameter Probes
Multiparameter probes have limited applicability in situations such as long-term monitoring
for DO because the membrane on the electrode can become fouled. Additional sensor calibrations
must be performed according to manufacturer specifications. Also, without an external power source
the probe has lImited continuous data recording capability. Table 3-1 shows some of the probe
specifications. The most serious limitation for current instrumentation is that many of the sensors
have predicted stability for a period of only one month.
3-9
-------
—
— - —=- —-=
-
:
FLOW
i RD —— -
ç
WELL — - - —
, — REFEREI4CE — -
— ELECTRODE —-
— — -
ION-$ELEC1tVE —...
ELECTROOES(S)-- -—
- — - -— -- —
TEMPERATURE PROBE - - __
— —
—
SATELLITE TRANSPONDER
Figure 3-4. Conceptual drawing of a well monitoring system using ion-selective electrodes.
3-10
SWITCH
-------
TABLE 3-I EXAMPLES OF IN Sri U PROBE SPECIFICA11ONS
PARAMETER
RANGE
ACCURACY
SENSOR
COMrENSATIOP4S
R OLUflON
CALl BRATION
R PONSE
liME
STAIILflV
owwr
OP11ONS
TEMPERATURE
-5 so
50•C
jOiSC
Ibermis i o s
cone rcqd
001 C
nose tcqd
too minutes
th’cc yean
mitput Is F.
SP IFIC
CONDUCTANCE
0 to 100
mSkm
1% of range
6-electrode ccli
automatic for temp
(25C)
4 digite
ECI or scawatef
standsith
one minute
six month
output In Mildly.
sducth Th6
cc asslsth4ty
outpui In jiS
p 11
0 so 4
u uil t i
02 unid
ti pH.
rebuildablc or
low ionic
strength
reference
electrode
sutonistIc (or
lcalpcssturc
001 unit
pH 7 butler.
pius one slope
buffer
mInutes
one month
cone
DISSOLVED
OXYGEN
0 to
mg/L
02 mg L
rebuiWab le
po1a,o apblc
I sill TC0OS
cc LoFlow —
sutomalic for temp
& isllmty
001 mglL
saturated sir.
Wi.kicr, cc
saturated water
two minutes
one month
vAt sillily
ronectlon, S
Suturalle.
REDOX
999 so
999 my
mV
Platinum
c le c trodc
none rcqd
I mV
quliihydione or
trinafen
two minutes
one month
nose
DEPTh
0 So 101)
m
04S ci
straIn-mugs
transducer
automatic for sp.
roaductascc
0) ii
.et rein in sit
one minute
one month
output In feet
LEVEL
0 to 10 ci
009 ci
stain -puge
transducer
automatic lot up
conductance
001 m
551 rein in air
one minute
one month
output in fast
LALiP IIW
0 to 70
ppt
02 pps
calculated from
s flc
conductance
none reqd
01 pps
uses calibration
from spcdflc
conductance
iso micuses
one month
none
(Fmm Hydrolab Corporation) ipeaflianons lot probe capable of monitoring four-loch or larger diameter wells Can also be used 1 t flow-though capability with addition of attachable flow .cap
-------
TADLE 3.1 Conbnucd
tb .)
PARAMETER
RANGE
ACCURACY
SENSOR TYPE
Tempetature
040C
±0.1 C
Tknnolioear amy
ConductivIty
010 .t .
0-100
jOOIi..... .- i
±0.1 mm
$ & 1jo& italnicia s eI
Tcmpctatule Cona d Condvc*ivtty
Vuiabk
j2% of ramie selected
Salinity
0-R)ppt
±05 ppt
pH
044
j(1I pH
Centhlaatlon pH electeode with Interial
siher-slivee chiodde f ec ‘1 ’
Dissolved O pcn
0 . ppm
j0.1 at tc npccatucc of cilthrattoo
Oalva.Ic e3c odc with a tumatk
VTC atmpcn.atios and le-slin
u
ORP
±3000 mcteis
±0.05 of .ctual oIIagc
Comblutios pladaum with sihec-
sibse chiodde tt — r cIa oJv
Depth
0-300 mdc i i
±1% of rao c
51II . steam .up-tempera1vie
compensated
(Oom Martek 1ns iimente mc) psoec enpante of mcsltect.g two-macA ot larger dtamcter wclla.
-------
3.5.2 InUne. Monitoring.. Multiparaineter. Row-Through Cells
Pumping individual monitoring wells and using in-line cells for monitoring wells on a regular
schedule requu’es manual labor hours that may impose logistical and cost restrictions on the
monitoring program. As with multiparameter probes, sensors on the flow-through ceLls must be
manually calibrated a irding to manufacturer direthons Table 3-2 shows some general specifications
of a commercially available unit.
TABLE 34 EXAMPLE OF co o(uaaALLy AVAflABLE FLOW-ThROUGH LSPECF1CAT1ONS’
RANGE
ACCURACY
S 4 5QR
TYPE
coMP 4SAflONS
CAlIBRATIONS
RESPONSE
TIME
Tc psriunn
.5 to 50 C
± G4 C
ibe tor
eons mqnu,d
noes requusd
95% so 10 --r-4.
Conducuv,tp
ito 100 MS!04
± 3% 50 t %
Dspcndso$ on sony
2 c1e iods
•
autconion s
tcapsatone ( C)
onedetcivily
cshbtosmr solution
95% t 510-
PH
0 to 14 uson
Dipen on
soitbinbon
cI tiods
iut ses r
tesopsinlus
pH bu
95% in 10 —f—’-
o r
. nj y
2% of reethig
pluilonuni
pins*nnso
el Uu sii
eons seqiwud
Zobsil solution
95% in 10 on .ds
(F o YSI Inso .,otatnd)
3.5.3 Ion-Specific Electrodes
Ion-specific electrodes must be used with an internal or an external reference electrode.
Fortunately, a single reference electrode can be used with any number of ion-selective electrodes as
long as they are immersed in the same solution.
Ion-selective electrodes have a vezy high internal resistance, thus the voltage of an ion-selective
electrode must be measured with a veiy sensitive (high input impedance) voltmeter. Such voltmeters,
which may be used with any number of electrodes, are readily available from electrode manufacturers.
Some voltmeters display concentrations of detected substan directly, thus eliminating the need for
manual calculations using an electrode calibration chart Ion-specific electrodes produce a voltage
response. As a result, they can be connected to chart recorders or data storage devices such as
computers to provide continuous monitoring of the analyse concentrations in the water being
analyzed. Electrodes respond relatively quickly (generally within two minutes) to sudden changes in
the concentration. LI desired, an electrode can be connected to an alarm system set to a pre-selected
contaminant level. Practical limits of detection for several electrodes are listed in Table 3-3.
The response of an electrode is affected by temperature changes. Thus, electrodes must be
calibrated in solutions having the same temperature as the water to be analyzed. Furthermore, the
water to be analyzed must remain at a relatively constant temperature. However, the effect of
temperature changes on electrode responses is well-known. Thus, a temperature measuring device
should be used to provide a correction to the electrode response.
There are, of course, some important limitations on the use of ion-specific electrodes. Perhaps
the most important is the non-selective nature of such electrodes. That is, some electrodes may
respond to more than one substance. For example, a chloride-sensing electrode will also respond to
3-13
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TABLE 3-3. PRACI’ICAL LIMiTS OF DETECrION FOR SEVERAL
ION-SELECFIVE AND GAS-SENSING ELECIRODES.
Electrode Detection Limit (ppm)
Ammonia 0.01
Bromide 0.4
Cadmium 0.01
Calcium 0.02
Carbon Dioxide
Qiloride 2
Oilorinc 0.01
Copper 0.001
Cyanide 0.2
Oilozide 0.02
Hardness 20 gpg
Lead 0.2
Nitrate nitrogen 0.1
Oxides of nitrogen 0.2
Oxygen 0.5
pH 2-12 pH units
Potassium 0.04
Silver 0.01
Sodium 0.3
Sulfide 0.005
cyanide and sulfide (Orion Research Inc., 1986a). The cyanide and sulfide electrodes will not respond
Lf the water is too acidic (Orion Research Inc., 1986b, 1988). A chemical analvss of the well water w ll
provide information regarding the suitability of using particular electrodes to analyze the water. In
some monitoring situations, their use may be inadvisable (Ritchey, 1986).
To obtain maximum accuracy, electrodes must be recalibrated on a regular basic. This
procedure requires that the electrodes be withdrawn from a well to the surface, calibrated, and re-
inserted into the welL The frequency of recalibration (weekly, monthly, semi-annually, etc.) depends
on the quality of the water in the well being monitored and the tendency for the electrode to drift off
calibration. Electrodes used to monitor relatively clean water will require infrequent recalibration,
3-14
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while electrodes used to monitor water confalning abundant biological activity or suspended oils may
need frequent cleaning and recalibration. Probably the best method for determining the optimum
recalibration frequency for electrodes used to monitor a particular well is to maintain and regularly
review recalibration data.
If electrodes are used in deep wells, their sign lc must be amplified to overcome the resistance
of the long electrical cables required. Electrode systems have been designed to utilize small radio
transmitters to broadcast the electrode signal (Lattimer, 1982).
Personnel assigned to install a well-monitoring system utilizing electrodes must be thoroughly
familiar with the uses and limitations of electrodes. The team should include an experienced chemist
and personnel trained in electronics in order to interface the electrodes with the desired electronic
equipment Although off-the-shelf, computer interfacing hardware and software are available, some
computer programming experience may be usefuL
3.5.4 Water-LeveL Monitoring
float systems and submersible strain-gauge type pressure transducers are relatively simple to
install in monitoring wells, and they can be Linked to data logging or telemetry equipment.
Studies performed to test the accuracy of water level monitoring devices have shown that over
approximately a one-year period the average absolute error for selected float systems and pressure
transducers is 0.027 feet and 0.098 feet, respectively (Rosenberry, 1990). The accuracy of acoustic
devices is reported to be approximately ±1 foot (Ritchey, 1986).
Measurement inaccuracies are caused by a number of factors, including systematic errors (e.g.
site-specific problems, instrument breakdown, surveying errors) or random errors such as weather
conditions or instrument calibration (Sweet et al., 1990).
3.6 SUM?vIARY
Multiparaineter probes are available from several commercial manufacturers for ut situ
monitoring in two-inch or larger diameter wells, depending on the modeL These probes can be used
at multiple sites or used in a single well to continuously monitor changes in general chemical and
physical parameters. Linking the continuous monitoring probe to a modem or telemetry system
allows rapid data transmission and the application of computer software that will signal an alarm if
parameter values reach predetermined levels. Field sampling and analysis procedures may be
warranted if the monitored values reach action levels. Monthly sensor calibration is necessary.
In-line, flow-through cells can be constructed in-house or purchased commercially. Flow cells
are used at the wellhead to periodically monitor ambient ground-water conditions. Sensor calibration
is necessary.
Ion-selective electrodes are currently available for measuring a wide variety of organic and
inorganic water contaminants. These electrodes are small, rugged, non-contaminating, inexpensive
compared to other analytical methods, and relatively simple to use. They can be used for analyses in
wells at great depths, or they can be used to measure contaminants in-line with water samples which
3-15
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han been pumped to the surface. Applications arc limited by various interferences, depending on the
water dtenthtiy. A chemical analysis of the wall water will indicate which electrodes %vuld be useable
in any partiatlar situation.
Several different types of ccntinuous water level monitoring devices are eommerciaily available
for monitoring temporal and spatial water level d i an e and apparent ground-water flow directions.
float reorders have been routinely used in monitoring programs for many years while awustic
devices and pressure transducers are relatively new on the market The three types an be linked to
data loggers or used with moderns for data transmission.
3.7 REFERENCES
Barcelona, M. J., J. P. Gibb, J. A. Helfrich, and t E. Oat 1985. Praakal Guide for Growid Water
Sampling. EPA 0W2-85/1O4. Illinois State Water Survey. Champaign, IL
Baxter Healthcare Corporation. 1989. Scientific Products Division. General Catalog. McGaw ParK
illinois.
Gamer; & 198& “Melting the Most of Field-Measurable Ground-Water Quality Parameters.’ Ground
Water Monitoring Review. 8(3): 60-66.
Gibb, J. P., R. M. Schuller, and R. A Griffin. 1981. “Procedures for the Collection of Representative
Water Quality Data From Monitoring Wells.’ Cooperative Groundwater Repon 7. Illinois State Water
Survey and Illinois State Geological Survey. Champaign, IL.
Koithoff, 1. M.. E. B. Sandell, E. I. Meehan, and S. Bruckenscein. 1971. Quanatanve Chemical Analysis.
The Macmillan Company; New YorK New York
Lattimet, R. F. 1982. GeoIo # and Oceanography. Allyn and Bawn; Boston, Massachusetts.
Nacht, S. 1. 1983. “Monitoring Sampling Protocol Considerations.” Ground Water MonuoMg Review.
3(3): 23-29.
Orion Research, Inc. l986a. Model 94-17 Chloride Electrode Instruction Manual. Boston,
Massachusetts.
Orion Research, Inc. 1986b. Model 94-16 Sulfide Electrode Instruction Manual. Boston,
Massachusetts.
Orion Research, Inc. 198& Model 94-06 Cyanide Electrode Instruction ManuaL Boston,
Massachusetts.
Ritchey, 3. D. 1986. “Electronic Sensing Devices Used for In-Situ Ground Water Monitoring.”
Ground Water Monitoring Review. 6(2): 108-113.
3-16
-------
Rosenbeny, D. 0. 1990. “Effect of Sensor Error on Interpretation of Long-Term Water-Level Data.”
Ground Wasa’. 28(6): 927-93t
Sweet,]. It, 0. Rosenthal, and D. F. Atwood. 1990. ‘Water Level Monitoring - Achievable Accuracy
and Precision.” GrowS Water and Vo4ose Zone Monaothig. ASTM SIP 1053. D. M. Nielsen and AL
Johnson, ES. American Society for Testing and Materials; Philadelphia, PA 178-192.
Torstensson, B. A. and A Si. Petsonic. 1988. “A Hermetically Isolated Sampling Method for
Ground-Water Investigations.’ In: Ground-Water Conwxnmaswrc Field Methods. AG. Collins and
A I. Johnson., ES. ASTM S iP 963. American Society for Testing and Matenals; Philadelphia. PA
274-289.
U.S. Environmental Protection Agency. 1986. RCRA4 Ground Water Moniroñng Technical Enforcement
Guidance (Aocumern. OSWER-99501. U.S. EPA, Offlix of Solid Waste and Emergency Responsç
Washington, D.C.
US. Environmental Protection Agency. 1989. “Indicators for Measuring Progress in Ground-Water
Protection.” EPAJ44O/6-8&V06. U.S. EPA, Officx of Ground Water Protection.
Walton-Day, K., D. L Macalady, M. H Brooks, and 1’. T. Vernon. 1990. “Field Methods for
Measurement of Ground Water Redox Chemical Parameters.” Ground Water Monuonng Review.
10(4): 81-89.
Willard. Hobart H., L. I . Merritt, Jr., J. A Dean. 1974. Insmsmenrai Methods of Ana&su. D. Van
Nostrand Company; New York, New York.
3-17
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SECI1ON 4
PORTABLE MONITORING METhODS
Portable monitonng methods involve light-weight equipment that can be readily carried into
the field by the user. Portable methods are applicable for WHPA monitoring by indirect sensing, or
anlaysis of the vac zone, or by direct anlaysis of ground-water samples. The methods described in
this section indude geophysica, immunoassays, soil-gas sampling and anaiys s, test kits, X-ray
fluorescence spectroscopy, and gas analysis equipment
4.1 GEOPHYSICS
4.1.1 Introduction
Physical property changes related to some kinds of contaminants can be remotely sensed using
geophysical monitoring systems. Because geophysical measurements detect the effect rather than the
contaminant, the physii3i characteriscies in a WHPA must be characterized before the monitoring
system is installed to establish a basis for identif ring changes occurring in an aquifer. A properly
designed geophysical monitoring system provides the ability to detect contaminants before they reach
a production well. ft also provides a mechanism to monitor the movement of contaminants so that
pumping rates within the weithead protection area can be adjusted, and contaminants can be removed
through reeoveiy wells with minimal effects on adjacent areas.
Surface and borehole geophysical measurements are useful components of any WHPA
monitoring strategy. Each has advantages and limitations; however, the use of both methods may
provide the investigator with more comprehensive information than possible with either method
alone.
Surface geophysical techniques may be noninvasive and can often provide data along lines over
large areas. Different methods can be used to remotely sense subsurface physical property contrasts
such as electrical properties, density, and magnetic susceptibility. Data interpretations are used to
relate physical properties to geologic or hydrologic objectives, including estimates of depth to water
level, stratigraphic thickness, location and movement of contaminated substances, and location of
buried objects that influence the movement of contaminants. The primaly WHPA targets of interest
are the location and movement of contaminants.
Borehole geophysical techniques (or geophysical well-logging) are invasive; however, these can
provide the investigator with information that may not be obtainable with surface methods. For
example, the borehole tool can be lowered to known depths In a well, making it a good “ground truth”
tool. The tool is in close proximity to subsurface formations of interest; therefore, it can produce
4-1
-------
better resolution than surface-based measurements. Borehole techniques can be used to obtain
information about lithology and to identify physical properties of the rock matrix. They can also
provide information about the thickness, porosity, bulk density, resistivity, and percent saturation of
aquifers and eonfining beds. (Keys, 1927).
4.1.2 Theory of Ooerat on
A Surface Techniques
Direct Current Resistivity--Direct current (DC) resistivity methods measure subsurface
distribution of electrical properties. Electrical current passes Into the ground via two electrodes
connected to an electrical current source. Resistivity is related to ohmic losses that occur when an
electric current flows through the earth. Depth of current penetration is related to the separation
between current electrodes and potential electrodes (Figure 4-1).
Resistivity is an intrinsic property that remains eonstant for a homogeneous isotropic material,
regardless of the amount of matenal measured or the electrode configuration (Bisdorf, 1985). The
subsurface generally will not consist of homogeneous isotropic material. Apparent resistivity or
average resistivity of all material through which current flows will be a function of the true resistivities,
depths, and thicknesses of the different subsurface materials down to the limit of current penetration.
Figure 4-1. Diagram showing basic concept of resistivity measurement.
Current
Source
Current FIow•
Through Earth
Current
— ——Voltage
4-2
-------
Thctre gnedc Methods-Electromagnetic (EM) techniques, Like DC resistivity methods, are
sensitive to changes in subsur6ce electrical properties. EM tatniques make use of an inductively
induced electromagnetic field to measure conduetivity changes (Figure 4-2). Conductivities are
measured by induthvity inducing secondaxy eddy currents in the earth and measuring the associated
magnetic field at some location. The apparent conductivity is not a t n t conductivity except when
measurements are Skan over a homogeneous, isotropic medium. Otherwise it is a composite value
which averages effects from diffczcut materials with varying thicknacri , depths, and conductivities
found within its range of detection. Depth of penetration is related to these parameters, but also
depends on signal frequency and the distance between source and receiver.
Ground Penetrating Radar—Ground penetrating rathr (GPR) uses high frequency
electromagnetic energy transmitted into the ground by antenna to map conductivity contrasts in the
subsurface. GPR differs from the other electromagnetic methods discussed because of the high
frequency of the signaL At radar frequencies, electromagnetic induction is not the dominant
propagation mechanism. Instead, the energy travels through the subsurface like a wave. This wave is
reflected, refracted, diffracted, or transmitted at the water table and other subsurface interfaces where
there are changes of complex perinittivity. Reflected energy is detected with a receiver antenna and is
used to create a continuous cross-sectional profile of the subsurface. A representation of transmitted
and reflected energy is shown in Figure 4-3.
Depth of investigation is dependent on the depth that the wave and its reflections can trawl
before they are attenuated by various loss mechanisms These loss mechanisms are controlled by the
electrical conductivity of the formation, clay content, water content, and particle size. Also, for given
subsurface conditions, depth of penetration generally decreases as frequency incrcascs.
B. Borehole Geophysia
Borehole geophysical methods comprise three general categories: mechanical, passive, and
active-source devices. Mechanical-source borehole tools use moving parts to obtain information about
the borehole environment Passive-source borehole methods involve those tools that are sensitive to a
particular property, but have no active source. Active-source borehole tools contain both source and
receiver. Table 4-1 summarizes the suite of borehole tools and their capabilities.
4.1.3 Methodolotv
A. Surface Techniques
Direct Current Resistivity-Several different electrode configurations, called arrays, are
commonly used for resistivity surveys. Three of the most widely used are the Sch lumberger, Wenner,
and dipole-dipole arrays (Violette, 1987; Zohdy, 1974).
Resistivity surveys can be used to conduct vertical depth soundings or horizontal profiling.
The objective of the former is to locate changes in electrical properties with depth. It is accomplished
by expanding the any symmetrically about ‘entrat point. The objective of horizontal profiling is to
locate lateral variat s in resistivity at a particular depth. In horizontal profiling, a fixed-spaced array
is moved across the surface of the earth. Array configuration in both horizontal and vertical
4-3
-------
FIELD
SURFACE
SECONDARY FIELDS
FROM CURRENT LOOPS
SENSED BY RECEIVER COIL
Figure 4-2. Illustration showing EM principle of operations.
4-4
-------
GRAPHIC RECORO R
SOIL
I I I I I I I I I
jIiIjHIiR c IiiiIi jtiii
Figure 4-3. illustration of ground penetrating radar system. Radar waves are relected from soil/rock
interface.
CONTROLLER
— — — —
GROUND SURFACE
4-5
-------
TABLE 4 -1. SUMMARY OF LOG APPLICATIONS
Requ
lied information on the properties of
Widely available logging techniques which
rocks,
fluid wells, or the groundwater system.
might be utilized.
UthoLo r and stratigraphic correlation of Electric, sonic, or caliper logs made in open
aquilers and ssoaated rocks holes, calibrated neutron or gamm .gamma
logs in open or cased holes
Total porosity or bulk density not resisting Calibrated long-normal resistivity Logs
aay or shale content Gamma logs
Permeability No direct measurement by logging; may be
related to porosity, injectivity, sonic amplitude
Secondaiy permeability--fractures, solution Caliper sonic, borehole televiewer, or television
openings logs
Location of water level or saturated zones Electric, temperature, or fluid conductivity in
open hole or inside casing. Neutron or
gamma-gamma logs in open hole or outside
casing.
Moisture content Calibrated neutron logs.
Inifitration Time-interval neutron logs under special
circumstances or radioactive tracexs.
Direction, velocity, and path of groundwater Single-well tracer techniques--point dilution
flow and single-well pulse. Multiwell tracer
techniques.
Dispeision, dilution, and movement of waste Fluid conductivity and temperature logs.
Gamma logs for some radioactive wastes, fluid
sampler.
Source and movement of water in a well Injectivity profile; flowmeter or tracer logging
during pumping or injection; temperature logs
Chemical and physical characteristies of water, Calibrated fluid conductivity and temperature in
including salinity, temperature, density, and the well; neutron chloride logging outside
viscosity casing; multielectrode resistivity
Determining construction of existing wells, Gamma-gamma, caliper, collar, perforation
diameter and position of casing, perforations, locator, and borehole television
screens _________________________________________________________
(continued
-------
TABLE 4-1. Continued
Guide to screen setting All logs providing data on the litho v, water.
bearing characteristiea and correlation and
thicimess of aquifers
Cementing Caliper, temperature, gamma .g mmç acoustic
for cement bond
Casing corrosion Under some conditions caliper, or collar
locator
Casing leaks and ( or) plugged screen Tracer and flowmeter
investigations is determined by depth of interest The dipole-dipole array allows a combination of
sounding and profiling.
The process of converting measured values (in this ease apparent resistivities and electrode
spacings) to a subsurface model is called inversion. Inversion is a mplished usüig speciaIi” d
algorithms that have in some cases been made user friendly and adapted for use on personal
computers (PQ).
EIec(rwn.gs etic Methods—Though there are several ‘pes of EM induction methods, this
discussion focuses on frequency-domain and transient (time-domain) EM. The source of the time-
varying EM field is an alternating or AC current (as opposed to the direct current of DC resistivity
techniques) flowing through the transmitter loop. A receiver loop is used to detect secondary field
effects. The loop may be moved across the surface, or one loop may be held fixed while the second is
moved. EM measurements can be used either for vertical soundings or as a tool for horizontal
profiling at a particular depth. This is a fairly tedious process, and the resulting data reduction and
interpretation must be done by a skilled geophysicists. Even then, resolution is often not great
enough to delineate targets with required resolution.
Ground Penetrating Radar-The transmitting antenna is moved across the surface of the
earth. The moving antenna continuously transmits pulses of high frequency energy into the
subsurface. Reflected energy is captured by a receiving antenna. The receiving antenna may be the
same antenna that is used as a transmitting antenna; an alternative is to have a separate receiver
antenna at a fixed distance from the transmitting antenna. It is advantageous to operate in the bistatic
mode to minimize noise.
The GPR systems allow for continuous data acquisition. It is important, however, to have a
system for locating the survey area on a map for later analysis purposes. GPR systems use a
broadband antenna with a particular center frequency. The higher frequency antennas have greater
resolution but are limited to detection of shallow targets. Resolution is reduced when lower frequency
antennas are used; however, detection depth is often increased. The larger antennas can weigh more
than 70 kilograms, which makes them unwieldy.
4.7
-------
Graphic recorders and video displays m k it possible to monitor data as it I collected. The
data can be displayed in various formats to show the position and amplitude of reflecting interfaces.
Usually data are presented with suivey distance and t -way trawl time as the t v axes, similar to the
presentation of seismic data. In many cases , this is all the data processing that is necessazy for
interpretation. It is also possible to use a magnetic tape recorder. This allows the data to be saved
and displayed on the graphic recorder at a later time. It also allows them to be used as input for
computer proemsing. which may be desirable for more complex interpretations. This will increase the
cost of the swwy. Both digital and analog tape recording systems are available.
B. Borehole Geophysica
Mechanical Devices—A good example of a mechanical logging device is the caliper log, which
measures the average diameter of the borehole by using t or more caliper arms (Walenco, mc).
This tool is used to obtain information for hole-diameter corrections for other log interpretations and
for information on possible fracture zones, casing conditions, and volume for cementing Another
mechanical log is the flowmcter, used for flow zone identification and flow rate measurements.
Mechanical flowmeters often are not capable of measuring flow rates if the well is not being pumped.
A fairly recent development is the low velocity, heat-pulsed flowmeter (Hess, 1982; Paillet ci aL, 1987).
This device uses a resistance-wire heating grid (activated by a pulsed electrical current) and
temperature-sensitive resistors to measure flow rates of as low as 2 liters per minute.
Passive Devices—This section discusses three standard passive borehole devices: the natural
gamma log, the spontaneous potential (SP) log, and the temperature log. The natural gamma log
measures the naturally occurring gamma emissions from the formation surrounding the borehole
(Walenco, Iric). Gamma emissions are often related to clay minerals present in the formation;
therefore, the natural gamma log is useful for determining the location of day layers and other
materials Like coal. The SP log measures DC voltage (or potential) differences between a moveable
electrode down the hole and a fixed electrode at the surface. Potential differences develop at the
contact between shale or clay beds and sandy aquifers; they are dependent on conductivity differences
between formation fluid and the fluid in the borehole. It is usually necessasy to have a conductive
fluid, such as drilLing mud, in the borehole. The Log is used to determine lithology, shale/clay content.
and water quality. Response is more complex when used in a hole without a conductive drilling fluid.
The log should generally be interpreted by someone with log analysis expertise .
Active Source Devices-Resistivity logs, sonic (or acoustic) logs, induding the acoustic
televiewer, and the remaining nudear logs are examples of active methods. The resistivity log operates
on the same principle as its surface counterpart. It is useful for determination of lithology and pore
fluid quality. The acoustic logs measure the time it takes for a pulsed, compressional sound wave to
travel a known distance from source to receiver. These devices are useful for determination of
porosity and for fracture detection. The active nuclear devices, both the ymma-gamma and the
neutron logs, are used for porosity, bulk density, and moisture content information.
4-8
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4.1.4 Annlies&,n to 1} IPA Mc?nitorin
A. Surface Tediniques
Dirad Qimnt R slsthity-The electrical resistivity of ground water is usually the controlling
factor ui formation resistivity. O’ nge in the electrical resistivity of ground water can sometimes be
linked to ch*ngri in ground-water quality. The presence of some (mostly inorganic) conraminirnts can
alter the resistivity of ground water enough to be detected with DC resistivity techniques. If an initial
resistivity survey were conducted during the wellhead protection area delineation phase, then
conducting subsequent suzve will serve to detect any changes in formation resistivity with time
Resistivity might be used to trigger ground-water sampling for electrically conductive contaminants in
the area. E esmples which demonstrate the use of the resistivity method for detection of ground-water
contamination indiide Fink and Aulenbach (1974), Rotix (1975), Sweeney (1984), and Urish (1 ).
Fiectromagritdc Methoda-.Comm rcially available EM tools are portable and easy to operate
by one or two tethni’, aris , under the supervision of a geophysicists. In addition, some instruments
allow measurements at several deptha. These are suitable for environmental applications. This, along
with their ability to detect lateral changes in electrical conductivity, makes EM tools a logical choice
for a surface monitoring tooL These toots can cover large areas fairly rapidly. If a careful survey grid
is made in the wdilbead protection area, periodic EM measurements can be repeated in the same
location and then compared. Any anomalous readings can be followed up with other monitoring
techniques for confirmation.
Ground Penetrating Radar--Applications of GPB to moni uring welihead protection areas is
dependent on the method’s ability to detect organic contaminants floating on the water table. It has
been suggested by Othoeft (1986) and others that some types of hydrocarbons, if present in the
subsurface in sufficient quantity, will prevent the radar ener from further penetration. These areas
would appear on the radar record as being nearly blank, since little or no ener r would penetrate.
The presence of hydrocarbons in the saturated zone would also attenuate the signal, but not to such a
large degree. Therefore, it may be possible to locate areas where hydrocarbons are present above the
water table.
B. Borehole Geophysres
Recently-developed tools have been developed with the hydrological or environmental
application in mind. A slimhole EM induction tool has been developed (Taylor, 1990; Bochiechio,
1990). The induction log can be used for many of the same applications as the single-point resistance
and multi-electrode resistivity fogs. With the induction toot, however, it is possible to log in dry holes,
fluid-filled holes and nonsteel-cased holes. The small diameter of the sonde makes measurements in
two-inch rnomtoring wells possible.
Mother significant advance for wellhead monitoring strate is a new logging application
used for the fluid conductivity logging tool (Pedler et al., 1990 Tsang et al., 1990). This device is used
to measure the elet :rical conductivity of the borehole fluid. With the new application, the borehole
tluid is replaced with a deionized fluid before logging takes place. Then slug testing or continuous
pumping is used to draw the native formation fluid back in the borehole. Variation in fluid electrical
conductivity with depth is used to determine the presence of fracture zones or even of individual
4-9
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fractures which have much greater hydraulic conductivity than the surrounding formation. In addition,
this technique can provide information about uS electrical conductivity, temperature, and pH (Pedler
et a !., 1990).
A third interesting development is the increasing use of the cone penetrometer for ground-
water sampling and monitoring applications. Cone penetrometers have traditionally been used for
determining engineering soil properties suth as plasticity values, stress data, and load-bearing
capabilities. More recently, new adaptations are allowing it to be used as a sampling device (Sergren
et aL , 1990) and a geophysical tool (Erchul, 1990). The cone penetrotneter is of interest because data
an be acquired relatively inexpensively without having to drill boreholes.
4.1.5 Urnitatiois/Perfonnance
A. Surface Techniques
Direct Current Resistivity-The limitations of the resistivity method are listed below
• The presence of nearby power lines, metal fences, railroad tracks, and buried utilities can
alter the surface current distribution and cause erroneous interpretations.
• Resistivity is a site-specific property; values which can indicate contaminated ground water
at one location may not do so in another nearby location.
• The technique requires a relatively large, costly field effort. It also requires experienced
workers (as working with current and voltage an be dangerous if done improperly).
• An understanding of physica is necessary.
• Hydrocarbons and organic contaminants usually do not change the electrical resistivity
enough to be detectable
Electromagnetic Methods—Many of the limitations of the DC resistivity technique also apply
to the EM techniques, as shown below
• The presence of nearby power lines, metal fences, railroad tracks, and buried utilities can
alter the eddy current distribution and cause erroneous interpretations.
• Conductivity is a site-specific property; values which can indicate conMminated ground
water at one location may not do so in another, nearby location.
• Geophysical expertise is necessary for proper data reduction and interpretation.
• Hydrocarbons and organic contaminants usuaily do not change the electrical conductivity
enough to be detectable.
• The method may not work if the near-surface is conductive
The limitations of tune-domain EM are, for the most part, similar to those of frequency-
domain EM, with the exception of poor vertical resolution. An added limitation of time-domain EM
is that the complexity of the set-up procedures and the necessity of computer-aided reduction and
interpretation means that time-domain EM cannot be used as a quick reconnaissance tool like the
frequency-domain instrumentation. This may be a disadvantage for weilbead protection, an effort that
requires frequent monitoring.
4-10
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Grvund Penefrating Radar-Limitations of GPR are Listed below.
• Depth of penetration in rocklsoil is usually limited to under 10 meters.
• R2d r sign I* are attenuated by the presence of moisture and conductive subsurface
materiaL
• R signAk are severely attenuated by the presence of some days.
• Cobble-sized and boulder-sized particles cause scattering of radar signals.
• The presence of nearby overhead power lines and metallic features on the surface can
inter& e with measurements.
B. Borehole Geophys
When deciding on which well logging methods are correct for an application, it is important
to consider the condition of the borehole or welL Some logs (such as resistivity and acoustic logs) can
only be run in fluid-filled holes. Resistivity, SP, and acoustic logs must also be run in non-’ e 4
(“open”) holes, unless information about the casing is desired. The induction logger, magnetic
susceptibility tools, and the borehole deviation log cannot be run in a steel-cased hole. Induction logs
are used in air-filled holes. Mditionally, logging tools with active nuclear sour (gamma-gamma
density log, neutron-thermal neutron log) are subject to various regulations and licensing procedures
that vaiy from state to state. Table 4-2 is a summary of the conditions affecting the different well
logging devices (Colog. Inc .).
4.1.6 Summary
Surface and borehole geophysical techniques are remote sensing methods that can be applied
to WHPA monitoring. The surface applications include direct current resistivity and electromagnetic
methods that can be used to detect and monitor the movement of electrically nductive or resistive
contaminants. In addition, ground-penetrating radar can be used to detect organic contaminants
floating on the ground-water table. Many types of borehole geophysical instruments (i.e. caliper,
flowmeter, natural gamma, spontaneous potential, temperature, resistivity, sonic, acoustic televiewer,
gamma- mmn and neutron logs) can be lowered down the well bore to provide depth-specific
hydrogeologic information such as lithologic charactensties and water quality
4-11
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TABLE 4-2 . SUMMARY OF CONDITIONS AFFECI1NG WELL LOGGING DEVICES
• Open Fluid Filled
Hole Only
o No Restriction
on Hole
• Cased Of Open
Fluid Filled Hole
A Active Nuclear Log to
be Run Only wi Stable
or Cased Holes Only
* Open or Non-Steel
Casing Only Dry or
Flud Filled
4I1t JJ/’
lIFORUATION DESIRED
Borehole Fkid Oualty
•
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S
S
S
U
AA SD
+5
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US
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,
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S S
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S S
S
S S
A
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U 0
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S
5555
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GeotechnicalStudies
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•
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S
S S
S S a
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*
*
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Lithology.StratlgrapI y S!S!!!S
L neral Identification S S S
PermeabihtyEstimates S•S •SS
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PreciousMetalExpi. •fSfS•••
RockProperties •• 5555
Shalness Evaluation • S •S•
HydroCarbonlnvestigation 555
UraniumExploratuon S
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WaterSaturation 55 S•• 5
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4-12
-------
4.1.7 References
Bergren, C L, R. C. Tuckflcld, and N. NI. Park. 1990. “Suitability of the Hydiopuncho for
Assessing Groundwater Cont n rn2ted by Volatile Organies’. J 1 . Proceedings of the Fourth National
Outdoor Action Conference on Aquifer Restoration, Ground Water Monitoring and Geophysical
Methods, Las Vegas, Nevada. 387-402.
Bisdorf,, R. 3. 1985. “Electrical Techniques for Engineering Applications. Ruilerin of the Association
of Engineenng Geo ogüt. 22(4): 421-433.
Bochicchio, R. N t 1990. ‘Borehole Induction to Complement the Mapping of an Electrically
Conductive Plume.” J Alinunmng RLik to the IfydroIo ic Enviro,vneiu. American Institute of
Hydrology Conference Las Vegas, Nevada, March 13-15. 210-218.
Colog, Inc. 1988. Catalog, Golden CO.
Erchul, R. A. 1990. “A Conductivity Cone Penetrometer to Detect Contaminant Plume Flow Rate.’
In: Proceedings of the Fourth National Outdoor Action Conference on Aquifer Restoration, Ground
Water Monitoring and Geophysical Methods, Las Vegas, Nevada. 419-428.
Fink, W. B. and D. B Aulenbach. 1974. “Protracted Recharge of Treated Sewage Into Sand, Part II.
Tracing the flow of Contaminated Ground Water with a Resistivity Survey.’ Ground Water.
12(4): 219-223.
Hess. A E. 1982. A Heat-Pulse Aowmeter for Measuring Low Velocities in Boreholes. U.S. Geol.
Sur., Open-file report 82-699., Denver, CO.
Keys, W. S. 1988. Borehole Geophysics Applied to Ground-Water Investigations, U.S. Geol. Sur.,
Open-file report 87-539, Denver, CO. 304 pp. (very eomplete bibliogiaphy).
Olhoeft, G. R. 1986. “Direct Detection of Hydrocarbons and Organic Chemicals with Ground
Penetrating Radar and Complex Resistivity.” In: Proceedings of the NWWA/API Conference on
Petroleum Hydrocarbons and Organic Chemicals in Ground Water—Prevention, Detection and
Restoration, Nov. 12-14, 19864 Houston. 284-305.
Othoeft G. R. 1989. “Geophysics Advisor Expert System.” EPAI600I4-89i023. U.S. Environmental
Protection Agency, Las Vegas, NV.
Paillet, F. L, A. E Hess, CH. Cheng, and E. Hardin. 1987. “Characterization of Fracture
Permeability with High-Resolution Vertical Flow Measurements During Borehole Pumping.” Ground
Water. 25(1): 28-40.
Pedlar, W. IL, M. 3. Barvenik, C. F. Tsang, and F. V. Hale. 1990. “Determin tion of Bedrock
Hydraulic Conductivity and Hydrochemistiy Using a Weilbore Fluid Logging Method.”
In: Proceedings of the Fourth National Outdoor Action Conference on Aquifer Restoration, Ground
Water Monitoring and Geophysical Methods, Las Vegas, Nevada. 39-53.
4-13
-------
Rowc, P. K 1975. Electrical Resütsvuy Eva art, M Solid Waste Aiposal FacilW et. EPA Report
SW-729.
Sweeney, J. J. 1984. ‘Comparison of Electrical Resistivity Methods for Investigation of Ground
Water Conditions at a Landfill Site.” Ground Water Monuciing Review. 4(1): 52-59.
Taylor, K., J. W. Hess, and S. W. Wheatcraft. 1990. Evah atkm of Selected Borehole Gecçhy cal
Methods for Flaxam’ow Waste Sue Invesilgatsons and Monitoiing. EPAiWO/4-90i029. U.S. Environmental
Protection Agency, Las Vegas, NV.
Tsang, C. F., P. Hufschmied, and F. V. Hale. 1990. “Determination of Fracture Inflow Parameters
with a Borehole Fluid Conductivity Legging Method.” Water Resource, Research. 26(4): 561-578.
Unsh, D. W. 1983. “l’he Practical Application of Surface Electrical Resistivity to Detection of
Ground-Water Pollution.” Ground Water. 21(2): 144-152.
Violette, P. 1987. Surface Geopkysical Techniques for Aqujfer Delineation and Welihead Protecnon. EPA
440/12-87i016. U.S. Environmental Protection Agency, Office of Ground-Water Protection.
Washington, DC.
Walenco, Inc. Water Well Geophysical Logs, Walenco, Inc., Bakersfield, CA. 55 pp.
Zohdy, A. A R., 0. P. Eaton, and D. R. Mabey. 1974. Application of Surface Geopkysics to Ground.
Water Invesnganons. U.S. Geological Survey Techniques of Water Resources Investigations. Book 2.
Chapter Dl. 116 pp. (good section on resistivity).
4-14
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4.2 IMMUNOASSAYS
4.2.1 Introduction
[ mm unoassays are analytical techniques based on protein molecules called anfibodS. The
binding of a specific antibody to it target analyse an be used to quantitate t’e extent of
contamination in an environmental sample. Specific antibodies an be deveiu ed to detect a singje
analyte or a small group of related compounds.
Antibodies are proteins that are pmdu in animals in response to the introduction of a
foreign substance, known as an antigen. When challenged with an antigen, an animals’s immune
system responds by synthesizing antibodies in blood cells known as B-Lymphocytes. Injections of an
antigen into an animal induce the formation of a broad spectrum of antibody moleaiS, subsets of
which react with different regions of the antigen molecule. Each antibody subset has the ability to
recognze and bind to a specific portion, or site, of the antigen.. (White and Van Etnon, 1989).
linmunoassays offer advantages over other ground-water monitoring applications. These
advantages include speed, sensitivity specificity, and cost effectiveness. Immunoassays, designed as
rapid, field-portable, serniquantitative methods or as standard quantitative laboratory procedures, can
be used for the analysis of a side variety of compounds. They are well suited for the analysis of large
numbers of samples and often obviate lengthy sample preparation. Immunoassays an be used as
screening methods to identify which samples need to be further analyzed by classical analytical
chemistry methods. The technology is especially applicable in situations where the analysis of an
analyse by conventional methods is not possible or cost effective (White and Van Ernon, 1989).
4.2.2 Theory of Oceration
There are two basic categories of immunoassays, isotopic, and nonisotopic. Each category is
based on the type of label used for detecting the antigen-antibody complex. Lcotopic methods, such as
radioimmunoassays (RIAs), use radioactive isotopes as labels. Nonisotopic methods include those
that have enzymatic, fluorescent, or chemiluminescent labels (White and Van Emon, 1989). Enzyme
immunoassays are the most commonly used immunoassays for analysis of toxic environmental
compounds.
Radioimmunoassays--
RIA tests provide sensitive, quantitative, analytical techniques that are well-suited to analyzing
trace levels of toxic compounds. To conduct an RIA test, a radioactively labeled antigen is used as the
label for detection. This radioactively labeled analyse competes with the analyte in the sample for
binding sites on the specific antibody. At higher concentrations of analyse in the sample, an
increasing amount of labeled antigen is displaced from the antibody. The antibody-bound antigen is
displaced from the free analyte and the radioactivity of each fraction is measured (Kimball, 1986).
Enzyme Immunoassays--
Enzyme inimunoassays use an enzyme label acting on a coloriznethc or fluorescent substrate.
The enzyme label provides sensitivity through amplification. Depending on the assay format chosen,
4-15
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either the specific antibody, the analyte, or a nonspecific secondary antibody can be labeled with the
enzyme (Engvall and Perlm nn 197 Ia,b; Van Wreinan and Schuurs, 1971). The pro s involved in a
typical enzyme ünmunoassay is shown in F Igure 4-4.
For typIcal enzyme immunoassay formats, the rate of color formation by enzymatic action on
the substrate is inversely proportional to the analyte concentration in the sample. Higher analyte
concentration in the sample inhibits the formation of colored, enzyme product (White and Van
Emon, 1989).
Fluorescent and theSumin nt Immunoassays—
Immunoassays that employ fluorescent or chemiluminescent labels offer the highest sensitivity.
fluorescent enzymatic substrates have been used to enhance the sensitivity of a variety of enzymes
commonly used for enzyme immunoassays. The major difficulty with this type of label is that it is
subject to interference and quenching from substance contained in the sample matrix. A variety of
approaches to limiting interference have been sunssfufly demonstrated (Soini and Hemmilia, 197%
ElkS. 1985).
4.2.3. Methodoloev
Saint environmental immunoassays are rapid, field-portable tests, which an be run in 5 to 30
minutes and are usually qualitative or semiquantitative. With some assays, 5 to 10 tests can be nan
simultaneously, an advantage that allows an analyst to run as many as 20 to 30 assays per hour. These
tests come in a variety of formats with antibody (or antigen) coated tuba, membranes, xnicroparticles,
or other solid phases. In some cases, tests are read visually. Others require a portable colonmerer or
spectrophotometer. Rapid field screening tests, however, are not as accurate or precise as the
laboratory-based tests. A typical field analysis kit is depicted in Figure 4-5.
Other environmental immunoassays are laboratory tests. These include laboratory enzyme-
linked imrnunosorbent immunoassay (ELISA) and RIA tests. For EUSA tests, a plate reader
containing a variable wavelength spectrophototneter (FIgure 4-6) is required. A counter is necessary
to run RIA test These laboratory test are quantitative and usually have much better accuracy and
precision than the field-portable test Between-laboratory coefficients of variation (CVs) are usually
in the 10 to 15 percent range, and in some studies (Harrison et aL, 1989) reasonably good correlation
(r=0.9 or above) has been found in comparing laboratory plate EUSA tests with a conventional
analytical method. Quantitative ELISA and RIA tests usually cost from $10 to $15 per test (as of
writing, 1991). Laboratory-based ELISA and RIA tests usually take several hours (to overnight) to
run, but sample throughput is high because 10 to 15 samples can be run on each plate. One analyst
could run 30 to 40 samples a day (in triplicate). In addition, the instrumentation necessary to fully
automate the assays with robotic systems is available commercially. With these systems, even higher
sample throughput is possible.
4.2.4 Application to WHPA Monitoring
The key to successfully applying immunoassay technology for WHPA monitoring lies in
understanding the advantages and limitations of the methods (Section 4.2.5) and in applying them in
appropriate situations (see Table 4-3).
4-16
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Figure 4-5. A typical field anlaysis kit.
Figure 4-6. Field portable spectrophotometer.
4-18
-------
Immunoassay methods are most applicable to the analysis of organic compounds that are
difficult or costly to analyze by other methods They are also very useful in situations where
characterization of a contamin2ted site involves screening large numbers of samples rapidly and
inexpensively.
Tmmunoassays are not useful for analyzing samples urnr ining unknown wnl2minanls or
complex mixtures. If extremely accurate and precise measurements are required (such as those
involving litigation or enforcement), quantitative laboratory iznznunoassays would be useful only if used
to complement conventional chemical analytical methods.
Full acceptance and implementation of iinmunoassay technology for environmental
monitoring relics on extensive validation and performance evaluation. Validation of the
immunoassays involves analyzing spiked and real samplcs doing comparison studies with conventional
methods, and conducting thorough performance evaluations. Immunoassay accuracy, precasion,
specificity, sensitivity, and other performance characteristics must also be investigated. Other issues to
address include interferences and matrix effects, cross-reactivity, ease-of-use, and ruggedness (White
and Van Emon, 1989). Guidelines for evaluation studies have been developed (Van Emori, 1989).
TabLe 4-4 presents a list of commercially available imniunoassays developed for environmental
contaminant measurements. Table 4-5 lists immunoassays that have been developed but are not yet
commercially available. Cross-reactants refer to compounds that are closely related to the target
analyte with which the test’s antibody interacts. The manufacturer can be contacted for additional
information on these tests.
4.2.5 Limitations/Performaace
Table 4-6 delineates the advantages and limitations of immunoassays. The following text
supplements the information presented in the table.
Immunoassays offer the following advantages for environmental analyses: speed, sensitivity,
specificity, simplicity, and savings.
Speed—Immunoassays have a much higher sample throughput than most conventional
analytical methods (Van Emon, 1986). For laboratory plate ELISAs, such as those developed
for the analysis of molinate in r ice field water (Harrison et aL, 1989), batches of 80 samples
per day could be analyzed. Rapid field-portabLe immunoassays such as the Rcs-I-Mune series
(marketed by Inimunosystems, Inc ., of Scarborough, NE) require only seven minutes per test,
and as many as five tests can be run simultaneously.
The instrumentation to fully automate laboratory plate ELISAs using robotics is commercially
available. With these systems, even higher sample throughput is possible.
Sensitivity--Many immunoassay tests are sensitive down to the ppb and sub-ppb range. Even
greater sensitivity is possible through fluorescent-labeling, enzyme application, and other
methods.
4-20
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Spec dly—Iminunoassays can be made wry sp flc if the proper antibody an be obtaSd
(through careful design of hapten and immunintinn scheme). An immunoassay which is
selective for a single isomer of the pesticide ailethrin has been developed and investigated
(Wing et at, 1978).
Slmpl1dIunoassa ’ such as the Antox Equate hydrocarbon water semen or the Rca-I-
Mune teats are short arid simple tests which rapist little trniSng to run, The Antox
Equate is a field-portable ELISA for BTX (benzene, toluene, and xylene) and related
compounds. The immunoassay is based on an antibodyaaS tube, and a portable
calorimeter is used to measure enzymatic color development
Tmmunoassay methods require much simpler and shorter sample preparation than
conventional techniques. As a result, they are suited for compounds such as aldiarb (Brady et
a]., 1989) and paraquat (Van Emon et aL, 1987) which are difficult to extract and analyze.
Savings—linmunoassays typically cost $5.00 to $15.00 a test, which is substantially less than
some of the conventional analytical methods.
As with any other method, irnmunoassays have disadvantages. Unlike OC/MS, immunoassays
cannot be used if the environmental sample contains an unknown compound or a complex mixture of
compounds. In some cases, immunoassays may not be as accurate and precise as conventional
analytical procedures. Due to the nature of antibodies, they are subject to interferences (from matrix)
and cross-reactivity with compounds other than the target analyte. More lead time is required for the
development of immunoassays because antibodies must be produced and characterized (White and
Van Emon, 1989).
The accuracy and precision of an immunoassay test depends on a number of factors, including
the type of assay, the protocol and how carefully it is followed, the quality assurance/quality control
(QAIQC) procedures and guidelines, and the extent of matrix interference. Optimal performance can
only be reached when protocols are carefully written and followed, and QAI’QC procedures and
guidelines are integrated into all phases of the development and manufacture of the tests.
Quantitative laboratory ELISA and RIA tests generally perform with greater accuracy and
precision than rapid, field-portable tests. Between-run and between-laboratory CVs (which vary with
concentration) generally range from 3 to 15 percent under controlled conditions. Accuracy is difficult
to define when comparison is made with a confirmatory method because the two methods may not be
measuring the same thing and are subject to different interferences.
Rapid, field-portable assays are designed to be qualitative or semiquantitative. They are
intended to be used to determine the approximate concentration range of analyte in a sample (within
±50 percent for example). If results indicate that a sample has a pollutant near or above a critical
concentration range the sample can be sent back to the laboratory for analysis by a more quantitative
method. Ac with laboratory-based immunoassays, the reproducibility is highly dependent on the
protocol, the QA/QC guidelines, and the extent of matrix interference. Coefficients of variation can
range from 5 to 50 percent, depending on these factors.
4.2.6 Suwwaxx
Immunoassay methods offer important advantages for WI{PA monitoring. Iminunoassays for
analysis of a variety of widely-used pesticides are now commercially available. Among the chief
advantages of immunoassays are their speed, sensitivity, specificity, simplicity, and savings.
To some extent, the specificity of the immunoassay tests can be controlled by producing
antibodies that are selective for a single compound, small groups of related compounds, or classes of
4-24
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Harrison, R. 0., A L Braun, S. 3. Gee, S. J. Obrien, and B. D. Hammock. 1989. “Evaluation of an
Enzyme-linked Tmmunnsorbent Assay (ELISA) for the Direct Analysis of Molinate (Ordram•) in
Riec Field Water,” Food and A icubural 1mmwvjdo ,. 1:37-51.
Huber, S. 3. and B. Hock. 1985. “A Solid-phase Enzyme linmunoassay for Quantitative
Detcrmin tion of the Herbicide Terbutryn.” I. Plans A P ’oeecr. 92(2): 147-156.
Ishikawa, E., M. Imagawa, H Selichi, S. Yoshitake, Y. Hamaguchi, and T. Ueno. 1983. “Enzyme-
labeling of Antibodies and Their Fragments for Enzyme Immunoa.ssay and Immunohistochemicai
Srainin&” I. of Immunoaxsry. 4(3): 209-327
Kimball, 3. W. 1986. introduction to immuno4og . 2nd ed. MacMillan Publishing Co; New York, NY.
Kohler. 6. and C Milstein. 1975. “Continuous CuLtures of Fused CalLs Secreting Anibodies of Pre-
Defined Specthcities.’ Nansre. 256: 495-497.
Lagone 3.3. and I L Van Vnn kie , 1975. “Radiounmunoassay for Dieldrin and Aidrin.” Research
Communications in Chemical Patholotj and Phwmacdog,. 20(1): 163-171
Luster, M. 1., P.W. AIbro, 0. Cark, K. Chac. S. K. Chaudhaty, L D. Lawson, J. T. Corbett, and i. D.
Mckinney. 1979. “Production and Characterization of Antisera Specific for Chlorinated Biphenyl
Species: Initiation of a Radioimmunoassay for Aroclors.’ To.L and 4p1d Pharm. 50: 147-155.
Parker, C. W. 1976. “Radioiminunoassay of Biologically Active Compounda.” Found immunoL Ser.
Prenti -Hall; Englewood Clith, New Jersey.
Rinder, D. F. and 3. R. Flccker. 1981. “A Radioimmunoassay for 2, 4-Dichlorophenoxy A tic Acid
and 2.4,5-Trichlorophenoxya tic Acid in Surfa Water.” BulL Environ. Contain. Toncol.
26: 375-380.
Soini, E. and I. Hemmilla. 1979. Fluoroimmunoassay: Present Status and Key Problems.” din.
Chem. 25: 353-361.
Van Emon, J. M., J. Seiber, and B. Hammock. 1987. “Application of an Enzyme-Linked
Immunosorbent Assay (ELISA) to Determine Paraquat Residues in Milk, Beef, and Potatoes.” BulL
Environ. Cotuam. Taxical. 3 490-497.
Van Emon, J. M. 1989. Report on identification and Quantification of Organic Compounds in Biological
and Envoonmenral Samples Using invaunochemical T&vüquer. EPA 6O0 X-89iO01. U.S. Environmental
Protection Agency, Environmental Monitoring Systems Laboratory, Las Vegas, Nevada. pp. 1-B4.
Van Emon, I. M. B. Hammock, and 3. Seiber. 1986. “Enzyme-linked Immunosorbent Assay for
Paraquat and its Application to Exposure Analysis.” Mai yrEcal Chemistiy. 58: 1866-1873.
Van Weeman, B. K and A It W. M. Schuurs. 1971. “Immunoassay Using Antigen Enzyme
Conjugates.” FEBS Lea. 15: 232-236.
White, R. 3. and 3. M. Van Emon. 1989. Report on Identification Techniques for Idenn ing and
Qsiannf,ing Organic Cony,ounds in Biological and Environmental Samples. EPAi O0/X-89t28& U.S.
Environmental Protection Agency, Environmental Monitoring Systems Laboratory, Las Vegas.
Nevada. pp. 1-A6.
Wing, K. D., B. D. Hammock, and D. A Wustner. 1978. “Stereoselectivity of a Radioimmunoassay
for the Insecticide S-Bioallethrin.” I. Agric. Food Chem. 26: 1328-1333.
4-26
-------
LEVEL
WATER TABLE
DIFFUSION
WATER-GAS
PARTITIONING
GROUND- WATER
CONTAMINATION
Figure 4-7. Contaminant volatilization and detection by soil-gas sampling and analysis.
SOIL
CONTAMINATION
4-28
-------
TO
VACUUM
PUMP
Gas Sampling. Active and passive sampling techniques can be used to collect soil gases. The
active soil-gas sampling method involves driving a sampling probe to a measured depth and
withdrawing a sample using a pump or evacuated container. Probes are commercially available in a
variety of models or can be fabricated from readily available materials. The basic design is a steel tube
less than an inch in diameter with one or several openings near the bottom end (Figure 4-8). The
probe is driven to the desired depth and a purgingI ampling mAnifnkl i connected to the surface end.
The sample is collected through the m2nifnld into a container. Syringes are good sample containers if
analysis is within a short time of sample collection. When samples are to be held for long periods of
time or shipped elsewhere for analysis, gas containers (e.g., steel conisters or glass sampling tubes)
provide longer holding times (EPA, 1991). The passive sampling technique makes use of samplers
that have a sorbent with an affinity for the target analytes in the ground for a measured period of
time. The most common passive sampling method consists of digging a hole approximately one foot
in diameter and one to five feet deep at a sampling location. A passive collection device such as a
badge or wire coated with activated carbon is either placed in the hole beneath an impermeable plate
orhunginsideaninvertedcan(Figure4-9). ThebaliowedicoUectVO forapenodof
time(oftenonthescaleofdaystoweeks)andthenisremovedandanalyzedforVOQ.
TO
VACUUM
PUMP
t
Figure 4-8. Various active soil-gas sampling probe designs.
1
GAS. TIGNT
/ SYRINGE
METAL
RING
5 151.5 TUBE
ANALYZIP4Q TUBE
tNO
4-30
-------
Sampling Plan. A sampling plan should include the expected target analyte(s), a detailed
sampling t hnique, an analytical methOd, the expected initial sampling locations, and the desired data
quality objectMa (DQOs) Since most soil-gas auzvey objectives require the comparison of data
among points to determine patterns of relative concentration the difference in values neub to be
determined as real or as a function of method precision or site-specific influences (EPA, 1991). The
QAIQC should Inclwlc at least replicate samples, sample splits, blank sampLes, amid depth
profiles.
Data Interpretalion. The diffusion transport of the contaminants can produce a decreasing
vapor-phase concentration gradient with increasing distance from the source, resulting in predictable
VOC soil-gas concentrations. However, additional site-specific conditions such as localized impervious
zones, an impermeable surface layer, or other conditions can provide different concentration gradients.
As a result, QA/OC m ures are extremely critical in decreasing sampling analytical variability as a
factor in soil-gas data interpretatIon.
4.3.4 Application to WHPA Monitoring
Applications of soil-gas measurement to WHPPs include site characterization activities such as
screening potential sources of contamination, delineating contaminant plumes, guiding placement of
soil boringa andfor monitoring wells, and testing storage tanks and pipelines for leakage. Soil-gas
measurements can also be used for monitoring the progress of remedial efforts and long-term,
periodic monitoring for early warning systems. Soil-gas surveys for site charactenzation usually can be
completed in a period of days to weeks using temporary probe installations.
The application of soil-gas sampling and analysis to monitoring remediation operations or
early warning detection of contamination requires committed sampling probes at points that
encompass suspected contaminant migration paths and various depths. Long-term monitoring also
requires QAIQC measures to ensure that fluctuations in soil-gas concentrations are real and not a
function of fluctuations in background concentrations or other unrelated events (Yamaguchi et aL,
1962). Also, unknown factors can affect the value of the site-speciflc soil-gas results. Unknown
factors include the vapor transport rate versus the liquid transport rate (i.e., when a component is
detected in the vapor phase, how far behind is the liquid phase?), the influence of vapor-phase
contamination on ground-water contaminant concentrations (i.e., can vapor-phase contaminants
contaminate ground water?), and subsurface conditions capable of contaminant degradation resulting
in altered and potentially undetectable compounds.
4.3.5 Limitations/Performance
Although the use of soil-gas sampling and analysis for contaminant characterization is
widespread (Kerfoot, 1988), the indirect nature of the technique produces limitations as to the
correlation between soil-gas concentrations and proximity to contamination. As a result, thorough
QA/QC procedures are required to identify variabilities in the analysis method, the sampling method,
and the site characteristica.
4-32
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4.4 TEST KITS
4.4.1 Introduction
The term “test kits ” as used in this document, refers to axnmercially available, self-contained
systems for qualitative ande r semiquantitative measurements of individual compounds or groups of
related compound daucs in solids, liquids, and gases . These kits n be used for quick and
inexpensive field saeening of environmental samples, and usually require little technieai background
to operate. Most test kits contain a complete set of sample handling and analysis containers, utensils,
and pre-p.ckaged analytiesi reagents (Figure 4-10). Positive results are usually indi ted by a color
change that occurs as the result of a reaction between the analyte and the test reagents. Quantititative
or semiquantitive results are usually based on comparison of the color intensity of the sample with
color intensities of sealed standards. Some kits require the use of simplified wet chemistry techniques.
Others incorporate indiestor reagents impregnated on paper, plastic films, or other appropriate
materials, or use reagent-filled tubes through which the sample 1. drawn. The development of test kits
is an area of active research interest and continued advancement in this area is expected.
Figure 4-10. Typleal test kit equipment.
rFt TF5J ___
JJ (_ __ . _ ltli
‘.øoIu
•cw,
r -
4-34
-------
A dity
Alkailnaty (hydrate)
Mkaliwty (total)
Mummum
Am
Mflmc y
Aromatic Ami
Carbcoate Peat iddea
Carbon Dicalde
Carbon Mo,onide
Otlonde
chtonac
Chrom ate (total)
Chromic Acid
Color
Cop r (iota! ioluble)
Cyanide (free)
Dip enylamioc
F uortdc
Fornaldebyde
4,4-MethylcoC Diphenylcue
Gbwl
Hardoem (omlaum)
Hardncu (total)
I1ydru nc
Hydrogen Pe icide
Hyrvgcn Sulfldc
TABLE 4-8 COMMERCIALLY AVAILABLE WET-CHEMISTRY KITS, BADGES, AND
WATER-TEST KITS AND RESPECIIVE TARGET ANALYTh&
war-
ANALYIE O4EM1S Y IQT
I WA1 ’ B.T ST
KIT
1.
:
L
;
•
L
G,L
:
:
;
L
L
L
S.L
SLO
0
0.L
O,L
0,L
:
.
j
.
•
.
0
0
0
!
•
:
•
:
:
:
:
L
L
L
L.
L
L
0,L
0
,
:
:
.
t:
•
:
L
L
L
I..
L
0
::
i
0
0
:
L
L
1
L
(Continued)
4-36
-------
TABLE 4-S. C tinacd
ANALY
WET
Q ISTRY JUT BADOE
WATER TEST
JUT
Tctramstkyl L
Thiopbosplata P tààdes
S. L, 0
ThM*ulhte
L
Tohaeos Dliaoc,iaste (iDE)
0
0
Total Ozidats
Q
T1$f dlty
Z c
. • L
Figure 4-11. Schematic drawing of a detector tube.
S — solid
L — liquid
G=gas
—VACUUM PUMP
ii
g
4-38
-------
target organic and inorganic compounds in solids such as vegetation and soil, liquids such as water
and extra , and gases. Lower detection limits are generally in the low-ppm range. Interfrrenee
compounds or conditions that may result in faLse positives or false negatives are usually noted by the
manufacturers. Innovative applications of the kits beyond the originkfly intended application may be
noted by the manufacturer or discovered by the user however, research is needed to ensure the results
obtained from innovative applications are both conantent with the capability of the teat kit and the
conditions at the site.
4.4.7 Rc rences
AQUAQUANT Reagent Test Kits, EM Science, P.O. Box 70, 480 Democrat Road, Gibbsuown, New
Jersey, 06027, (8 (X)) 222-0342.
CHEMets Test Kits, Chemetries Incorporated, Route 28, Calverton, Virginia, 22016, (703) 788-9026.
CHLOR-N-SOL 50, Dexail Corporation, One Hamden Park Drive, P.O. Box 6556 Hamden,
Connectiaat, 06517, (2030 288-3509.
COLORTEC Hydrogen Sulfide Detector, VICI Metronies, 2991 Corvin Drive, Santa Clara, California,
95951, (408) 737-0550.
Drager Detector Tubes, National Drager Incorporated, Ecolyzer Division, P.O. Box 120, Pittsburgh,
Pennsylvania, 15230, (412) 787-8383.
EM Quant Test Strips. EM Science, P.O. Box 70,480 Democrat Road, Gibbstown, New Jersey, 08027,
(800)222-0342.
EnviroGard Tnazine Test Kit, Millipore Corporation, 80 Ashby Road, Bedford, Massachusetts, 01730,
(617)275-9200.
EnzyTec Pesticide Biosensor, EnzyTec Incorporated, 8805 Long, Leneza, Kansas, 66215, (800) 634-
2607.
Field Test Kit, Hanby Analytical Laboratories, 4400 South Wayside, Suite 107, Houston, Texas, 77087,
(713) 649-4500.
Gallard-Schlesinger Industries Incorporated, 584 Mineola Avenue, Cane Place, New York. 11514,
(516) 333-5600.
Hach Water Test Kits, Hach Company, P.O. 389, Loveland, Colorado, 80539, (800) 227-4224.
Hanna Water Analysis Test Kits, }T2nna Instruments of America Incorporated, 584 Park East Drive,
P.O. Box 849-P, Woonsocket, Rhode Island, 02895, (401) 765-7500.
LaMotte Air Pollution Test Kit, LaMotte Chemical Products Company, P.O. Box 329, Chestertown,
Maryland, 21620, (800) 344-3100.
4-40
-------
4.5. X-RAY FLUORESCENCE SPEC ROSCOPY
4.5.1 Introduction
The flald-portabic, X-ray fluorescence system (FPXRF) is used for real-time identification and
quantitation of inorganic conthmin*ntL The sampling strategy for FPXRF is optimi ed through the
use of geostatitzca in order to obtain representative samples and to minimize the estimation error in
producing the concentration isopleth maps. The FPXRF is easily carried and is sealed so that it can
be decooMminAted in the field (Figure 4-12).
The analyte range for FPXRF is from chlorine to uranium. Detection limits, quancitation
ranges, and a racy of the measurements vary depending on the sample matrix and the isotope
source used for the analysis. Detection limits generally fall in the range of 200 to 400 mg/kg for most
analytes. A pre c site-specific, detection limit for each analyte for each matrix can be calculated only
after the condusion of the field wo&
Prior to using the FPXRF, site-specific, intrusive samples (physical samples from the media of
concern (EPA, 1%7) must be collected. These samples, which are representative of the physical and
chemical matrices of the various soil types, arc totally digested and analyzed in a laboratory. The
laboratory results are used to develop site-specific calibration standards (SSC) in order to minimi’e the
matrix-specific, enhancernent absorption effects encountered on any unique site.
Accuracy and precision data for each sampling effort can be determined from the results of
the quality control check samples analyzed periodically during the sampling. The short analysis time
(30 seconds) and low per sample cost allow data to be collected from many measurement points. This
approach provides a high degree of representativeness for the spatial distribution of contaminants over
the waste site.
Though the methodology described in this section addresses the analysis of soil matri , the
measurement procedure can be modified for aqueous samples, sludges, and other solid wastes (Clark
& Thornton, 1989, Piorek & Rhodes, 1980).
4.5.2 Theow of Operation
X-ray fluorescence is based on the principle that photons produced from an X-ray tube or
radioactive source bombard a sample to generate fluorescence (Jenkins et al., 1981). The incident
photon bombardment creates vacancies in one or more of the inner electron shells, and the vacancies
cause instability within the atom. As the outer shell electrons seek stability by filling the vacancies in
the inner electron shells, the atom emits energy (fluorescence), which is characteristic of the atom
(Figure 4-13). Most elements under the photon bombardment fluoresce simultaneously to produce a
spectrum of characteristic radiation. It is this spectrum that the FPXRF detector senses and counts.
There are two types of X-ray fluorescence spectrometers, energy dispersive and wavelength
dispersive. The principal differen between these two types of instruments are the method of
detecting the fluorescent energies of specimen and the method of quantifying the analyles of interest
The portable instruments used in FPXRF utilize energy dispersive spectroinetry.
4-42
-------
CH RACTE I$ TIC
ADt*TlON
Figure 4-13. Bohr model atomic excitation.
The electronic unit has 32 calibration memories called “models.” Each model can be
calibrated independently for as many as six elements and can be used to measure elements from
chlorine to uranium if the proper isotope source is available. The measured sample intensities are
regressed against the calibration curves to yield a)ncentrations.
4.5.3 Methodology
Site-Specific Calibration Standards--
A suite of 10 to 30 samples (depending on the number of analytes), spanning the
concentration range of the analytes of interest, must be obtained from the site in question. These
samples are sent to a laborato iy for total digestion and analysis. If previously characterized, total
digestion samples exist, then a suitable selection of these samples will suffice. These samples become
the SSC standards.
The FPXRF instrument can be used during a site reconnaissance to assist in selecting samples
to be characterized for SSC standards. The instrument is calibrated with a suite of natural or spiked
soil standards containing the analytes of interest With the generically calibrated instrument, a relative
range of the analytes of interest can be determined, and a suitable suite of samples can be selected for
charactenzation as SSC standards.
SSC standards are characterized for the elements on the EPA’s inorganic Target Analyte List
(Table 4.9) in an approved laboratoty by a total digestion method (Bernas, 1%8; Buckley and
Cranston, 1971). Characterization is by U.S. EPA Contract Laboratory Program (CLP) protocol
instrument analysis (EPA, 1989). The digestion is performed in an oven or microwave (U.S. Bureau
of Mines, 1983) digestion bomb with aqua regia and hydrofluoric acid. The total digestion is necessary
because XRF yields a total elemental analysis regardless of the phase (mineralogy) or speciation
(oxidation state) of the analyte, whereas the standard CLP extraction (EPA, 1989) produces partial
extraction results as a function of the mineralogy. Incomplete elemental characterization of the SSC
standards yields biased calibration curves in the FPXRF instrument
4-44
-------
Data Acquisitisa
Plotting
Figure 4-14. Wellhead protection screening with FPXRF.
because more measurements can be taken with the FPXRF units than by conventional sampling and
analytical methoth. Another advantage is that the FPXRF in situ measurement eliminates sample
collection, handling, and preparation, thereby reducing the overall sampling error. Increased sampling
density and reduction of the sampling error, combined with the spatial interpolation by the
geostatistical software produces a representative model of the contaminant distribution on the site
The most significant limitation of FPXRF is its relatively high detection limits. Instrument
detection limits generally fall between 200 and 400 mg/kg for most analytes, but the limit of
quantitation (ACS Committee on Environmental Quality, 1983) can run as high as 800 mg/kg. These
values must be compared to the remediation lewis on the site in question.
Data Transfer & Processing
.l • • $. vs•q
Final Product
4
4-46
-------
Jenkins, R., R. W. Gould, and D. Gulcke 1981. QuanWalive X-ray Spectromeriy. Marcel Docket, Inc .;
New York New York.
Meltzer, C and Bi-Shia King. : Advance.r in X-ray Ana ir, Volume 3. Proceedings of the thirty
ninth annual nf nce on applications of X-ray analysis, Steamboat Springs, CO. Beem Laboratory,
Uvermore, CA, U.S. Geological Survey, Menlo Park, CA
Outokumpu Electronica, Inc. 198& X-Mer 880 Portable F Analyser (Jperaang Iiimt crwru. OEL, Inc.,
Princeton, NJ.
Piorek. S. and J. R. Rhodes. 1980. “In-situ Analysis of Waste Water using Portable Preconcentration
Techniques & a Portable XRF Analyzer.” Proceedings of the Electron Micros py & X-ray
Applications to Environmental and Occupational Health Analysis Symposium, Pennsylvania State
University, Oct. 14-17, 1980. In Advances In X-ray Analysis, volume 3, Proceedings of the Thirty
Ninth Annual arnference on Applications of X-ray Analysis, 1990, in Steamboat Springs, Co.
Rub, G. A, R. E. Enwall, W. H. Cole III, tvt L Faber, and L A Eccles, 1991. “X-ray Ruorescence
Field Method for Screening of Inorganic Cont2miniants at Hazardous Waste Sites.” k: Hazardo s
Waste Measuremen&r. E. P. M. S. Simons, Ed. Lewis Publishers; Chelsea, Michigan.
U.S. Bureau of Mines. 1983. A Microwave System for the Acid Diuolutwn of Metal and Mineral Samples.
Analytical Support Services Program Technical Progress Report 120.
U.S. Environmental Protection Agency. 1987. Data Quality Objectives for Remedial Response Activities:
Development Process. EPA/540/G-87R)03. U.S. EPA, Washington, D.C
U.S. Environmental Protection Agency. 1989. Contractor Laboratory Program Statement of Work for
Inorganic Analyses. SOW No. 788, Attachment A.
4-48
-------
TO
INSTRUUtNT
Figure 4-15. Hand-held sampling probe.
4.6.4 Application to WHPA Monitoring
The primary use of OVMs and OVAs in wellhead protection is the screening of welihead
spaee and collected samples for VOCs. OVMs and OVAs are most commonly used to monitor
worker safety during drilling operations and to screen soil cores for high VOC coneentrations. Other
more recently proposed uses of OVAs (Robbins 1990) indude analysis of soil-gas samples collected in
sample bags and head-space analysis of ground-water samples.
4.6.5 Umitations/Performance
Lower detection limits (generally 0.1 ppm), upper detection limits (2,000 to 20,000 ppm), and
operating condition limits of OVMs and OVAS (operating in either mode) are specified by the
manufacturers. The OVAs are sensitive to low oxygen conditions because the FID detector uses
oxygen from the sample to mix with hydrogen to create a flame. A low-oxygen sample may extinguish
the flame. For example, a low-oxygen condition can be produced when the OVA directly measures
the gas from a soil-gas probe.
Although both OVMs and OVAs provide a readout (in survey mode) of total detectable
compounds in ppm equivalents of standard, the total value from the OVA is more representative than
that of the OV! L This discrepancy results from the differing responses of the PD and FID to
compounds. When a series of detectable compounds p c.c a PD detector, the PD responds
differently for each compound. In contrast, the FID response to most detectable compounds is nearly
the same.
lAoouy
AsssMm.y
4-50
-------
SECTION 5
MOBILE MONiTORING METhODS
5.1 INTRODUCTION
The need for rapid sample analysis during emergency responses to accidents involving
regulated substanees and the management of remediation efforts under the Comprehensive
Environmental Responsc Compensation, and Liability Act (CERCLA) and the Resour
Conservation and Recovery Act (RCRA) has underscored the need for mobile laboratories for
environmental analysis (EPA, 1984). Mobile monitoring methods are different from portable
methods. The equipment is close to laboratory quality and is to heavy to hand-carry to the field.
The use of a mobile laboratory as a WHPA monitoring method enables real-time analyses for target
compounds and provides data quality at or near the level of an analytical laboratory. Mobile
laboratories can contain dedicated analytical instrumentation or can employ a modular arrangement to
allow adaptation of instrumentation for specific analytical purposes.
Current chemical analysis methods of solids, liquids, and gases for organic and inorganic
compounds involve the use of several major analytical instruments and some associated sample-
preparation units. Most of these instruments have associated EPA-approved methodologies that
describe their use in a standard method so that results from different laboratories can be compared.
Although these analytical instruments were originally designed for use in a controlled laboratory
environment, the development of rugged, efficient, and compact electronica has allowed some
laboratory-only analytical equipment to be adapted to unconventional laboratory environments.
The mobility of the instrumentation requires at a minimum, a consistent power supply and
appropriate supplies such as carrier gases. Samples for mobile analysis often require collection into an
intermediate device before introduction into the instrument however, some instrumentation may be
capable of analyzing the sample in sini. The type of instrumentation installed in the mobile laboratory
is determined by the types of anlaytes expected. This section lists some of the more common
instrumentation and describes chromatographic and spectrometric techniques.
5.2 THEORY OF OPERATION
A mobile laboratory can either be leased through a consulting or contracting firm or owned
by the agency responsible for monitoring the WHPA. The physical arrangement of a mobile
laboratory can range from a converted passenger van to a stand-alone trailer. The support services
such as electricity, running water, gas hookups, fume hoods, and solvent cabinets can easily be adapted
for the scale of vehicles. Mobile laboratories can be fitted with committed analytical and support
equipment in order to provide a specific service or can be arranged generically to accommodate a
variety of instrumentation sizes and requirements (Figure 5-1). In any mobile laboratory application,
5-i
-------
the desired sample matriz number of samples, sample preparation, sample analyses, and DQOs will
dictate the appropriate equipment and instrumentation to be induded in the laboratory.
Most analytical instrumentation was originAlly int n’4ed for use in fixed, laboratory
environments due to the size of the instrumentation or the dependence of the instrumintation on a
stable or sterile operating environin nt, and most esiting EPA-approved analytical methode are
targeted towarde these particular instruments. 1 instrumentation in mobile laboratories consists of
either normal laboratory equipment or redesigned laboratory instrumentation which has been
modified for portability and ease of operation.
Table 5-1 lists stand2rd analytical instrt’m ntation that could be modified for application in a
mobile laboratory. The table also delineates the type of compound that each instrument can detect
= Inductively coupled plasma
spectroscopy
TABLE 5-L DEGREE OF LABORATORY INDEPENDENCE OF INSTRUMENTATION
USED FOR CHEMICAL ANALYSES
. Instrument Use
Compounds
Detected
.
EPA
Chromatographic Techniques
Lab
X
Mobile
X
Organies
X
Inorganica
Matrix
G’
Method
Yes
Gas Chromatograph
Gas Chromatograph wI Mass
X
X
X
: 0
YeS
Spectrometer
.
:
Gas Chromatograph wI
X
X
X
S. L
Yes
Purge and Trap
;
Gas Chromatograph wf
X
X
X
S
No
Thermal Desorption
•:
High Performance Liquid
X
X
X
L
Yes
Chromatography
SoectrometricTechnioues
X
X
X
:
S. L
Yes
Ion Mobility Spectroscopy
Atomic Aborption (Furnace
X
X
X
S. L
Yes
and Flame)
ICP-AES 1
X
X
X
S
Yes
X-Ray Fluorescence
X
X
x
S
Yes
Fiber Optic Chemical
X
X
X
S, L, G
No
Sensors
diseh r DITIIC
emission
5-3
-------
X-ray fluoreseence in vtves bombarding a prepared solid sample th X-ra and reading die
remitted, diaracteribc X-ray remediation. Field-portable XRF I d .ii d in Section 46. Laboratory
instrumentation and sm ii r field rnstrumenta have also been used m mobile applications.
Fiber optic chemical sensots involve transmitting light to a sensor in contact with an analyte.
The interaction bet n the sei r and the analyte resulti in the light being absosbed or refracted or
can result in the occorrenee of fluoreseence . The resulting altered light ts collected and returned to a
spectrometer for spectral analysts. Detail regarding theory, application, and mobile use can be found
in Section 6.4.
5.3 METHODOLOGY
The use of the analytical instrumentation in a mobile setting consists of the particular
instrumentation and the method chosen for analysts, inherent specifications of the instrumentation
naturally dictate the sample matrix and potential operating conditions, Sampling and analytical
methods can be determined by EPA-approved methods or can be customized applications.
Most mobile analytical instrumentation is complicated; therefore, an experienced operator
should be employed. This provides a measure of assurance that analytical results are a function of the
sample arnstitucnts and the analytical methodology, and not a function of the instrumentation. If
castom analysis methods are used, appropriate QAIQC m ’- ures muu be included to ensure the
validity of the analytical results.
5.4 APPLICATION TO WHPA MONITORING
Analytical instrumentation contained within a mobile laboratory is capable of analyzin&
within a short time frame, soil, liquid, and gas samples. The instrumentation can also provide data
quality ranging from EPA-approved methods to rapid screening. Soil-core, ground-water, and soil-gas
samples can be taken during WHPA monitoring activities or source characterization Surveys.
Although the variability associated with the analytical methodobgy and instrumentation is easily
determined and controlled, the variability associated with the collection and han&ng of specific
samples can be quite large. As a result, appropriate sample collection methods and QA/QC measures
are mandatory for maintaining sample representativeness and identity
5.5 LIMITATIONS/PERFORMANCE
All of the instrumentation listed above has associated detection Limits or sensitivities, and the
analytical variability can be determined easily. The use of instrumentation in mobile conditions could
require adaptations that alter the expected detection limits or sensitivities. Variability in results may
also result from sampling and sample-handling methods.
5-5
-------
SECTION 6
MONITORING TECHNOLOGIES UNDER DEVELOPMENT
Monitoring technologies are continuously being advaneed. For example, advances in mediczne,
warfare agent monItoring, contraband sensing, and forensica are being applied to ground-water
monitoring capabilrnes. This section provides an overview of some technologies that are expected to
be commercially available within the decade. Some of the most promising technologies are ion
mobility spectromeny 1 molecular optical spectroscopy, electrochemical sensors, mass sensitive sensors,
extraction membranes, and biosensors.
6.1 ION MOBILflY SPECTROMETRY
6.1.1 Introduction
Ion mobility spectrometry, which has also been known as gascous electrophonesis and plasma
chromatography, is used to detect and characterize organic compounds as vapors at parts-per-billion
(ppb) concentrations in air (Etceman, in press). The EMS output is a mobility spectrum which is
useful in compound identification (Bell et al, in prep.). IMSs, ranging from hand-held to laboratory
bench models, are becoming available commercially.
The applications of IMSs as mobility detectors in chromatography, environmental sensIng, the
detection of chemical warfare agents, forensic uses, and contraband sensing were briefly outlined by
Eiceman (1991). The first expansive use of EMS technolo was the deployment by the U.S. Army of
hand-held chemical agent monitors produced by Graseby Ionica Ltd. Designed for vapor detection,
these military units pointed out that IMS technology could be the basis of simple-to-use, fieLd
Recent research indicates a growing interest in the use of IMS for field applications. Dam
(1984) demonstrated that EMS was suitable for monitoring certain toxic industrial chemical vapors.
Carrico Ct at (1966) mentioned that compact EMS systems should be able to function as portable
alarms for several classes of organic vapors. Eiceinan et at (1990) showed in field trials that the
military configuration of IMS was useful as a point vapor sensor for establishing the presence of
contaminated patches of soils. Plume shapes and boundaries were aLso determined. Reategui et at
(1988) discussed applications for EMS as a vapor monitor for field screening applications, though
details were not provided. In addition, six papers on the subject were presented at the preliminary
program for the Second International Symposium on Field Screening Methods for Hazardous Wastes
and Toxic C emieals (Burroughs, 1991; Davis, 1991; Hoffiand and Shoff, 1991; Bell and Eiceman,
1991; Richter, 1991; Snyder et aL, 1991).
6-1
-------
units can be preprogrammed into these modes for specific analytes (it., a maximum of 5 analytes i i
the positive mode and 3 in the negative mode). These hand-held units use a liquid crystal display of
bars that relate to preprogrammed concentration levels. The more sophisticated packages enable the
operator to reprogram the instrument They also provide more capability in terms of quantitative
measurements and compound identification. To advance [ MS technology in the identification of
mixtures whjle rrSnttining cost and size efficiency, gas chromatography is being combined with [ MS
(Meuzelaar et a!., 1990).
6.1.4 Application to WHPA Monitoring
Although most [ MS research emphasizes vapor sampling and monitoring, ongoing work is
relevant to WRPA monitoring strategies. For enmple the analysis of water samples for several
organic compounds is being performed in a laboratory demonstration of IMS under the U. S. EPA
SiTE Program (Koglin and Poxiomek, 1990). The results will indicate how well some of the existing
commercial [ MS instruments can detect selected organic compounds in water. Mditionally, New
Mexico State UniveSty under the sponsorship of the U. S. EPA Office of Exploratory Research, is
enmining lidS as a rapid, inexpensive field screening method for organic contaminants in water.
Though preliminary findings seem promising there are still uncertainties, including the
predictive/Interpretive capabilities that are governed by the ionization chemistry and the suitability of
the [ MS interface with aqueous samples. in sine monitoring of water has also been proposed with a
submersible [ MS that could fit into monitoring wells.
The sensitivity of the [ MS is generally in the low ppm to low ppb range with the possibility of
parts-per-trillion (ppt), depending on the anaiyte and instrument parameters.
6.1.5 Umitations /Performan c e
There is still much to learn about IMS applications. For example, several fundamental issues
need to be resolved concerning the handling of complex mixtures. Compounds can be measured
independently but not always simultaneously The response of a particular analyte may be influenced
by the presence of other chemicals. The many ions that might form in a complicated mixture of
compounds would undoubtedly interact with each other. Such interactions need to be understood to
take full advantage of [ MS capabilities.
The development of in situ monitors also presents challenges. For example, monitors must be
developed to fit into confined places such as monitoring wells. Generally, miniaturization of
monitors results in the loss of sensitivity. Researchers must also design interfaces that allow a vapor
sampler to be openS with aqueous samples and develop an lidS probe that can tolerate high
humidities over a sustained period.
6.1.6 Summary
[ MS is emerging as a technique for the detection and characterization of organic compounds
as vapors at the ppb level in air. More attention is being paid to exploit [ MS for environmental
applications. There are still issues to be resolved, especially the handling of complex mixtures without
sacrificing cost and equipment compactness. There is also a need to extend the concentration range
for quantitative determinations.
6-3
-------
Hill, ILK Jr., W. F. Siems, R. IL St. Louis, and D. 0. McMinn. 1990. “Ion Mobility Spectrometty.”
62(23): 1201A-1209A .
Hoffland, L D. and D. B. Shoft February 1991. ion Mobility Spectromctry as a Field Screening
Technique.” Proceedings of the Seumd International Symposium on Field Screening Methods for
Hazardous Wtes and Toxic Qteniicak U. S. Environ ntal Protection Agency, Las Vegas, Nevada.
Karasek, F. W. 1970. “The Plasma Chromatograph.” RerearchlDevekçmeiu. 2 1(3): 34.
Karasek, F. W., 0. S. Tatone, and D. M Kane. 1970. “Study of Electron Capture Behavior of
Substituted Aromaties by Plasma Chromatography.” AnaL Chem. 45(7): 1210-1214.
Karasek, F. W. 1974. Plasma Chromatography.” AnaL C7iem. 46(8): 710A-718A.
Karasek. F. W., K K Hill, Jr., S. H. Kim, and S. Rokushika. 1977. “Gas (Iromatographic Detection
Modes for the Plasma Otromatograph.” I. C7irom. 135: 329.339.
Koglin, E. N. and E. 3. Poziomek. November 1990. “Opportunities for Technology Transfer to the
U. S. Environmental Protection Agency through the Superfund Innovative Technology Evaluation
(SITE) Program.” Proceedings of the 1990 Sdentific-Conkiencc on Chemical Defense Research, U.
S. Chemical Research, Development and Engineering Center, Aberdeen Proving Ground. Maryland.
Leasure, C. S., M. E. Fleischer, G. K. Anderson, and 0. A. Eiceman. 1986. “Photoionizanon an Air
with Ion Mobility Spectrometry Using a Hydrogen Discharge Lamp.” AnaL Chein. 58(11): 2142-2147.
Meuzelaar, H. L C.. N. S. Arnold, D. T. Urban, P. Kalousek, A. P. Snyder, and 0. A. Elceman.
November 1990. Mao-Portable Gas Chroniatography(Ion Mobility Spectrometr r GC-CAM.”
Proceedings of the 1990 Scientific.Conference on Chemical Defense Research. U.S. Chemical
Research, Development and Engineering Center. Aberdeen Proving Ground, Maryland.
Poziomek, E. J., 0. A Eiceman, and T. E. Mitchell-HalL November 1990. “Potential Transfer of Ion
Mobility Speczrometxy Technology to Environmental Applications.” Proceedings of the 1990
S&ntific-Conference on Chemical Defense Research. U. S. Environmental Protection Agency
through the Superfund Innovative Technology Evaluation (SITE) Program. Las Vegas, Nevada
U. S. Army Chemical Research, Development and Engineering Center. Aberdeen Proving Ground,
Maryland.
Reategui, J., T. Bacon, G. Spangler, and 3. Roehl. October 1988. “Ion Mobility Spectroanetzy for
Identification and Detection of Hazardous Chemicals”. Proceedings of the First International
Symposium on Field Screening Methods for Hazardous Waste Site Investigations. U. S.
Environmental Protection Agency, Las Vegas, Nevada. 349-358.
Richter, P. February 1991. “Remote and In Situ Sensing of Hazardous Materials by Infrared Laser
Absorption, Ion Mobility Spectrometry and fluorescence.” Proceedings of the Seornd International
Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals. U. S.
Environmental Protection Agency, Las Vegas, Nevada.
6-5
-------
v’s .
.,, JI,.,I..., ••,••,,• •.
1,101 1.1,1 1,1.1 i•. ‘Is s...
—a ,I,IA, I
S I sI I I I . lilI £
ii I J 1 t I
I I
I.e I II I I I S..
Figure 6-1. Major regions of the electromagnetic spectra.
Absorption o irs when a molecule is raised to a higher energy state (electronic or
vibrational). This higher energy state is achieved when a molecule of the sample absorbs a photon of
energy. In the simplest case (sometimes called the Beer-Lambert Law), a parallel beam of light,
perpendicularly incident on a sample, can be absorbed or transmitted. The logarithm of the ratio of
the incident tight to the transmitted light, usually called absorbance or optical density, is directly
proportional to the concentration of the analyte.
IR absorption spectroscopy is used to measure absorption in the near- to mid-IR spectral
range (Coithup et at., 1964; Griffiths and DeHaseth, 1986). In the mid-IR region, peaks are often
sharp, and individual peaks can be correlated to specific chemical group stretches or deformations.
This feature makes the inid-IR region very useful for chemical dassification or identification. Spectra
in the near-rn range are broader, vibrational peaks overlap, and combinations of vibrational
frequencies are observed. Therefore, spectral deconvolution and pattern recognition procedures are
necessaty for signal discrimination before identification of specific chemical constituents is possible.
An inelastic scattering process (Raman scattering) is normally used to measure in the visible
or near-IR spectral range (Colihup et al., 1964; Vo-Dinh, 1989; Long, 1977). Laser Raman
spectroscopy is a technique that complements IR spectroscopy because the two techniques provide
different kinds of information about vibrational transitions and related chemical groups.
Characteristic frequency shifts associated with vibrational transitions and changes of electrical
polarizability (or distortion of the electron cloud) associated with a molecule are measured with this
technique, thus allowing identification of specific analytes of interest.
6-7
-------
“I’,
“I’
6.2.3 Methodolo
UV-vis absorption spectroscopy is often used for quantification or identification. The
technique can be applied directly or after chemical reaction with a reagent to produce a highly colored
product in the visible spectrum (Jungreis, 1985). It is also used in conjunction with liquid
chromatography. Field deployable and hand-held instruments are available for measurements in the
visible region.
Field-deployable instruments and methods have been used in mobile laboratories to make
UV-vis luminescence measurements (Montgomezy et aL, 1985; Remeta and Gruenfeld, 1987).
Portable instruments are under development. Several American Society for Testing and Materials
(ASTM) standard methods are available for luminescence analysis of oils and creasotes, fluorescent
aromacies, substituted aromaties, and PANs (ASThI, 1988a, b). Other methods are being developed
for phenols, PCBs, fluorescent pesticides, other fluorescent heterocycles, and uranium.
Dispersive IR spectrophotometers and Fourier Transform IR spectrophotometers (s i ixa) are
available as field-deployable instruments for identification, classification, and quantification of total ad
and grease. They are also used to identi volatile organic chemicals (Grant and Eastwood, l9 ).
Long-path length ti as arc used for air monitoring; portable gas-cell dispersive IR instruments are
used for industrial hygiene monitoring applications (Small et al., 1988). t’TiKs are frequently used as
detectors with GCs (Griffiths and He*uy, 1986; Ourka, in press).
A number of pattern recognition techniques and expert systems have been developed to aid in
the classification or identification of petroleum oils or other complex PAN mixtures. For example,
methods have been developed for mid-rn and fluorescence spectra (Puskar et al, 1986; Sogliero c i aL,
1985). Different approaches are required for the two techniques because room temperature
fluorescence spectra have fewer and broader peaks than mid-rn spectra.
FOCS will be useM for in situ monitoring activities. They are used with a variety of
spectrosuipic techniques. Enstrumenfation is available to support FOCS sysytems. The major obstacle
is the development of analyte-specific coatings to selectively monitor individual compounds.
Figure 6-2. Fiber optic chemical anlaysis system.
6-9
-------
TARL.E L AflUCAflON OF U TROGOOP0C Th IN!QU 1fl MAJOR OWMICAL OROUPS
MAJOR OSEMICAL GROUPS
IJV ViS ABSORrI1ON
(N ViS I.UMIN05CEI4( J
MID INFRARED
A OI?TlON
NORMAL
RAMAN
ORJMETRIC
Fl (JOROSIBTEIC [
INOROANK3
CAflONS
• SUbpp.
pp..ppb
RARE EARflIS
pp. ppb
URANIUM
ppTV
ANIONS
pp.
• pp.ppb
CYANIDE
gip ppb
1 0 0p p .
OK0ANIC
AaoMA1 alsuusIuvEo AROMA11c5
i
s
io pp.
100
PHENOLS
ppb
loop,.
POLYAIOMATICCOM P’OUNO S
>1 pp.
pp. p.
pp.
pp.
PAN,
i .
W Opp.
COMPLRX PAH UIXIIJRE
l pp.
p0
pp. p0
rElROLEUM OILSmREASES
I pp.
ppb
2OWTES
I .. pp.
5 p0
METE*OCVC1 E1
pp.
pp. ppb
pp.
I0 pp.
PYPJDIIIE
p .
HYDRAZINE
p,_
•
ppm
pp. ppb
l 00 lOpp.
app.
P P S11QDES
p0
i io p.
I 00 pp.
DY
ppm
ljpp . p.
I I0 pp
I 00
OTHER 0ROAMI
.oi desamad
pp.
100 pp.
pp.
ais .p.fl flCT’WTWfl V Wfl •pWr W I
fl Lain n f l Ca
napiMvw
.W
9’
• SURPm ENN*JI RAMAN HAS MUOS L ER D ThCflON UMflI FOR SOME ( MrOU14D6
NCF ALL COMPOUNI$ WIThIN QA PEThCI
PANT PER MI WON
fiLl enni pain . . , _ ns .
•rOLYaELORIHA1 RWHW(YL$
WTDI DERJVATIZAIION
pps PART PER TRIUJON
- a ir..
-------
TABLE 64 ADVAPITAG AND LZMrI*TIONS OP VARIOUS 3PBC1RO6 fSC METHODS
ADVAWrAO L TAD.ONS
UV.V AORFTTOW
MAt JRE (NIQUE
UIRUMENTA1 O$ READILY AVAILABLE
GOOD QUANITTA11VE A URACY FOE SINGLE OOMPOUIIDS AND
SPECTRAL DATA AVAILABLE
CrENSIVE SAMPLE PREPAL411ON
UNRE FIC (OO O’ABED 101* *240
w
MODERATR $ENS21IVTTY
QUAKITrAIT0N MAY BE A 7 TED BY SOLVENT.
POLAETTYOF UM. O CAL OOMPL S
UV•VIS LUMU(ES (CE (FLUORES (CE AND PKOSPHO* lCE3
MOET SENRITIVE METHOD POE TRACE AND UL1ATRACE
ANALYSIS WHEN APVUCABLE
IN UMEWTADO$ READILY AVAILABLE
1(0 iERENCE BY WAlER
FEW INTERFERENCES BY NONAROMA1ICE
SOME STRUCTURAL SPEaFIQTY. ENHANCED BY SPECIAl
TECHNIQUES
VERY SELECtIVE. ENHANCED BY TIME AND WAVELENGTh
VARL4JILZTY
LDuaTRDT0 OD uw wmi PA Y IGON
LTTh40I (CE D 5 (t lJA1j.Y p UNT
PBE IVA11zW)
EBLA11V .Y UWSPE FIC FOR STRUCTURAL
LNFORMA1ION (COMPARED 101*)
QUAN’ITIAlION COMPUCA1 BY DIPFEW
IN QUANTUM Y1fli QUERagNO.
MOENVIRONMENTS
UMITED REFERENCE SPECTRA AVAILABLE
INFRARED (DISPERSIVE AND FOURIER TRANSFORM
KIOMLY SPECIFIC STRUCTURAL DATA ON FUNCTIONAL GROUPS FOE
cL IFYINO OBOANICE
MA11JIETRD*IIQUE
INSTRUMENTA11ON WIDELY AVAILABLE
REALTiME FLOW.i1(ROUOH VAPOR AI’PIJCATIONS . OC-FliR
SPECTRAL UBRARINS AVAILABLE
MI LOW SDISTTIVTTY (LESS SENSrIIVE ThAN
W4ES I C E)
WATER IS DPIERPENENT (HO ppTNOUSAND
DETECTION WTTH SAMPLE CELl.)
FIlE CAlf IOLERATE SOME WATER
(BACEOROUND SUBTRACTiON)
REQ UIRES SPECIAL OFflCI SOLVEWTi
OUAWTrTAIION DIPFICULI
WEAR OPTICAL SOURCES AND DEIICIORS
NEAR INFRARED
SOUR AI (D OPTICAL MA1ERL*LS B i i ai ThAN MID 1*
OPTiCALLY GOOD SENSOR MATERIALS
CAN DISI1NOUISH MAJOR COMPONENTS OF SIMPLE MIXTURE
FEWER INIERFEREICESThAII 1410- 1*
L SPCTRAL STRUCTURE ThAI ( MID1R
- OVER10NE OVERLAP
- Sr CT
•IWIERPRETA1ION COMPUCATED
NOT USEFUL FOE COMPLEX MATRICES
SiGNAL PROCEISINO AND PATTERN
RECOON ON REQUIRED
(C vcd)
643
-------
Paman spectrosoopy remains a laboratory research Inhnique became of its relatively complex
instrumentation and low sensiliS Recent advances in surfuct-enhancad snan indicate that
sensitivities can be increased fur at least some classes of analytes adsorbed on special substrata This
provides a possible future application for WHPA monitoring adivities after more research.
FO especially colorimetric and Quomnietric season, in addition to other c hemical season
such as electrochemical, conductivity, or mass sensors, have potential for remote in situ monitoring.
Several techniques, including laser-excited luminescence, laser-excited surface-enhanced Rsinan and
FOG, merit further research and development to explore possibilities of improved WHPA
monitoring applications
6.2.7 References
Angel, S. IL and N i L Mynck. 1989. V 4nfi Surface-Enhsnesd Raman Spectroscopy Using
a Diode Laser.” AnaL C7rem. 61(15); 1648-165 2 .
ASTIL 1988a. “Standard Practice for Identification of Chemicals in Water by fluorescence
Spectroscopy.” Annual Book of ASThI Standards, American Society for Testing and Materials,
Philadelphia, D 4763-88, VoL iLOL
PIST I L 1988b. “Standard Method for Comparison of Waterborne Petroleum Oils by fluorescence
Aiialysis” Annual Book of ASTM Standards, American Society for Testing and Materials,
Philadelphia, D3650-78 (Reapproved 19 ), VoL 11.02.
Becker, R. S. 1969. Theosy and lsueipresasion of Fluorescence and Phosphorescence. Wiley lnterscience;
New York, New York.
Beriman, 1. 1971. Handbook of Fluorescence Spectra of Arosnanc Molecu les. Second Edition, Academic
Press; New York, New Yo&
Burgess, C and A. Knowles, Eds. 1981. Techniques in 4sthk and U ltraviolet Specirometry, Vol. II.
Chapman Sd Hall; London, England.
Bushaw, B. A. 1983. ICinetic Analysis of Laser Induced Phosphorescence in Uranyl Phosphate for
Improved Analytical Measurement” Presented at the 16th Oak Ridge Conference on Analytical
Chemistry in Energy Technolo Knoxville, TN.
Carrabba, lvi Ni, R. B. Edmonds and ltD. RauL 1987. “Feasibility Studies for the Detection of
Organic Surface and Subsurface Water Contaminants by Surface-Enhanced Rainan Spectroscopy on
Silver Electrodes.” Mat Chess. 59 2559-2563.
Chase, D. R and B. A. Parkinson. 1981 “Surface-Enhanced Rainan Spectroscopy in the Near-
Infrared.” AwL Specrsusc. 42(7): 1186-1187.
Christesen, S. D. 1981 “Raman Cross Sections of Chemical Agents and Simulants.” AwL Specsrosc.
42(2): 318-321.
6 -15
-------
Jungreis, E. 1985. Spot Teit An4 ü. John Wiley & Sons; New York, New York.
lC2minlki, R., F. 3. Pureell, and E Russavage 1981. ‘Vranyl Phosphoresemce at the Parts-per-
Trillion Le eL AnaL Ownr. 53: 1093.
Kelly, J. 3., C IL Barlow, T. M ringwj and I. a Caltit . 1989. “Prediction of Gasoline Octane
Numbers from Near-Infrared Spectral Features in the Range 660-1215 urn.” AnaL C7sem. 61: 313-320.
Klainer, S. IL, D. K Dandgs, IC. Goawami, L A. Eccies, and S. 3. Simon. 198& “A Fiber Optic
(leinical Sensor (FO( ) for Monitoring Gasoline.” : In Situ Momwnng with Fib 4xics. Pan 3.
EPAI 0WX-88P259. U.S. Environmental Protection Agency, Environmental Monitoring Systems
Laboratoiy, Las Vegas, NV.
Kla i ner,SJvL,lC.Gosrn,D.KDandgc,S.LSimon,N.RHerron ,D.Ewood ,andLAEccles.
1990. ‘Environmental Monitoring Applications of Fiber Optic Oi mieal Sensors (FO(S).” Ownical
Sensors, 0.5. Wolfl,ei, Ed. CRC Hand bock of F ber-C ,dc. Boca Raton, FL
Long, D. A 1977. Roman Specn’osccçy. McGraw-Hill International; New York, New York.
Marley, N. A, C K. Mann, and T. 3. VickerL 1985. °R m2n Spectroscopy in Traoa Analysis for
Phenols in Water.” AppL Speczrosc. 39(4): 628.633.
McKinney, G. L IL K. Y. Lau, and P. F. Lott. 1972. “A Rapid fluoromctric Determination of
Cyanide. Microchem J. 17: 375-379.
Miller, 3. N., Ed. 1981. Standards in Fluorescence Specwomerrj. Chapman and Hall; London, England.
Montgomery, R. E., D. P. Remeta, and M. Gruenfeld. 1985. Rapid On-Site Methods of Chemical
Analysis ” In: Contaminwed Land. M A. Smith, Ed. Plenum; New York, New York. 257-309.
Murphy, E. 1st and D. D. Hostetler. March 1989. “Evaluation of Chemical Sensors for In Situ
Ground-Water Monitoring at the Hanford Site.” Pacific Northwest Laboratory Report PNL-6854
(UC-403). Prepared for the U.S. Department of Ener by Battelle Memorial Institute.
MuncH, 3. N. 1985. The Theory of the Electronic Spectra of O, ganic Molecules. John Wiley & Sons;
New York, New York.
Olsen, K. B., J. W. Griffin, D. A. NeLson, B. S. Matson, and P. A Eschbach. 1988. ‘Prototype Design
and Testing of Tho Fiber-Optic Spectrochemical Emission Sensors.” Proceedings, First International
Symposium on Field Screening Methods for Hazardous Waste Site Investigations. US.
Environmental Protection Agency, Environmental Monitoring Systems Laboratory, Las Vegas, NV.
117-125.
Parker, C A. 1968. Phowiwninescence of Solutioiu with Applications to Photochernisoy and Ana&*al
Chemisny. Elsevier London, England.
6-17
-------
Vo-Dinh, T. 1989. “Surface.Enh nced 2mAn Spectroscopy.” Zn: C7temicai Anatvse.r of Po vcycIic
A,vmau c C w,çewidr. T. Vo-Dinh, Ed. Wiley & Sons; New York, New Yo& 451-4
Williamson, J. t t, I L J. Bowling, and R. L McCreery. 1989. “Near-Infrared R m2n Spectroscopy
with a 783-nm Diode Laser and CCD Array Detector.’ AjpL Specwosc. 43(3): 372.375.
Wollbeis, OS. 198& “Fiber Optical fluorosensors in Analytical and ainical Chemistiy’ J :
Mckcailar LimWieicence Specbviccq Methods and 44p&a Is: Pan 2. S. (}. Schulman, Ed. John
Wiley & Sons; New York, New York.
Woollerton, 6. R., S. Valin, and T. Gibeault. 196& ‘The Kwik-Skrene Analytical Testing System
Description of a Tool for Remediation of PCB Spills.” Proceedings, First International Symposium
on Field Screening Methods for Hazardous Waste Site Investigations. U.S. Environmental Protection
Agency, Environmental Monitoring Systems Laboratory, Las Vegas, NV 387-388.
Zhang, Y. and W. R. Seitz 1989. “Single Fiber Absorption Measurements for Remote Detection of
2,4,6-Trinitrotoluene.” AnaL Chim. Acta. 221: 1.9.
6.3 E crRACnoN MEMBRANES
6.3.1 Introduction
A variety of information is available on the use of solid-phase extraction. For example. one
application bibliography lists over 500 articles to assist practitioners in choosing procedures for the
extraction and purification of a wide variety of chemical compounds (Analytichem International).
Most manufacturers of solid.pbase extraction products also provide simple guides for sample
preparation and choice of sorbents. Applications are not limited to environmental contaminants.
Several references provide insight on the potential application of extraction membrane
methodology to WHPAs. The use of solid-phase membranes in the form of 25- or 47. mm disks for
the extraction of pesticides, PCBs, and phthalates at the microgram per liter range is described in
Hagen et aL (1990). Standard filtration equipment (a suction flask) was utilized. Ground water,
surface water, and laboratory tap water samples were used for pesticide, PCB, and phthalatc analysis,
respectivety. The membranes were obtained from Analytichem International with a typical
composition of 90% (by weight) of octyl (Cs)- or octadecyl (C18)- bonded silica particles and 10%
fibrillated potytetrafluorethylene. Recoveries exceeding 80 to 90% were obtained for the classes of
compounds examined. This work demonstrates the utility of such membranes for preconcentration
purposes.
Recent research addresses the potential of utiIi’ir g solid phase extraction membranes as part
of a field screening method (Poziomek et aL, 1991). The research involves using commercially
available extraction membranes to preconcentrate contaminants onto the membranes by sorption
from aqueous solution followed by nondestructive spectroscopic measurements in the field.
Depending on the analytes being measured and the system parameter, the measurements could involve
UV.vis luminescence directly, colorimetry/fluorometry with appropriate reagents. XRF analysis, and
radioactivity measurements.
6-19
-------
Refrrences to a variety of material, that have been emmii for solid-phase extraction
appliestions ean be found in a paper by Carr and Harris (1988). These include cellulose, earbon,
fiberglass, recites, Oiekx 100, XAD, Tenex, and glass or sues gel derivatized with alkyl chains .
Analytes em be sorbed either directly onto the surface or through specific chemiesi interactions.
Organic analytes preconccntrated on the support arc usually extracted with an appropriate
solvent The extract is then analyzed using an appropriate laboratory method such as GC, GCIMS, or
liquid chromatography-mass spec*rusoo (LC-MS). The WHPA field screening application would
involve eYamining the extraction membrane directly. Laboratory analysis would be an option after
field screening.
6.3.3 Methodology
C18 Empore membrane disks for adsorption of anthracene from water ware analyzed
nondestructively by solid-state fluorescence spectroscopy (Poziomek et aL, 1991). These experiments
simulated dip-stick or water-well insertion modes. Tabs were cut from the membrane disks and
suspended without stining in aqueous solutions arnthning ppb concentrations of anthracenc at room
temperature. The tabs were exposed to the solutions for given time intervals at different
concentrations of anthracene. The tabs ware then withdrawn, allowed to dry in air, and examined
using fluorescence spectroscopy. Various relationships were found (e.g., linear increase in fluorescence
intensity for 10 ppb anthracene versus time (minutes to daysi). The results reported are preliminary,
but very promising.
Carr and Harris (1988) concentrated pyrene from methanol-water solutions onto a C-18
derivatized porous silica column. They examined the column fluorescence as the pyrene was being
sorbed and later allowed to desorb. The C18 silica was packed into a custom, fabricated, quartz tube
(43 nun long, 3.2 mm outside diameter, and 0.96 mm inside diameter). The tube was held in place by
a brass cuvette. It represented a flow cell arrangement so that the sorpnon/desorption of the pyrene
could be followed in real time by measuring the column fluorescence. Membrane technology was not
used in thiscase. Nevertheless, the reported results add support to the possibility of monitoring the
sorption of pollutants onto membrane tabs in real tune. ft would be difficult to adapt a column flow
cell to field operations. However, the useof membrane tabs inadipsnck mode or in wellswithflber
optic spectroscopy seems attractive top (Poziomek et al., 1991).
Wyzgol et al. (1990) have proposed the use of a combination of membrane extraction and
attenuated total reflection IR spectroscopy for continuous measurements of waste water and air in
industrial plants and during remedial actions. The extraction and spectroscopic pro ures are
combined to give real-time measurements of various organic compounds. The limits of detection have
been estimated to be from 0.3-60 mg/L, depending on the compound.
Leyden and Luttrell (1975) immobilized metal-ion chelating functional groups by reacting
silica gel with various silylating reagents. They concluded that these materials have potential as
preconcentration aids for X-ray analysis. This work is cited to indicate the potential scope of
combining solid-phase extraction with various spectroscopic techniques in field screening of not only
organic compounds but also metal ions.
6-21
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&3.6 Sllmmkiy
The use of solid-phase extraction membranes to preeoncentrate pollutants onto the
membranes by sorption from aqueous solution followed by nondestructive spectroscopic measurement
baa potential as a field screening method for WHPA monitoring. Attractive features in nhre the use
of comm dally available extraction m mhranes and portable field instrumentation. The enneept
ailo flenbility in choosing oonfigurauons for use in WHPA monitoring (e.g., dipsndcs, standard
filtration, or placement into wells at various positions to profile eontamination zones). These
applications are in the initial stages of development and require validation studies.
6.3.7 References
Analytichem InternationaL Application Bibliography. Analytichem International, 24201 Frampton
Avenue, Harbor City, CA, 90710.
Carr, 3. W. and 3. M. Harris. 198& “In Situ Fluorescence Detection of Polycycic Aromatic
Hydrocarbons following Preconcentration on Alkylated Silica Msorbents.” AnaL Chem.
60(7): 698.702.
Hagen, D. F., C. F. MarkeH, and GA. Schmitt 1990. “Membrane Approach to Solid-Phase
Extractions.” AnaL Client. Acta. 236: 157-164.
Leyden. D. E. and G. H. Luitrell. 1975. ‘Preeoncentration of Trace Metals Using Chelating Groups
Immobilized via Silylation.” AnaL Chem. 47(9): 1612-1617.
MacCarthy, P., R. W. Kiusman, and J. A. Rice. 1987. “Water Analysis.” AnaL Chem.
59(12): 308R-337.
MacCarthy, P., R. W. Klusman, and 3. A. Rice. 1989. “Water Analysis.” AnaL Chem.
61(12): 269R-304R.
Poziomek, E. 3., D. Eastwood, R. L Lidberg, and G. Gibson. 1991. “Extraction Disks and
Microporous Films for Spectroscopic Field Screening Applications.’ Proceedings of the Seeond
International Symposium on the Field Screening Methoda for Hazardous Wastes and Toxic
Chemicals. U.S. Environmental Protection Agency. Environmental Monitoring Systems Laboratory,
Las Vegas, NV.
Taguchi, S., LO. Eiyukl, K. Masuyama, L Kasahara, and K. Goto. 1985. “Application of Organic
Solvent-Soluble Membrane Filters in Preconcentration and ‘)etermination of Trace Elements:
Spectroinetric Determination of Phosphorus as Phosphomolybdenum Blue.’ Ta ansa 32(5): 391-394.
Wyzgol, R. C, P. Heinrich, H. 3. Hocbkamp, A. Hatzilazaru, K. Lebioda, S. Aschhoff and B.
Schroder. 1990. “Membrane-ATR-Method for the Continuous Determin2uon of Chlorinated
Hydrocarbons in Air and Water.” : Cosuaminaceti Soil 9O. F. Arendt, M. Hinsenveld, and W. J.
Van den Brink, Eds. Kluiver Academic Publishers; Boston, MA. 799-800.
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6.4.4 Application to WHPA Monitoring
The application of SAW and 0CM technology to WHPA monitoring s nis promising for
both vapor and aqueous solution monitoring because of the variety of compounch which might be
sensed. Organic chemical vapor sensing applications probably have a better chance of success because
more is b wn about this application than solution monitoring. 1 design of probes should indi
membranes to protect their sensor coatings when immersed in solution. The 0CM probes would
have a greater chance of success as in sini water monitors than the SAW devices because more is
known about their use in solution. The 0CM and SAW technologies are still developing and have
not been applied routinely to ground-water monitoring.
6.4.5 LimitationsiPerformancc
The major technology barrier to the development of mass sensitive and other chemical
sensors is the proper selection of the sensor coating materials. A comprehensive review on the
re’c’arch and development of sensor coatings is available (Poziomek, 1989). Several problems persist,
impeding rapid development of the technology. For example, no information base on chemical
reactions and mol ilar association effects in vapor-solid and liquid-solid phases exists to draw on for
the development of chemical sensor coatings. In addition, few guidelines describe the sclection of
solid phase coatings for use in conjunction with chemical sensors, and standard methods for screening
and evaluating tkWe solid phase coatings in sensor applications are not readily available
(Poziomek and EngthnAnn. 1990). Most likely, an array of QCM and/or SAW microsensors would be
ne ssary to increase selectivity. Single sensors that are specific to a particular pollutant or a class of
chemicals are conceivable; however, a sensor array would broaden the utility of the technologies.
6.4.6 Summary
SAW and QCM rnicrosensors measure changes in mass when analytes sorb and/or react with
the device coatings. Such devices have attracted the attention of the sensor community because of
their simplicity, ruggedness, and low cost. The major applications to date have been for organic
chemical vapor sensing, but the use of the devices, especially QCMs in solution, is beginning to
emerge. Specific application to WHPAs seems promising. However, the major technology barrier
toward exploiting the potential of SAW and 0CM microsensors is proper selection of the sensor
coatings. Guidelines need to be established to help practitioners choose coatings.
6.4.7 References
Ballantine, D., A. Snow, M. Klusty, 0. Chingas, and H. Wohltjen. 1986. USAF/NRL Surface
Acoustic Wave Sensor Program. NRL Memorandum Report 5865, Naval Research Laboratory,
Washington, DC
Ballantine, D.S., Jr. and IL Wohltjen. 1989. “Surface Acoustic Wave Devices for Chemical Analysis.”
AnaL Chem. 61(11): 704A-715A.
Guilbault, 0G. and J.M. Jordan. 1988. “Analytical Uses of Piezoelectric Crystals: A Review.” CnL
Rev. AnaL Chem. 9(1): 1-2&
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Two early reviews give an appreciation of the principles of spectroelectrochemistiy and the
progr m during the first decade since its disaweiy (Kuwana and Heineman, 1976 H in man ,
1978). A recent review on the application of spectroelcctrochcmistiy in analytical chemistry provides
62 references (W dring et aL , 1990).
6.5.2 Theory of Operation
Electroactive species change at an electrode by the addition or removal of electrons. In
spectroelectrochemstry, spectral measurements are made on the solution adjacent to the electrodes as
tire clectrochegnical process proceeds. In some cases , the surface itself is examined. Thus,
spectroseopy is used as a probe to observe the ansequen of an elecirochemIcnl pro s. A typical
output would be several spectra of a particular substance obtained for a series of potentials. However.
one is not limited to the use of transmission spectroseopy. Specular reflectance and internal
reflectance spectroseopy have been used as well. Since its inception in 1%4, the “spectro” part of
spectroelectrocheinistry has been expanded to include electron spin and nuclear magnetic resonance as
well as luminescence and scattering spectroseopics. Ultraviolet and visible spectroelectrochenustry are
now quite eommonly used to identify electrode reaction products and intermediates. Several
improvements have been made, including the use of fiber opries for the propagation to and subsequent
illumination and detection of light at electrode surfa . Infrared and Raman spectroseopy are also
being applied more frequently to electrochemical problems. Several sources delineate theory and
provide specific examples of the different types of spectrosenpy that have been used (Heineman ci al,
1984; Gale, 1988 McCreery, 1986; Sharpe er al, 1990).
65.3 Methodolofv
Through spectroelectrochemistzy, it is theoretically possible to determine the composition of
solutions and electrode adsorbed specres. The technology allows elucidation of reactants,
intermediates, and products.
Recent developments in methodologies inc lude (1) an IR thin layer cell with a gold or
platinum working electrode that serves as a minor for the light beam, (2) mercurylsolution interfaces
for study of adsorbtion, (3) angle-resolved IR spectroelectrochemistry for in mu depth profiling of
electrodelelecsrolytc inrcthccs (4) surface-enhanced Paman spectroscopy (SERS) for studying
adsorption and electroreducuon at silver electrodes, (5) surface-enhanced resonance Raman
spectroseopy for monitoring electrode surface reactions of biological molecules, (6) improvements in
cell geometries and novel applications of UV-vis spectroclectrochemistry, (7) the use of fiber-optic
absorbance probes in cenjunction with a buLk electrochemical cell, (8) improvements in optically
transparent spectroelectrochemical cells, including the fabrication of high surface area working
electrodes, (9) improvements on long optical path length cells for simultaneous electron spin
resonance - electrochemical investigations, and (10) extended X-ray adsorption fine structure
spectroelectrochernistry (Widring et aL, 1990).
The use of spectroelectrochemistiy has elucidated the basic chemistry that occurs on the
surface of an electrode. Examples of compounds and ions studied recently using any one of a variety
of spectroelectrochemistry techniques include ethanol, carbon monoxide, methanol, sulfate,
formaldehyde, tetraphenylporphyrin-metal complexes, benzoic acid, benzoate, cyanate, ferrocyanide,
dioxouranium (VI), hexakis (arylisocyanide) chromium (III), polythiophene, dopamine, pyrrole,
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Heinem n , W. R. “Spectroelectrochemistry. 1978. AnaL Chenv. 50(3): 390A-402A (1978).
Heinem*n, W. R., F. ?vL Hawkridge, H. N. Blout 1984. : Ekcwoanalydca! Cliemuvy. A J. Bard,
ed. Decker, New York. Vol 13, pp. 1-113.
Kuwana, T., R. K. Darlington, and D. W. Leedy. 1964. “Electrochemical Studies Using Conducting
Gloss Indicator E1CctTOdCS ” AnaL Chem. 36: 2023 (1984)
Kuwana, T. and W. R. Hcinem 1976. “Study of Electrogenerated Reactants Using Optically
Transparent Electrodes.” Acc. C7zon. Ret. 9(9): 241-248.
McCreeiy, R. L 19$6 “Spectroelectrochemistry.” J : Pkj tica1 Methc4, of Chemiwy. Vol.2. B. W.
Rossiter and J. F. Hamilton, Ed t Wiley New York, NY. Chapter 7,591-661.
Sharpe, L it, W. it Heinenian, and R. C Elder. 1990. “EXAFS Spectroelectrocheniistiy.”
Cliem.Rev. 90(5):705-722.
Weber, S.G. and J. T. Long. 1988. “Detection Limits and Selectivity in Electrochemical Detectors.”
AnaL C7ie n. 60(15): 903A-9 13A.
Widring, C. A, M. D. Porter, ?L D. Ryan, T. 0. Strein, and A 0. Ewing, 1990. “Dynamic
Electrochemistiy Methodology and Application.” AnaL Chem. 62(12): 1R-20R.
6.6 BIOSENSORS
6.6.1 Introduction
First reported by Cark in 1962, biosensois are relatively immature tools of analytical
chemistry and are regarded by some as emerging technology. For the purposes of this report, a
biosensor is defined as an analytical device that incorporates a biologically active material in intimate
contact with an appropriate transduction element in order to detect (reversibly and selectively) the
concentration or activity of chemical species in any type of sample (Arnold and Meyerhoff., 1988).
This definition relates to the type of (bio) chemical reaction that provides the analytical output
(usually electrical).
6.6.2 Theory of Operation
Biosensors are classified into two operational types: biocatalytic and receptor biosensors.
1. Biocatalvtic biosensors - the sensing tip of the detection probe contains a very small
amount of immobilized biocatalyst which communicates between the analyte and the detector element.
As analytes mow from the sample medium into the biocatalytic area at some diffusion controUed rate,
they are converted into a form that is measurable by the detector. At the same time, the converted
form of analyte (product) diffuses out into the sample medium at some rate. At steady-state
conditions, the signal at the detector relates to the concentration of the analyte in the sample.
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Z Multiple enzyme systems promise synergistic benefits. Their combination can be used to
form new biosensori to increase sensor selectivity and to ampli , chemically the sensor response
(Arnold and Meyerhoff, 1988).
3. Fiber optic biocatalytic biosensors use the immobilization of an enzyme at the tip of an
optical fiber, and detection is through opto-electronic m’ans . Other bK sensors use electrochcmical
means to send their signal through shielded, metallic conductors to the analytical instrument. An
advantage of fiber optic devices over electrocheinical devices is their capability to use a single fiber for
monitoring multiple wavelengths. A disadvantage is that fiber optic cables are usually made of quartz,
making them considerably more expensive and less durable than electxical conductors.
6.6.4 Application to WHPA Monitoring
The number of available ground-water monitoring biosensors, even in concept or prototype
form, is currently very limited. Biosensors for the detection of sulfate anions (Kobos, 1986) and
ammonium ions (Reidel et al., 1985) have been described.
6.6.5 Limitations/Performance
High enzyme levels in the detector produce faster biocatalytic reactions, but the sensor
response is limited by diffusion. Low enzyme levels in the detector produce slower biocatalysis, and
sensor performance depends on reaction rates. The current list of analyses that are detectable through
fiber optic biocatalytic biosensors contains little of interest to WHPA monitoring (Arnold and
Meyerhoff. 1988).
Biosensors generally have two main components: (1) a molecular recognition, or biological
entity, and (2) a signal-producing entity, or the component connected to the analytical
instrumentation. Biosensor research and development requires a large measure of creativity to gain an
optimal union between these two components. As biosensors are further developed and improved
through innovative technology, applications can be expected in medicine, agriculture, biotechnology,
military applications, and environmental studies such as ground-water monitoring for WHPAs.
6.6.6 Summary
Few analyses can be monitored with biosensors; nevertheless, the technique is worthy of
continued research. The medium of conveying the signal from biosensor to analyzing instrument for
ground-water monitoring for WHPAs should be based on electrically-conducting cable in which
ruggedness and cost are controlling considerations. The literature reports many biosensors, but this
research focuses mainly on biomedical monitoring of analyses not expected to be found in ground
water. Biosensors have been described that can monitor sulfate ions and ammonium ions.
6.6.7 References
Albery, W. 3., P. N. Bartlett, A E. Cass, D. H. Cranston, and 3.0. D. Haggert 1986.
“Electrochemical Sensors: Theory and Experiment I. Chem. Soc 82: 1033.
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SECI1ON 7
CASE STUDIES
This section describes two case studies that exemplify innovative applications of monitoring
technologies for drinking water. The flmt case study is the Orange County Water District, (OCWD)
located in Southern California. The OCWP is monitoring ground water using “Multiport Wells”
equipped to countinously measure temperature and water level This data is linked to a centralized
computer and water fn nAgement data base system. The second case study is the State of Florida’s
Ground Water Quality Monitoring Network and related applications of continuous remote monitoring
station that utilize telemetry.
7.1 ORANGE COUNTY (CALIFORNIA) WATER DISTRICT: INNOVATIVE
APPROACH TO GROUND-WATER MONiTORING USING AN IN-SITU, MIJI.JI-
LEVEL, CONTINUOUS GROUND-WATER DATA ACQUISITION SYSTEM
The OCWD manages a large alluvial ground-water basin in the coastal plain of southern
California (Figure 7-la). Today the OCWD supplies more than 65 percent of the total water demand
of the 1.8 million people within the District.
The portion of the basin managed by OCWD vers an area of about 300 square miles and
has a useable storage of approximately 1.5 million acre-feet. Though the fresh water aquifers extend
to depths up to 4,000 feet, at this time, most production occurs above a depth of 1,500 feet
(Figure 7-ib).
Prior to OCWD implementing recharge activities, the natural safe yield of the basin was about
60,000 acre-feet per year. With a ground-water dem iid of more than 250,000 acre-feet per year, the
District must artificially recharge the basin and control sea water intrusion. The recharge facilities,
located on more than 1,600 acres of land along the Santa Ma River, consist of about 1,000 wetted
acres of in-river and shallow and deep spreading basins. Water is diverted into these facilities from
storm and base flows of the Santa Ana River and from the California and Colorado River Aqueducts.
As much as 350,000 acre-feet per year can be recharged in these facilities, depending on the
availability of water from local and imported sources.
In addition, sea water intrusion caused by the large pumping depressions in the central part of
the basin poses a potential problem in certain areas near the coast The District controls this problem
by injecting imported water and reclaimed wastewater into coastal aquifer zones. The District also
monitors ground-water contamination problems in the basin and is active in District-financed
remedial investigations and clean ups.
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This multifaceted program requires a comprehensive monitoring system to provide the data
for management decisions. The District has begun a 10-year program to install up to 150 deep and
shallow, multi-level monitoring wells throughout the basin. The objective of these wells is to provide
an areal as well as vertical understanding of the basin hydrogeology. Typi lly, these wells are about
1,500 feet in depth, but range from 300 to 2,000 fret. After investigating and experimenting with
several construction methods, including nested, cluster, and single standpipe wells (Figure 7-2), the
District selected the MP system (Westbay Instruments Inc.), which consists of a single standpipe with
multiple screens. A comparison of the alternate methods is given by Black et al. (1988). The
monitoring wells are constructed of 4-inch in diameter, mild steel casings and screens. Screens are
isolated in the annulus with a mixture of bentonite chips and coarse-grained sand that is placed by
pumping through a tremie pipe (Figure 7-3). The MP System isolates the screens on the interior of
the casing with water-inflated packers. This system allows the District to isolate, monitor, and sample
any or all aquifers penetrated by any given well for both piezometric pressure and water quality.
These wells have been useful in lo ting contaminants, determining hydraulic characteristics of
individual aquifers, and identifying flow pathways as water moves from the recharge areas of the basin
toward the points of extraction.
The District has installed more than 20 deep and 50 shallow monitoring wells, which provide
more than 300 monitoring points for collecting samples and obtaining water pressure measurements.
A water quality sample is taken from each point in each well once per quarter for the first year and
twice per year thereafter. Pressure measurements are carried out eveiy month. However, as the
number of monitoring wells increases, the manpower required to conduct the monitoring and
sampling increases to a point that would eventually be economically unacceptable to the District
Recognizing this dilemma, the District decided to participate in a research and development project
with Westbay to find a more efficient method of conducting the needed monitoring. Several wells are
currently fitted with this down-hole monitoring equipment to evaluate its effectiveness.
M*$AS ,p.M DII’ 1 M I IV V
Li H
Figure 7-2. Comparison of methods for monitoring ten eve1s between 0 and 1,500 ft.
:“
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THE MOSDAX SYSTEM
The MOSDAX System is a multi-level, continuous, ground-water pressure monitoring system
for use with MP System monitoring weik MOSDAX consists of a series of probes with pressure
transducezs (pressure probes), which are located at selected measurement ports in the MP monitoring
well, and a surface module which is placed at the weilbead (Figure 7-4). Data are collected from each
of the probes based on user-selected criteria and are transmitted to the surface module for storage or
passed on to a host computer using telemetry techniques (dedicated telephone line, cellular phone, or
radio).
Figure 7-4. Schematic illustration of MOSDAX System monitoring fluid pressure at multiple levels in
an MP System well.
_a be
Cei ,ipwl.I
Dais Sioii and
ao ! iem Ky S iis
OSOAZ Ptob. .oca%se.
II MIII ,j’smI9lU Peu
liP Cas. g iC i’
..u11
Ouiifl i.1iIsn I
P o SI,o.n
7-5
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Figure 7-5. Cartoon schematic showing idealized ground-water monitoring system.
distinct from the fluid outside the casing). The procedure requires deactivating each probe so that it
reads the pressure inside the MP casing. Following the performance check, the probes can be
reactivated to continue monitoring formation fluid pressures. Using this technique, the sensor drift
can be checked. It is possible to carry out this check remotely through the telemetry system. The
communications protocol between the probes and the surface module contains error checking routines
to detect errors in the transmission. If an error is detected, the SMCU can request a retransmission.
Data are stored in the surface module in a memory-efficient form that is not readable without
special conversion routines. Manipulating or altering the raw data is difficult. In addition, each of the
raw data files contains a header which includes information from the originating probe, such as serial
number, sensor calibration constants to be used, and date and file tracing information.
Innovative Monitoring of Recharged Groundwater
The OCWD operates an extensive recharge facility, known as the Forebay, along the Santa
Ana River, in Anaheim, California. Because the Orange County ground-water basin is located at the
end of the Santa Ana River watershed, it is the recipient of often poor-quality waters generated
primarily from three sources. The first, and foremost, is the high-nitrate tertiary treated waste water
a , ,., a. (a*.iI •o •a I II
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Innovative Monitoring Strategies Using Soil Gas Surveying to Evaluate a Groundwater VOC Plume
In Januazy 1987, a City of Orange production well was shut down due to the detection of
chlorinated VOQ above state drinking-water standards. OCWD determined the extent of VOC
contamin tion of the shallow ground water in the vicinity of the contaminated well through the use of
soil-gas surveys to identify potential source areas, and the construction of ten 100- to 200-foot deep
monitoring wells to delineate the lateral extent In addition, three existing 1,500- to Z000-foot deep
multiscreen monitoring wells were sampled to evaluate the vertical extent migration potential of the
plume. Although only the western edge of the plume has been defined to date, a ground-water
extraction and treatment system is being installed to minimize further VOC migration. Mditional
wells will be constructed to delineate the full extent of the plume for future remedial planning and
source identification.
SUMMARY
OCWD plans to continue with a program of installing monitoring wells and collecting
ground-water pressure and chemical data as required to meet the needs of the ground-water producers
in the basin. Accurate and timely data will be provided by a data collection network which will rely on
automatic data collection and telemetiy techniques to transfer the data directly to a central location.
To efficiently store and retrieve a large amount of project data, OCWD is developing their WRMS.
The WRMS program will be a network data base which will store data, from virtually every aspect of
the ground-water resource. The information includes well design information, lithologic logs,
geophysical testing results, geochemical data, and water-level data. The data base will be linked to
graphic and modeling tools to facilitate evaluation. Generation of contour maps and cross-sections
based on the information contained in the data base or developed from models will become easy and
routine. This program, coupled with the data continuously generated from the MOSDAX-equipped
MP monitoring wells, will help OCWD meet its mission and responsibilities well into the twenty-first
century.
REFERENCES
Black, W. H., J. A. Goodrich, and F. D. Patton. 1988 “Groundwater Monitonng for Resource
Management” Proceedings of the International Symposium on Artificial Recharge of Groundwater.
Ivan Johnson and Donald Finlayson, Eds. Anaheim, CA. 446-454.
Black, W. H., H. R. Smith, and F. D. Patton. 1986. “Multiple-level Monitoring with the MP System.”
Proceedings of the Surface and Borehole Geophysical Methods and Groundwater Instrumentation
Conference and Exposition. Denver, CO. 41-61.
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The Floridan aquifer is underlain by a confinmg bed and is overlain, throughout most of the
state, by the intermediate aquifer system (or intermediate confining unit). However, in some areas, the
Floridan is found exposed at or near land surface (Figure 7-7).
In 1 3, the Florida Legislature passed the Water Quality Assurance Act a portion of which
required the Department of Environmental Regulation to “establish a ground water quality
monitoring network designed to detect or predict contamination of the state’s ground water resources”
(Florida Statutes, Chapter 403.063). To facilitate this effort, the act requires that the Department
work cooperatively with other federal and state agencies, including the five water management districts
(Figure 7-8), and other government agencies in the establishment of the network.
The three basic goals of the Ground Water Quality Monitoring Program are:
• To establish the baseline water quality of major aquifer systems in the state.
• To detect and predict changes in ground-water quality resulting from the effects of
various land use activities and potential sources of contamination.
• To disseminate water quality data to local governments and the public.
Figure 7-7. Principal aquifers within Florida.
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• Background Network, designed to help define background water quality through a
network of approximately 1700 wells that tap all major potable aquifers within the stare.
• The Very Intense Study Area (V!SA) Network, designed to monitor the effects of various
land uses on ground-water quality within aquifers in selected areas.
• Private Well Survey, designed to analyze ground-water quality from 50 private drinking
water wells in each of Florida’s 67 counties. This data will supplement the Background
Network by providing additional sampling points, while indicating the general quality of
water consumed by private well owners. This survey is a joint effort between the Florida
I)cpartment of Health and Rehabilitative Services and the Department of Environmental
Regulations.
BACKGROUND NETWORK
Before changes in ground-water quality can be detected, baseline water quality must be
determined. The term baseline differs from background in that it refers to current regional ground-
water quality. This may or may not be synonymous with background, or pristine, ground-water quality
that existed before measurable human impact on the aquifer. A well in the Background Network is
designed to monitor an area of the aquifer that is representative of the general ground-water quality of
the region. It is not designed to be associated with degradation from contamination sources.
The first sampling of each well in the network involves the measurement of a comprehensive
set of field, chemical, microbiological, and naturally o irring radioactive parameters (Table 7-1).
These analyses, combined with historical data, can be used to estimate baseline ground-water quality.
This process of establishing current baseline helps to delineate areas where ground-water quality has
degraded. Once this baseline has been determined, data from future monitoring of the network will
continually evaluated to determine changes in water quality over rime.
After the initial samples are collected and analyzed, background montroring wells are
periodically sampled for a small group of indicator parameters, in an attempt to detect the onset of
degradation or contamination.
Among the indicator parameters selected, the analysis for VOCs is used as a way to detect the
presence of organic chemicals in the samples. If a sample is found to contain significant
concentrations of VOCs, further analyses for specific organic parameters are conducted.
Development of the Background Network occurred in the following phases:
• Phase I: Data collection, compilation, and location of existing wells which could be
incorporated into the network
• Phase II: Selection and drilling of initial monitoring wells.
• Phase I lL Initial sampling of the Background Network to determine ground-water quality
trenda and define baseline.
• Phase IV: x of wells found to contain significant concentrations of one or more
parameters.
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• Phase V: Refinement of the network through removal of redundant wells and affected wells
and drilling of additional wells where needed.
• Phase VI: Ongoing periodic x to define variations in ground-water quality over tune.
VISA NETWORK
The VISA Network monitors specific areas of the state that are believed to be highly susceptible
to ground-water contamination, based on predominant land use and hydrogeology. A VISA well is
designed to monitor the effects of multiple sources of contamination on water quality within a
segment of the aquifer.
Development of the VISA Network is broken down into the following phases:
• Phase I: Evaluation of data to determine areas of predominant land use (Table 7-2).
• Phase II: Determination of relative susceptibility to contamination of each potable aquifer.
• Phase III: Determination of percentage use of each aquifer as a source of potable water.
• Phase IV: Selection of VISAS based on above data.
• Phase V: Data collection, compilation, and selection of suitable existing wells within each
VISA.
• Phase VI: Drill additional wells as neede4
• Phase VII: Sample VISA wells.
Areas of predominant land use were located using the Florida Summary Mapping System, a
microcomputer geographic information system developed at the University of Florida. The system
contains land use data derived from ad valorem tax information for each of Florida’s 67 counties. This
data has been summarized to each square mile section of the state based on the Public Land Survey
System (section, township, and range).
Aquifer vulnerability was determined using DRASTIC, a mapping system developed jointly by the
U.S. EPA and the National Water Well Association. DRASTIC is an acronym representing the seven
hydrogeological parameters considered most indicative of relative pollution potential. These are:
D- Depth to water
R - Net recharge
A - Aquifer media
S-Soil media
T - Topography
I - Impact of the vadose zone
C - Hydraulic conductivity
Each of these parameters is mapped separately, and numerical scores are assigned to each map
polygon. The seven parameter maps form overlays which are combined to create a composite
DRASTIC aquifer vulnerability map. The score for each polygon in each overlay is multiplied by a
weighting factor, and the weighted scores are summed to produce a DRASTIC index for each polygon
on the composite map. Higher scores indicate higher relative pollution potential. Statewide
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DRASTIC mapping is scheduled to be completed in the summer of 1990, for the Surficial and
Floridan aquifrr sysS At that time, maps for each county will be published.
All welk in the VISA Network will be sampled for a standard list of paramen Additional
parameters which are not in the standard list, but are suspected to oceur based on land use, also will
be mcl.ieIM For enm pie, in industrial areas, produce used or proe ns 4 by facilities within the VISA
will be included in the parameters to be sampled likewise, in agriasitural and urban areas, suSances
typically produced as byproducts of these land uses will be determined and monitored.
Data from VISA wells will be statistically compared to like parameters sampled from
Background Network wells representing the same aquifer segment, to determine the effects of land use
and site hydrogeolo upon ground-water quality. By analyzing this data, reasonable predictions can
be made on the effects of siting similar land uses in hydrogeologically similsr areas of the state.
PRiVATE WELL SURVEY
The Florida Department of Health and Rehabilitative Services is conducting a survey of private
drinking water systems to determine the general water quality of these welLs. The two departments
have entered into a cooperative agreement to select up to 70 wells per county (50 primaxy, 20 backup)
for the study, using the same criteria developed to select existing Background and VISA wells. The
Department of Health and Rehabilitative Services is sampling these wells for approximately 180
parameters and these analyses will supplement data generated by the Ground Water Quality
Monitoring network.
Automated Remote Monitoring System
To meet their monitoring requirements, several of the agencies have installed computerized
automated remote monitoring and transmitting systems called Supervisor Control and Data
Acquisition (SCADA) systems.
The SCADA system links a computer, located at a centralized site, to remote field monitoring
and structure control stations using a two-way radio transmitter link.
The field monitoring stations measure hydrological data including ground-water level using
floats with encoders, transducers, or sonic devices and selected water quality parameters using available
sensors such as DO, electrical conductance, or pH.
The stations are also used to monitor hydrographic data such as reservoir and canal levels,
inflow and outflow, and water control structures. Additionally, meteorologic parameters are measured
including air temperature, wind-speed, wind-direction, evapotranspiration, rainfall, barometric
pressure, and relative humidity.
These monitoring stations can be equipped with radio-transmitter/receiver terminals placed in
remote locations and powered by solar cells. The remote radio terminals are capable of automatic
event reporting. The data is generally recorded hourly and radio interrogated four-times daily. The
system uses radio repeater stations to relay the data transmissions from the remote field sites to the
central control center although data transmission can be accomplished using microwave, satellite
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SUMMARY
The sampling frequency and chemical parameters to be monitored at each site are based on
several factors, including Network well classification (Background, VISA, HRS), land use activity,
hydrogeologic sensitivity of the site, and available funding. Wells near suspected sour of
contamination will be sampled more frequently than wells in undeveloped or background areas.
Data generated by the Ground Water Quality Monitoring network will be statistically analyzed
to:
• Establish baseline and background water quality. This will allow estimation of ground-
water quality by aquifer anywhere in the state.
• Determine current ground-water quality statewide and predict future changes to it as a
result of anthropogenic activities.
• Determine the degree of degradation of water quality in VISAs.
• Refine the network where needed to maximize information generated at a minimum cost
The hydrogeological data collected through this monitoring program will be used to map in
detail the extent and thickness of the major potable aquifers of Florida. Local mapping will be
conducted to more thoroughly define individual water-bearing zones within each aquifer system.
Additionally, water level data will be collected from each well. This information, along with similar
data generated by other governmental agencies and the private sector, will be used to delineate
physical ground-water divides. This will aid in determining the boundaries of ground-water basins.
When ground-water basins for each monitored aquifer have been determined, chemical data
from the Network will be used to establish the baseline water quality of smaller aquifer segments
within each basin. These chemically similar aquifer segments will be subdivided using statist1c t
techniques. Definition of these aquifer segments wilt be based on concentrations of parameters
present in the aquifer. Therefore, aquifer segments may differ in extent and thickness for each
parameter or group of chemically related parameters tested. It is from these data that water quality
maps will be produced for each sampled parameter.
Data generated by the Ground Water Quality Monitoring program will provide information for
preparation of numerous water quality maps. It will also help with future land use planning, zoning
decisions, and the development of more effective Local Government Comprehensive Plans. The raw
data, screened for accuracy through various statistical analyses and field checking, is available to the
public. Data from the network will help state and local governments evaluate the effects of land use
and changes in ground-water quality through time. Information regarding this program may be
obtained from:
Ground Water Quality Monitoring Program
Department of Environmental Regulations
Bureau of Drinking Water & Ground Water Resources
2600 Blair Stone Road
Tallahassee, Florida 32399-2400
Tel: (904) 4 8-36O1
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