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Ref. No. [UMCES] CBL 2016-013
ACT VS16-04
28
RESULTS of MOORED FIELD TESTS
Moored field tests were conducted to examine the performance of the HOBO U26 RDO to
consistently track natural changes in dissolved oxygen over extended deployment durations of 11-
18 weeks. In addition, field tests examined the reliability of the instrument, i.e., the ability to
maintain integrity or stability of data collection over time. Reliability was determined by
quantifying the percent of expected data that was recovered and useable. The performance of the
HOBO was examined in three separate field deployment tests at various ACT Partner sites to
include a range of biogeochemical conditions. The range and mean for temperature and salinity for
each test site is presented in Table 4. The final reference temperature data was computed from the
mean of two RBR thermistors and a SeaBird SBE that were mounted at the same sampling depth
as the test instrument. Immediately before each deployment the HOBO was exposed to a
laboratory reference tank for 3-4 measurements to confirm good working status and provide an
initial offset against its latest calibration (Table 5). In all cases the HOBO was calibrated by ACT
personnel according to manufacturer instructions just prior to the pre-deployment check.
Table 4
. Range and average for temperature, and salinity at each of the test sites during the sensor field
deployments. Temperature and salinity were measured by at least 2 RBR temperature loggers and a
SeaBird SBE 26 (or SBE26plus) mounted on the instrument rack for the duration of the deployment.
SITE
(deployment period/duration)
Temperature
°
C )
Salinity
Keweenaw Waterway
Min.
0.04
0.00
9Jan – 22Apr
Max.
5.2
0.01
(n = 104 days)
Mean
0.7
0.01
Chesapeake Bay
Min.
19.3
4.7
20May – 5Aug
Max.
36.7
13.7
(n = 78 days)
Mean
25.6
10.9
Kaneohe Bay
Min.
23.1
27.3
24Sep – 21Jan
Max.
29.1
34.7
(n = 121 days)
Mean
25.8
33.4
Table 5.
Results of the pre-deployment check for the HOBO U26 for each deployment site. The DO of the
reference solution is based on the mean of three Winkler titrations of the reference tank during the exposure.
Ambient water was used for the reference solution at each deployment site.
Deployment Site
Reference
Solution
Measurement
Temperature
Reference Solution
DO (mg/L)
Instrument
DO (mg/L)
MTU
Site Water
11.7
o
C
10.193
10.67
CBL
Site Water
21.6
o
C
7.983
8.17
HIMB
Site Water
26.6
o
C
6.547
6.71