Ref. No. [UMCES] CBL 2013-020
ACT VS12-03
Crude Oil sensors exhibited their greatest response sensitivity to QS, with near linear response
through 5000 ppb QS (Figs. 4 & 5). The Crude Oil sensor exhibited a lower detection limit for
QS (1 ppb) than the CDOM sensor (10 ppb). The CDOM and Crude Oil sensor response to
increasing challenge concentration was approximately 20 times lower for those compounds with
fluorescence maxima outside the optical window wavelength centers of the instruments filter set
(e.g. Carbazole) and hence lower predicted EMM
QSE
intensities (Figs. 4-6, panel B). In contrast
the Refined Fuel sensor exhibited highest sensitivity to carbazole followed by NDSA and #2
Diesel Fuel and approximate 4.5 x lower sensitivity to QS through 1000 ppb challenges.
Ancillary water quality conditions for turbidity and CDOM are presented for each
challenge compound at each of the concentrations tested (Fig. 7). In general the challenge
compounds, except for BB3, had little effect on turbidity levels and the instrument response
reflected the fluorescence properties of the challenge compound (Fig. 7, panel A). BB3
additions increased measured turbidity, but since none of individual sensors were responsive to
this particular challenge compound, no obvious quenching effects were evident at the higher
challenge concentration levels. Spectroscopically derived CDOM levels were compound
specific (Fig. 7, panel B) and reached asymptotes above 10 ppb additions, well below the
instruments’ response capacity (>100 ppb for QS and #2 diesel fuel oil).
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