United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Las Vegas NV 89114
Research and Development
EPA-600/S7-84-067 June 1984
Project Summary
The Feasibility of Using Fiber
Optics for Monitoring
Groundwater Contaminants
Thomas Hirschfeld, Terrance Deaton, Fred Milanovich, and Stanley M. Klainer
This report contains the results of the
initial feasibility study for a research
program undertaken to develop the
technology needed to use fiber optics
for monitoring groundwater contami-
nants. The technology appears especial-
ly well suited to the requirements of
detection monitoring, where a few
indicator parameters can be measured
continuously by sensors placed down
small-diameter monitoring wells. Data
are generated at a remote, centrally
located fluorimeter, connected to the
sampling sites by inexpensive optical
fibers.
The analytical method is laser-induced
fluorescence, which gives the desired
sensitivity. The optrode, a chemical
system and/or a mechanical device at
the distal end of a fiber optic, furnishes
the needed specificity. Various fiber
and optrode configurations have been
evaluated and their applications to
groundwater monitoring are .discussed.
Feasibility is shown for physical meas-
urements such as temperature, pres-
sure, and pH. Chemical detection and
quantification methods for the actin-
ides, inorganic and organic chlorides,
sulfates, alcohols, aldehydes, pesticides
and tracer materials are presented.
Finally, it is shown that the need for
smaller diameter wells (as compared to
conventional sampling methods) and
the ability to make up to 50 unattended
In situ measurements using a reasonably
priced, centralized fluorimeter system
connected to the sampling sites by
inexpensive optical fibers results in
acceptable economy.
This report was submitted 'in fulfill-
ment of DOE contract number W7-
405-ENG-48 by Lawrence LJvermore
National Laboratory under the sponsor-
ship of the U.S. Environmental Protec-
tion Agency. This report covers work
performed during the period from
January 1. 1982 to September 30,
1982.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
When it was learned that Lawrence
Livermore National Laboratories (LLNL)
was developing technology to make re-
mote measurements of pH, temperature,
and various ion concentrations in hostile
environments for the Department of
Energy by means of laser-induced fluo-
rescence spectroscopy over optical fibers,
EPA recognized the possibility of using
the technique for groundwater monitor-
ing. The specificity, sensitivity, and remote
measurement capabilities of fiber optic
fluorescence spectroscopy appear to be
ideally suited to EPA's needs. This report
is an overview of what has been accom-
plished at LLNL for EPA and what is
feasible using fiber optic techniques in
regard to RCRA groundwater detection
monitoring needs.
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Results
EPA asked LLNL to consider the feasi-
bility of monitoring six categories of
groundwater pollutants. The results were
as follows:
a. Inorganic chloride—Analysis is ac-
complished using the reaction of
Cl~ with silver fluoresceinate to
release the fluorescent fluorescein.
Data exist to 10 ppm with projec-
tions of sub-ppm sensitivities.
b. Organic chloride—Ageneral analyt-
ical method based on the complete
oxidation of organic chloride by
chromic oxide to yield Cl~ and the
subsequent reaction with silver
fluoresceinate is being developed.
At present, only the two individual
reactions have been successfully
tested. Detection limits appear to be
dependent on the AgCI solubility.
c. Aldehydes—Measurement is ac-
complished by the quenching of
normally fluorescent Schiff re-
agents by aldehydes.
d. Alcohols—Selective oxidation of
alcohols to aldehydes is accom-
plished and then the degree of
quenching of Schiff reagents is
determined.
e. Sulfate—The release of fluorescent
chloranilic acid from barium chlor-
anilate by the reaction with SO< is
the chosen analytical method.
f. Pesticides—An initial effort indi-
cated that an enzymatic reaction
based on cholinesterase inhibition
by pesticides is a good detection
method. The complexity of the
approach makes it subject to re-
evaluation.
Measurement techniques for other
parameters are also presented.
The use of tracers in groundwater is
important both for research purposes and
for followingthe route of contamination
for specific injection sources. In this study,
fiber optic detection of fluorescent tracers
such as Rhodamine 6G, brilliant sulpho-
flavine, and fluorescein was evaluated at
concentrations of 1 part-per-million and a
fiber length of 100 meters. Extrapolation
of the data indicates that at 300 meters,
detection limits could reach 1 part-per-
billion or less.
Temperature, pressure, pH, and Eh
(oxidation potential) have also been meas-
ured. These measurements are important
because they give information about the
contaminant species which is present.
Temperature can be measured ove/ a
wide range to 0.1 °C and over a restricted
span to 0.01 °C from 20 to 250°C. Pres-
-Syre can be resolved to 0.01 PSI, and pH
is resolvable to 0.05 pH units over the
complete pH scale. Eh can be determined
to 0.1 Vfrom 1.1 to-0.6 V. Methods for
pH and Eh are presently being further
developed.
Conclusions
Results of the feasibility study show
that remote fiber fluorimetry is well suited
to the requirements of groundwater detec-
tion monitoring. This approach has the
potential of qualifying and quantifying
groundwater contaminants in the sub-
parts-per-million (ppm) range. Tracer
materials can be detected below one part-
per-billion (ppb). In addition, measure-
ments can be made of the physical
properties of groundwater which affect
contamination. Finally, a preliminary
economic study indicates that this method
may be less expensive than extant moni-
toring techniques.
T. Hirschfeld. T. Deaton, andF. Milanovich are with Lawrence Liver more National
Laboratory, Livermore, CA 94550; and S. Klainer is with S. T. E. Technical
Services, Inc., San Ramon, CA 94583.
Charles K. Fitzsimmons is the EPA Project Officer (see below).
The complete report, entitled "The Feasibility of Using Fiber Optics for Monitoring
Groundwater Contaminants,"(Order No. PB84-201 607; Cost:$11.50, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89114
•it U.S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7727
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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