263
oil components are associated with MOS and track the fate of that oil over time in
complex mixtures.
Tracking the chemical changes of oil that become associated with MOS in the
open ocean is particularly challenging as one would have to be on site during the
event and be able to collect the MOS from the water column in a very gentle fashion. An alternative approach is to collect MOS from laboratory mesocosms that
simulate the process of MOS formation (Quigg et al. 2016). Using this mesocosm
approach, it is possible to compare marine snow formed by biota in clean seawater
(control) to marine snow formed in seawater saturated with crude oil or wateraccommodated fraction (WAF) (Wade et al. 2017).The mesocosms produce MOS
in sufficient quantity that oil associated with the sinking particles can be extracted
using methylene chloride from MOS isolated by filtration onto glass fiber filters
(0.7 microns pore size). Once extracted, the oil associated with the marine snow
could be examined by ESI-FTICR-MS (Wozniak et al. 2018) and
13
C NMR
(Hatcher et al. 2018).
Another simulation methodology, described by Passow et al. (2012), involves the
production of marine snow in roller tanks, done in conjunction with mesocosm
experiments described above. These roller tanks are designed to simulate settling in
a deep oceanic system where marine snow settles through the water column for an
extended period of time. The particles formed in such systems settle to the bottom
of the tanks when the experiment is terminated by stopping the rollers. In the case
described here, the settling occurred for a period of 4 days after the initial set-up.
Once terminated, the marine snow was allowed to settle to the bottom of the tank
where it was then collected. Solvent-soluble oil that had been associated with the
particles was extracted using methylene chloride, subjected to ESI-FTICR-MS
analysis, and compared to extracts from natural particles without oil (control), as
well as to the initial Macondo surrogate oil.
By examining the extracts from Macondo surrogate oil and MOS from WAF
tanks after 4 days of settling, FTICR-MS is able to illustrate the transformations
that the oil associated with MOS undergoes during settling. ESI-FTICR-MS shows
that the polar compounds of the initial surrogate oil are primarily molecules containing a small number of oxygens (CHO 1 , CHO 2 , CHO 3 , CHO 1 N, CHO 2 N).
Association of oil with sinking particles over the course of just 4 days, Fig. 15.5,
can significantly alter the oil, mainly by increasing the oxygen content of molecules as is typically observed for long-term (>100 days) weathering of oil (Aeppli
et al. 2012; Chen et al. 2016). The distribution of CHO molecules in the initial oil
is dominated by CHO 2 , with DBE distributions centered between 3 and 5. Following
association with MOS for 4 days, oil shows a change to CHO x where x is mainly
3–5 oxygens, having DBE values distributed between 5 and 7 with a pronounced
shift toward higher DBE. The H/C ratio for molecules can also be used as an indicator for alteration, where H/C ratios in the initial oil are generally between 0.75
and 2.0, typical for mostly aliphatic and alicyclic structures. The 4-day oil displays
H/C ratios extending to lower values (H/C 0.5), suggestive of increasing proportions of aromatic structures when combined with the shift toward higher DBE. The
alterations shown by FTICR-MS are consistent with studies investigating the
15 Applications of FTICR-MS in Oil Spill Studies
oil components are associated with MOS and track the fate of that oil over time in
complex mixtures.
Tracking the chemical changes of oil that become associated with MOS in the
open ocean is particularly challenging as one would have to be on site during the
event and be able to collect the MOS from the water column in a very gentle fashion. An alternative approach is to collect MOS from laboratory mesocosms that
simulate the process of MOS formation (Quigg et al. 2016). Using this mesocosm
approach, it is possible to compare marine snow formed by biota in clean seawater
(control) to marine snow formed in seawater saturated with crude oil or wateraccommodated fraction (WAF) (Wade et al. 2017).The mesocosms produce MOS
in sufficient quantity that oil associated with the sinking particles can be extracted
using methylene chloride from MOS isolated by filtration onto glass fiber filters
(0.7 microns pore size). Once extracted, the oil associated with the marine snow
could be examined by ESI-FTICR-MS (Wozniak et al. 2018) and
13
C NMR
(Hatcher et al. 2018).
Another simulation methodology, described by Passow et al. (2012), involves the
production of marine snow in roller tanks, done in conjunction with mesocosm
experiments described above. These roller tanks are designed to simulate settling in
a deep oceanic system where marine snow settles through the water column for an
extended period of time. The particles formed in such systems settle to the bottom
of the tanks when the experiment is terminated by stopping the rollers. In the case
described here, the settling occurred for a period of 4 days after the initial set-up.
Once terminated, the marine snow was allowed to settle to the bottom of the tank
where it was then collected. Solvent-soluble oil that had been associated with the
particles was extracted using methylene chloride, subjected to ESI-FTICR-MS
analysis, and compared to extracts from natural particles without oil (control), as
well as to the initial Macondo surrogate oil.
By examining the extracts from Macondo surrogate oil and MOS from WAF
tanks after 4 days of settling, FTICR-MS is able to illustrate the transformations
that the oil associated with MOS undergoes during settling. ESI-FTICR-MS shows
that the polar compounds of the initial surrogate oil are primarily molecules containing a small number of oxygens (CHO 1 , CHO 2 , CHO 3 , CHO 1 N, CHO 2 N).
Association of oil with sinking particles over the course of just 4 days, Fig. 15.5,
can significantly alter the oil, mainly by increasing the oxygen content of molecules as is typically observed for long-term (>100 days) weathering of oil (Aeppli
et al. 2012; Chen et al. 2016). The distribution of CHO molecules in the initial oil
is dominated by CHO 2 , with DBE distributions centered between 3 and 5. Following
association with MOS for 4 days, oil shows a change to CHO x where x is mainly
3–5 oxygens, having DBE values distributed between 5 and 7 with a pronounced
shift toward higher DBE. The H/C ratio for molecules can also be used as an indicator for alteration, where H/C ratios in the initial oil are generally between 0.75
and 2.0, typical for mostly aliphatic and alicyclic structures. The 4-day oil displays
H/C ratios extending to lower values (H/C 0.5), suggestive of increasing proportions of aromatic structures when combined with the shift toward higher DBE. The
alterations shown by FTICR-MS are consistent with studies investigating the
15 Applications of FTICR-MS in Oil Spill Studies