Ref. No. [UMCES]CBL 2013-018
ACT VS12-04
A summary of the physical and water quality conditions experienced over the duration of
the moored deployment are presented in Table 3. Water temperature ranged from 25.3 to 29.4
°C and salinity varied from 3.9 to 9.9. Chlorophyll and CDOM are quite high at this location
and can contribute significantly to the fluorescent properties of the ambient seawater.
Table 3.
Ancillary physical and water quality conditions for the moored field deployment test conducted
in Winans Cove, Baltimore Harbor, Baltimore, MD.
Site
Temperature
(
o
C)
Salinity
Chlorophyll
(µg/L)
CDOM
Turbidity
(NTU)
Baltimore
Harbor
Min
25.3
3.9
2.6
1.17
1.3
Max
29.4
9.9
44.8
2.48
6.0
Mean
27.0
8.2
16.6
1.52
3.0
The time series response of the Hach FP 360 sc during the moored deployment in
Baltimore Harbor is shown in Figure 8. During the deployment 33 discrete reference samples
were collected and analyzed for hydrocarbon. Only three samples, one on 8/22 and two on 8/24
had any detectable level of hydrocarbons as analyzed by TestAmerica using GC-FID. The
instrument response was relatively consistent over the deployment, averaging approximately 400
ppb Oil during the initial few days and 600 ppb Oil during the two week re-deployment period.
Four notable excursions from background levels occurred during the time series and one of these
(detected value of 1000 ppb Oil) matched up with positive detection level in the reference
sample (35 ppb) (Fig. 10, panel A). There was no apparent tracking of instrument response to
variation in temperature or salinity (Fig. 8, panel B), or with chlorophyll, CDOM, or Turbidity
despite substantial variation in these parameters (Table 3 and Fig. 8, panel C).
Representative EEM fluorescent maps for reference samples collected on five different
dates are shown in figure 9. EEM characteristics were fairly consistent over time and
fluorescence intensity maxima are quite offset from the optical window range of the filter set.
The average EEM
QSE
for the reference samples yielding non-detects was 1401.1 (± 60.5) cps
while EEM
QSE
for the two 25 and 35 ppb reported TPH detects were 1418.4, 1419.5 and 1482.9
cps respectively, higher, but within the environmental range observed during this deployment.
The Hach FP 360 sc response averaged 469.3 (± 23.1) ppb Oil during non-detect periods and
469.3, 498.3 and 980.9 ppb Oil at the 25 ppb and 35 ppb reported TPH detects. Therefore in
these particularly natural waters the FP 360 sc began to detect ambient oil contamination at
levels above 35 ppb TPH.
The FP 360 sc response was plotted against the TPH results by GC-FID (Fig. 10, panel
A) and against the corresponding EEM
QSE
intensities from the same reference samples (Fig. 10,
panel B). On one of the two occasions where detectable TPH concentrations were observed in
the reference samples the instrument response increased from a background of approximately
469 ppb Oil to 981 ppb Oil. While the instrument response clearly had a linear relationship with
EEM
QSE
intensities of the reference samples (Fig. 10, panel B) the reference sample with the 35
ppb detectable TPH did not actually give the highest EEM
QSE
intensity. It is unclear what other
factors might have contributed to the unexpectedly high response, or if the intensity level of the
positive reference sample was biased in any way.
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