586
suspended in the subsurface (Malone et al. 2018; Chap. 4; Pesch et al. 2018; Chap. 5)
from ultra-deep spills. Much controversy remains, however, regarding the roles of
physical processes vs. the use of SSDI (subsurface dispersant injection) in determining the proportions of small droplets forming from each, and this cannot be
satisfactorily resolved from the imperfect field data arising from DWH and the
small-scale laboratory experiments conducted to date (Murawski 2020; NASEM
2019).
The Ixtoc 1 spill, although much shallower (54 meters) than DWH (1500 meters),
provides useful insights into deeper blowout phenomena both at the time of that
spill and from subsequent reanalysis of historical data. The Ixtoc 1 subsurface blowout resulted in large quantities of methane and other gasses surfacing above the
wellhead, where they were ignited, producing petrogenic polycyclic aromatic
hydrocarbons (PAHs) and other materials (Soto et al. 2014), some of which were
deposited on the sea floor (Chap. 13). The “DeepSpill” experiment conducted in
2000 (Johansen et al. 2003) assessed the behavior of an 800-meter deep release of
diesel fuel and methane (“dead” oil and gas released simultaneously). That experiment determined that little if any methane gas, and by extension most of the BTEX
compounds in crude oil, would surface in a blowout similar to DWH, which was
subsequently validated with airborne sensors over the DWH well site (deGouw
et al. 2011; Ryerson et al. 2012).
The formation of oiled marine snow (MOSSFA or Marine Oil Snow Sedimentation
and Flocculent Accumulation), although apparent to researchers from previous
tanker accidents, was never considered a significant sink or pathway for spilled oil
sequestration at the ocean bottom. In particular, the location of Ixtoc 1 near a major
deltaic river system off Ciudad del Carmen, Campeche, Mexico, provided a source
of fine particulate clay material and, combined with the use of over one million gallons of dispersants, was a contributing factor to a large-scale, intense “dirty blizzard” of oiled marine snow emanating from Ixtoc 1 as documented in contemporary
sediment cores (Chap. 13). It would be nearly 40 years later that N would be
increased to two for oil blowouts leading to major MOSSFA events (Chap. 13).
Retrospective analyses of satellite imagery collected coincident with the Ixtoc 1
spill (e.g., using the Coastal Zone Color Scanner, CZCS, which was launched in
1978, the year previous to the Ixtoc 1 blowout, and Landsat imagery) document
important features of the surface expression of that massive and sustained well
blowout (Sun et al. 2015). Although not as precise as currently available satellite
imagery products, the relationships between geographic extent and prevailing surface transport features, as well as the intermittent surface concentrations are apparent (Sun et al. 2015). Such data are important for calibrating three- and
four-dimensional trajectory models (discussed later) required by oil spill
responders.
Research conducted prior to DWH on the toxicity and use of dispersants (summarized in NRC 2005) was primarily undertaken in order to comply with government certification requirements for potential dispersant use in oil spill response.
Significantly, this research evaluated the relative toxicity of various dispersant forS. A. Murawski et al.
suspended in the subsurface (Malone et al. 2018; Chap. 4; Pesch et al. 2018; Chap. 5)
from ultra-deep spills. Much controversy remains, however, regarding the roles of
physical processes vs. the use of SSDI (subsurface dispersant injection) in determining the proportions of small droplets forming from each, and this cannot be
satisfactorily resolved from the imperfect field data arising from DWH and the
small-scale laboratory experiments conducted to date (Murawski 2020; NASEM
2019).
The Ixtoc 1 spill, although much shallower (54 meters) than DWH (1500 meters),
provides useful insights into deeper blowout phenomena both at the time of that
spill and from subsequent reanalysis of historical data. The Ixtoc 1 subsurface blowout resulted in large quantities of methane and other gasses surfacing above the
wellhead, where they were ignited, producing petrogenic polycyclic aromatic
hydrocarbons (PAHs) and other materials (Soto et al. 2014), some of which were
deposited on the sea floor (Chap. 13). The “DeepSpill” experiment conducted in
2000 (Johansen et al. 2003) assessed the behavior of an 800-meter deep release of
diesel fuel and methane (“dead” oil and gas released simultaneously). That experiment determined that little if any methane gas, and by extension most of the BTEX
compounds in crude oil, would surface in a blowout similar to DWH, which was
subsequently validated with airborne sensors over the DWH well site (deGouw
et al. 2011; Ryerson et al. 2012).
The formation of oiled marine snow (MOSSFA or Marine Oil Snow Sedimentation
and Flocculent Accumulation), although apparent to researchers from previous
tanker accidents, was never considered a significant sink or pathway for spilled oil
sequestration at the ocean bottom. In particular, the location of Ixtoc 1 near a major
deltaic river system off Ciudad del Carmen, Campeche, Mexico, provided a source
of fine particulate clay material and, combined with the use of over one million gallons of dispersants, was a contributing factor to a large-scale, intense “dirty blizzard” of oiled marine snow emanating from Ixtoc 1 as documented in contemporary
sediment cores (Chap. 13). It would be nearly 40 years later that N would be
increased to two for oil blowouts leading to major MOSSFA events (Chap. 13).
Retrospective analyses of satellite imagery collected coincident with the Ixtoc 1
spill (e.g., using the Coastal Zone Color Scanner, CZCS, which was launched in
1978, the year previous to the Ixtoc 1 blowout, and Landsat imagery) document
important features of the surface expression of that massive and sustained well
blowout (Sun et al. 2015). Although not as precise as currently available satellite
imagery products, the relationships between geographic extent and prevailing surface transport features, as well as the intermittent surface concentrations are apparent (Sun et al. 2015). Such data are important for calibrating three- and
four-dimensional trajectory models (discussed later) required by oil spill
responders.
Research conducted prior to DWH on the toxicity and use of dispersants (summarized in NRC 2005) was primarily undertaken in order to comply with government certification requirements for potential dispersant use in oil spill response.
Significantly, this research evaluated the relative toxicity of various dispersant forS. A. Murawski et al.