THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
&EPA
U.S. Environmental Protection Agency
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ETV Joint Verification Statement
TECHNOLOGY TYPE:
MULTI-PARAMETER WATER QUALITY PROBE
APPLICATION:
MEASURING WATER QUALITY
TECHNOLOGY NAME:
Ocean Seven 316
COMPANY:
General Oceanics, Inc.
ADDRESS:
1295 N. W. 163d Street PHONE: 305-621-2882
Miami, FL 33169 FAX: 305-621-1710
WEB SITE:
E-MAIL:
http://www.GeneralOceanics.com
sales@GeneralOceanics.com
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology Verification (ETV)
Program to facilitate the deployment of innovative or improved environmental technologies through
performance verification and dissemination of information. The goal of the ETV Program is to further
environmental protection by substantially accelerating the acceptance and use of improved and cost-effective
technologies. ETV seeks to achieve this goal by providing high-quality, peer-reviewed data on technology
performance to those involved in the design, distribution, financing, permitting, purchase, and use of
environmental technologies.
ETV works in partnership with recognized standards and testing organizations; with stakeholder groups,
consisting of buyers, vendor organizations, and permitters; and with the full participation of individual
technology developers. The program evaluates the performance of innovative technologies by developing test
plans that are responsive to the needs of stakeholders, conducting field or laboratory tests (as appropriate),
collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are conducted in accordance
with rigorous quality assurance (QA) protocols to ensure that data of known and adequate quality are generated
and that the results are defensible.
The Advanced Monitoring Systems (AMS) Center, one of seven technology areas under ETV, is operated by
Battelle in cooperation with EPA's National Exposure Research Laboratory. The AMS Center has recently
evaluated the performance of multi-parameter water probes. This verification statement provides a summary of
the test results for the General Oceanics, Inc., Ocean Seven 316 water probe.

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VERIFICATION TEST DESCRIPTION
The Ocean Seven 316 was evaluated by comparing pre- and post-calibration results and their measurements with
standard reference measurements and handheld calibrated probes. The Ocean Seven 316 was deployed in
saltwater, freshwater, and laboratory environments near Charleston, South Carolina, during a 2 '/2-month
verification test. Water quality parameters were measured both by two Ocean Seven 316s and by reference
measurements consisting of field-portable instrumentation and water analyses of collected water samples. During
each phase, performance was assessed in terms of pre- and post-calibration results, relative bias, precision,
linearity, and inter-unit reproducibility. The saltwater site was at the National Oceanic and Atmospheric
Adminstration (NOAA) Pier Romeo on the Cooper River, the freshwater site was at Lake Edmunds,
approximately one mile from the NOAA Center for Coastal Environmental Health and Biomolecular Research
(CCEHBR), and the controlled site was the CCEHBR mesocosm facility in Charleston, South Carolina. Test
parameters included dissolved oxygen (DO), conductivity, temperature, pH, and turbidity.
Saltwater testing was conducted at two locations. The original location was in a small tidal creek tributary of the
Charleston Harbor. However, due to structural problems at that site, the probes were redeployed at the NOAA
Pier Romeo on the Cooper River. Pre- and post-calibration data obtained at the first location are presented in the
verification report; however, no reference data from that location are presented. The saltwater test lasted for 31
days, during which time the Ocean Seven 316s monitored the naturally occurring range of the target parameters,
collecting data every 15 minutes, 24 hours a day, except on days when the probes were in the laboratory for pre-
and post-calibration checks. Reference sample collection times were rotated among the morning, afternoon, and
evening hours throughout the test. More intense sampling occurred at the beginning (Days 1 and 2) and the end
(Days 29 and 30) of the sampling period when samples were taken at 15-minute intervals for eight hours, except
on Day 29, when only four hours of sampling occurred because of weather conditions. For the duration of the
saltwater test, the Ocean Seven 316s were deployed at depths between approximately three and 10 feet, varying
according to the tide. Freshwater testing was conducted at Lake Edmunds. Because this site is shallower than the
Cooper River, only one depth (approximately 3 feet) was used; however, the same sample collection schedule
was followed. As in the saltwater portion of the verification test, the Ocean Seven 316s monitored the naturally
occurring target parameters, while simultaneous reference measurements were made, again rotating among
collection times. More intense sampling occurred at the beginning (Day 3) and the end (Day 23) of the sampling
period, when samples were taken at 15- to 30-minute intervals for periods ranging between six and eight hours,
as weather permitted. The third, and final, stage of testing occurred at the CCEHBR mesocosm facility. The
mesocosm tanks were filled with saltwater/freshwater and drained daily, simulating a tide. Water samples were
collected during each test day throughout the normal operating hours of the facility (nominally 6 a.m. to 6 p.m.).
During this period, the mesocosm was manipulated to introduce variations in the measured parameters. The
turbidity of the system was varied by operating a pump near the sediment trays to suspend additional solids in
the water. Conductivity was varied by adding freshwater to the saltwater during one of the fill-and-drain cycles.
Variations in temperature, pH, and DO were driven by natural forces and the changes in the other test
parameters. Over all three sampling periods, approximately 6,000 data points were collected by the Ocean Seven
316s, and 132 sets of reference measurements were obtained.
QA oversight of verification testing was provided by Battelle. Battelle QA staff conducted a technical systems
audit, a performance evaluation audit, and a data quality audit of 10% of the test data.

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TECHNOLOGY DESCRIPTION
The following description of the Ocean Seven 316 was provided by the vendor and does not represent verified
information. The 16-bit, multi-parameter Ocean Seven 316 is available with two diameters: 100 millimeters (mm)
and 75 mm. The measurement sensors have time constants of 50 milliseconds (ms) for physical parameters and
3 seconds (s) for chemical parameters. A high-precision resistor acts as a reference for the accuracy of the sensor
electronic amplifiers. This resistor has a thermal drift of 1 part per million/°C and is temperature-compensated.
The Ocean Seven 316 is microprocessor-controlled and can measure, store, and transmit sensor data. For real-
time data acquisition, the Ocean Seven 316 operates unattended, and data are uploaded at the end of the
measuring cycle. An automatic power management procedure switches the Ocean Seven 316 off between the
data acquisitions. The internal battery package consists of 10 batteries that allow the Ocean Seven 316 to operate
continuously for about 20 hours. The Ocean Seven 316 can be equipped with an external battery package that
greatly extends operation time. The Ocean Seven 316 stores up to 32,000 data sets and is equipped with sensors
to measure pressure, temperature, conductivity, salinity, oxygen, pH, and oxidation-reduction potential. Salinity
is automatically calculated from conductivity, temperature, and pressure values.
VERIFICATION OF PERFORMANCE
Pre-and post-calibration results: Pre-and post-calibration tests were performed for pH, DO, and conductivity
since only those parameters are adjusted during calibration. The results showed that pH measurement values
were accurate within a range of 99 to 108% of the true values, DO measurement values were accurate within a
range of 82 to 105% of the true values, and conductivity measurement values were accurate within a range of 94
to 104% of the true values.
Relative bias: A summary of the average relative bias for each deployment setting is provided in the table
below. The temperature biases were less than or equal to 0.11% for all deployment settings. Conductivity, pH
(reported as H+ concentration), and DO biases were between 2 and 36% for both units under all deployment
settings. The conductivity bias was consistently positive, indicating that generally, the Ocean Seven 316s reported
a higher conductivity than the handheld reference probe. The DO bias was consistently negative for each
deployment setting. The bias for turbidity ranged between -44% and 420%.


Saltwater
Freshwater
Mesocosm


% Rel. Bias
% Rel. Bias
% Rel. Bias
% Rel. Bias
% Rel. Bias
% Rel. Bias
Parameter
Units
GO Probe #1
GO Probe #2
GO Probe #1
GO Probe #2
GO Probe #1
GO Probe #2
Temperature
K
-0.09
-0.06
-0.11
-0.03
-0.07
-0.09
Conductivity
mS/cm
21.5
10.6
9.21
15.1
2.62
1.96
DO
mg/L
-21.9
-24.8
-28.6
-20.4
-6.19
-15.3
H+
mol/L
28.2
28.8
35.5
-23.9
-20.3
-31.2
Turbidity
NTU
269
-43.9
318
420
146
111
Precision: Precision was determined during the mesocosm deployments and is reported as percent relative
standard deviation (%RSD). The %RSD values were lowest for pH and temperature, ranging between 0.02%RSD
and 0.07%RSD. Precision for conductivity was 1.08%RSD and 1.07%RSD for the two Ocean Seven 316s.
Precision values were not determined for DO or turbidity because data from stable periods of operation were not
available for analysis.
Linearity: Linearity was assessed by comparing probe readings against the reference values for each of the
parameters at each deployment location. The table below provides the results of this comparison by showing the
slope, intercept, and coefficient of determination (r2) at each site for the Ocean Seven 316. Linearity was highest
for conductivity and temperature, with a strong correlation for most of the parameters during mesocosm
deployment, with most r2 values greater than 0.84.

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GO
Probe # Parameter
Saltwater
Freshwater
Mesocosm
Slope
Intercept
r2
Slope
Intercept
r2
Slope
Intercept

1
Temp
0.93
20.49
0.85
0.96
10.92
0.99
0.97
9.35
0.98
2
Temp
0.94
18.47
0.86
0.91
28.11
0.91
0.85
45.84
0.95
1
Cond
1.17
-1.59
0.92
1.23
-0.05
0.93
1.05
-0.08
0.99
2
Cond
1.17
-1.55
0.92
1.19
-0.01
0.93
1.04
-0.09
1.00
1
DO
0.16
3.15
0.06
0.67
0.33
0.66
0.97
-0.22
0.56
2
DO
0.36
1.95
0.12
0.82
-0.10
0.92
0.63
1.39
0.66
1
pH
0.94
0.00
0.55
0.26
0.00
0.53
0.62
0.00
0.88
2
pH
0.94
0.00
0.55
0.48
0.00
0.78
0.62
0.00
0.84
1
Turb
0.63
7.67
0.05
2.64
10.18
0.14
1.05
5.88
0.88
2
Turb
0.49
0.43
0.12
4.86
0.21
0.32
1.09
5.42
0.85
Inter-unit reproducibility: Analysis of inter-unit reproducibility, presented in the table below, showed that the
average difference in temperature readings between the two Ocean Seven 316s tested was 0.08°C, over a range
of 24 to 34°C. The difference in conductivity averaged 0.04 mS/cm over a range of 0.3 to 44 mS/cm. Analysis of
inter-unit reproducibility showed that the average difference in readings for DO was 0.55 mg/L, while the Ocean
Seven 316 DO readings varied from 3 to 15 mg/L. The average difference in pH readings was 0.12 over a range
of 6.8 to 8.7. The average difference in turbidity readings was 8.96 NTU, while the actual turbidity measurement
ranged from 0 to 197 NTU. The magnitude of the inter-unit reproducibility results was affected by spatial and
temporal changes in the sampling environment. For example, the Ocean Seven 316s were sampling in an
environment that was changing 8°C over a 24-hour period. Because the Ocean Seven 316s were not sampling in
exactly the same location, differences in temperature, caused by the 24-hour fluctuations, resulted in some
difference in measurement by the Ocean Seven 316s. Similar behavior occurs in any location that experiences
dynamic changes in the environment. The comparison of relative bias (as described above) is also a measure of
inter-unit reproducibility. The relative biases of the two Ocean Seven 316s were comparable for temperature,
DO, and conductivity, but showed larger differences for pH (freshwater only) and turbidity.

Average Difference between GO Probe #1 and GO Probe #2


Temperature
Conductivity
DO

Turbidity
Location
°C
(mS/cm)
(mg/L)
DH
(NTU)
Saltwater
0.01
0.10
0.34
0.07
8.18
Freshwater
0.11
0.02
0.60
0.24
17.67
Mesocosm
0.13
0.01
0.71
0.06
1.02
Average
0.08
0.04
0.55
0.12
8.96

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Other factors: The probes were set up to collect data with minimal difficulty, and data were downloaded
without incident using the provided data cable and a Windows-based PC. The Ocean Seven 316s verified in this
test cost $15,000 per unit.
original signed bv Gabor J. Kovacs 3/21/03
Gabor J. Kovacs	Date
Vice President
Environmental Sector
Battelle
original signed bv Gary J. Foley	4/29/03
Gary J. Foley	Date
Director
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
NOTICE: ETV verifications are based on an evaluation of technology performance under specific, predetermined
criteria and the appropriate quality assurance procedures. EPA and Battelle make no expressed or implied
warranties as to the performance of the technology and do not certify that a technology will always operate as
verified. The end user is solely responsible for complying with any and all applicable federal, state, and local
requirements. Mention of commercial product names does not imply endorsement.

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