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Ref. No. [UMCES] CBL 2015-011
ACT VS15-04
4
standard deviation of the differences between the Troll 9500 and reference pH during its
operational period was 0.10 ±0.01 (N=10), with a total range of 0.09 to 0.11.
At Chesapeake Bay the field deployment test was conducted over 30 days with a mean
temperature and salinity of 5.9
o
C and 12.8. The measured pH range from our 107 discrete
reference samples was 8.024 – 8.403. The Troll 9500 operated continuously over the entire 30
day deployment and generated 2756 observations; however after the first six hours a significant
measurement deviation occurred and continued throughout the test. Only the first 26 instrument
measurements and only one matched reference sample pair were considered useable. Ambient
pH measured by the Troll 9500 over the first six hours ranged from 8.34 to 8.82. The first
sampling pair from March 12
th
had a difference from the reference pH of -0.002 indicating the
probe was in good operating condition at the time of deployment. No summary statistics are
calculated for the remaining deployment.
At Lake Michigan the field deployment test was conducted over 29 days with a mean
temperature and salinity of 21.2
o
C and 0.03. The measured ambient pH range from our 98
discrete reference samples was 8.013 to 8.526. The Troll 9500 operated continuously over the
29 days of the deployment and generated 2673 observations with a measured range in ambient
pH from 8.24 to 9.57. The average and standard deviation of the difference between the Troll
9500 and reference pH for the entire deployment was 0.60 ± 0.15 with a total range of 0.27 to
0.90.
It is unfortunate that internal malfunctions occurred at three of the four field test sites
since the sonde appeared to working very well upon initial deployment. As noted by the
successful Great Lakes deployment, the continuous 15 – 30 minute time-series provided by the
test instrument was able to resolve a significantly greater dynamic range and temporal resolution
than could be obtained from discrete reference samples. Continuous in situ monitoring
technologies, such as the Troll 9500, provide critical research and monitoring capabilities for
helping to understand and manage important environmental processes such as carbonate
chemistry and ocean acidification, as well as numerous other environmental or industrial
applications.