United States
Environmental Protection
Agency
Research and Development
Office of Energy. Minerals, and
Industry
Washington DC 20460
EPA 600 7 79 103
April 1979
Evaluation of
Present Chemical
Standards in
Relationship to
In Situ Marine
Water Quality
Measurements

Interagency
Energy/Environment
R&D Program
Report

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                 RESEARCH  REPORTING SERIES

 Research reports of the Office of Research and Development, U.S. Environmental
 Protection Agency, have been grouped into nine series  These nine broad cate-
 gories were established to facilitate further development and application of en-
 vironmental technology. Elimination  of  traditional grouping was  consciously
 planned to foster technology transfer and a maximum interface in related fields.
 The nine series are:

      1.   Environmental Health Effects Research
      2.   Environmental Protection Technology
      3.   Ecological Research
      4.   Environmental Monitoring
      5.   Socioeconomic Environmental Studies
      6.   Scientific  and Technical Assessment Reports (STAR)
      7.   Interagency Energy-Environment Research and Development
      8.   "Special" Reports
      9.   Miscellaneous Reports

 This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
 RESEARCH AND DEVELOPMENT series. Reports in this series result from the
 effort funded under the 17-agency Federal Energy/Environment Research and
 Development Program. These studies relate to EPA's mission to protect the public
 health and welfare from  adverse effects of pollutants associated with energy sys-
 tems. The goal of the Program is to assure the rapid development of domestic
 energy supplies in an environmentally-compatible manner by providing the nec-
 essary environmental data and control technology, Investigations include analy-
 ses of the transport of energy-related  pollutants and their health and ecological
 effects; assessments of, and development of, control technologies for energy
 systems; and integrated assessments of a wide range of energy-related environ-
 mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                           EPA-600/7-79-103
                                           April  1979
EVALUATION OF PRESENT CHEMICAL STANDARDS
 IN RELATIONSHIP TO IN SITU MARINE WATER
          QUALITY MEASUREMENTS
                   by

              D. G. Deliman
              D. G. Harden
              L. L. Launer
              M. D. Sands
              H. G. Stanley
    Interagency Agreement No. D5-E693
         Program No. EPA-78-BEA
      Program Element No. 1  NE 625C
             Project Officer
           Gregory D'Allessio
 Office of Energy, Minerals and Industry
  U.S. Environmental Protection Agency
           Washington, DC 20460
 This study was conducted as part of the
  Federal Interagency Energy/Environment
    Research and Development Program
  by Interstate Electronics Corporation
       Ocean Engineering Division
           Anaheim, California
              Prepared for
          National Oceanic and
       Atmospheric Administration
           Rockville, MD 20852
 Office of Energy, Minerals and Industry
    Office of Research and Development
   U.S. Environmental Protection Agency
          Washington, DC 20460

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                                 DISCLAIMER
     This report was assembled by the Test and Evaluation Laboratory, National
Ocean Survey, National Oceanic and Atmospheric Administration, from informa-
tion received under contract with the Ocean Engineering Division, Interstate
Electronics Corporation, Anaheim, California.  Approval does not signify that
the contents necessarily reflect the views and policy of the National Oceanic
and Atmospheric Administration or the U.S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorsement
or recommendation for use.

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                                  FOREWORD


     The Department of Commerce, National Oceanic and Atmospheric Administra-
tion (NOAA), has been given the responsibility to monitor seawater pollution
related to energy exploration and development.  In situ measurements of chemi-
cal parameters are becoming more important because of the large volumes of
data which are required for monitoring seawater pollution, but which cannot
be achieved with conventional discrete sampling and subsequent laboratory
analysis.  The more detailed information that is needed to understand the
complex chemical processes involved requires that sensors be used for contin-
uous in situ monitoring and/or profiling with depth.  Inevitably, however,
some confusion exists about the accuracy and precision of data collected from
different in situ instrument arrays.  Present standards, calibration proce-
dures, and uncertainties in the data collected with in situ water quality
systems, as well as how these standards, calibration procedures, and systems
contribute to this confusion, will  be evaluated in this report.  Parameters
most commonly measured and those which show promise for future development
are discussed.
                                     "James P. Sullivan
                                      Contracting Officer's Technical
                                      Representative
                                      Test and Evaluation Laboratory/National
                                      Oceanic and Atmospheric Administration
                                      m

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                                  ABSTRACT
     This report represents the findings determined by Interstate Electronics
Corporation Oceanic Engineering Division during a 9-month study entitled
"Evaluation of Present Chemical Standards in Relationship to In Situ  Marine
Quality Measurements" (Contract 6-35234), performed for the U.S.  Department  of
Commerce, National  Oceanic and Atmospheric Administration (NOAA).  The  purpose
of the program was  to determine what standards are currently available  and
their suitability for validating present in situ water quality measurements,
and to assess the accuracy of measurement traceability from the in situ
instrument to a recognized standard.  The assessment included the determina-
tion of measurement uncertainty and resulted in recommendations for the
development of necessary standards.

     Mhile development and use of in situ measurement systems in  the  marine
environment is in its infancy, the ease with which in situ systems gather
large volumes of data for environmental studies, pollution monitoring,  and
other applications  is such that their continued use and growth is assured.
Because their use is recent, inattention to establishing standards has  made
suspect the absolute accuracy of the data and, thus, the comparability  between
data sets.  Most users have devised their own techniques of assuring  the  rela-
tive accuracy of their in situ data, but no recognized standard techniques
exist.

     It was found that deficiencies exist in two areas:  (1) lack of  an ade-
quate (multiple point) primary standard for some parameters (e.g., salinity
and dissolved oxygen); and (2) failure by in situ system users to follow
standard methods (where they exist) for calibration and standardization.  The
study recommends:  (1) the establishment of standard reference materials  and
methods for calibration and standardization to assure accuracy of parameters
measured in situ; and (2) the development of specific means to achieve  trace-
ability to these standards.
                                     IV

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                                 CONTENTS
Foreword	iii
Abstract	    iv
Figures	    vi
Tables	    vi
Abbreviations 	   vii
Symbols	  viii
Acknowledgments 	    ix

   1.  Introduction 	   1
   2.  Conclusions	3
   3.  Recommendations	4
            Calibration and standardization materials 	   4
            Calibration procedures	4
            Documentation procedure 	   5
            Support services	5
   4.  Traceability of Calibration to Common Standards	7
            Standard references 	   7
            Calibration and standardization techniques	10
            Accuracy and reliability	14
            Alternate calibration techniques	17
            Measurement degradation 	  18
   5.  Reference Standard Requirements for Chemical In Situ
       Instrumentation	19
            Reference standards for currently measured parameters ....  19
            Extention of in situ instruments to parameters not
            now measured	21
            Survey of national accuracy requirements	23
            Instrumentation 	  25

References	35
Appendices

   A.  Description of two variations of in situ instrumentation
       systems	37
   B.  Experimental cruise for comparison of calibration
       accuracies	40

Glossary	49

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                                    FIGURES


Number

   1  Intercalibration cruise sampling station locations,
                                   TABLES
Number                                                                    Page

   1  Representative Instrumental Capabilities	15
   2  Representative Analytic Capabilities	16
   3  Common Standards for Calibration	17
   4  Ranges of Common Oceanic Parameters  	 19
   5  Parameters Measured In Situ—Present and Future
        Applications	22
   6  Estimates of Best Oceanic  In Situ Accuracies	25
   7  Partitioned Standard Deviations from Intercomparison
        Experiment	30
   8  95% Confidence Intervals with Paired T-Tests for Significant
        Difference Between Sample and Calibration Measures	31
B-l   In Situ Systems Used for Experimental Cruise	42
B-2   Laboratory Methods Used on Discrete Samples for
        Experimental Cruise 	 42
B-3   Summary of System Accuracies	43
B-4   Horiba:  U-7 Water Quality Checker	44
B-5   Hydrolab:  6D Surveyor	45
B-6   Martek:  Mark V Digital  Water Quality Analyzer	46
B-7   Plessey Environmental Systems:  Model 9400
        Telemetering Sensor System  	 47
B-8   Yellow Springs Instruments:  Model 57 Dissolved
        Oxygen Meter	47
B-9   Beckman Select-Mate 	 48
B-10  Orion pH Meter	48
B-ll   Beckman RS 7-C Induction Salinometer	48
                                     VI

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                            LIST OF ABBREVIATIONS
ABBREVIATIONS

ASTM
CalCOFI
CI
cm
CTD
CUE
DMRP
DO
GEOSECS
Hz
I.A.P.S.O.  --
KHz
kg
mA
mg/1
MIL/STD
ml
mm
mS/cm
mv
NA
NBS
NORPAX
OCS
ppm
ppt
QC
SI
SRM
STD
TDWG
American Society for Testing Materials
California Cooperative Fisheries Investigation
confidence interval
centimeter
in situ conductivity, temperature, and depth measuring system
Coastal Upwelling Experiment
Dredged Material Research Program
dissolved oxygen
Geochemical Ocean Sections
Hertz
International Association of the Physical Sciences in the Ocean
kiloHertz
kilogram
milliampere
milligram per liter
military standard
milliliter
millimeter
mi Hi Siemens per centimeter
millivolt
not available
United States National  Brueau of Standards
North Pacific Experiment
Outer Continental  Shelf
parts per million
parts per thousand
quality control
The International  System of Units
standard reference material
in situ salinity,  temperature, and depth measuring system
Test Documentation Working Group
                                     Vll

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                               LIST OF SYMBOLS





SYMBOLS



°C    -- temperature in degrees Celsius1



Eh    — oxidation reduction potential in millivolts



KC1   -- potassium chloride



n     — number



Na2S  — sodium sulfide



Q£    -- oxygen



%     -- percent



%o   -- parts per thousand



pH    -- negative logarithm of hydrogen ion concentration



Vac   — alternating current voltage



Vdc   — direct current voltage

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                               ACKNOWLEDGMENTS


     Because of the amount of interest and the number of personal  contribu-
tions to this study, it is impossible to acknowledge individually  all  of the
contributors to the program.  In addition to the information generously pro-
vided by instrument manufacturers throughout the world, there were over 300
personal communications from correspondents in the United States and 24
foreign countries.  This evidence of worldwide interest in accurate oceanic
measurements should provide the necessary incentive to develop uniformly
accepted calibration and standardization techniques.

     The staff of the Oceanic Engineering Division would like to express
special thanks to the volunteers from Saddleback College and Fullerton College,
the teams of marine technicians for the experimental cruise, Moss  Landing
Marine Research Center, LFE Environmental, Inc., and the following instrument
manufacturers who provided instruments:

          Hydrolab Corporation

          Yellow Springs Instrument Company

          Martek Instruments, Inc.

          Horiba Instruments, Inc.

          Beckman Instruments, Inc.

          Orion Research, Inc.

          Great Lakes Instrument, Inc.

          Pi Instruments, Inc.


     Appreciation is extended to the Contract Officer's Technical  Representa-
tive, Mr. J. Sullivan of the Test and Evaluation Laboratory of the National
Oceanic and Atmospheric Administration, for his patience, technical support,
and guidance, and to Mr. R. Farland of the NOAA Office of Ocean Engineering
for his assistance in program development and technical review.  A special
thanks is given to Ms. C. Gariepy of the Test and Evaluation Laboratory for
typing the manuscript.
                                     IX

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                                  SECTION 1

                                INTRODUCTION


     Under this study, Interstate has considered the chemical  parameters
(dissolved oxygen and pH) and two supporting physical  parameters  (temperature
and salinity) which are routinely measured in situ in  the  marine  environment.
The study evaluated present standards in relationship  to these water  quality
measurements, and has explored the traceability of those standards.   While
this study emphasizes investigation of dissolved oxygen, pH,  temperature, and
salinity, it is noted that currently 19 parameters are measured in  situ, and
59 other parameters are under consideration.  Estimates of the range  and
accuracy required of in situ measurement, present and  future,  were  determined
by surveying major groups using in situ sensors and by reviewing  manufactur-
er's recommended procedures and published specifications.

     In situ marine monitoring systems remotely sense  the  oceanic parameters,
or transferable property from which the parameter can  be derived, while the
sensor package is submerged.  Frequently considered as in  situ monitoring are
those pumped systems that provide a continuous flow from the  location of
interest.  Sub-classes of in situ monitoring systems can be characterized by
the nature of the platforms (unmanned moored buoys, drifting  buoys, or manned
ships) or by the method of measurement (automated, continuously profiling
systems, or towed systems).  User contacts reveal a significant increase  in
the use of continuous profiling systems for coastal zone water quality mea-
surement and for pollution control and monitoring.  While  they are  a  rela-
tively recent innovation, they deserve special consideration  because  of their
potential.

     Today's emphasis on conservation of the marine environment results in
the greatest number of measurements being made in the  relatively  shallow
waters of the coastal zone, where depths typically are less than  50 meters.
The vertical gradients of water properties in shallow  bodies  of water are
frequently great and can vary widely over short time spans.  Therefore, there
is considerable interest in maintaining accuracy and in sampling  at short
intervals.  Since rapid sampling frequency cannot be met using conventional
discrete sampling techniques such as Nansen casts, there has  been an  increase
in the use of continuous profiling systems.   A brief description  of two
classes of in situ instrumentation is provided in Appendix A.

     The design of profiling systems integrates the sampling  process  with on-
board data processing and analysis.  This is highly desirable in  order to
cost effectively meet the mission objectives of some users, such  as waste-
water treatment districts that perform nearly continuous monitoring at out-
falls.  The cost of post-survey data analysis by hand  methods is  prohibitive

                                      1

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and introduces unacceptable errors.  The automatic data reduction and analy-
sis capabilities of the continuous profiling systems results in great quanti-
ties of data quickly and neatly produced and ready for user interpretation.
Of significant importance in saving labor costs is the system's ability to
print the data on the various Federal, State, and local government report
forms with a minimum of hand labor, such as typing and drafting of charts.

     A discussion of the components of error in and between in situ systems
and a demonstration during an experimental  survey of the errors induced by
different participants using different in situ instruments under nonstandard
procedures are offered as a compelling argument for the procedural  recommend-
ations that follow.  Because of difference  in usage of a number of terms such
as "Precision Standard" and "Calibration,"  definition of selected terms as
they are used in this report appear in the  glossary.   The pertinent cruise
data which form the basis for comments in the text are included in  Appendix  B.

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                                  SECTION 2

                                 CONCLUSIONS


     1.  An addendum to the contract document states, "What the Government
needs to know is that if a measurement is made in situ, would one get the
same answer if a sample were taken at the same place and the same time and
analyzed in a laboratory with laboratory methodologies?"  The results of this
study answers this question with an emphatic "NO!"  While this situation must
be remedied, a successful solution will require a well-planned, long-term
commitment  from the  Federal Government that includes recognizing the impor-
tance of data quality in the evaluation of proposals, grants, and Government
conducted oceanographic measurement programs.

     2.  In situ measurement is not at a state of routine data comparability
between different instruments measuring the same parameter or for a single
instrument operating at different time intervals.  Accuracies attained are
less than desirable for absolute measurements associated with research activi-
ties.  The relative accuracy of in situ systems, coupled with their ability
for continuous sampling and rapid data collection, is often justification for
their use in monitoring programs or for coastal research programs.

     3.  Inter-user calibrations are not presently part of routine survey
operations.  The GEOSECS program does come close to the practice by central-
izing the responsibility for the calibration and maintenance of instrumenta-
tion used by all  investigators within the program.  However, there is no
interface with investigators outside the program who may utilize the data.

     4.  Standard reference materials and/or calibration methods are not
utilized by institutions or programs.  Variations in standardization methods
may exist.   This situation is very widespread.   Manufacturer's specifications
and Recommendations vary; users' application of manufacturers'  recommendations
varies as well.  Data derived from in situ measurements of a parameter by
different instruments or by different programs  do not seem to be comparable.

     5.  For current monitoring needs, adequate standards are currently avail-
able for temperature and pH.  There are inadequate, multiple-point standard
reference materials for salinity and dissolved  oxygen.

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                                  SECTION 3

                               RECOMMENDATIONS
     A comprehensive program plan for quality assurance must be developed for
 in situ marine water quality measurements, their calibration, and standardi-
 zation.  This program should be under the guidance of a single agency oriented
 to the marine environment to insure the goals will be attained.  Observations
 of past programs of similar nature conducted by committees of agencies reveal
 that the dilution of authority results in failure to achieve the objectives.
 Program elements would include:

 CALIBRATION AND STANDARDIZATION MATERIALS

     The program must include a standard reference material with well-defined
 accuracy for all parameters.  Specifically:

     1.  Develop a series of standards for salinity that encompass the range
 from 0 to 40 ppt in 5-ppt increments with an accuracy to 0.002 ppt.

     2.  Develop a series of dissolved oxygen standards for the range from 0
 to 10 ppm in increments of 2 ppm with an accuracy of 0.05 ppm.

 CALIBRATION PROCEDURES

     Instrument calibration procedures utilized on Government-funded programs
 must be required to satisfy traceability to accepted standards and have formal
 documentation.  A major source of error in any system is the calibration and
 standardization routine.  The military and space programs have used this type
 of procedure for many years.  These programs require manufacturers to develop
 a recommended calibration procedure which is verified, with the calibration
 traced to a recognized standard.  The verification process is commonly con-
 ducted by an independent calibration laboratory or at the manufacturer's
 facility under the supervision of a Government inspector.  The verification
 process also recommends calibration frequency.  Inputs from the manufacturer
 for calibrating marine in situ monitoring instruments would be considered by
 the agency responsible for procedure development.   Current user practices for
calibration would also be considered for the procedural  development.

     It is expected that responses from users and  manufacturers will be
diverse and dependent on instrument capabilities and on program accuracy
requirements.   But these must be considered for the development of a uniform
procedure.   For example, the frequency of calibration may vary with class of
required measurement and type of instrumentation.   A temperature sensor may

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require recalibration and certification  once  a  year to  ensure  0.5°C  accuracy,
or as frequently as bimonthly for an accuracy of 0.02°C.

     The verification of instrument calibration could be  indicated by a  certi-
fied seal or sticker.  The sticker provides information on  the date  of cali-
bration and the required date for recalibration.  The official  calibration
procedures should be distributed by a central  issuing agency that is respon-
sible for receiving and updating as required.

     Questions that require resolution of differences between  methods would
be resolved by a Test Documentation Working Group (TDWG)  that  includes repre-
sentatives from the sponsoring agency, instrument designers, standards organi-
zation, instrument test operators, and data users.  In  addition to the devel-
opment of calibration procedures, the TDWG would provide  information on  future
requirements for parametric standards and sponsor the development of standards.

DOCUMENTATION PROCEDURE

     A standard documentation procedure  with  the information basic to
assessing data quality includes:

     1.  The standard reference material  used including the date of  receipt
and handling since receipt.

     2.  A uniformly practiced and accepted Calibration and Intercalibration
Procedure which would include method accuracy and precision, the frequency
required for calibration, and the time lapsed since the previous calibration.
The calibration procedure must also include specific instructions  for  field
standardization procedures.  The field standardization procedure should
include the limits of acceptable variation.

     3.  A standard data reporting format including the number of  replicates,
mean and standard deviation of the calibration, and standardization  procedure.

SUPPORT SERVICES

     The sponsoring agency should consider undertaking the  following program
support:

     1.  Preparation of guidelines for evaluation of proposals for marine
water quality measurement to insure that a proportion of any project is
dedicated to calibration of instruments  and to the supporting  tasks  for  data
quality assurance.  It is strongly recommended that data  quality assurance
requirements be listed in the contract specifications.

     2.  Compilation and maintenance of a comprehensive directory  of manu-
facturers and users of in situ chemical  oceanographic instrumentation  and the
data types and quality resulting from these programs.

     3.  Preparation of test, calibration, and standard traceability proce-
dures for in situ instruments.

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     4.  Preparation and maintenance of a comprehensive handbook  on  marine
instrumentation and procedures.

     5.  The organization and scheduling of seminars  to transfer  this  tech-
nology to the user community.

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                                  SECTION 4

               TRACEABILITY OF CALIBRATION TO COMMON STANDARDS

STANDARD REFERENCES

     In situ measurements in the marine environment are subject to most  of the
problems that degrade laboratory measurements, with additional  problems
attributable to field conditions.  Investigation of the error sources  and
their effect on the accuracy of the measurement can be classified  as  qualita-
tive or quantitative, following the Shewhart (1) concept.   The  number  assigned
to a distance or a chemical concentration is quantitative.   Qualitative
sources of error arise from the apparatus, reagents, operator,  sequence  of
operations, and ambient conditions involved in quantifying  the  measurement.

     A statement on the accuracy of the quantitative number is  an  indication
of the information content of that number within the framework  of  the  intended
application.  The application will usually dictate the degree of accuracy
sought and the effort required to achieve it [Eisenhart (2)].  The accuracy
achievable when calibrating a system of measurement to a primary reference
material with an assigned value (systematic error) depends  on the  precision
of the measurement technique and operation involved, as well  as on the accu-
racy of the assigned value of the primary reference material.

     In making a measurement, the individual involved must  take care  to  assure
the measurement is of a unique property and not a combination of properties,
such as interference from other sources (specificity).  Second, no systematic
errors should be permitted to cause a bias in the distribution  of  repeated
measurements of the property.  Third, the degree of precision,  which  is  the
ability to reproduce the same number on repeated measurements of the  same
material, must be at least as good as the desired accuracy  of measurement.
When these three aspects of the measurement process are assured, the  accuracy
of the measurement can approach its state-of-the-art level.

     Accuracy is measured by referencing a measurement to a standard  using a
methodology that has been shown to achieve acceptable results.   The practice
of establishing reference standards (the primary reference  units and  the
methodology of measurement) has been set out in some detail at  the National
Bureau of Standards (NBS) by Cali et al (3).  The development of a measurement
system has five major components as stated by NBS:

      "Component 1 :  A Rational. Self-Consistent System of  Units of Measure-
       ment.  International agreement suggests this system  should  be  the
       System Internationale de Unites (SI) [Cali et al (3)].
      °l
       'Component 2:  The Materials Necessary to Realize in Practice the SI
       Units and Their Derivative's"!  In much of the world, these well-charac-
       terized materials are called Standard Reference Materials (SRM's)  and
                                      7

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 are prepared,  measured,  and certified,  in most  instances,  by national
 standards  laboratories.   The key  characteristic  of an SRM  is that the
 properties of interest  be measured  and  certified on the  basis of accu-
 racy.   At  NBS  there  are  three routes  that are used to accomplish this
 goal :

 (a)  Measurement  of  the  property  using  a previously validated reference
      method.   By  definition,  a  reference method  is a method demonstra-
      ted to be accurate  and reproducible.

 (b)  Where previously established reference methods do not exist, two
      or more  independent,  reliable  measurement methods are used.  A
      reliable  method is  one of  high precision, but one whose system-
      atic  biases  have not  been  fully  discovered  and evaluated.

 (c)  The third route is  a  variation of  the second.  Where a previous
      issue of  an  SRM is  available to  be used to  assure intralaboratory
      quality  control, many laboratories can be formed in an ad hoc net-
      work  to  perform the work.  Each  laboratory  uses the method felt to
      be most  reliable (and accurate)  under that  laboratory's operating
      conditions,  but must  run the known SRM in parallel with the
      unknown  as a check.   The results will be used only when the certi-
      fied  value of the prior  SRM  is obtained.

"Component  3:   Reference  Methods of  Measurement Used With or Based on
 SRM's.  A  reference  method is defined as "a method of proven and
 demonstrated accuracy."   These  have been called  umpire methods,
 referee methods,  standard  methods,  and  so forth.   Absolute accuracy,
 implying methods  with no systematic biases, is an  unattainable goal,
 not achievable by mortals.   It  is important to realize that the cost
 of obtaining  greater accuracy increases exponentially.  Therefore,
 only  that  degree  of  accuracy  required should be  sought, making allow-
 ance  for advances in the state-of-the-art.  A good guideline is to
 strive  for a  reference method whose accuracy is  three times better
 than  that  currently  required  by the end user.  The definition and
 development of reference methods  is a time-consuming, expensive, and
 complex process,  involving the  following steps:

 (a)   A  group of experts  surveys the literature to  choose a candidate
     method—one  expected  to  have small systematic biases.  They also
      decide what  the accuracy goal  should be for the reference method,
      considering  the required end use.

 (b)  A  central laboratory  is  chosen to  coordinate the work; develop the
     statistical  design; prepare  and distribute  samples that have been
     previously measured by the central laboratory using an independent
     method of known accuracy,  but  one  not usually available to the
     field  in  question;  and distribute  the SRM (a  necessary precondi-
     tion  being the  availability  of the appropriate SRM).

 (c)  The group of experts,  in conjunction with the central laboratory,
     writes the first version of  a  detailed procedure (protocol) and
     helps  select a  group  of  measurement laboratories (usually 6 to 10
                                8

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      laboratories) willing  to  cooperate in performing the work called
      for  in  the  protocol.

 (d)   The  central  laboratory distributes the protocol, sample, SRM, and
      instructions to  the  cooperating laboratories.  The cooperating
      laboratories perform the  work according to a schedule.  The ana-
      lytical  data plus  other pertinent information are returned to the
      central  laboratory.

 (e)   The  group of experts and  qualified personnel from the central
      laboratory,  including  statisticians, analyze the data, identify
      sources  of  error,  then revise the protocol to eliminate the
      errors.

 (f)   Steps di  and  e^ are  repeated as often as necessary until the accu-
      racy goal is achieved.

 (g)   The  protocol is  written in final form and published in a journal,
      a  collection of  reference methods, or another appropriate publica-
      tion.

"Component 4:   Establishment of Compatibility into a Wider Area of
 Technology via the SRM  and  Reference Method.  Components 1, 2, and 3
 are  sufficient in themselves to bring about accurate measurements in a
 few  well-qualified laboratories.  The real problem is, however, to
 improve the  quality of  and  make compatible the measurement in the
 average laboratory on a routine basis.  There are two aspects to this
 problem,  one  involving  the  field  (routine) methods per se, the other
 concerned with commercially produced (in-house) working standards.

 As reference  methods  and  SRM's become available, responsible groups
 should  begin  the  assessment of the various field methods currently in
 use.  Mhen the test materials  to  be used in the assessment process are
 characterized on  an absolute (accuracy) basis via the reference method
 and  SRM,  the  inaccuracies of the  tested field methods will become
 readily apparent.

"Component 5:  Assuring the Long-Term Integrity of the Measurement
 Process.   Measurement systems  are notorious in one respect—unless
 carefully monitored,  they tend to get out of control.  Loss of preci-
 sion is usually  the first indication that the measurement process is
 not  in  a  state of quality control.  In most measurement laboratories,
 this question is  one  of almost daily concern and one that has been
 extensively  studied and addressed.  Although each individual labora-
 tory must ultimately  be responsible for assuring its own quality con-
 trol, professional societies and  governmental agencies can, and often
 do,  provide  a mechanism that helps to assure, to a degree, long-term
 control.

 If SRM's  and  reference  methods are available, the mechanism for assur-
 ing  the long-term integrity of the measurement process in a large
 number  of measurement laboratories is quite straightforward:

-------
       (a)  The sponsoring or testing agency prepares a series of test samples
            incorporated in a suitable matrix that cover the range of values
            likely to be encountered in real life.

       (b)  The properties are determined by the sponsor's laboratory (or
            laboratories) using the reference method to obtain values of known
            accuracy.

       (c)  The test samples, as unknowns, are distributed.with suitable
            instructions and reporting forms to the laboratories under test
            who perform the work as instructed.  In true blind studies,  these
            samples will not be differentiate from daily, routine samples.

       (d)  Results are returned to the sponsoring agency and statistically
            analyzed.  In a well-designed and controlled program,  each labora-
            tory should receive back the following information for each  prop-
            erty tested:  its day-to-day precision within the laboratory; the
            accuracy of the method used; its rank compared to other labora-
            tories using the same methodology; the accuracy  of its method
            compared to alternative methods; a statement of  acceptability of
            the results (if norms for that technology have been established).

     Through a survey of the more visible users and manufacturers  of in  situ
instruments in the marine environment, an overview of current needs and  prac-
tices for calibration and standardization evolved.   Then through a field
experiment the amount of error arising from these practices  was demonstrated.
In the following sections the current needs and practices are described  in the
context of the NBS recommendations.

CALIBRATION AND STANDARDIZATION TECHNIQUES

Definition of Terms

     The terms "calibration" and "standardization"  are widely used by a  number
of individuals often implying the same meaning.   The differences however are
significant.  Calibration is the process of examining instrumental  response
to a series of prepared standards that bracket the expected  concentration to
be measured in the environment.   The standards must be traceable,  that is, of
a certified concentration.   Calibration must be performed at multiple points
over the analyses  range to adequately determine the instrumental  response to
the concentration  change.   Primary standards are directly traceable to a
certified source such as the National  Bureau of Standards.   Secondary chemical
standards may be prepared by dilution of a primary standard  or prepared  from
reagent grade chemicals in the laboratory by the analyst.  They are regarded
as secondary standards because of the potential  errors involved during prepa-
ration.   The errors include:  analytical  balance accuracy and time since last
inspection, purity and quality of the reagents,  and the quality of the water
used to prepare the solutions.   Other variables  include the  cleanliness  of the
preparation area,  type and condition of the mixing  and storage container,
stability of the solution,  and human expertise.

     Standardization is a procedure performed in the field that brings the
instrumental response into the previously prepared  calibration curve.
                                     10

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Generally, at least two points in the field should be  taken  with  every  profile
or with 8-10 discrete measurements.   This  can  only be  accomplished when
sampling from a sampler that houses  the in situ  probe  and  a  series of water
bottles.  When an in situ measurement is taken,  a  water  bottle must  be  sig-
naled to collect a sample.  This procedure will  limit  the  variability
resulting  from spatial and temporal  differences in the  water column.   Cer-
tainly, as R. A. Home (4) points out in "Marine Chemistry," the  sample will
go through some changes as it is brought to the  surface  and  the various gases
in solution rearrange in proportions.  The bottle  composition and cleanliness
must be controlled so as to not contaminate the  sample.  However, there is
presently no other acceptable way of evaluating  how effectively the  in  situ
probe is operating in the environment.   The differences  tend to increase with
the distance of the water column sample from the surface.   For example, carbon
dioxide is nearly twice as soluble at 1,000 meters as  in surface  waters.  The
concentration of carbon dioxide, of course, plays  a significant role in deter-
mining the pH of the water.

     The sensitivity of an instrumental measurement is defined as the change
in signal or instrument output per unit change of concentration.  The range
of measurement is regarded as the span  of concentrations in  which the probe
may be used to provide acceptable data  within  the  stated performance specifi-
cations.  The limit of detection is  the lowest detectable  signal  which  is
normally equal to twice the ambient  or  normal  background noise.

One-Point Calibration

     A one-point calibration implies  that  the  instrumental  response  is  linear,
can be internally normalized, or the  slope of the  response curve  is  linear
over the measurement range.  This assumption cannot be made  unequivocally  for
all instruments under all conditions.  In  addition, care must  be  taken  to
insure that the response curve has not  rotated around  the  calibration point.
To justify one-point calibration, adequate field and laboratory data must  be
collected to verify that the response for the  measurement  type  does  not rotate
or otherwise change under ambient conditions where problems  are identified.
A variety of corrective procedures may  be carried out.  As an  example,  con-
sider the galvanic dissolved oxygen  probe which  must be calibrated  using
salinities similar to the salinity of the  environment  being  measured.   Cali-
bration remains a particularly difficult problem where significant  salt con-
centration gradients occur, such as  between surface and deeper waters or  in
an estuarine stream where the salinity  may range from  less than 5 parts per
thousand to 35 parts per thousand.  While  commercial probes  have  recently
become available to compensate for this effect,  it is  not  clear how  well  they
actually operate.  Additionally, the  speed of water across the membrane may
affect the metered response.  Flow must be below the minimum level which  dis-
torts the membrane, yet above the level of stagnation.  Because this effect
(flow versus measured oxygen) plateaus, some instrument manufacturers have
installed agitators near the probe surface to  reach the effective speed where
small changes in flow do not significantly alter response.   Other physical
variables which affect one point calibration for in situ instruments include
the length of the cable between the probe and  electronics  packages,  pressure,
temperature, and trace inorganic constituents  (i.e., sulfide).

     The selection and use of a one-point calibration  is not recommended
                                      11

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unless adequate field and laboratory data have been collected to support the
linear curve assumption with full consideration of various field conditions,
such as the effects of pressure, temperature, salinity, flow across the mem-
brane, cable length, and concentrations of chemical constituents.

Recommended Means of Instrument Calibration and Standardization

     All in situ marine measurements must be related directly to an accurate
standard.  The integrity or exact value of the standard must meet or exceed
the level of accuracy achievable by the instrument and satisfy the program
objectives.  The National Bureau of Standards recommends a standards accuracy
three times better than the user's required accuracy [Cali et al (3)].   There
is limited value to water column profiling with an instrument which can only
reflect relative rather than absolute values, particularly when most moni-
toring programs require several years worth of data to assess potential sub-
lethal trend impacts which necessitate data inter-comparability.  Data  integ-
rity derives from adequate documentation which traces instrument calibration
with verified field standardization.  The calibration and standardization
procedures must be formalized and documented to spell out the approach, scope,
and limits of in situ monitoring.

     The documentation required includes the data of instrument calibration,
type and integrity of standards, standardization values, and succeeding cali-
bration results.  Instrument repair and maintenance should also be documented.
Ideally, instruments could be categorized in a manner that would indicate the
type preferred for each application (e.g., deep sea) and for achievable levels
of accuracies.

     Documented calibration procedures should be required in every oceano-
graphic program.  Often when commercial  firms are responding to a  Government
or industrial   request  for proposals that involve monitoring, price is  a major
award factor.   As such, the low bidder may short cut data integrity in  order
to come up with the lowest price.  The presence of a universally accepted and
endorsed calibration and standardization procedure would close this obvious
gap.  Additionally, the procedures should be under yearly review to incorpo-
rate the most recent technology.

     Training is a key element in performing the calibration.  The procedures
must be clear, concise, and supported with performance data and literature
references.  A variety of in situ instruments are available at different
prices.  Each has the manufacturer's suggested calibration procedures.   This
divergence and a lack of adequate documentation cause difficulty in training,
with a consequent source of error in data comparability.

     Standards used for calibration must serve a large community for a  variety
of needs ranging from compliance monitoring to the pure research scientist.
They should be accessible to the analyst, relatively inexpensive,  convenient
to use, made of constituents which are stable over time, and of a  certifiable
concentration.

     For each  of the parameters under study, at least two levels of data
quality assurance should be incorporated into marine in situ monitoring pro-
grams.  First, instruments should be calibrated at several points  over  the
                                     12

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expected range of measurement, under conditions approximating critical  envi-
ronmental conditions, and with universally accepted standards.  Second, in
the field, samples should be collected in parallel  with the in situ monitoring
to verify instrument operation.  Comparable techniques must be used for cali-
bration and standardization.  In the following sections, methods are presented.

Salinity--
     Induction-type conductivity or salinity in situ probes, because of their
size, are often very difficult for the user to calibrate.  Usually manufac-
turers calibrate the units at their facilities prior to delivery and recommend
return annually.  The survey of users indicated that very rarely are the
instruments returned unless a major repair is required.

     A typical calibration procedure using the available standards is
described.  Briefly, a series of 200-liter tanks are prepared to contain a
specific salinity water.  A bench or laboratory salinometer, calibrated to
Standard Seawater, is used to verify the salinity tank values.  The in  situ
probe is then placed in each tank, and the values are recorded.   A control
sample of the water used to prepare the salinity tanks must also be analyzed.
The accuracy of the method can be determined quite simply and is traceable
back to a primary standard.  The method is not without limitations.  Ideally
the laboratory salinometer should be calibrated with a primary standard at
several points.  However, at the present time, only one salinity standard is
available (Standard Seawater).  Also typical variations in environmental
conditions, beyond pressure and temperature, should be incorporated into the
calibration program.

     Field standardization is required for data quality assurance.  In  the
field, the analyst must collect discrete water samples at the probe during the
time of measurement and analyze them by a reference method such  as a labora-
tory salinometer.  At least two samples should be collected with each profile
or each daily use in the case of a fixed monitoring device.  The analyses of
these samples should be performed in real time while on station  to verify
calibration, otherwise whole sets of data might later be found unacceptable.

     Standard Seawater is the only primary salinity or conductivity standard
available to the analyst; it has a nominal  salinity of 35 ppt.  This standard
has a reported accuracy of ±0.001 ppt, however systematic variations exceeding
this level have been observed.  The name "Eau de Her Normale" was changed in
1960 to "Standard Seawater" and the name of the agency which distributes this
standard was changed from "Depot d'Eau Normale" to "Standard Seawater Service."

     The "Standard Seawater Service" is an agency under the "International
Association of the Physical  Sciences of the Ocean"  (I.A.P.S.O.).   "Standard
Seawater" is certified in chlorinity only, but has  been widely used as  a
standard for salinity determinations from conductivity measurements. Addi-
tional  certified standards should be available at 10 ppt, 20 ppt, 30 ppt, and
40 ppt.  These standards would limit the extrapolation errors in calibration.
Pressure effects should be considered but they cannot be easily  simulated at
a low cost in the laboratory.
                                      13

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Temperature--
     Temperature sensors should be routinely verified against  an  NBS  cali-
brated platinum thermometer in the laboratory with a  water bath accurate  to
0.01°C.  Currently both quartz and platinum reference thermometers  are  in use
as standards, with the platinum predominating.  An accuracy of .004°C is
readily achievable according to NBS (5).   Response should  be checked  at
several points over the intended range of use.

     In the field, standardization procedures can be  performed with the aid
of reversing thermometers mounted on the  water bottles.

Dissolved Oxygen--
     The conventional  method of in situ dissolved oxygen probe calibration is
the modified Winkler titration.  Air-saturated seawater  at room temperature  is
typically measured with the probe, and then by the Winkler and by adjustments
made to the instruments.  Some analysts check the probe  response  to zero  by
immersing the unit in a solution to which a small amount of sodium sulfite
crystals has been added, or in seawater purged with nitrogen gas.  A  micro
burette procedure using dilute reagents delivers exceptional accuracy.  Typi-
cally in situ dissolved oxygen instruments are calibrated  at one  point  in the
field.  No chemically certified standard  is produced  or  available in  the
United States for dissolved oxygen calibration.  Recommendations  have been
made for a physical standard preparation.  This procedure  would involve
purging a seawater solution with various  proportions  of  atmospheric air and
nitrogen gas to provide incremental solutions to saturation.   The actual  con-
centration of the standards may be determined by the  modified  Winkler method
or by other conventional methods such as  gas chromatography (J. Sullivan,
NOM/NOS pers. comm.) or colorimetry.  However, these methods  are time  con-
suming and require more expensive instrumentation.

     In the field, standardization must be determined by simultaneous collec-
tion of discrete water samples at the probe using a rosette or other  multiple
sampling device.

pH-
     pH buffers are available from a variety of commercial manufacturers  or
may be prepared by the analyst according  to NBS specifications.   Whatever the
case, pH meters must be laboratory calibrated at several values over  the
range of use, and standardized at a minimum of two points.  The narrow range
of pH values in ocean waters enhances the ability to  calibrate instruments
properly.

     For field standardization, a discrete water sample  from a water  bottle
located adjacent to the probe must be collected.

ACCURACY AND RELIABILITY

Replication Error

     Replication errors are observed when different values are measured for  a
known homogenous environment.  However, replication problems may  occur if the
water sample collected in the environment is from a different  point in  time
or different water mass.  In situ probes  must be carefully calibrated to
                                     14

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achieve the stated accuracy of the manufacturer.   Typically,  manufacturers
quote precision-accuracy figures for their instruments  which  often  differ  from
the analytic figures.   Also, the operator tends  to read the meter value  as  an
absolute value.   If a  manufacturer's specifications for a  dissolved oxygen
unit are ±0.1  ppm, the user should only record the display value to this
significant figure.  However, the analyst may ascribe an accuracy to the mea-
surement which cannot  be verified by the analytic technique.
             TABLE 1.   REPRESENTATIVE INSTRUMENTAL CAPABILITIES
                 DATA FROM MANUFACTURERS SPECIFICATION SHEET
Parameter
Manufacturer
(Model No.)
Dissolved Oxygen
Plessey (9050)
YSI (Model 57)
Montedoro-Whi tney
(Dor-IB)
Ocean Data
Salinity
Plessey (9050)
YSI (33)
Temperature
Plessey (9050)
Plessey (4005)
YSI (Model 33)
Montedoro-Whi tney
(MK III A/B)
Ocean Data
PH
Plessey (4005)
Montedoro
(DPH-1B)
Ocean Data
Accuracy

±0.15 ppm
NA
±0.10 ppm
±0.20 ppm
NA

+0.02 ppt
±0.9 ppt at 40 ppt;
±0.7 ppt at 20 ppt

±0.02°C
NA
NA
NA
NA

NA
±0.005 pH units
NA
Precision

±0.10 ppm
±0.10 ppm
NA
NA
±0.20 ppm

±0.003 ppt
NA

±0.004°C
±0.50°C
±0.1°C at -2°C;
±0.6°C at 45°C
±0.03°C
±0.1°C

±0.02 pH units
NA
±0.1 pH units
Range

0 to 15 ppm
0 to 25 ppm
0 to 10 ppm
0 to 20 ppm
0 to 20 ppm

30 to 40 ppt
0 to 40 ppt

-2 to 35°C
-2 to 35°C
-2 to 50°C
-5 to 45°C
-5 to 40°C

2 to 14 pH units
0 to 14 pH units
0 to 14 pH units
 NA - Not Available
                                      15

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   The accuracy and precision typically reported by manufacturers, based on
 instrumental capabilities  for dissolved oxygen, range in accuracy from 0.1 to
 0.2 ppm and  from ±0.1 to ±0.2 ppm in precision.  The applicable measurement
 range is commonly from 0 to 20 ppm,   Salinity probes typically have a reported
 accuracy ranging from 0.02 to 0.9 ppt, with a precision of  ±0.003 ppt.  The
 greater accuracy range is  available with an instrument of 30 to 40 ppt range.
 Temperature  units have an  accuracy of 0.02 to 0.1°C, with a precision ranging
 from ±0.004  to ±0.1°C over a usual range of -2 to 35°C.  pH probes generally
 have a precision of ±0.02  to ±0.1 pH units over the range of 2 to 14 pH units.
 The instrumental capabilities of representative in situ instrumentation are
 summarized in Table 1.

 Analytical  Error in Calibration

   The accuracy of standards can only be verified by the best analytical
 techniques.  The technique must be relatively simple, and should be low cost
 and relatively quick to perform.  The modified Winkler as it appears in
 Strickland and Parsons (6) has a reported precision of ±0.079 ppm over the
 range of 0.081  ppm to super saturation.  pH standards are available to four
 significant  figures through NBS, while the Environmental  Protection Agency (7)
 lists a precision of ±0.1  pH units.   Salinity as performed by the wet chemical
 method in Strickland and Parsons (6) offers the analyst two ranges from 4 to
 40 ppt, with a precision of ±0.06 ppt at 30 ppt or 30 to 40 ppt with a
 precision of ±0.023 ppt at 33 ppt.  The end point may best be determined  by
 the conductivity titration method.  Temperature may be measured with NBS  cali-
 brated quartz thermometers to an accuracy of 0.02°C over a very wide range.
 The representative analytic techniques  for calibration are listed by parameter
with precision and range data in Table  2;   Table 3 lists  the common standards
 used for calibration.

  	        TABLE 2.   REPRESENTATIVE ANALYTIC CAPABILITIES
       Parameter/Source
     Precision
      Range
   Dissolved Oxygen
     Strickland &
     Parsons (1972)

     Environmental
     Protection Agency
     (1974)
   PH
     EPA
   Salinity
     Strickland  &
     Parsons  (1972)
±0.079 ppm
±0.20 at 7.5 ppm
±0.1 at 3.5 pH units
±0.12 at 7.7 pH units
±0.12 at 8.0 pH units
±0.06 ppt at 30 ppt
±0.023 ppt at 33 ppt
0.081 - 12.96 ppm


NA
                                                          0 -  14  pH  units
 4 to 40 ppt
30 to 40 ppt
 NA -  Not  Available
                                     16

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                TABLE 3.  COMMON STANDARDS FOR CALIBRATION
Parameter
Sal inity
(through
conductivity)
Dissolved
Oxygen
pH





Temperature

Accepted
Standard
Standard Seawater
Winkler - Mod. Azide

NBS Buffers
NBS Buffers
NBS Buffers
NBS Buffers
NBS Buffers
NBS Buffers
NBS Buffers
National Bureau of
Standards Quartz
Calibration
Thermometer
Cone./
Accuracy
35 ppt
(nominal )*
Variable

3.557**
4.004**
6.863**
7.415**
7.669**
9.183**
10.014**
-80 to
250°C/
±0.002°C

Appl i cable
to
In Situ
Calibration
No
No

No
No
No
No
No
No
No
Yes with
water bath

Several
Point
Cal.
No
Variable

Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

 *at 15°C and 1  atmos.  with  batch-to-batch  variations  as  high  as  0.01  ppt;
  within batch variation of 0.001  ppt.
**uncertainty of ±0.005 at 25°C.


ALTERNATE CALIBRATION TECHNIQUES

Temperature

     The options open to the analyst for temperature sensor calibration  are
few.  All that can be determined  by calibration is  that the sensor is
responding accurately.   The type  of water bath used is not critical  but  should
be calibrated against a recently  checked NBS standard thermometer which  is
accurate to at least the level  of probe accuracy required.

Salinity

     Salinity standards may be prepared in the analytical  chemical laboratory
from a synthetic seawater mixture or with the proper proportions  of at least
reagent-grade chemicals.  However, because of the number of variables  involved
(i.e., micro-balance accuracy, age and conditions purity of the reagents,
analytical techniques, and the quality of the water used to prepare the solu-
tions), the accuracy of the final solutions cannot be assured  beyond two to
three significant figures.
                                     17

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Dissolved Oxygen

     A technique some manufacturers recommend for dissolved oxygen probe cali-
bration is to wave the probe in the air.  The meter value should correspond to
a chart value taking into account the barometric pressure and temperature.
Frequently these data are not sufficient for statistical treatment but ade-
quately demonstrate that the readings did not correspond to the Winkler values
when the probe was calibrated by waving it in air.  This method is not a
preferred technique for one-point calibration or standardization.   Discussions
with NOAA personnel indicate that it is not possible to obtain reproducible
results.
     The analyst may prepare his own standards from the analytical  chemical
laboratory, reagent-grade chemicals.  This option is also not recommended for
reasons outlined in the salinity discussion.

MEASUREMENT DEGRADATION

     Measurement degradation cannot be easily determined without standardiza-
tion.  The accuracy and precision of a unit can only be evaluated by compari-
son with a standard reference technique.  For this reason calibration with
standardization is essential to collect meaningful data.

     Most in situ instruments automatically check for proper electronic opera-
tion but have no means for determining the condition of the sensor.   This
obvious disadvantage must be confronted in future design efforts.

     The variance as a result of instrument degradation is presently undefin-
able, but could be resolved by repetitive calibration.   Sensors may  slowly
degrade until  the malfunction is obvious.  The period between new part instal-
lation and degradation is a wide band where several  errors may occur.
Cleaning, replacement, and other activities affect probe calibration, sensi-
tivity, and accuracy.   While these activities are required, frequent calibra-
tion and standardization are essential  to detect when measurements  begin to
diverge systematically from the calibrated accuracy.
                                     18

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                                  SECTION  5

    REFERENCE STANDARD REQUIREMENTS FOR CHEMICAL IN SITU INSTRUMENTATION
REFERENCE STANDARDS FOR CURRENTLY MEASURED PARAMETERS

     The evaluation of standards  for in situ measurements  must  be  related  to
the present instrument accuracy and precision capabilities.   Ideally,  the
standard reference material  should be more accurate than the probe,  which
would allow for instrument improvement with time.   Allowances for  variations
in instrument capabilities and the user's requirements should also be  made.

Sensitivity

     The sensitivity of in situ probes to changes  in concentration of  dis-
solved oxygen and salinity is reportedly less than the manufacturer's  stated
overall accuracy.  Only pH sensors are more sensitive than required by both
research and survey groups.   Clearly, care should  be used in reporting data
to the correct degree of precision.  As an example, a conductivity probe with
a  sensitivity of only 0.25 mS/cm used with an instrument having a  stated
accuracy of OJO mS/cm is not providing data to the stated accuracy of the
instrument.

     Probes are not totally selective for one parameter.  Dissolved oxygen
probes respond to such energy sources as light and water movement.  Various
ions present in seawater may produce a response in the probe.  (O.H. Carpenter,
University of Miami, pers. comm.).

Limit Of Detection For Parameters Now Measured

     The normal oceanic range of values of temperature, salinity,  dissolved
oxygen, and pH are found in Table 4.


                TABLE 4.  RANGES OF  COMMON OCEANIC PARAMETERS



Minimum
Maximum
Temperature
(°C)

-2
+30
Salinity
(ppt)

20
40
Conductivity
(mS/cm)

17
60
Dissolved
Oxygen
ppm
0
15
PH
(Units)

7.7
8.5
                                      19

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 Interferences Associated With Parameters Now Measured

 Temperature--
     Temperature probes are generally stable under environmental conditions
 and are considered reliably accurate for up to 6 months of in situ use (8).

 Conductivity—
     Conductivity may be measured by seawater-coupled transformers or elec-
 trode devices; however, electrode devices are easily fouled, polarized, and
 corroded in seawater and are seldom used.  Conductivity cells are still sub-
 ject to hysteresis effects, and techniques using STD and CTD devices should
 be rigidly controlled to minimize this problem.

 Salinity--
     Salinity measurements in situ are conversions by electronics circuits of
 conductivity and temperature sensors.  Lack of linearity and inability to
 perform the necessary complex calculations reduce accuracy.  Digital elec-
 tronics may reduce the analog errors now present.

 Dissolved Oxygen—
     Membrane electrodes used to measure oxygen have a very slow response time.
 Nonmembrane (naked) electrodes are sensitive to hydrodynamic properties of the
 environment and are easily fouled.  Compensation for temperature and pressure
 effects has been successfully applied to depths of 3,000 meters (9).

 pH-
     pH system nonlinearity is commonly caused by reference electrode mal-
 functions and drift (10).  Although this is not large in laboratory tests
 (0.003 pH in 24 hours), it is commonly severe in field instruments due to
 fouling of the glass membrane after about 24 hours of use (11).  Another  prob-
 lem is with cracks in the reference cells which frequently are not detected
with a one-point calibration.

Accuracy For Parameters Now Measured

     Accuracy, as used here, refers to how closely a set of measurements
 cluster about a chosen reference standard value, and as such includes random
and systematic errors.  The accuracy of an in situ measurement system depends
on the integrated functioning of its components, including the operator,  under
 field conditions.  Although often reported, laboratory accuracies of equip-
ment designed to operate in situ are not adequate descriptions of instrument
accuracy.   In tracing a measurement from the field environment through the
measurement device to the final  recorded value, a number of possible errors
are encountered.

     First is the error due to inexact correspondence between the probe's
response and the ambient condition; this is called sensitivity.  The response
in the probe must then be translated into an electric potential which is
transmitted to a measuring device.  The error in this step is called probe
accuracy.

     The electrical  and electronic instability of the device results in two
additional  errors.   The first error is more or less random over a long period
                                     20

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of time and is referred to as repeatability.  The second is vectored over
time and is usually measured as 24-hour stability, or drift.  The display of
the measured value results in the error called readability.  Manufacturers
often lump these errors in a total instrument accuracy value, which may or may
not reflect the greater portion of the actual system accuracy.

     In addition to the errors accumulated when making a measurement under
controlled conditions, in situ instruments are variously affected by pressure,
temperature, and other physical and chemical conditions present in the envi-
ronment.  Compensation for environmental  conditions may be built into the
instrument or, as in the GEOSECS program, it may be desirable to correct raw
measures by means of shipboard or laboratory computer systems.  The error due
to inexact compensation for environmental conditions should be considered when
reporting total accuracy.

     Platinum temperature transducers have a representative overall accuracy
of ±(K01 percent.  Reversing thermometers have an overall  accuracy of about
±0.02°C.  Inductively coupled transformers for salinity measurements have
a transfer function accuracy of about ±0.02 ppt.   Dissolved oxygen electrodes
have a reported accuracy of ±1  percent (±0.1 ppm) as stated in manufacturers'
literature.

     The International  Biophysics Corporation reported the problem of inter-
preting manufacturers'  stated accuracies  for dissolved oxygen.  "It is our
opinion that, with the present state-of-the-art of dissolved oxygen measure-
ment, it is impossible for most manufacturers to  meet their stated accuracy
specifications across the entire dissolved oxygen and temperature ranges."(12)

     Temperature transducers now used for oceanographic purposes introduce
errors due to nonlinearity, stability, response time, usable life, and main-
tenance.  Platinum thermometers can be obtained with a drift of only 0.011°C
over 6 months (8).  Copper and platinum thermometers have a linearity of
±0.01°C from -2°C to +20°C using the Callender-Van Dusen equation (5).

     Temperature thermistors of the oxide type exhibit an aging effect and an
increase in resistance with time.   About  0.5 to 1.5% of the resistance varia-
tion occurs within the first week of use.  Changes of 1% may still occur after
several  months of use.   Exposure of the thermistor to a temperature slightly
higher than that to which it will  be subjected (in a process also called
aging) may reduce drift to as little as 0.04% per year (8).  Since thermistors
are nonlinear, best least-square fits with third- or fourth-degree polynomials
yield a temperature compensation of no better than ±0.01°C (Q).   A three therm-
istor compensation network has  shown an actual  linearity of only ±0.04°C.

EXTENSION OF IN SITU INSTRUMENTS TO PARAMETERS NOT NOW MEASURED

     Reference standard requirements should be established for parameters not
now measured.   Manufacturers and researchers are  currently developing a wide
range of instruments designed for in situ use.   Reference  standard development
should proceed in parallel  with in situ instrument development to assure data
accuracy and reliability.

     Currently, 19 parameters are measured in situ and other parameters (Table
                                      21

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5) are under consideration for application to seawater.  Studies of stability
and accuracy have begun for some of the specific ion electrodes.  It is diffi-
cult to predict the future acceptance for routine application of any system.
However, the rate of growth of human impact on the environment will  encourage
more continuous monitoring of parameters.  Parameters of more imminent concern
might be identified from review of the environmental problems under study and
the parameters of concern to the studies.  Heavy metals should be a leading
contender for in situ measurement.  Cadmium, mercury, and lead are among the
more important.  Vanadium has been found to be associated with the heavy
fractions of petroleum.

                    TABLE 5.   PARAMETERS MEASURED IN SITU       	
     Presently Measured
        Calcium
        Chloride
        Chlorophyll
        Conductivity, electrical
        Dissolved oxygen
        Fluoride
        Fluorescein  (flushing studies)
        Hydrocarbons
        Light attenuation
     Possible Future Application

        Aluminum
        Ammonia
        Antimony
        Arsenic
        Barium
        Bromine
        Cadmium
        Calcium
        Carbon dioxide
        Cesium
        Chlorine
Magnesium
Oxidation-Reduction Potential
PH
Potassium
Rhodamine-B (flushing studies)
Salinity
Sodium
Temperature
Transmittance, optical
Turbidity
Chromium
Cobalt
Copper
Dysprosium
Europium
Fish "species" density
Fluorine
Gallium
Germanium
Gold
Indium
                     continued
                                     22

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                           TABLE  5.   (continued)
     Possible  Future Application
        Iodine
        Iron
        Lithium
        Lawrencium
        Lead
        Magnesi urn
        Mercury
        Molybdenum
        Neodymium
        Nickel
        Niobium
        Nitrate-Nitrogen
        Nitrite-Nitrogen
        Reactive phosphate
        Osmi urn
        Particulate matter
        Plankton "species"  density
        Platinum
Potassium
Selenium
Silicates
Silver
Sodium
Strontium
Sulfide
Sulfur
Tin
Titanium
Tungsten
Total Kjeldahl nitrogen
Total Phosphorus
Uranium 238
Vanadium
Yttrium
Zinc
Zirconium
SURVEY OF NATIONAL ACCURACY REQUIREMENTS
     For the purposes  of this  study,  manufacturers  and instrument users were
contacted in the United States.   Also,  users  from Japan,  West Germany,  the
Soviet Union, France,  Poland,  Australia,  the  United Kingdom,  and Kenya  were
contacted.  A limited  field survey of operational in situ equipment calibra-
tion and standardization techniques,  as well  as present and desired levels of
accuracy, was conducted.  Individuals contacted were involved in major  marine
sampling programs, including the Coastal  Upwelling Experiment (CUE), the
California Cooperative Fisheries Investigation (CalCOFI), the North Pacific
Experiment (NORPAX), Geology-Chemical Sections (GEOSECS), Outer Continental
Shelf (OCS), and the Dredge Material  Research Program (DMRP).  These programs
represent sponsorship by the Bureau of Land Management, the U.S. Army Corps
of Engineers, the Environmental  Protection Agency,  the National Science Foun-
dation, and the National Oceanic and  Atmospheric Administration, which  includes
the National Marine Fisheries  Service.  While it is not an exhaustive review
of the practitioners,  it accomplishes the intended purpose of indicating the
current practices and establishing the scale of accuracies sought by major
users.  The survey included 60 individuals representing 10 institutions opera-
ting within 8 major programs under 6  sponsors.  Additional information  was
gathered  from the industrial and scientific literature.
                                      23

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     U.S. Government research and funding agencies such as the Department of
Commerce's National  Oceanic and Atmospheric Administration; the Environmental
Protection Agency; the Department of the Interior's Fish and Wildlife Service,
Bureau of Land Management, and Geological Survey; the U.S. Army Corps of
Engineers; and the National Science Foundation routinely support water quality
measurements with in situ sensors.

     State and local environmental  monitoring agencies often acquiesce to
specifications of U.S. Government agencies; some establish their own accuracy
specifications for water quality.  Some of these local government programs
have grown in scope and have eclipsed the more widely known national  program.

     A wide range of international  programs are under way with still  another
specification of accuracy.  The most common in situ measurements among all
users are temperature, electrical conductivity, pH, dissolved oxygen, and
pressure (or depth).  A summary of the accuracy requirements for these param-
eters (except depth) among research and environmental  survey groups  is given
in Table 6.  As part of the teaching program, schools  and other groups often
perform cursory surveys which include measurements on  the parameters under
study.  These measurements will  sometimes find their way into public archives,
although such accessory measurements are often considerably less accurate than
those required by research and survey groups.  Survey  requirements  correspond
closely with manufacturers' stated best accuracies.  Frequently, researchers
require more accuracy (except for salinity) than possible with commerical
equipment.  For both groups, the observed accuracy reported for dissolved
oxygen is considerably less than the desired accuracy.  In summary,  the survey
revealed:

     °For the most part, instruments in present use have been used  for several
      years or more.  Reliability is generally conceded as good for  all  but
      one CTD unit at the University of Washington which was a relatively
      early model.

     °No one expressed much enthusiasm over future prospects to develop sen-
      sors for additional parameters or for refining those sensors  presently-
      available.   The need for more accuracy and finer resolution was recog-
      nized by two or three individuals but not to the extent that  they would
      promote such an undertaking.   The problem arises from the very low con-
      centrations found for most environmental parameters and the high noise
      band likely to surround the measurement itself.

     °Approximately the same attitude, that little benefit would be  gained,
      persisted in answer to the question of improvements in calibration and
      standardization.  The parties recognizing the need for standards were
      survey or monitoring groups,  whereas research groups were concerned with
      instrument capabilities.

     °While it cannot be quantified, it seems as if those individuals using
      the in situ instrumentation in long-term monitoring are able  to operate
      with less exacting equipment and are more concerned with standardization
      between installations.  By contrast those in the experimental  group seek


                                      24

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      exact  data  and  are  satisfied  to assure their values within their own
      experimental  "structure."   This "structure" may  include one  investigator,
      a  department, or  a  program.

          TABLE  6.   ESTIMATES  OF BEST  OCEANIC  IN SITU ACCURACIES

Error Sources
Probe Sensitivity
Probe Accuracy
Repeatability
Readability
In Situ Errors
Drift (24 hour)
Temp. Compensation
Pressure Compensation
(10,000 m)
Water Agitation Error
Manufacturer Stated
Accuracy
Research Observed
Required Accuracies
Research'
Survey
Accessory
Temperature
(°C)

0.01
0.015
0.01
0.01

0.5
0.01
0.81
-

0.02
0.01

0.01
0.05
1.0
Dissolved
Oxygen
(ppm)

0.25
0.1
0.1
0.05

-
0.008
-
0.05

0.01
0.5

0.01
0.1
1.0
Salinity
(ppt)

0.25
0.30
0.003
0.002

-
0.33
-
-

0.02
0.30

0.03
0.03
0.5
PH
(units)

0.0025
0.004
0.001
0.01

0.003
0.02
-
-

0.01
0.10

0.02
0.5
0.5
INSTRUMENTATION

Frequency of Standardization Required

     The majority of users were found to use Standard Seawater only when cali-
brating by an automated laboratory salinometer.   The standardization procedure
is only carried out a few times during an experiment, or once in several
months.  Errors from instrument drift, degradation, fouling, and reliability
indicate standardization should be carried out frequently.

     Cross checking between two instruments provides a partial quality check
on resulting values (J.H. Carpenter, University of Miami and K. Grasshoff,
                                     25

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 University of Kiel,  pers.  comm.).   Cross  checking  of  discrete  samples  against
 a continuous  profiler  generally cannot  be used  to  verify more  than a few  per-
 cent of continuous monitoring  data,  but should  be  used  in  conjunction  with  in
 situ instruments  no  less  frequently  than  once in every  profile, or every  few
 days for non-mobile  instrument packages (A.  Bainbridge, GEOSEC, pers.  comm.).

 Present Uncertainty  In  Instrument  Measurements

      An attempt to quantify  an estimate of uncertainty  in  instrumental measure-
 ments was  terminated when  the  review of user practices  disclosed a lack of
 traceability  to a common  reference material  or  reference method.  Quantitative
 values  of  percent uncertainty  should be estimated  as  average percent deviation
 from the known mean.   Percent  error of  the measurement  is  determined by
 attempting  to  repeat a  single  measurement  many  times  on a  parameter of known
 value.   The spread of the  data points estimates this  error.  In lieu of quan-
 tification, a  discussion of  the  sources of uncertainty  and the potential  quan-
 tifiable uncertainty as a  function of the  standards available  is provided.

 Manufacturers' Standardization Procedures--
      Nonlinearity of an instrument results in a curve when data points derived
 from that  instrument are plotted against the actual values.  This in itself
 does not constitute an  error.   However, when converting the instrument output
 to standard units of measure some error is produced.  This error is measured
 by the  magnitude of difference between  the resulting  converted measure value
 and  the actual value.   It  should be noted  that simplistic analog conversions
 within  the  instruments  are often considerably nonlinear with a resulting large
 conversion  error.  For this  reason GEOSEC  has removed analog conversions from
 their oxygen meters and are  using ship-board computer conversions.   The GEOSEC
 technique  is a considerable  improvement over commonly used techniques,
 although some researchers  do not consider  the shipboard routine conversion to
 fully meet their standards.

      Temperature—Manufacturers of CTD's and STD's  recommend the system be
 returned to their lab approximately once per year for calibration.   The CTD
 or STD  is placed in a constant temperature-salinity water bath (verified by
 NBS  methods), and the thermistor and conductivity cell are then adjusted.   NBS
 has  a standard adequate for calibrating temperature sensors.

      Salinity--!.A.P.S.O.  Standard Seawater is  the  standard reference for cal-
 ibration of both in situ and laboratory salinometers.   It is  in routine use in
 the  oceanographic community and is the salinity reference.   It is  considered
 difficult to duplicate the solution in the laboratory.  Currently,  Standard
 Seawater is being distributed  by the Institute  of Oceanographic Sciences in
 Surrey, England.   This standard solution has  a  certified uncertainty   of
 ±0.001 ppt chlorinity.   Calibration to the standard using potassium chloride
 techniques has a reported  uncertainty maximum of ±0.01 ppt  salinity.   The  best
American refractometers have a reported accuracy of ±0.05  ppt  salinity; how-
ever, a Russian interferometer system has  a reported accuracy  of ±0.01  ppt
salinity.

      Dissolved oxygen-- Sagami  Standard Seawater Reference  Solution Source
prepares and distributes worldwide  CSK standard seawater  reference solutions,
including one  for dissolved oxygen.  The solution  is used  without  dilution,
                                      26

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and the colorimeter technique is based on a standard color development to
calibrate absorbance in a spectrophotometer.  In general, the Sagami  samples
are designed to remain stable for at least 1 year after preparation.   The most
widely used dissolved oxygen reference standard worldwide are modifications  of
the Winkler procedure.

     Calibration of dissolved oxygen probes often uses air saturated  water as
a standard.  The maximum accuracy of this technique is 0.1 percent,  due to
problems with variations in air quality and supersaturation at low tempera-
tures encountered in the field (13).

     £H--Standard pH buffer solutions are prepared by many chemical  and manu-
facturing companies to the exact formulas prescribed by the National  Bureau
of Standards.  The certified accuracy of these standards is ±0.01  pH units.
There is good reason to conduct seawater sensor calibration at something
greater than a pH value of 7.0.  Testing at a pH of 8.0 rather than  7.0 has  an
immediate advantage of being closer to the seawater average of pH  8.0 to 8.3.

     Buffer solutions are less stable than powder buffers.  Solutions in
storage are stable up to a year, whereas buffer powder or buffer tablets can
be stored indefinitely.  However, with buffer powders, the mixing  methods in
the field must be as accurate as normal analytical methods followed  in an
equipped chemistry laboratory.

     Instrument standardization to a pH buffer standard has a maximum reported
accuracy of ±0.02 pH units at 25°C as measured with a precision pH meter.
Problems of comparing standard pH buffer solutions to measurements in seawater
result in an additional error due to interferences that should be  solved by
setting up rigid standards for seawater buffer solutions and standardization
methodology.

     Users' calibration and standardization—Users often choose different
standards since a common standard is not recognized for most of the  parameters.
The procedure for calibration standardization is produced from manufacturers'
instructions, laboratory manuals, research journals, and text books,  or are
invented to meet the user's specific needs.  Considering these circumstances,
comparison of data between independent researchers is questionable.   The need
for comparable water quality measurements necessitates the development of
reproducible standard analytical techniques.

     Users introduce four additional errors into the measurement process.
Without proper control of these errors, data cannot be considered  standardized.

     "Procedures may be modified by a laboratory to meet their needs.  Such
      modifications change the procedural error and are referred to  as pro-
      cedural modification errors.

     °Human errors are procedural errors resulting from the measurement being
      taken by different ope""-1-™"

      Training error result:
      make the measurement.
 II Ml IIUII t I IV/IO U I C (JlUUCUUlUl  C
 taken by different operators.


°Training error results when  operators  of different levels  of learning
 ma Uo + ha mnaciiv»om««•*-
                                      27

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      °Technology  errors  result when  new  instruments are developed.  The spread
       of data  points  due  to  different  instruments making the same measurement
       estimates this  error.   It  is necessary to subtract from this value
       instrument  error,  standardization  error, and, if necessary, operator
       error, as well  as  sampling error to obtain the actual value.

      The necessity of using  rigid procedures during calibration, standardiza-
 tion,  and measurement is  stressed.   The  inaccuracies resulting from inade-
 quately  trained personnel  following  many manufacturers' techniques are docu-
 mented by the  cruise  results  (Appendix B).  Improved procedures, such as are
 documented  in  the CalCOFI/GEOSECS procedures manuals, should be used at all
 times. (Note:  Errors may still arise  from other facets of sampling design.)

      The GEOSECS  program  determined  that calibration of equipment at exces-
 sively short intervals actually resulted in a degradation in overall  accuracy.
 If  the instrument can be  determined  to have a known bias, the data can be
 readily  corrected by  computer programming or manual data correction.

      "Temperature sensors usually must be calibrated by the manufacturer,
       while most  users are only able to make a few crude comparisons (±0.1°C)
       to a  laboratory thermometer.

      °CTD and  STD systems  are usually field standardized by simultaneously
       profiling and collecting discrete water samples, then comparing the CTD
       or STD temperature  and salinity data with measurements of the water
       samples  taken by reversing thermometers and laboratory salinometer.

      °For salinity and pH, the user will  make dilutions of the standard solu-
       tion  to  obtain  a set of working standards to calibrate the sensor or
       probe.   Ideally, the sample value will  fall  within the range of the
       working  standards.    The user often prepares his own standards by dis-
       solving  reagent grade  (99% or greater purity) salts into distilled
       de-ionized water.   To eliminate the matrix effect, an ionic strength
       buffer should be added to the standard solution.   The standard  method
       of calibrating  in situ salinity instrumentation is by the laboratory
       salinometer method.  The standard instrument for salinity measurements
       is  considered to be  the high accuracy-precision laboratory salinometer.
       This  type of salinometer uses the inductive coupling  technique  to mea-
       sure  conductivity and is automatically temperature- and pressure-compen-
       sated.

     °Dissolved oxygen sensors can be coarsely standardized with air-saturated
      seawater.  If the temperature of the water is known,  solubility tables
      will  provide an "accurate"  value of the percent saturation.

     In situ dissolved oxygen measurements are usually calibrated against  the
standard Winkler method performed on  water bottle samples.   Calibration is
performed using distilled water for freshwater work.   Even  though bottle
samples are not exactly comparable to in  situ measurements, in situ measure-
ments are often terminated when discrepancies are found between reversing
thermometer or water bottle sample values and in situ values  (A.  Bainbridge,
GEOSECS,  pers.  comm.).  Some users  cross-calibrate between  two in situ  systems
without close calibration to any  outside  standard.   The University of Miami
recalibrates both  in situ systems if  a  difference  of greater  than 0.1  ppm  Of
                                     28

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oxygen is found (J.  Carpenter,  University  of Miami,  pers.  comm.).

Cruise Reports

     The at-sea operation was  carried out  April  13,  1977,  to  further  study the
problem of standardization and calibration technqiues,  and to determine  the
comparability of measurements  obtained using the calibration  and  standardiza-
tion techniques recommended by equipment manufacturers.   The  at-sea operation
utilized electronic  in situ instrumentation systems  and standard  sampling
techniques for dissolved oxygen,  pH, temperature, and  salinity.   The  survey
was conducted at five stations in Monterey Bay,  California.   Temperature,
salinity, dissolved  oxygen, and pH were measured at  the surface,  and  at  depths
of 5, 10, 20, 30, 40, and 50 meters (Appendix B).

     Calibration of  the equipment prior to the cruise  was  performed according
to manufacturers' specified procedures:  dissolved oxygen  was calibrated
against air-saturated seawater; conductivity with Standard Seawater;  pH  by
standard NBS buffer  solutions; and temperature probes  by the  constant tempera-
ture bath method in  comparison with a platinum thermometer.   The  instrument
systems were under manufacturers' calibration.  A representative  of LFE  par-
ticipated in the cruise procedures along with Interstate Electronics  Corpora-
tion personnel.  Four in situ systems were tested:  Horiba, Hydrolab, Martek,
and Plessey Environmental Systems.  All four parameters were  measured by the
Horiba, Hydrolab, and Martek systems; the Plessey system did  not  measure pH
and dissolved oxygen.

     In addition to  the in situ instruments, a Beckman (RS7C) Laboratory
Salinometer was used to measure conductivity, Winkler  titrations  were used  to
measure dissolved oxygen, and a reversing thermometer  was used to measure
temperature.  These  methods were used as checks on the in situ instrument
performance.  Conductivity measurements were performed by inductive coupling
and multiple electrode sensors (from which conductivity ratios were determined
and subsequently converted by use of tables).  Dissolved oxygen was measured
by membrane polarographic electrodes; pH was measured  by glass electrodes;  and
the temperature sensors were resistance transducers.  All  instruments were
capable of measuring the oceanic range of each parameter.  All water  samples
were collected with  standard Nansen bottles.  Depth was calculated by triangu-
lation when necessary after measuring the wire angle.

Statistical methods--
     The 95% confidence interval was calculated on each system for each  param-
eter as a measure of the accuracy of the method employed.  The confidence
intervals were calculated using the method given by J. Freund (14) for small
samples.  The sample variance was estimated for each system as the sum of the
squared deviations from the calibration procedure.  The following procedures
were assumed to  be calibration procedures:

          Winkler method:                    dissolved oxygen
          Calibrated reversing thermometer:  temperature

          Beckman laboratory salinometer:    salinity
          Statistical mean pH value:         pH

                                     29

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      The  mean  square  differences  were  calculated  between  the  in situ method
 and  the calibration method  by  the paired  value method  to  eliminate distribu-
 tion dependency  and the  effects of depth  and  location  (15).   Tests for signif-
 icant differences  between techniques were performed  by means  of the small
 sample paired  t-test  for comparing a sample mean  to  a  theoretical mean (14).

      This  total  interval may be partitioned into  the uncertainty caused by the
 analytical  method  (precision)  and the  uncertainty attributable to systematic
 error (calibration).   Partitioning of  the interval into two t-statistic inter-
 vals (precision  and systematic) is  shown  in Table 7.

   TABLE 7.   PARTITIONED  STANDARD  DEVIATIONS FROM  INTERCOMPARISON EXPERIMENT
Parameter
Temperature
Salinity
Dissolved oxygen
PH
Methodology
0.010
0.102
0.175
0.113
Systematic
0.18
0.470
1.007
0.365
Total
0.28
0.572
1.182
0.478
 Cruise observation results--
      Considerable differences were found between the values reported by the
 various in situ instruments.  Only one temperature system, two dissolved oxy-
 gen systems, and one pH system demonstrated a lack of significant difference
 from  the chosen calibration system (Table 8).

      Sampling was inadequate to determine behavior of the measurements due to
 pressure differences.  Statistical interpretation is also limited by the lack
 of replication.  Even under the best of circumstances, it is essentially
 impossible to obtain a true replicate measure in such a heterogenous environ-
 ment.  Since all measurements were made during a 10-hour cruise, no discussion
 of drift, marine biofouling, durability, or reliability is warranted.

      All  parameters showed a greater standard deviation due to systematic
 error than to methodology (Table 7).   This suggests considerable calibration
 error, and points out the problem of independent calibration of systems by
manufacturers and the nonequivalency of calibration techniques used for
 different instruments.

      It is suspected that part of the error between methods could be reduced
 by a uniform calibration procedure.  No single procedure was devised that
could accommodate the differences in equipment structure.  Ship-environment
 interaction, such as bilge effluent,  propwash, and engine cooling effluent,
was a potential problem.   Precautions were taken to avoid such problems, and
the data  did not reflect these influences (increased standard deviation values
of surface water quality measurement).
                                    30

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     Depth compensation  requires  an  accurate measurement of  pressure.  Two
systems incorporated pressure  transducers  in their  in  situ systems.  The other
systems used cable length markings and  triangulation  (when wire angle was
greater than 5°)  to estimate depth.   One system  uses  the bonded strain gage,
which is considered a very accurate  method of  determining depth (8).  This
transducer is automatically temperature-compensated;  accurate  compensation  is
important since gage impedance varies significantly with temperature (8).   No
comparison between cable lengths, pressure transducers, or triangulation tech-
niques was attempted.  Fortunately,  since  wire angles  were slight on this
particular cruise, the inaccuracy of depth measurements was  not considered  a
major problem.  In rougher seas,  the cable length and triangulation method  of
depth estimation is much less  accurate  than a  pressure transducer.   Placement
of more weight in the sonde would improve  some of the systems  environmental
applicability.  The sonde unit is very  light and easily responds to  ship move-
ment and currents.  This is a  very undesirable characteristic  as water depth
uncertainty becomes a problem.

         TABLE 8.  95% CONFIDENCE INTERVALS WITH PAIRED T-TESTS FOR
      SIGNIFICANT DIFFERENCES  BETWEEN SAMPLE AND CALIBRATION MEASURES
Parameter
Temperature




Salinity



Dissolved Oxygen


pH



System
A
B
H
C
D
A
B
H
D
C
B
A
G
A
B
H
n
13
24
18
24
20
11
25
19
22
25
24
11
24
13
23
19
95% C.I.
0.171
0.103
0.115
0.195
0.111
9.02
0.127
3.28
0.016
0.374
0.525
1.69
0.07
0.03
0.04
0.05
Std. Error
0.097
0.050
0.055
0.095
0.053
4.049
0.061
1.489
0.008
0.183
0.508
0.816
0.008
0.015
0.018
0.023
Probability
of Difference
from Standard
3.38*
4.22*
3.27*
4.29*
2.67
3.28*
4.82*
4.35*
3.56*
3.91*
2.12
0.64
16.0*
2.72
3.21*
3.43*
  *  =  99%  probability of a difference
 (*  =  significance  level of better than 0.01)

      Temperature—The 95% confidence interval covers 2.8% of the average
 sample  mean,  or  ±0.28°C.  One was consistently high, recording values outside

                                     31

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the confidence interval 69% of the time.  All the values recorded by another
system were lower than the sample mean  (by an average of 3%) and outside the
confidence interval in 48% of all measurements.  This consistently large range
between systems suggests calibration (systematic) error.

     The reversing thermometer and only one thermistor system showed close
agreement at all stations and depths.  The response time for all systems
varied between 30 and 60 seconds.  During the cruise, all the temperature
measuring systems operated properly, and no repairs or replacements were
necessary.  All systems were reliable, relatively sensitive, and had a short
response time.  Previous studies yielded similar results (8).

     The reading uncertainty standard deviation for one system was ±0.16°C,
which is 0.10°C greater than the uncertainty reported by NOIC Instrument Fact
Sheet #75004.  The uncertainty for another system was ±.09°C, which is 0.08°C
greater than the uncertainty reported by NOIC Instrument Fact Sheet #76012.

     Sa1inity/conductivity--Previous CalCOFI studies have determined that the
expected salinity range of Monterey Bay is 33.0 to 34.0 ppt for the summer
months.  Since values from two systems were far outside this range, these
values were not included in the sample mean and confidence interval calcula-
tions.  One system reported values of about 18.8 ppt, and the other system
about 27.3 ppt.  The 95% confidence interval  calculated from readings of the
remaining three systems was ±0.57 ppt, or approximately +1.5% of the sample
mean.

     Two systems showed significant agreement at all stations and depths.
Both systems  recorded salinities lower than a third system; however, reported
values were six and five significant figures, while the third gave three
significant figures.   This difference in data reporting with the resulting
recording errors could partially account for the range between salinity values.

     Conductivity is  a function of salinity,  temperature, and pressure.
Therefore to  achieve  accurate conductivity values, precise measurement of
these three parameters is essential.   Compensation for temperature and pres-
sure variations is included in all  salinity data presentations.   All  salinity
recording systems compared in this  study measured conductivity.   Two systems
used inductive coupling techniques, and the others used multiple electrodes.

     Polarization could have been a problem since all  instruments used less
than the recommended  1  KHz power source (8).   Response time varied between 1
and 3 minutes for all  systems.   Mechanically  the five systems were reliable,
excepting the gross errors in two of the systems.

     Dissolved oxygen--The 95% confidence interval  for dissolved oxygen is
±1.18 ppm, or approximately ±15% of the sample mean.  The wide range of values
reported for  the same sample yields a relatively large confidence interval,
often as large as 15-20% of the sample  mean.   No two systems agreed more
closely than  0.2 ppm.

     During the measurement of dissolved oxygen, the expected sample collec-
tion problems were accompanied by a significant number of system malfunctions.
Approximately one half of the membranes had to be  replaced.   After the membrane
                                      32

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was replaced, the system's response was  tested  but  additional  performance  data
were not collected.   One of the six electrode  systems  developed  a  white
clogging precipitate.  After 22 readings,  two  others  did  not  function  at all.
One system probe was accidently set down in the bottom sediment, which
resulted in the failure of all  its  sensors (temperature,  dissolved oxygen,  pH
and conductivity).

     Improper membrane installation could  account for some of the  inconsist-
encies.  Manufacturers' instructions for the replacement  of membranes  are
sometimes vague and confusing.   Other possible  problems include  uncertainty of
sensor's depth, electronic drift, and other previously stated factors.

     The response times for the in  situ  dissolved oxygen  systems ranged  from
20 seconds to 4 minutes; in almost  all  cases they were greater than the  manu-
facturer's specification.   The response  time of all sensors of this type
(polarographic membrane) will increase with decreasing temperature, and  opera-
tion at 0°C would thus require longer equilibrium times according  to Sectarian
Instrument communication to NOIC Fact Sheet #76011, 1976.

     In this study, the data accuracy (compared to  Winkler titration)  and
precision values were much poorer than the values stated  in the manufacturer's
specifications.

     £H--For field measurements of pH, the 95% confidence interval was ±0.47
pH units.  Two systems were very close to  the mean  of the four systems.
Comparable deviations from replicate readings (precision  errors) were observed
between the shipboard lab and each  in situ system.   Three responded similarly
with changes in station and depth.   These systems agreed  closely at approxi-
mately one half the stations.  Another system's values were inconsistent  with
the sample mean and the pH profile.  All systems appeared to  function properly
and no sensor repair or replacement was  necessary.   Response  time  was gener-
ally between 1 and 3 mintues.  The large uncertainty under field conditions is
in agreement with previous studies  (8).

Environmental  Perturbations

     In situ measurements eliminate errors incurred through sampling and
sample handling.  However, in situ measurements are considered more difficult
to make.  Standardization and calibration are a serious problem, but when a
discrete sample is obtained by water bottle from the ocean "...its temperature
and pressure changes.  These changes displace rapid equilibria so  that by the
time our sample has reached the surface its chemical composition has already
changed."   (4 )  Contamination from containers, addition or losses of dis-
solved gasses, settling,  precipitation, and decomposition of life  forms
further contribute to non-in situ measurement error (4 ).  In situ measure-
ments  should reflect ambient conditions with greater accuracy than non-in situ
techniques.  However, in  situ measurements also have a set of problems.
Instruments which function accurately in the laboratory under closely con-
trolled environmental conditions must still function accurately under a
rigorous  range of pressure, temperature, water movement, turbidity, light, and
chemical  and biochemical  conditions.  Ionic strength and complex  formation may
shock  dissolved oxygen electrodes  (F. Millero, University of Miami, pers.
comm.).
                                      33

-------
     Temperature compensation methods are somewhat better understood than
pressure compensation methods.  Plessey and Hydrolab in situ systems include
temperature-compensated, bonded strain-gage transducers to measure depth.  The
YSI 5514 instrument uses a depth-compensated system.  However, the combined
temperature and pressure effects on dissolved oxygen and pH are only partly
understood.  Temperature measurements should be pressure-compensated if a
high degree of accuracy (±0.01°C) is required, as there is a change in
indicated temperature caused by pressure effect on the sensor.  An effect as
high as 0.81°C at 10,000 meters has been reported (16).  Accurate compensation
can only be carried out by means of a shipboard computer system; commercial
conversion procedures are often inadequate to meet the needs of researchers
(A. Bainbridge, GEOSEC, pers.  comm.).

     The problem of measuring  perturbations of measures due to pressure
effects, pollutant interference, temperature compensation, and buffering
effects is partly due to the lack of standards of reference.   The lack  of
known values of comparison contributes  to the problem of defining the meaning
of an in situ value.   Additional errors  may arise due to the  unexpected
behavior of parameters in situ, and the  variability of the quality of
standards.
                                    34

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                                 REFERENCES


 1.   Shewhart,  W.  A.   Statistical  Method  from the Viewpoint of Quality Control.
     U.S.  Department  of  Agriculture, Washington, DC, 1939.

 2.   Eisenhart,  C.  Realistic  Evaluation  of  the  Precision and Accuracy of
     Instrument  Calibration  Systems.   Journal of Research, U.S. National
     Bureau of  Standards,  67C  (2):  pp.  161-187,  1963.

 3.   Call, J.  P.,  T.  V.  Meters,  R.  E.  Michaelis, W.  P. Reeo, R. W. Senaro,
     C.  L. Stanley, H. T.  Yolken and H. H. Ku.   The  Role of Standard Reference
     Material  in Measurement Systems.   NBS Monograph 148, U.S. National Bureau
     of Standards,  Washington,  DC,  1975.

 4.   Home, R.  A.   Marine  Chemistry.   John Wiley and Sons, New York, NY, 1969.
     568 pp.

 5.   National  Bureau  of  Standards,  U.S. Platinum Resistance Thermometry.  U.S.
     National  Bureau  of  Standards,  Washington, DC.   Monograph 126, 1973.
     129 pp.

 6.   Strickland, J. D. H.  and  T. R.  Parsons.  A  Practical Handbook of  Seawater
     Analysis.   Fisheries  Research  Board  of  Canada,  Ottawa, Canada.  Bulletin
     167,  2nd  edition, 1967.  310 pp.

 7.   Environmental  Protection  Agency,  U.S. Methods of  Chemical Analysis of
     Waters and  Wastes.   U.S.  Environmental  Protection Agency, Washington,  DC,
     1974.  239  pp.

 8.   Texas Instruments,  Inc.  The State of the Art of  Oceanographic and
     Meterological  Sensors.   Texas  Instruments,  Inc.,  Dallas, Texas.   Volume 1,
     1970.  150 pp.

 9.   Green, M.  W., R. D. Gafford, and  D.  G.  Rohsbaugh.  A Continuous Profiling,
     Deep-Submersible Dissolved Oxygen Monitor.  Marine  Technology Journal,
     Volume 2,  1970.   pp.   1485-1502.

10.   Westcott,  C.  C.   Selection of a Reference  Electrode.   Industrial  Proce-
     dures IP-EC-1 , Beckman  Corporation,  Scientific  Instruments  Division,
     Irvine, California, 1976.   4 pp.

11.   Phelps, K.  D., and  A. D.  Beck.  Sensing and Simulating the  Marine
     Environment.   U.S.  Environmental  Protection Agency,  Narragansett, Rhode
     Island, 1973. pp.   361-369.
                                      35

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12.  National Oceanographic Instrumentation Center, U.S. Discrete Oxygen
     Analyzer.  International  Biophysics Corporation, Irvine, California.
     U.S. Department of Commerce, National Oceanic and Atmospheric Administra-
     tion, National Ocean Survey, National Oceanographic Instrumentation
     Center.  Instrument Fact Sheet (IFS-76009), 1976.

13.  Carpenter, James H.  New Measurements of Oxygen Solubility in Pure and
     Natural Water.  Limnology and Oceanography, (11):  pp. 264-277, 1966.

14.  Freund, J.  Mathematical  Statistics.  2nd  edition, Prentice Hall, Engle-
     wood, NJ, 1971.   274 pp.

15.  Sokal,  R. and J.  Rohlf.  The Principles and Practice of Statistics in
     Biological Research.   Biomedics,  W. H. Freeman and Company, San Francisco
     California, 1969.   776 pp.

16.  Zobell, C. E.  Thermal  Changes Accompanying the Compression of Aqueous
     Solubility to Deep Sea Conditions.   Limnology and Oceanography (4):  pp.
     463-471 , 1959.

17.  Hulse,  G. L.   The  Plunkett  In Situ  Monitoring System.   New York State
     Marine  Science Research Center,  State University of New York, Stony Brook,
     NY, 1975.  201  pp.

18.  Bradshaw, A., and  K.  E. Schleicher.  The  Effect of Pressure on  the Elec-
     trical  Conductance  of Seawater.   Deep Sea  Research  (12):   pp.   151-162,
     1965.
                                     36

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                                 APPENDIX  A

      DESCRIPTION OF TWO VARIATIONS  OF IN  SITU  INSTRUMENTATION SYSTEMS


THE PLUNKETT SYSTEM

     The Plunkett is a semi automated system that  permits  continuous  sampling
in vertical  and horizontal  planes.   The system  was  developed  in  1969 at the
State University of New York,  using  proven, commercially  available components.
The Plunkett system has three  major  components:  the  sampling unit,  the wet
lab, and the electronics module.   The sampling  unit incorporates a submersible
centrifugal  pump at the lower  end of a flexible hose.   Vertical  sampling  can
be accomplished from the surface  to  80 meters.   For horizontal sampling,  a
second centrifugal pump operates  through a hull intake.   Parameters  measured
directly at the pump intake include  salinity, temperature,  and depth.   Sea-
water is pumped to the wet lab unit  on deck where pH,  dissolved  oxygen, in
vivo chlorophyll, and turbidity are  routinely measured.   Taps are provided
for unfiltered seawater for additional analyses..

     The electronics module includes signal processing and  analytical  instru-
ments for determining the height  of  the sampling unit above the  seabed, the
depth of the sampling unit below  the surface, temperature,  pH, dissolved
oxygen, salinity from the direct  and backup salinometer (thermosalinograph),
and underwater photometry.  Graphic  recording equipment in  the form  of a
multipoint analog stripchart recorder provides  a continuous indication of
system performance and real-time  sensor information,  and  acts as a backup
recording medium in the event  of failure of the digital  data  acquisition
system.  The data acquisition  system can accommodate up to  40 channels.

System Calibration

     Calibration of the system was conducted in two separate programs:  labor-
atory and field.  The salinometer is calibrated against Standard Seawater.

     The thermistor bridge system for direct temperature  measurement uses the
manufacturer's calibration method and curves.   System calibration consists  of
substituting precision resistors for the thermistor in the  bridge.  A 12-point
calibration is used, and this  may be expanded over a narrow temperature range.
The resistors are compared to a National Bureau of Standards 1 ohm primary
standard resistor.  Total accuracy is rated at  no greater than the greatest
error present, the 0.1°C accuracy of the thermistor.  There is no regular
calibration of the thermistor against a primary standard; therefore, changes
in thermistor characteristics  due to physical   aging, pressure, damage, etc.,
would not be apparent to the operator.

     The pressure transducer for intake depth measurements is calibrated only
                                      37

-------
 in  the field  by  lowering  it  on  a  handline marked  in 10-meter increments to 50
 meters.   The  calibration  potentiometer  is adjusted for a voltage input of 50
 mV  to  the data acquisition system.   The transducer is then raised in 10-meter
 steps, and the voltage on the digital voltmeter is checked.  The accuracy of
 the depth reading  is  expressed  as ±0.5  digit values on the meter.

 On-Deck  Measurements

     The dissolved oxygen probe is calibrated against the Winkler titration
 using  the instrument  company's  field calibration  procedure.  This procedure
 consists of placing the probe in a plexiglass sampling chamber, pumping sea-
 water  through the system, and comparing the values obtained with the modified
 Winkler  titration.

     pH  calibration is conducted by  comparison of the probe value against a
 laboratory pH meter value, submerging the sensor in a standard buffer solution.
 The probe is equipped with an automatic temperature compensator.  The accuracy
 of  the calibration method is reported as ±0.002 at the buffer points and
 ±0.005 with the buffer and sample in the same range between points.

     The in vivo chlorophyll  system utilizes a fluorometric determination.
 Calibration consists of blanking the fluorometer by the Turner and Lorenzen
 methods,  followed by calibration against acetone extractions  with a  minimum of
 15  samples and a standard chlorophyll reference.

     The  turbidity system is  calibrated by blanking the fluorometer  with
 particle-free distilled water.   Discrete samples of seawater  of known volume
 are collected from the discharge line.   The  samples are then  filtered through
 a preweighed millipore filter.   The filter is  re-weighed,  and the weight of
 particulate matter is  plotted as suspended solids  per volume  of seawater
 sample by which fluorometer  values can  be  checked  (17).

 THE "FISH"

     The  "fish,"  which was developed  and used  by the  Institute  of Marine
 Resources of the  University of  California, Berkeley,  is  towable at speeds up
to 5 knots, and can be programmed  for sampling  from the  surface to 30 meters,
permitting both vertical  and  horizontal  profiling.   The  system  monitors  the
following parameters to  the indicated accuracies:

     "Depth:  0-30  m ±0.1  m

     °Temperature,  full  range:   ±0.02°C

     °Conductivity,  full  range:  0.3%

     "Dissolved oxygen,  full  range:   1%  of full  range

     °pH, sulphide  ion, and Eh:  within  1 mV of  electrode voltage

     °Ambient  light:   detects changes within 1%  of full scale

     Similar design concepts  have  been available from commercial manufacturers
 uch as the Hydrospace Corp., Towed Automatic Profiler, and Hermes Ltd., which
 ffers  the "Batfish."

                                     38

-------
Calibration Techniques  for the  "Fish"

     This type system has  unusual  calibration  requirements.  The parameter
values are recorded with  a precision of ±1  digit  on  either a 16-mm single
frame movie camera or alternately  on a  digital  cassette  recorder.  In turn,
the basic accuracy of the  overall  system is  dependent  upon the accuracy of
the internal reference  voltage.  Therefore,  the aim  of the calibration proce-
dure was to ensure the  internal  reference accuracy rather than traceability
to a defined standard.   For example, traceability of the temperature sensor
to the manufacturer's test and  calibration of  the thermistor.

     Dissolved oxygen calibration  is performed in a  seawater bath containing
a sample of fully oxygenated water of  known  salinity.  The sample is agitated
to read oxygen saturation  equilibrium.   Calibration  of the dissolved oxygen
probe is performed every  time the  membrane is  replaced.

     pH calibration is  accomplished with standard buffer solutions and is
corrected for alkaline  error due to the presence  of  cations and  temperature
effects.

     The sulfide sensor is calibrated  in the laboratory  with a solution of
variable S activity. The solution is  made by  bubbling gaseous H2S in a 0.25
molar Na2S and 0.5 molar  KCL solution  and by changing  the  pH by  adding 1
molar acetic acid.

     The Eh sensor is checked occasionally by  measuring  the Eh potential  of a
standard oxidizing solution that has an Eh value  of  430  mV.  Experience  indi-
cates that the Eh value obtained is within 10  mV  of  the  standard value with-
out any special electrode cleaning.

     The conductivity sensor is calibrated against a temperature-compensated
laboratory-grade salinometer.  Pressure effects are  neglected  during  calibra-
tion but corrections for  pressure  are  incorporated during  the  data analysis
phase using the Bradshaw and Schleicher tables (18).
                                     39

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                                 APPENDIX  B

         EXPERIMENTAL CRUISE  FOR COMPARISON OF CALIBRATION ACCURACIES


     An  intercomparison cruise was conducted on April 13, 1977, in Monterey
 Bay aboard  the  Ship R/V Oconostota for the purpose of directly comparing the
 in situ  measurement accuracy of instruments measuring dissolved oxygen, con-
 ductivity  (salinity), temperature and pH to laboratory results.  Four in situ
 systems, each with an individual operator, were simultaneously operated at a
 number of discrete depths to a maximum of  50 meters at five widely spaced
 stations to offer a range of environmental variability.  The station locations
 sampled  appear  in Figure 1.  All analytical systems were calibrated before the
 cruise according to the manufacturers' recommended procedures:  dissolved
 oxygen using air-saturated water; conductivity using Standard Seawater; and pH
 using buffer solutions.  Temperature and pressure sensors were calibrated by
 the manufacturer using constant temperature baths and high pressure chambers
 respectively.   LFE Environmental Labs supported Interstate's staff by cali-
 brating  instruments, performing laboratory analyses, and by participating in
 the supervision of cruise operations.

     Laboratory analysis for the traceability of standards for dissolved
 oxygen and conductivity were performed at LFE's certified laboratory located
 in Richmond, California.  To ensure proper handling of samples from point of
 origin to laboratory, senior laboratory personnel  participated in the opera-
 tion, collected the samples, and were responsible for transport.

 In Situ  Instruments

     Specifications for parameters measured by each of the in situ  systems
 and laboratory systems (shipboard and shore based) used appear at the end of
 this section in Tables B-l  to B-ll.   In situ salinity was measured  with in
 situ and laboratory systems using either inductive coupling or multiple elec-
 trode techniques.   Dissolved oxygen  membrane polarographic electrodes and
 glass pH electrodes were used in both laboratory and in situ measurements.
 Temperature-compensated bonded strain gage transducers were used  by the
 Plessey and Hydrolab system to measure in situ depth.   Temperature  sensors
were all  resistance transducers with one platinum  transducer and  four types  of
thermistors.

     Most of the systems were capable of measuring the full  pH range, 0 to  14.
All  systems were capable of measuring temperature  from 0  to 35°C, and three
 systems could accurately measure in  the  5 to  45°C  range.   All  instruments
were capable of measuring dissolved  oxygen  concentration  levels from  0  to 20
 ppm.   Many scales  were  available for  the measurement of electrolytic  conduc-
tivity in mS/cm.  The most  common  range  of  measurement was  0 to 60  mS/cm.
The  systems predominantly employed an automatic  temperature compensation
arrangement.
                                     40

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if.
                        SOQUEI
                                             MONTEREY   BAY
                                                 SCALE 1:210 668
                                                         WATSONVIUE
                                              .   y»  J f  tt I™'*'*! LOnoi
                                                  ^ /  /[/Moil Londi
Figure 1.   Intercalibration  cruise sampling station locations.

                                 41

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     TABLE B-l .   IN SITU SYSTEMS USED FOR EXPERIMENTAL  CRUISE
        Manufacturer
                   Parameters  Measured
           Horiba:


          Hydrolab:



           Martek:


          Plessey:
                Dissolved  Oxygen,  pH,
                Conductivity,  Temperature.

                Dissolved  Oxygen,  pH,
                Conductivity,  Temperature,
                Depth (Pressure).

                Dissolved  Oxygen,  Tempera-
                ture, Conductivity,  pH.

                Conductivity,  Temperature,
                Depth (Pressure).
              TABLE B-2.   LABORATORY METHODS USED ON
             DISCRETE SAMPLES FOR EXPERIMENTAL CRUISE
   Method or
   Instrument
Parameters Measured
   Where Measured
Reversing
Thermometer

Orion pH meter

Beckman pH meter

YSI D.O. meter

Winkler titration

Beckman Salinometer
    Temperature


         pH

         pH

 Dissolved Oxygen

 Dissolved Oxygen

     Salinity
Shipboard Laboratory


Shipboard Laboratory

Shipboard Laboratory

Shipboard Laboratory

Shore Based Laboratory

Shore Based Laboratory
                                 42

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TABLE B-3.   SUMMARY OF SYSTEM ACCURACIES
MANUFACTURER
Horiba
Hydrolab
Martek
Plessey
Environmental
Systems
SYSTEM
MODEL
U-7
Surveyor-
GDI 2
MK V
CTD9400-5
ESTIMATED
COST
2,950
5,000
4,950
20,000
CONDUC-
TIVITY
±2.5
mS/cm
±0.5% fs
±0.5
mS/cm
±0.03
SALINITY
N.A.
0.5 ppt
±0.5
ppt
N.A.
TEMP-
ERATURE
±0.5°C
±0.25°C
±0.1°C
±0.02°C
pH
±0.1
±0.1
±0.1
±0.02
DISSOLVED
OXYGEN
±1.0
mg02/l
±0.5% fs
±0.1
mg02/l
±2% fs
DEPTH
N.A.
±1.5% fs
±0.1% fs
± .25% fs
Information from manufacturer's product bulletins
fs = full scale
N.A. = not available

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              TABLE B-4.  HORIBA:  U-7 MATER QUALITY CHECKER
  Parameter
Method of Measurement
Range of Measurement
Temperature
Compensation
pH
Temperature

Dissolved
Oxygen

Conductivity
  Glass electrode
  Thermistor

  Membrane type
  Galvanic cell

  4-electrode sensor
  0 to 14 pH units


  0 to 40°C


  0 to 20 mg02/l


  0-50.0 mS/cm
  or
  0-100.0 mS/cm
  or
  0-1000  mS/cm
Automatic
0 to 40°C

Not Required

Automatic
0 to 40°C

Not
Available
Indicator:  Light-emitting diodes - 3 digits.

Power Required:   Rechargeable battery (nickel-cadmium cell)  or 117 Vac.

Cable Length:  2.  meters with an optional  length of 10 meters.

Weight:  Instrument -  0.63 kg
         Sensor -  0.82 kg
         Shipping  weight - 6.35 kg with case
                                    44

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TABLE B-5.  HYDROLAB:   6D SURVEYOR

Parameter
Temperature
Conductivity

pH
Depth
Dissolved
Oxygen
Method of Measurement
Thermistor
4-electrode a-c cell ;
pure nickel
electrodes

pH electrode,
reference
electrode, pair
Pressure transducer
Passive polarographic
cell
Range of Measurement
-5 to 45°C
0 to 1000 uS/cm
0 to 10,000 uS/cm
0 to 100,000 uS/cm

2 to 12 pH units
0 to 200 meters
0 to 10 mgOg/l
0 to 20 mg02/l
Temperature
Compensation
Not Required
Automatically
corrected to
25°C for
salinities up
to 35 ppt and
temperatures
between 0 and
45°C
standard
correction
0 to 45°C
Automatic
Automatic
0 to 45°C
Power Requirement: (Circulatory) 12 vdc.
Cable Length: 100 meters
Size: Length 53 cm, Diameter 17 cm
Weight: 7 kg
                45

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         TABLE B-6.   MARTEK:  MARK V DIGITAL WATER QUALITY ANALYZER
 Parameter
Method of Measurement
Range of Measurement
Temperature
Compensation
Temperature

PH
Conductivity
Dissolved
Oxygen
Thermo!inear array

Combination pH
electrode with
silver-silver
chloride
reference

Platinized nickel
electrodes
Polarographic
gold-silver
electrode
 -5 to 45°C

0 to 12 pH units
Not Required

Automatic
0 to 1000 uS/cm
     or
0 to 100 mS/cm

0 to 20 mgO£/l
Not Required
Automatic
with in
situ
stirrer
Power Required:  Regulated self-contained internal  rechargeable battery pack
with built in charging circuit, external  18-36 Vdc, or 105-125 Vac, (210-250
Vac), 50/60 Hz.

Cable Length:  50 meters

Size:  5.72 cm x 38.1  cm

Weight:  0.9 kg
                                    46

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                 TABLE B-7.   PLESSEY  ENVIRONMENTAL  SYSTEMS
                   MODEL 9400 TELEMETERING SENSOR SYSTEM
 Parameter
Method of Measurement
Range of Measurement
Temperature
Compensation
Temperature
Conductivity
Depth
    Platinum
    Resistance
    Transducer

    Inductive
    Coupling
    Technique
    Bonded
    Strain-gage
  -2 to 35°C
                                        0 to 60 mS/cm
  0 to 300 meters
  0 to 600 meters
  optional
Not Required
Automatic
temperature
and pressure
correction

Automatic
Power Required:  150-250 mA constant current at a minimum of 33 V dc plus
cable drop;equipped with strip chart recorder.

Cable Length:  300 meters (moored)
               600 meters (profiling)

Weight:  13.6 kg (in air)
           9.1 kg (in water)
  TABLE  B-8.   YELLOW SPRINGS  INSTRUMENTS:  MODEL 57  DISSOLVED OXYGEN  METER
  Parameter
 Method  of  Measurement
 Range  of Measurement
 Temperature
 Compensation
 Temperature

 Dissolved
 Oxygen
    Thermistor

    Polarographic
    electrode
    -5 to 45°C

    0-5 mg02/l
    0-10 mg02/l
    0-20
 Not Required

 Automatic
 from
 -5 to 45°C
 Power  Required:   Two  disposable  "C"  size carbon  zinc  batteries  (provide
 approximately  1000  hours  operation).

 Size:   21  x  27.5  x  9  cm

 Weight:   2.5 kg
 Cable  Length:   15 meters
                                      47

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                      TABLE  B-9.   BECKMAN  SELECT-MATE
Parameter
PH
Method of Measurement
Combination electrode
Range
0 -
of Measurement
14 pH
Power Required: 9 Volt battery operated (120/220V
Capability: Lab System Only
Size: 26 x 22 x 12 cm Weight: .

68 kg
units
Temperature
Compensation
Manual
- 50/60 Hz optional).

(1.5 Ibs)

TABLE B-10. ORION pH
METER

Parameter
pH
Method of Measurement
Combination electrode
Range
0 -
Power Required: 120 Vac, 50/60 Hz
Capability: Lab System Only
Size: 17 x 20 x 20 cm Weight: 2.
of Measurement
14 pH units
Temperature
Compensation
Manual
3 kg (5.1 Ibs)

             TABLE B-ll.  BECKMAN RS 7-C INDUCTION SALINOMETER
 Parameter
Method of Measurement
Range of Measurement
 Operating
Temperature
Salinity
The ratio of conduc-
tivities and salinity
is read directly from
tables, such as the
UNESCO International
Oceanographic tables.
  0 to 49 parts per
  thousand salinity
  0 to 40°C

Accuracy ±1°C
Power Requirement:  120 Vac, 50/60 Hz
Capability:  Moist sea atmosphere requirements of MIL-E-16400,  and shipboard
vibration MIL-STD-167 Type 1.

Size:  51 x 41  x 28 cm

Weight:   13.6 kg (30 Ibs)
                                     48

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                                  GLOSSARY
     The scope of this glossary is  limited  to  the  special area of knowledge
and word usage applicable to the text  of this  report.  The definitions and
terms were researched from the sources of information  listed at the end of the
Appendix.  Most definitions have been  quoted verbatim  from these references.


accuracy:  1.  The extent to which  the results of  a  calculation or the
     readings of an instrument approach the true values  of the calculated or
     measured quantities, and are free from error.   2.   Conforming exactly to
     truth or to a standard.  3.  When applied to  methods of analysis, a mea-
     sure of the error of a method  may be expressed  as a comparison of the
     amount of element or compound  determined  or recovered by the test method
     and the amount actually present.

analog:  Pertaining to data in the  form of continuously  variable  physical
     quantities.

automatic data processing (ADP):  The  utilization  of electronic  data
     processing equipment (computer) to perform any  variety  of tasks  involving
     informational data.
baseline:  A main line taken as or representing a base.   The point or li
     from which a start is made in an action or undertaking.
ne
baseline assessment survey:  The planned sampling or measurement of parameters
     at set stations or in set areas in and near disposal  sites for a  period
     of time sufficient to provide synoptic data for determining water quality,
     benthic, or biological conditions as a result of ocean disposal  opera-
     tions.

benthic:  That portion of the marine environment inhabited by marine organisms
     which live permanently in or on the bottom.

buffer:  A solution selected or prepared to minimize changes in hydrogen ion
     concentration which would otherwise occur as a result of a chemical
     reaction.

calibrated accuracy:  When applied to methods of analysis, the difference
     between the indicated parameter value and its accepted value (known
     value); determined by calibrating an uncontaminated sensor in the mea-
     suring system.

calibration:  1.  To determine, by measurement or comparison with a standard,
     the correct value of each scale reading on a meter or other device, or
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     the correct value for each setting of a control knob.  2.  To determine
     the settings of the control devices so that a system will operate or
     perform within certain limits.  3.  Periodic standardizations of equip-
     ment and instruments.

cation:  A positively charged atom or group of atoms, or a radical, which
     moves to the negative pole (cathode) during electrolysis.

coastal waters:  Ocean waters seaward to the territorial limits and waters
     along the coastline (including inland streams) that are influenced by
     the rise and fall of the tide.

conductivity:  Measure of the ability of a solution to carry electrical cur-
     rent and thus, a measure of ion concentration in water.  High ion concen-
     trations may render water unpalatable or even toxic to plants and animals.

continuous profiler:  As applied to water quality measuring systems,  implies a
     system that makes uninterrupted measurements of parameters as a  function
     of the sensor package depth.

criteria:  A standard on which a judgment or decision may be based.  (See
     standard,)

data:  Any representations, such as characters  or analog quantities,  to which
     meaning might be assigned.

data acquisition:  The phase of data handling that begins with the sensing of
     variables and ends with a magnetic recording or other record of  raw data;
     may include a complete radio telemetering  link.

data base:   A collection  of information in machine-readable form.

data processing (information processing):   Any  operation or combination of
     operations on data,  including everything that happens to  data from the
     time they are observed or collected to the time  they are  destroyed.

digital:  Relating to calculation by numerical  methods  or by discrete units.

dissolved oxygen (DO):   The oxygen in  sewage, water,  or other  liquid  usually
     expressed in parts  per million (ppm).   Oxygen has  a low solubility in and
     is nonreactive with  water.   Its solubility is  dependent on water  temper-
     ature  and partial  pressure  in accordance with Henry's Gas  Law.   Because
     of this  temperature  dependence,  DO tends to  be critical during periods  of
     high temperatures  since oxygen solubility  is at  a  minimum  while  biologi-
     cal  activity,  and  its  corresponding oxygen demand,  is at  a peak.   Dis-
     solved  oxygen  is one of the  key parameters in  assessing the  quality  or
     degree  of pollution  in water.   Its  measurement is  required for waste
     water  treatment,  fisheries  research,  baseline  studies,  and enforcement
     monitoring.

Eh:  The  redox  potential measured  in millivolts.   Positive values  indicate the
     presence  of surplus oxygen.   Negative  voltage  indicates a  reducing envi-
     ronment,  most  commonly caused  by  the  presence  of sulfides.   (See  redox
     potential.)                      5Q

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electrode:  The conductor by which  current  enters and leaves an electrolyte
     when subjected to an externally  impressed  potential .

electrolyte:  Any substance which,  in solution  or fused, exists as electri-
     cally charged ions that make the liquid  capable of  conducting a  current.
     Seawater is an electrolyte.

electronic data processing (EDP):   Processing data  by equipment that  is  pre-
     dominantly electronic in nature, such  as an  electronic  digital computer.

error:  1.  Any discrepancy between a computed, observed,  or measured quantity
     and the true, specified, or theoretically correct  value of that  quantity.
     2.  Error of measurement may be systematic or  accidental.  Accidental
     errors are slight variations that occur  in successive measurements  by  the
     same observer.  Causes are generally intangible.   They  may follow the  law
     of chance.

GEOSECS:  The acronym for Geochemical Ocean Sections,one of  the major programs
     of the International Decade of Ocean Exploration,  a multinational cooper-
     ative study of the world oceans during the period  1970-1980.

hysteresis:  An effect, involving energy loss, found to varying degrees  in
     magnetic, electric, and elastic media when they are subjected to varia-
     tion by a cyclical applied force.

in situ:  1.  In the original location (in the environment).  2.   In  the
     natural or original position.

in situ system:  Typically, seawater sampling equipment and  various analytical
     instruments which measure various parameters while on station.  The data
     from the instruments are displayed in real time on strip chart analog
     recorders, and the same data are digitized on magnetic  tape  for subse-
     quent  computer analysis.  (See  pump-thru-system.)

in vitro:   Pertaining  to a  biological reaction taking place  in an artifical
     apparatus  (in glass or  in a test tube,  beaker, etc.).

in vivo:  Pertaining to a  biological reaction taking place in a living cell or
     organism.

ion:   Electrically charged  atom or group of  atoms.

linearity:  The maximum  deviation  between  an actual instrument reading and the
     reading  predicted by  drawing  a  straight line  between the upper and lower
     calibration  points.

mariculture:   The  cultivation  of marine organisms  by exploiting their natural
     environment.

marine:   Pertaining to the sea.

measurement:   The  process  of determining the value of  some  quantity  in  terms
      of a standard  unit.
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meter sensitivity:  The accuracy with which a meter can measure a  voltage,
     current, resistance, or other quantity.

metrology:  The science of measurement.

monitoring:  1.  The act of observing and recording laboratory and field
     environment test conditions, test specimen responses,  and performance
     parameters.  2.  The acquisition of data at approximately the same loca-
     tion and at some fixed frequency.  (See  measurement.)

monitoring station:  Particular point at which representative samples  of  a
     body of water are collected periodically.

multiparameter capability:  Ability to measure several  constituents simul-
     taneously.

nutrients:  Substances essential to bacterial growth and function.  Chief
     among these are carbon, nitrogen, phosphorus,  and  sulfur, but a number  of
     trace elements have been shown to be essential  to  growth (K,  Ca,  Mg,  Fe,
     Mn, Zn, Co, Cu, and Mo).

ocean instruments:  Devices which measure parameters of the  marine environ-
     ment, including oceans, estuaries, large fresh water bodies,  the  air
     directly above these waters, and the sea floor below.

ocean:  Those waters of the open seas lying seaward of  the baseline from  which
     the territorial sea is measured, as provided  for in the Convention on the
     Territorial Sea and the Contiguous Zone.

ocean water:  Water having between 20,000 and 40,000 mg/1  dissolved material
     whose ionic ratios correspond closely to those specified in "Standard
     Specification for Substitute Ocean Water," ASTM Method  D1141-52 (1971).

operational:  Ready for or in condition to undertake a  destined function.

oxidation reduction potential (ORP):   See redox.

parameter:  A measurable biological,  chemical, or  physical characteristic,
     e.g., temperature, pressure, currents, etc.,  the size of sediment grains
     or fish.

parts per million (ppm):  A ratio of pounds per million pounds, grams  per
     million grams, etc.  Approximately equal  to milligrams  per liter, expres-
     sing the concentration of a specified component.

pH (Hydrogen Ion Concentration):  A term used to describe the hydrogen-ion
     activity of a system.  The pH of a solution is defined  as the negative
     logarithm of hydrogen ion concentration, and  is thus an expression of the
     acid or alkaline character of the solution.   A solution of pH 0 to 7 is
     acid, pH of 7 is neutral, pH over 7 to 14 is  alkaline.   pH is of  major
     importance in dealing with treatment of  water  and  wastewater  since it
     affects taste, corrosivity, chemical  reactions and biological  activity.
     Since certain wastes tend to be  strongly acidic or basic, sharp changes
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      or extremes  of pH may  indicate the presence of pollution in receiving
      waters.

physical parameter:   Most  common,  nonchemical characteristics of water,
      including color,  specific  conductance, threshold odors, turbidity, and
      dissolved and  suspended  solids.

pollution:  The addition of  sewage,  industrial waste, or other harmful or
      objectionable  material to  water  at a concentration or in sufficient
      quantity to  result  in  measurable degradation of water quality.

precision:  1.  The  quality  of being exactly or  sharply defined or stated.
      2.  The  degree of refinement with which an operation is performed or a
      measurement  stated.  3.  Adapted for extremely accurate measurements.
      4.  Held to  low tolerance  in manufacture.  5.  When applied to methods
      of analysis, a measure of  the  reproducibility of a method when repeated
      on a homogeneous sample  under  controlled conditions, regardless  of
      whether  or not the  observed  values are widely displaced from the true
      values as a  result  of  systematic or  constant errors present throughout
      the measurements.   Precision can be  expressed by the standard deviation.
      6.  Narrowness of limits within  which one  may assume true value  of
      measured quantity—the narrower  the  limits, the better the precision.

prototype:  A model  suitable for use in complete evaluation of  form, design,
      and performance.

pump-thru-system:   Typically water is  pumped  from  known depths  to the  ship's
      deck, where it is conducted to instruments which measure  salinity,
      temperature, dissolved oxygen,  pH.   In  situ  sensors  measure  pump depth,
      temperature, and submarine light transmission.   {See vertical profile.)

quality assurance:  Testing  and  inspecting all of  or a portion  of the  final
      product to ensure that the desired quality level of  product reaches  the
      customer.

quasi:  Having some resemblance.

random error:  An error that can be  predicted  only on a statistical basis.
      (See error.)

range:  1.  The difference between the maximum and minimum of a variable
      quantity.  2.   When applied to methods  of  analysis, the difference
      between the smallest and largest of  n observations  is also closely
      related to the standard  deviation.

reagent:  A substance, chemical  or solution used in the laboratory to  detect,
      measure, or otherwise examine  other  substances,  chemicals, or solutions.

redox potential:  Voltage difference at an inert electrode  immersed in a
      reversible oxidation-reduction system;  measurement  of  the state  of  oxi-
      dation  of the system.   Also known as oxidation-reduction  potential
      (ORP).   (See  Eh.)

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 reliability:  1.  The probability that a component part,  equipment,  or  system
      will satisfactorily perform its intended function under  given circum-
      stances, such as environmental  conditions,  limitations as  to operating
      time, and frequency and thoroughness of maintenance  for  a  specified
      period of time.   2.  The amount of credence placed in  a  result.  3.  The
      precision of a measurement, as  measured by  the variance  of repeated mea-
      surements of the same object.

 repeatability:  The degree to which  an instrument or technique  provides the
      same result when exposed to identical  input conditions.

 replicate:  One of several  identical  experiments,  procedures, or samples.

 rosette type sampler:  A water sampling device consisting of  a  group of six or
      more cylinders arranged in a circular  or rose pattern frequently equipped
      with a sensor package  for making simultaneous measurements.  Used to
      obtain multiple  samples on a single cast.

 representative sample:   Water sample  whose  measured  values are  characteristic
      of the body of water from which  the sample  has  been taken.

 reversing thermometer:   A mercury-in-glass  thermometer  which  records tempera-
      ture upon being  inverted and thereafter  retains its reading until
      returned to the  first  position.

 salinity:   Total  amount  of  dissolved  salts  (°/00)  in seawater; commonly the
      dominant factor  controlling density of seawater.   The measurement of
      salinity (and  temperature)  can be  used in the open ocean as tags to
      identify water masses  as  they spread laterally between other masses,  or
      move  along  the ocean floor.

 sampling:   Obtaining  small  representative quantities of materials for analysis.

 seawater:   The water  of  the  seas, distinguished from fresh water by its
      appreciable  salinity.   The distinction between the usage  of salt water
      and seawater is  not very  sharply drawn.  Commonly, seawater is  used as
      the antithesis of specific types of fresh water, as river water, lake
      water, rainwater, etc ., whereas salt water is merely the antithesis  of
      fresh water  in general.

sensitivity:  The ability of the output of a device, system, or  organism to
      respond to an input stimulus.   Mathematically, the ratio  of the  response
     or change induced in the output  to a stimulus or change in  the  input.
     The degree to which a substance  can be detected in the  presence  of  inter-
      fering components which have properties differing  only  very sliqhtly
     from those of the substance.

sensor (primary detector; sensing element}:   The  generic name  for a device
     that senses either the  absolute  value or a change  in a  physical  quantity
     such as temperature, pressure,  flow rate, or pH, or the intensity of
     light, sound or radio waves and  converts  that change  into a useful  input
     signal for an information-gathering system;   a television camera  is
     therefore a sensor,  and a transducer is a special  type of sensor.
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stability:  The measure of the length of time a measuring system,  once  cali-
     brated, continues to measure the actual  parameter value within  the cali-
     brated _ accuracy without the need for readjustment or recalibration.
     Stability performance is based upon the  measurement of standard cali-
     brating solutions with an uncontaminated sensor.

standard:   1.  An accepted reference sample used for establishing  a  unit for
     the measurement of a physical  quantity.   2.  Constituting or  affording
     a standard for comparison or judgment.

Standard Seawater (normal water):  Water whose chlorinity lies between  19.30
     and 19.50 parts per thousand,  determined to within ±0.001 per thousand,
     which  is used to calibrate or  standardize salinity measuring  devices or
     methods.

standardization:  1.  The adoption  of generally accepted uniform procedures,
     dimensions, materials, or parts that directly affect the design of a
     product or a facility.  2.  The process  of establishing by common  agree-
     ment engineering criteria, terms, principles, practices, materials, items,
     processes, and equipment parts and components.

standardized product:  A product that conforms to specifications resulting
     from the same technical  requirements.

STD (salinity-temperature, depth recorder):  An instrument for continuously
     measuring the temperature, electrical  conductivity, and depth.   It auto-
     matically determines water salinity from the temperature-conductivity-
     salinity relationships.

synoptic:  In general, pertaining to or affording an overall  view.

system reliability:  The probability that a system will  accurately perform  its
     specified task under stated environmental conditions.  (See reliability.)

thermistor:  A resistive circuit component, having a high negative temperature
     coefficient of resistance, so  that its resistance decreases as  the tem-
     perature increases; a stable,  compact, and rugged two-terminal  ceramic-
     like semiconductor bead, rod,  or disk.

titration:  A method of analyzing the composition of a solution by adding
     known amounts of a standardized solution until a  given reaction (color
     change, precipitation, or conductivity change) is produced.

transient response:  Rate at which  a system responds to a step change.

transmissometer:  A light-path device for measuring attenuation of light in
     water due to scattering and absorption.

turbidimeter:  An instrument for measurement  of turbidity, in which a standard
     suspension usually is used for reference.

turbidity:  1.   The property in water that inhibits light penetration.   Tur-
     bidity is caused by suspended  and colloidal matter, either from natural
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     erosion or industrial  and domestic waste.   2.   Highly turbid water may
     contain large amounts  of organic material  acting as food for microbes,
     producing further growth and, consequently, increasing turbidity.

validation:  The act of testing for compliance  with a standard.

vertical  profile:  A graphical representation whose ordinate shows the  varia-
     tion of some oceanographic quantity along  a straight line against  hori-
     zontal distance on this line as abscissa.
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