Ref. No. [UMCES]CBL 2013-021
ACT VS12-05
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 FLCDRTD fluorometer 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 ranged from 820 to 1250 counts over the deployment period and appeared to
co-vary with salinity and/or temperature as noted by similar periodicity (Fig. 8, panel B). The
most notable excursion occurred during a corresponding sharp decline in salinity. There was no
obvious response to the three positive TPH detection timepoints. There was no apparent tracking
of instrument response to variation in 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 1062 (± 27) cps while
EEM
QSE
for the two 25 and one 35 ppb reported TPH detects were 1046, 1079 and 1097 counts
respectively, within the environmental range observed during this deployment. The FLCDRTD
fluorometer response averaged 1072 (± 21) counts during non-detect periods and 1047, 1080 and
1071 counts at the two 25 ppb and one 35 ppb reported TPH detects. Therefore in these high
CDOM natural waters the FLCDRTD would likely begin to detect ambient oil contamination at
levels above 35 ppb TPH.
The FLCDRTD fluorometer 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). Instrument response was not noticeably higher for any of the three
detectable TPH concentrations observed in the reference samples. 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.
