14 / 57
Ref. No. [UMCES] CBL 2015-010
ACT VS15-03
supplied the cell warmer. Past experience at Byrne’s lab has shown that this system can
maintain cells at a constant temperature within ± 0.1
o
C or better. After the initial dye reading,
the sample was re-blanked and then a second 10 µl aliquot of dye was added and the R-ratio re-
measured to enable a correction for the effect of the dye addition on the sample pH. By
performing the perturbation measurement on each sample we could directly calculate the
appropriate adjustment for each sample individually. The final temperature of the solution in the
cuvette was measured with a bead thermistor upon completion of the second dye reading and
recorded on the datasheets to define any deviation from the specified reading temperature.
In addition, at the freshwater site an unpreserved sample collected in a 300 ml BOD
bottle was incubated at the same temperature as the equilibration chamber and cell jacket until it
reached a constant temperature of 25°C, and the pH was subsequently read on a recent two-point
calibrated Metrohm electrode. The electrode was calibrated daily at 25.0
o
C.
After each use the Van Dorn sampler, fill tubing and cuvettes were thoroughly rinsed
with deionized water to prevent any build-up of salts or dye.
Ancillary Environmental Data
- At each of the mooring test sites, two calibrated CTD packages
were attached to the test rack and positioned to best characterize the salinity surrounding the
mooring. The CTDs provided an independent record of conductivity and temperature measured
at 15 minute intervals. In addition, four RBR Solo temperature sensors were deployed at each
site to establish an accurate temperature history for the site. The RBR sensor has a stated
accuracy and resolution of 0.002°C and 0.00005°C respectively. In conjunction with each water
sample collection, technicians recorded basic site-specific conditions on standardized log sheets
including: date and time, weather conditions (e.g., haze, % cloud cover, rain, wind
speed/direction), air temperature, recent large weather events or other potential natural or
anthropogenic disturbances, tidal state and distance from bottom of sensor rack, and any obvious
problems or failures with the instruments. Datasheets were transmitted on a weekly basis to the
ACT Chief Scientist for data archiving and ACT personnel performance QA/QC.
Each test site either established or identified the closest meteorological station (and river
discharge gauge where appropriate) that could record air temperature, humidity, directional wind
speed, precipitation on a continuous basis to help identify the timing and intensity of any event
based changes at the field test locations.
Ancillary data was used in a qualitative sense to understand the history of weather
patterns and changes in ambient water quality conditions. These data were not used for any
direct calibration, correction, or statistical comparison to the reported salinity test data.
14