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Industrial-scale dumping of organic waste to the deep ocean was once common practice, leaving a legacy of chemical pollution for which a paucity of information exists. Using a nested approach with autonomous and remotely operated underwater vehicles, a dumpsite offshore California was surveyed and sampled. Discarded waste containers littered the site and structured the suboxic benthic environment. Dichlorodiphenyltrichloroethane (DDT) was reportedly dumped in the area, and sediment analysis revealed substantial variability in concentrations of p,p-DDT and its analogs, with a peak concentration of 257 μg g −1 , ∼40 times greater than the highest level of surface sediment contamination at the nearby DDT Superfund site. The occurrence of a conspicuous hydrocarbon mixture suggests that multiple petroleum distillates, potentially used in DDT manufacture, contributed to the waste stream. Application of a two end-member mixing model with DDTs and polychlorinated biphenyls enabled source differentiation between shelf discharge versus containerized waste. Ocean dumping was found to be the major source of DDT to more than 3000 km 2 of the region's deep seafloor. These results reveal that ocean dumping of containerized DDT waste was inherently sloppy, with the contents readily breaching containment and leading to regional scale contamination of the deep benthos.
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Ocean Dumping of Containerized DDT Waste Was a Sloppy Process
Veronika Kivenson,
Karin L. Lemkau,
Oscar Pizarro,
Dana R. Yoerger,
Carl Kaiser,
Robert K. Nelson,
Catherine Carmichael,
Blair G. Paul,
Christopher M. Reddy,
and David L. Valentine*
Interdepartmental Graduate Program in Marine Science, University of California, Santa Barbara, California 93106, United States
Marine Science Institute, University of California, Santa Barbara, California 93106, United States
Australian Centre for Field Robotics, University of Sydney, Sydney 2006, Australia
Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
02453, United States
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02453,
United States
Department of Earth Science, University of California, Santa Barbara, California 93106, United States
SSupporting Information
ABSTRACT: Industrial-scale dumping of organic waste to
the deep ocean was once common practice, leaving a legacy of
chemical pollution for which a paucity of information exists.
Using a nested approach with autonomous and remotely
operated underwater vehicles, a dumpsite oshore California
was surveyed and sampled. Discarded waste containers littered
the site and structured the suboxic benthic environment.
Dichlorodiphenyltrichloroethane (DDT) was reportedly
dumped in the area, and sediment analysis revealed substantial
variability in concentrations of p,p-DDT and its analogs, with a
peak concentration of 257 μgg
1,40 times greater than the
highest level of surface sediment contamination at the nearby
DDT Superfund site. The occurrence of a conspicuous
hydrocarbon mixture suggests that multiple petroleum
distillates, potentially used in DDT manufacture, contributed to the waste stream. Application of a two end-member mixing
model with DDTs and polychlorinated biphenyls enabled source dierentiation between shelf discharge versus containerized
waste. Ocean dumping was found to be the major source of DDT to more than 3000 km2of the regions deep seaoor. These
results reveal that ocean dumping of containerized DDT waste was inherently sloppy, with the contents readily breaching
containment and leading to regional scale contamination of the deep benthos.
Deep ocean disposal of industrial, military, nuclear, and other
hazardous waste was a pervasive global practice in the 20th
century, the full magnitude of which remains unknown. In the
United States, records indicate that 5097 million tons of
industrial waste were dumped at sea,
representing an
unknown fraction of the total quantity. This ambiguity is due
to sparse documentation as well as illegal and clandestine
disposal operations. The extent to which containerized waste
escaped containment, referred to here as sloppy dumping,
also remains uncertain. Abandoned industrial waste deep-sea
dump sites exist along all coastal states,
and one such site,
located in the Southern California Bight, is the focus of this
study (Figure 1A). According to a technical report by
Chartrand et al.,
this area may contain 336000504000
barrels of acid sludge waste from the production of dichlor-
odiphenyltrichloroethane (DDT), in addition to various other
containerized waste streams.
Prior to this work, the
disposition of this waste and the status of its containment
was unknown.
DDT is an organohalide insecticide that was used
extensively in the 20th century, leading to a precipitous decline
in mosquito-borne malaria morbidity and mortality rates.
However, due to its indiscriminate use, recalcitrance, lipophilic
bioaccumulation, and adverse impacts on ecosystem and
human health, it was banned in 1972 for domestic use in the
Montrose Chemical Corporation (MCC) was the largest
global supplier of DDT, manufacturing 800000 tons of the
compound at their Los Angeles County plant from 1947 to
Received: October 17, 2018
Revised: February 10, 2019
Accepted: February 18, 2019
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© XXXX American Chemical Society ADOI: 10.1021/acs.est.8b05859
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1982; production following the US ban was exclusively for
The sole product MCC manufactured, technical
grade DDT, was sold to other companies for formulation into
more dilute commercial insecticide products.
The composi-
tion of technical grade DDT was 6580% p,p-DDT (the main
insecticidal compound), 1521% o,p-DDT, and small amounts
of other compounds, including impurities in the form of 1,1-
dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and 1,1-
dichloro-2,2-bis(p-chlorophenyl)ethane (DDD).
tionally, both DDE and DDD are common breakdown
products of DDT, and along with the DDE metabolite, 1-
chloro-2,2-bis(4-chlorophenyl)ethylene (DDMU), are fre-
quently detected in the environment. DDE, the result of
abiotic or aerobic degradation of DDT, is typically the most
abundant compound.
We use the shorthand notation
DDX to refer collectively to o,p-DDT, p,p-DDT, o,p-DDE,
p,p-DDE, o,p-DDD, p,p-DDD, and p,p-DDMU and DDX
as the summed concentration of DDT, DDD, DDE, and
DDMU (or DDX*for instances where DDMU was not
included). In cases where DDT or a metabolite is described
without a specied isomer, this refers to the sum of both
isomers (e.g., DDE = p,p-DDE + o,p-DDE).
Waste-management practices at MCC included discharge of
DDT-laden waste products into storm drains and the sewer
Figure 1. (A) Map of the study region. (B) Multibeam bathymetry from AUV Sentry dive 208. (C) Close-up view of selected area from panel B,
highlighting topographic anomalies consistent with barrels. (D) Sidescan sonar from AUV Sentry dive 208 highlighting anomalies consistent with
barrels. (EH) Images of waste containers from AUV and ROV photo-surveys (I-P).
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system from 1950 to 1971,
leading to contamination of the
Palos Verdes Shelf (PVS) with 8701450 tons of DDT.
Because of this and other waste, the PVS was added to the US
National Priorities List for uncontrolled hazardous contami-
nation, otherwise known as Superfund site designation, and at
the time of this publication, remediation is ongoing.
MCC also engaged in another form of DDT waste discharge
not accounted for in the creation of the Superfund site:
permitted ocean dumping of containerized solid waste. The
ocean disposal of these manufacturing byproducts resulted in
at-sea dumping of an estimated 20003000 barrels per month,
equal to 1 million gallons of waste per year, from 1947 to
Ocean dumping practices were prescribed by the
California Department of Fish and Game, US Coast Guard,
and Los Angeles Harbor Department, specifying that waste-
hauling companies dump barrels at designated locations in the
basins othe coast of Southern California, 16 km oshore;
however, short-dumping at locations closer to shore was
common practice.
Dumping of other containerized waste,
including caustic and acid waste produced by petroleum
reneries, also occurred in these areas.
The DDT contents of MCCs waste barrels was substantially
lower than the composition of the product they sold. While not
explicitly documented, it has been estimated to contain 0.5
1% DDT, totaling 384767 tons of DDT; the remainder was a
mixture of sulfuric acid, organic substances, and water.
However, a patent on DDT acid waste treatment describes
this mixture as about 2% DDT, 72% sulfuric acid, 25% p-
chlorobenzene-sulfonic acid, with traces of water and hydro-
chloric acid.
Thus, we surmise that the total DDT content of
waste in ocean-dumped barrels may have been as high as 2%,
resulting in the revised range of 0.52%, and a total discharge
of 3841535 tons. The upper limit of this revised estimate is
comparable to DDT released at the White Point outfalls, on
the nearby PVS Superfund site (8701450 tons of DDT).
In addition to the ambiguity about the total amount of DDT
dumped into the deep ocean as containerized waste, several
other factors contribute to the complexity of understanding the
fate and impact of these materials. First, minimal record
keeping was performed as to what, where, when, and how
waste was dumped. Second, site access is limited and costly
due to the 900 m site depth, which requires substantial
resources (e.g., the use of specialized submersibles for
identifying relatively small seaoor anomalies and for benthic
sampling, as well as the cost of the associated vessel). Third,
potential shelf sources
complicate interpretation of DDT
origin. Fourth, decades of overprinting from environmental
processes such as burial, suspension, redistribution, and
biodegradation have undoubtedly altered the sites chemical
Fifth, the hydrophobic nature of DDT
and its potential association with organic matter, including
sorption to hydrocarbons, has previously been found to
inuence localized concentrations
and may aect DDX
distributions in basin sediment. Sixth, spatial variability related
to the location of dumping provides for an expectation of
heterogeneity. Finally, the integrity of waste containers is
unknown, precluding an accurate assessment for the spatial
distribution of contamination. Given these ambiguities, the
scale of ecological eects is uncertain and the long-term fate of
the disposed material remains unknown.
In this work, we describe a nested approach to the
exploration of deep ocean waste dumpsites as applied to the
suboxic San Pedro Basin (SPB), located othe coast of
southern California (Figure 1A). We rst apply autonomous
underwater vehicle (AUV) technology to identify sea oor
anomalies consistent with containers and to collect associated
images of the sea oor. We then use a remotely operated
vehicle (ROV) to collect sediment cores for analysis of
chlorinated hydrocarbon and hydrocarbon distributions, to
generate insights into the industrial processes that gave rise to
the contamination, as well as the weathering and biogeochem-
ical processes that occurred since deposition. Finally, we apply
these ndings to provide a framework for dierentiating the
major sources of DDT contamination at the regional scale.
This nested approach has considerable potential for other areas
of seaoor exploration, in addition to exploration of deep-sea
waste disposal sites.
Mapping and Sampling. These sites were accessed using
the AUV Sentry and the ROV Jason. The AUV Sentry was
deployed to collect high-resolution multibeam echosounder
(MBES) bathymetry,
which was processed shipboard to
identify positive elevation anomalies consistent with barrels.
The ROV Jason was deployed to enable closer inspection of
the observed features and sampling of the sediments.
Following ROV retrieval, sediment cores were sectioned at
2 cm intervals and samples stored at 20 °C for chemical
analysis. Further description of the mapping and sampling
information is provided in the SI Methods.
Analytical Methods. Extensive chemical analysis by means
of one-dimensional and comprehensive two-dimensonal gas
chromatography (GC and GC ×GC) with mass spectrometry
(MS), ame ionization detection (FID) and high resolution
time of ight mass spectrometery (HR-ToF-MS) were
conducted to analyze chlorinated and other hydrocarbons as
described previously,
and the methods used in this study
are described in full in the SI Methods.
DDX Mass Balance. DDX source attribution for each core-
top sample
was calculated assuming a mass balance of two
end-members: sediment near to the White Point sewage
outfalls (DDX:PCB = 13.8) and dumped barrels that
contain DDX but no PCBs (DDX:PCB = ). The
following mass balance results:
dPVS s (1)
where fdis the fraction of DDX attributed to deep-sea
disposal for a given sample; RPVS is the DDX:PCB ratio
assumed for the PVS endmember (13.8); and Rsis the
DDX:PCB ratio for a given sample. The full list of
compounds, concentrations, method detection limits and other
relevant information about data processing for gure plots is
included in the SI Methods.
Discovery and Observations. According to a 1985
technical report by Chartrand et al.,
practices for industrial
waste dumping at specic locations in the SPB and Santa
Monica Basin (SMB) were established in 1947 by the
California Department of Fish and Game, US Coast Guard,
and Los Angeles Harbor Department. However, dumping at
unassigned locations was known to be common practice.
One of the assigned dumpsites (Figure 1A) is located near an
existing methane hydrate study site, and we were twice
aorded the opportunity to use robotic marine technology to
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explore the seaoor in this area. Samples for the current study
were collected from two adjacent locations (J2-603 and J2-
746) within the study site (Figure 1A and Figure S37).
In 2011 and 2013, we developed and applied a nested
approach to investigate seaoor features near the assigned
dumpsite in the SPB. This approach included use of AUV
Sentry for identication of seaoor anomalies by multibeam
echosounder (Figure 1B,C), side scan sonar (Figure 1D), and
stereopaired imaging (Figure 1EH), followed by the use
of ROV Jason for detailed visual surveys (Figure 1IP) and
sample collection. We focused on the landward side of the
assigned dump area, with logic dictating that shorter trips
would be desirable for those who conducted dumping
operations. About 60 waste barrels were visually located at a
water depth of 900 m. All barrels were partially buried in the
sediment, though it was not possible to dierentiate initial
emplacement versus subsequent sedimentation. Some of the
barrels were clearly not intact (Figures 1L and S4,S6),
including barrels with apparent puncture marks (Figures
1E,N and S22), while the presence of gas inside other barrels,
observed during sampling, suggests that they were at least
partially intact. Dierent barrel and cylinder types were present
at the site (Figures 1EP and S1S35), implying multiple
waste origins, consistent with the report of Chartrand et al.
The stereopair imaging from AUV Sentry was used to estimate
the volume for several of the barrels and cylinders (Figure
S36). Some barrels had dimensions consistent with standard
110-gallon and smaller drums, while others were consistent
with XL-type gas cylinders. There is evidence to suggest that
the waste was dumped purposefully. Many barrels occurred in
groups of identical appearance (Figures 1M and S18S21).
Concrete footings for barrels and cylinders chained at the neck
to a footing around their base suggest intentional ballasting.
Additionally, the distribution of barrels on the seaoor
corresponds to an imprecise line, as would occur if barrels
were ooaded from a moving barge (Figures 1C and S37
The biota associated with barrels at this low-oxygen (<10
μM) site
is fundamentally dierent from other settings
where barrels serve as articial substrate for the growth of
sessile organisms, including sponges, anemones, and tunicates,
and provide habitat for crabs, starsh, and brittle stars.
those settings, sessile organisms sometimes form distinct
structures on barrels, resembling bioherms.
In this study,
sponges were observed on some barrels, for example, Figure
1E,G,O, and one of the barrels apparently hosted dozens of
snails (Figure S4C). However, rather than promoting
substantial macrofaunal growth, the barrels in this oxygen-
limited environment primarily host microbial communities,
including apparent mats of lamentous sulfur bacteria atop
some barrels and ring-structured microbial mats on the
sediment surface surrounding some barrels (Figures 1F,HK
and S2S35). In some instances, the bordering microbial ring
formation dierentiates the appearance of the sediment surface
inside versus outside the ring (Figures 1F,J,K and S7, S25,
S27S29, and S35).
Disposition of Chlorinated Hydrocarbons in Sedi-
ments. Sampling was conducted under the presumption that
many of the barrels contained DDT, based on the report of
prolic dumping at or near the study site.
Using the ROV
Jason, 19 sediment cores were collected (four in 2011 and 15
in 2013) (Tables S1S6) to reconstruct the chronology,
magnitude, and spatial distribution of contamination, including
an association with barrels and their microbial ring features.
Target analytes included isomers of DDT and its degradation
products, DDD, DDE, and DDMU. While these compounds
have been monitored extensively at the PVS, few analyses have
been conducted in the SPB, despite reported waste disposal
operations in the region.
DDT and its degradation
products were present in all cores, and the concentrations were
highly variable (Tables S1S6). Notably, proximity to barrels
does not appear to control DDX (Figures S37 and S43S45
and Table S7); sediment with the highest DDX was
collected away from barrels, including one core with high
DDX concentrations (core 11-1A) taken at a conspicuous
mound. These ndings indicate the disposal process was
inherently sloppy, which we dene here as intentional disposal
of containerized waste wherein the waste ultimately escapes
the container.
The DDX chemical data set consists of 386 concentrations,
comprised of four metabolites across ve depth horizons (at 2
cm resolution to a depth of 10 cm) for 19 cores (two of which
were subsampled, see Methods) and is summarized in Table
S8. Here, we consider the ndings in terms of three discrete
sediment intervals (Table S1S3) representing dierent eras
based on the assumption of uniform sedimentation at a rate of
postdisposal (core-top 02 cm; after domestic
DDT use and disposal ended), peak disposal corresponding to
dumping operations (midcore 46 cm), and predisposal
(down-core 810 cm; preceding widespread DDT use or
disposal). Depth proles of DDX for representative cores
from the sampling sites (J2-603 and J2-746) are shown in
Figure 2 along with the metabolite distribution by depth
The postdisposal (core top) DDX concentrations are
variable (Table S1), with a maximum of 800 ng g1and a
mean of 106 and 201 ng g1at the J2-603 and J2-746 sites,
respectively (Figure S46A). Postdisposal sediment overlying
high DDT intervals is not systematically enriched in DDX
compared to other samples. DDE was dominant in many
combination of DDE originating from waste in barrels, and
an additional input of DDE from the PVS, where DDE is an
abundant contaminant.
Data from another study reveals a
similar trend of relatively low DDX surface concentrations
(dominated by DDE) overlying very high DDX intervals in
the SPB.
These observations are consistent with ongoing
burial of DDX and only minor amounts of vertical
redistribution post deposition.
However, substantial DDT concentrations were also
observed in surface sediment not associated with underlying
intervals of high DDT, indicating that a recent or ongoing
source is also present. This is consistent with two samples
collected for a study by the Southern California Coastal Water
Research Project (SCCWRP), which also found elevated
surface concentrations of DDX.
Importantly, one of our
samples and one of the SCCWRP samples from the SPB have
elevated concentrations of DDT, in excess of that measured for
the highest DDX sample at the PVS,
suggesting a
contemporary, nonshelf source of DDT to the SPB. These
observations are consistent with the possibility that the
contents of the barrels are slowly leaking or that DDT
remobilization from buried sediment is occurring with spatial
heterogeneity, as might be caused by limited burrowing activity
of infauna.
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The 46 cm depth interval corresponds to the recorded
period of disposal. Measured DDX concentrations from the
J2-603 samples are low in two of four cores, while the other
two cores have elevated concentrations, one with DDX of
257 μgg
1, the highest of our data set (Table S5). For the
samples collected at J2-746, both the highest DDX
concentration (1520 ng g1) and the mean (370 ng
g1) were substantially lower than the concentrations meas-
ured at J2-603 (257 000 ng g1and 64 600 ng g1, respectively;
Table S8). Again, this is suggestive of a nonuniform
distribution of discarded waste, demonstrating the occurrence
of hotspot contamination including elevated proportions of
For the two cores with the highest DDX in the 46cm
interval (cores 11-1A and 11-1B; Table S5,S6), the sediment
from this interval was split (see the Methods), and the
concentrations for each split were found to dier by an order
of magnitude. The DDX*for core 11-1B and its split (S-
core 11-1B) were 256 μgg
1and 26 μgg
1, respectively while
core 11-1A and its split (S-core 11-1A) had concentrations of
96 μgg
1and 7.9 μgg
1. These data highlight substantial
heterogeneity in chemical concentrations across dierent
spatial scales: between the two adjacent sites, within a single
site (e.g., between dierent cores collected during a single
dive), as well as within a 2-cm core section. Large dierences in
DDX concentration have recently been noted on the
centimeter scale for PVS sediment pore water,
and the
patchy concentrations of DDX may be inuenced by the
hydrophobicity of DDT
and its sorption to hydrocarbons or
organic matter present in sediment.
In the predisposal sediment horizon (810 cm), most of the
DDX concentrations, as well as the mean and median
DDX, are substantially lower compared to those of
the overlying intervals (Table S3). Nonetheless, measurable
concentrations are apparent in our samples as well as in a core
previously collected near this site for another study (NOAA
core V),
consistent with slight downward redistribution in
the sediment. Notably, DDMU in the 810 cm depth horizon
from the J2-746 cores is common and accompanied by little or
no other DDX compounds, indicating this is not an artifact of
coring (Figure S46C). The presence of DDMU to the
exclusion of other metabolites in this depth horizon suggests
downward transport and subsequent degradation are occurring
in situ. For example, DDE can anaerobically degrade to
Distinguishing Contamination from Shelf and Deep
Basin sources. The PVS Superfund site is among the most
Figure 2. DDX depth distribution for two representative cores, one
from each expedition: (A) J2-603 in 2011 and (B) J2-746 in 2013.
Concentrations are shown on a log scale (note dierent axes). Shown
at right is the distribution of DDX compounds corresponding to each
depth interval shown at left.
Figure 3. (A) Bathymetric map showing SCCWRP core-top sampling locations used for comparison in this study. Note that leftmost station is NW
of the PVS. Also shown are Dumpsites 1 and 2 (in the SMB and SPB, respectively). (B) Ratio of the DDX:PCB by station type with median
(line) and the interquartile range (box) shown; the green dashed line shows the end-member ratio for the PVS reference site. (C) Percent of
DDX attributed to deep-sea disposal by location, as determined by the mixing curve, derived from eq 1 (see DDX Mass Balance). The detailed
(color) legend is as follows: red outline, white ll: SPB; light red ll: SMB north; dark red ll: SMB south; black diamond: Core 11-1B; grey
diamond: minimum estimate determined using method detection limits for PCB for Core 11-1A; green box: PVS reference site. For data from
this study, DDX*and PCB*were used.
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contaminated sites globally for chlorinated hydrocarbons, with
a surface sediment DDX concentration of up to 6.5 μgg
measured recently near the White Point outfalls.
The PVS is
commonly considered the primary source of DDT contami-
nation to the Southern California Bight, for which 71% of
surface sediments are enriched in DDX.
We asked what contribution deep ocean dumping could
have on the DDX inventory of the two oshore basins in this
region, an area comprising over 3000 km2. To make this
estimate, we developed a mass balance using the proportion of
DDX to polychlorinated biphenyls (PCB), an approach
similar to that suggested by Venkatesan.
PCBs are similar to
DDTs in terms of hydrophobicity, recalcitrance, and years of
disposal, but were neither manufactured in California nor
present in MCC waste barrels.
Importantly, PCBs
were commingled with DDT in the Los Angeles County
Sanitation District outfalls at White Point.
We chose the
most heavily DDX-contaminated core sample at the White
Point outfalls (DDX:PCB = 13.8) (Figure 3A,B) as an
endmember representative of the Palos Verdes Shelf.
An analysis of core-top DDX:PCB from a recent
monitoring campaign by SCCWRP
reveals that the deep SPB
(n= 4) and adjacent Santa Monica Basin (SMB) (n=7)
(Figure 3A) contain ratios of 48.254.1 and 24.365.8,
respectively, substantially greater than for the PVS and other
shallower environments (Figure 3BandTable S10).
Application of mass balance to these deep basin samples and
cores from this study (using DDX*) yields a DDX
fractional contribution for deep sea disposal ranging from 71 to
80% for the SPB and 4379% for SMB (Figure 3C), with
some percentages as minimum estimates (the method
detection limit values were used when PCB was below
detection limits).
To further validate the assumptions inherent to this
approach, diagnostic characteristics of DDX originating from
deep disposal were identied and assessed. Here, we examine
high-concentration DDX cores from this study as well as from
a core collected in the SPB in 1989, reported in a NOAA
technical document
(Table S9). First, the ratios of
DDX*:PCB are consistent with the premise that deep
ocean waste disposal is the source of persistent DDX
contamination in the SPB. Second, ocean-dumped barrels
contained waste from technical-grade DDT, which has
approximately a 4:1 ratio of p,p-DDT to o,p-DDT.
cores from this study yield ratios of 4.05 and 4.50; NOAA core
data are also in agreement. Third, high DDX*was also
measured in these samples and is dominated by DDT or DDD
(>50%), inconsistent with material transported from the PVS
which is dominated by DDE and DDMU.
sediment strata containing high DDX correspond to the
timing for containerized waste dumping.
Although the spatial resolution of sampling is overly coarse,
these results are consistent with a scenario in which a majority
of DDX in the two borderland basins adjacent Los Angeles
derive primarily from deep ocean disposal, rather than the
highly publicized disposal to the PVS.
Chemical Complexity of Discarded Waste. To better
understand the provenance of waste dumped at the site, we
conducted additional chemical analysis including GC-FID on
J2-603 sediment (Figures S47S49) and additional analyses
on the sediments with the highest concentrations of DDT (2
4 and 46 cm depth horizons of core 11-1A and 46cmof
core 11-1B). The occurrence of multiple distinct petroleum
fractions was identied by GCFID and GCMS in the form
of a multimodal distribution of the unresolved complex
mixture (Figure 4B), triggering subsequent analysis by GC ×
MS (Figure 4 and SI part 2 and part 3).
Using comprehensive two-dimensional chromatography,
these modes were resolved into ve mass islands in
chromatographic space (Figure 4), four of which we attribute
to industrial petroleum distillates, based on the pattern of mass
distribution. The rst eluting mixture comprises a minor
fraction of the total mass, and contains branched and cyclic
hydrocarbons containing 915 carbons. The compounds in
this mass island are primarily branched, isoprenoidal, and
straight-chain alkanes along with C0C4decahydronaphtha-
lenes (decalins) with the C2-decalins as the most abundant
members of this suite of compounds. The second eluting
mixture contains aromatic and cyclic hydrocarbons with 12
20 carbons, likely representing a light distillate cut similar to
diesel fuel. Compounds of note in this mixture include a
distinctive family of m-xylenes substituted with tertiary butyl or
other tertiary alkyls (Figure 4D). The abundance of these
unusual compounds suggests formulation by a second
industrial process, beyond simple distillation. This moderately
polar mixture has a lower boiling point than for DDT, making
it a candidate solvent for extraction and purication following
DDT synthesis. The third mass island contains compounds
commonly found in petroleum: tricyclic terpanoids (cheilan-
thanes), a tetracyclic terpanoid, and two steranes with
prominent m/z218 ions (diginane and 20-methyldiginane).
The fourth mixture is a petroleum residue that is dissimilar in
its biomarker distribution to regional oil seeps of the Monterey
(Figure 4E). This fourth mixture appears to be
consistent with a tank bottomresidue left behind after
distillation, based on the presence of 2-methylanthracene and a
tentatively identied (by GC ×GC retention position) hopene
structural analog to 17α(H)-22,29,30-trinorhopaneboth
indicators of petroleum rening.
Collectively, the presence
of four apparent petroleum distillate cuts suggests complex
petrochemical use during DDT manufacture, potentially
overprinted by mixing of waste streams.
The mass resolving power of GC ×GCHRToFMS
enabled a search for organo-chlorine ions across the full GC ×
GC chromatogram (Figure 4A, SI Part 2), capitalizing on the
mass dierence between chlorine isotopes. A complex mixture
of mainly chlorophenyl-containing compounds was identied
(Figure 4A) using the identication criteria indicated,
described in full in SI part 2 and part 3. In addition to DDT
and common degradation products (DDE, DDD, and
DDMU), several notable compounds were detected, including
dicofol isomers (peak 15), tris(4-chlorophenyl)methane
isomers (TCPMe, peaks 16 and 17), dichlorodiphenylmethane
isomers (DDM, peaks 3 and 4), and dichlorobenzophenone
isomers (DBP, peaks 5 and 6) in addition to a variety of related
compounds for which mass spectra did not match known
compounds (SI part 2 and part 3). Dicofol, synthesized from
DDT, is an acaricide that is currently in use in the United
States and was recently classied as a candidate persistent
organic pollutant in the Stockholm Convention.
pheric and current-driven transport has been previously noted
for dicofol, and this compound was detected in low
concentrations (<15 ng g1) in sediment at 10 SCCWRP
stations, primarily in Los Angeles/Long Beach bays and
Since dicofol is currently in use, it is dicult to
Environmental Science & Technology Article
DOI: 10.1021/acs.est.8b05859
Environ. Sci. Technol. XXXX, XXX, XXXXXX
determine its long-term fate in the environment, due to a lack
of temporal resolution for monitoring data (e.g., nonsurface
sediment). The presence of dicofol in buried strata observed
here hints at its persistence in the environment. TCPMe has
been described as an inadvertent byproduct of DDT
and has been detected globally in birds and
including in Southern California dolphins and
Concentrations of DDX compounds in these
dolphins were greater than 1 order of magnitude higher than in
dolphins from other locations around the world, and TCPMe
(an unmonitored compound) was second only to DDE.
Under environmental conditions, TCPMe may be much more
persistent than DDT and its analogs; however, despite
evidence of its persistence and bioaccumulation, TCPMe is
rarely studied in marine sediments.
DDM and DBP are
anaerobic degradation products from dehalorespiration of
and recent work suggests that DBP may be a main end
product of DDT degradation.
The presence of DDM and
DBP at low relative abundance suggests the trace occurrence of
this anaerobic microbial process is associated with these
Biogeochemical Processes. Several lines of evidence
indicate that dumped wastes structure benthic biogeochemical
processes, including the occurrence of microbial mats on the
barrels, the microbial ring structures that surround some
barrels, and the presence of putative metabolic products from
Figure 4. Chemical composition of DDT waste from core 11-1A, color coded by chromatographic island. (A) Chlorine-containing compounds
identied by unique mass assignment with GC ×GCHRToFMS. Peaks labeled 117 are each chlorinated, with a subset of structures
identied as described in the matching identication criteria. Compound identities are as follows: (1)(2) Trichloroethenyl benzene (3)
Bis(chlorophenyl)-methane isomer A (4) Bis(chlorophenyl)-methane Isomer B (5) 2,4'-Dichlorobenzophenone (6) 4,4'-Dichlorobenzophenone
(7) o,p'-DDMU (8) p,p'-DDMU (9) o,p'-DDE (10) p,p'-DDE (11) o,p'-DDD (12) p,p'-DDD (13) o,p'-DDT (14) p,p'-DDT (15) Dicofol Isomers
(16) 2,3',4"-TCPMe (17) 4,4',4"-TCPMe. Inset shows the relationship between ring double bond equivalents (RDBE) and carbon number,
highlighting prevalence of chlorinated aromatics. (B) GC ×GCToFMS chromatogram shown in mountain view, with the total signal collapsed
in white at rear to simulate a one-dimensional chromatogram. (C) GC ×GCToFMS chromatogram shown in plan view, color coded to
highlight ve mass islands. (D) Partial GC ×GCToFMS chromatogram illustrating a putative family of m-xylenes substituted with tertiary
alkyl groups. (E) Partial GC ×GCToFMS chromatogram annotated to identify common petroleum biomarkers.
Environmental Science & Technology Article
DOI: 10.1021/acs.est.8b05859
Environ. Sci. Technol. XXXX, XXX, XXXXXX
dehalorespiration. Based on their lamentous appearance, the
mats likely comprise dominant populations of sulde-oxidizing
bacteria. Sulde sources from underlying sediment may include
sulfate-reducing bacteria, coupled to the organic components
spilled from the waste containers, or driven directly by reduced
metal surfaces of the barrels.
Core collection also revealed that sediment near some
barrels was supersaturated with gas, which began bubbling
rapidly upon core removal, despite the ambient pressure of 91
bar. Gas ebullition provides one possible explanation for the
distinct appearance of the sediment surface immediately
surrounding some barrels as seen in Figure 1F,K,L, though
the process of gas generation remains unknown. Initially, we
suspected active methanogenesis, facilitated by the deposited
waste, caused gas buildup. However, measurements of
interstitial methane concentrations from cores (Table S11)
within 1 m of gas release yield a maximum concentration 19
μmoles per liter of bulk sediment, which is orders of magnitude
too low to support a free gas phase. Nonetheless, in one core,
the methane concentration increased with depth more than is
and thus, the source of the observed gas remains
uncertain; we therefore consider other possible sourcing
mechanisms. One potential source of the gas is from the
barrels themselves, some of which were also observed during
sampling to contain a gas charge. While possible, it is dicult
to envision how the gas would migrate downward into the
sediment and laterally away from the barrel. A second potential
source is nonmethane microbial gases produced through
respiration (CO2), denitrication/anammox (N2,N
2O), or
fermentation (CO2,H
2). Still, it remains dicult to envision
how these gases would accumulate to the point of ebullition at
91 bar ambient pressure. A third potential source is cathodic
H2derived from electrochemical reactions
corrosion of metallic components of the barrels. A fourth
potential source is from acidication of bicarbonate and
carbonate to CO2, driven by highly acid material in the barrel.
For any of these mechanisms, it remains unclear how the gas
phase is sustained near to the sediment surface for extended
periods of time, given dissolution and diusion.
Environmental Impacts. Pervasive disposal of wastes to
the coastal ocean in the mid-20th century was ill-conceived
insofar as the potential for oceanic impacts was all but ignored.
From the chemical plants of Southern California, barrels of
chlorinated (and other) wastes were dumped into a low
energy, low-oxygen benthic environment that is typically
incapable of supporting respiratory demands for large macro-
fauna. Contrasting with the potential of this site for long-term
sediment burial, the disposal process was inherently sloppy,
with the discarded waste escaping containment and entering
the sedimentary system. The resulting legacy includes a
striking persistence of the discarded xenobiotic wastes,
including DDT and other chlorinated organics, as well as
petroleum-derived residues.
Despite typically low oxygen concentrations, the San Pedro
and Santa Monica basins host some infauna and experience
occasional ushing events that allow for additional benthic
To understand the potential toxicity of
sediments, we compared our results with the NOAA sediment
quality guidelines for the eects range median (ERM), above
which adverse eects are likely.
For DDX*, the ERM is
46.1 ng g1
(note that in this study the o,p- isomers are
included for assessing DDX*values). Across samples from
the top 6 cm of sediment cores in this study, 86% exceed the
ERM value for DDX*, and the median concentration is 4.8-
fold greater than the ERM. Hotspot contamination exceeds the
ERM by >160-fold. As suggested in previous studies, eects
range values should be referenced with caution: the relevant
sediment quality guidelines have been criticized for low
accuracy (overestimating toxicity), relatively high variability
(in regard to observed incidence of adverse eects), and not
accounting for the eects of bioaccumulation
and may
also further underestimate sediment toxicity due to the
exclusion of known DDT metabolites such as DDMU.
Nonetheless, sediment quality guidelines provide a well-
recognized metric that is commonly used for the context of
sediment toxicity and clearly demonstrate a potential for toxic
eects in the majority of sediments sampled.
Stemming from our observations, several questions remain,
including our contrasting ndings of regional scale DDT
mobilization versus local preservation and sediment burial as
well as the underlying biogeochemical processes active or relict
around the wastes. The variability that accompanied waste
disposal practices undoubtedly contributes to these uncertain-
ties and also to the potential impacts on the broader
ecosystem. Despite the uncertainties, these ndings serve as
a cautionary tale for the disposal and dispersal of containerized
industrial waste from even a quiescent benthic environment.
SSupporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.est.8b05859.
Detailed description of the mapping and sampling,
analytical, and DDX mass balance data and methods,
images of additional barrels, maps of dumpsite location,
and chemical concentrations for each depth horizon and
metabolite analyzed (PDF)
Identication of compounds in sediment-core extracts
Compound identication criteria and comparison
Corresponding Author
Veronika Kivenson: 0000-0002-5715-3126
David L. Valentine: 0000-0001-5914-9107
Present Address
(K.L.L.) Western Washington University, Bellingham, WA
Author Contributions
V.K. and K.L.L. contributed equally.
The authors declare no competing nancial interest.
This material is based upon work supported by the National
Science Foundation Graduate Research Fellowship for V.K.
under Grant No. 1650114. Expeditions AT-18-11 and AT-26-
06 were funded by the NSF (OCE-0961725 and OCE-
1046144). Any opinions, ndings, and conclusions or
recommendations expressed in this material are those of the
author(s) and do not necessarily reect the views of the
Environmental Science & Technology Article
DOI: 10.1021/acs.est.8b05859
Environ. Sci. Technol. XXXX, XXX, XXXXXX
National Science Foundation. We thank the captain and crew
of the RV Atlantis, the pilots and crew of the ROV Jason, the
crew of the AUV Sentry, the scientic party of the AT-18-11
and AT-26-06 expeditions, Justin Tran for assistance with the
preparation of multibeam data, M. Indira Venkatesan for a
helpful discussion of the NOAA datasets, and Nathan Dodder
for advice on the procedure for compound identication.
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Environ. Sci. Technol. XXXX, XXX, XXXXXX
... Sixty percent of the wastewater comes from industrial establishments and the rest from residential sources (Cash, 2020). The marine life-forms in the Los Angeles Outer Harbor are not only exposed to contaminants brought in by these transport mechanisms, they are also exposed to legacy levels of DDT derivatives and polychlorinated biphenyls (PCBs) in sediments due to a massive DDT dump in the nearby San Pedro Basin (currently designated a Superfund site), as well as PCBs deposited between 1947 and 1971 offshore of the Palos Verdes Peninsula (Kivenson et al., 2019;Malins et al., 1987;Moore, 1999). ...
... With the passage of time and the recent revelation that close to half a million barrels containing DDT production waste are falling apart near the study area (Kivenson et al., 2019), two questions are asked in this study: (1) whether the Los Angeles Outer Harbor white croaker population is still as robust as it was 20 years ago, and (2) whether morphometric differences among fish of the same species could be quantified systematically for use in spot-checking the robustness of white croaker and queenfish populations in the Los Angeles Outer Harbor. In this regard, the values of Fulton's condition factor a and the growth coefficient b obtained earlier for white croaker (Love et al., 1984;Moore, 1999) are compared with those obtained in the present study. ...
... For white croakers, a general decrease in size can be observed in Figure 4A and B, meaning that the average white croaker (female or male) shrank in size over the study period. This loss in size occurred concurrent with evidence pointing to deteriorating drums containing DDT production byproducts at the nearby US Environmental Protection Agency (USEPA) Superfund site (Kivenson et al., 2019). For an average queenfish, no such loss in size can be observed for the females in Figure 4C, but a size increase of the males can be seen over the same period in Figure 4D. ...
Sediments and water columns in the Los Angeles Outer Harbor, a major port behind a breakwater, contain DDTs and PCBs from a nearby superfund site and contaminants brought in by ships, boats, stormwater, a river and a wastewater outfall. White croaker, a bottom feeder, and queenfish, a water column feeder, are two bioindicators for this marine ecosystem whose conditions are assumed to be robust for this role at all times. The current study tests this benign assumption amidst progressively increasing DDTs/PCBs levels in their tissues. Results, as evident by progressively shrinking gonads, show a less than robust white croaker population particularly. While the males are generally larger than the female fish, the length (standard (SL) or total (TL)) and body mass (BM) of 80 white croakers collected over a period of eight years were found to be similar irrespective of gender (177 mm, 212 mm and 114 g, respectively). Queenfish (67) did not show such similarity over the same period (female: 152 mm SL, 177mm TL, 56 g BM; male: 145 mm SL, 172 mm TL, 50 g BM). The site‐specific expressions/values capturing the current conditions of these fish are SL=0.835[TL]–1.68 (r 2=0.914, n=68) and SL=0.891[TL]–8.88 (r 2=0.961, n=50) for white croaker and queenfish, respectively. In the allometric growth equation BM=a[SL] b , a and b are 2.83×10‐4 and 2.49 (r 2=0.817) for white croakers, and 6.10×10‐5 and 2.73 (r 2=0.825) for queenfish, respectively. The relative coefficients of condition K n are 0.97±0.07 and 1.01±0.12 for white croakers and queenfish, respectively. Molecular level studies are needed to establish definitively the links between DDTs/PCBs bioaccumulation in fish tissues and the robustness of the fish populations. This article is protected by copyright. All rights reserved.
... A popular pesticide, DDT, was banned in the United States in 1972, due to its adverse impacts on ecosystems and persistence in the environment (USEPA, 1975). Although the ban began almost 50 years ago, DDT is still detected in biota, sediments, and soils throughout the country (Feingold and Benoit, 2018; Kivenson et al. 2019). In 2004 to 2005, 44% of all resident loons died on Squam Lake, NH, U.S.A., followed by ongoing low reproductive successes (Vogel, 2010). ...
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Research on declines in loon populations at Squam Lake, New Hampshire, U.S.A., point to multiple potential causes since 2005, including dichlorodiphenyltrichloroethane (DDT). This study narrows down sources of DDT in a small sub-watershed by focusing mainly on collecting and analyzing soil and sediment samples, achieving rapid source area determination of DDT. We find presence of p,p’ isomers of DDT and DDE in the Bennett Brook sub-watershed arising from long-term soil and sediment storage of applications 60 years ago, plus a concentrated and current source area at a former barn. Highest concentrations, 723 μg/kg p,p’-DDT and 721 μg/kg p,p’-DDE, occur in the soils adjacent to the barn’s foundation remnants. DDT exceeds that of the metabolite, DDE, in many soils around Bennett Brook, including but not limited to the barn site. In soils where DDT>DDE, we infer mechanisms that delayed breakdown of DDT over the last 60 years. A Pb-210 dated lake sediment core, collected near the outlet of Bennet Brook, shows continuous accumulation of p,p’-DDE and p,p-DDD after 1951. These residuals likely derived from multiple sources within the sub-watershed, including orchard soils, the barn site, and from mobilized sediment deposits following extreme floods in the watershed. Although the DDT residues fall below mandatory soil remediation levels for the State of New Hampshire, Bennett Brook sediments exceed sediment quality guidelines for protection of aquatic life. Crayfish collected in Bennett Brook have significantly higher concentrations of p,p’-DDE than crayfish collected elsewhere in Squam Lake.
... Overall melt supply to the axis, rather than spreading rate, is the key parameter controlling the tectonic and volcanic accretion styles that shape the seafloor. For example, at ultra-slow spreading rates lithospheric accretion can range from almost amagmatic and avolcanic spreading, with detachment faults emplacing mantle in the lithosphere and exposing it at the seafloor, to ridge segments with major central volcanoes (e.g., South-West Indian Ridge; Cannat, 1996;Kivenson et al., 2019). Except for fast-spreading ridges, which are well-supplied magmatically and show limited variability in accretion style, spreading rate is therefore not an accurate indicator of the resulting seafloor morphology at scales of 1-10 km, which changes as a result of variability in the availability of melt to accommodate plate separation (Figs. 3 and 5). ...
Coastal reintroduction sites for California condors (Gymnogyps californianus) can lead to elevated halogenated organic compound (HOC) exposure and potential health impacts due to the consumption of scavenged marine mammals. Using nontargeted analysis based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS), we compared HOC profiles of plasma from inland and coastal scavenging California condors from the state of California (CA), and marine mammal blubber from CA and the Gulf of California off Baja California (BC), Mexico. We detected more HOCs in coastal condors (32 ± 5, mean number of HOCs ± SD, n = 7) than in inland condors (8 ± 1, n = 10) and in CA marine mammals (136 ± 87, n = 25) than in BC marine mammals (55 ± 46, n = 8). ∑DDT-related compounds, ∑PCBs, and total tris(chlorophenyl)methane (∑TCPM) were, respectively, ∼7, ∼3.5, and ∼148 times more abundant in CA than in BC marine mammals. The endocrine-disrupting potential of selected polychlorinated biphenyls (PCB) congeners, TCPM, and TCPMOH was determined by in vitro California condor estrogen receptor (ER) activation. The higher levels of HOCs in coastal condors compared to those in inland condors and lower levels of HOC contamination in Baja California marine mammals compared to those from the state of California are factors to consider in condor reintroduction efforts.
There is increasing interest in understanding the chemical and biochemical processes that occur in marine environments and ecosystems. In particular, the contamination of oceans and coastal waters by oil, industrial waste, agricultural products and plastics are a major issue. Given the vast nature of the ocean and the widespread pollution from increasing human activities, this presents a considerable challenge for monitoring. Recent advancements in chemical/bio-sensors has enabled rapid and real-time information to be obtained on countless different substances. Sensing technologies and analytical devices are becoming an important and necessary part of understanding the impact of many pollutants on the ocean.
Anthropogenic imprints have become a fundamental part of most ecosystems. Our chemical footprint is often detected using targeted approaches, whereas xenobiotics are embedded within the large pool of dissolved metabolites, altered by biotic and abiotic mechanisms. Thus, it is necessary to simultaneously study anthropogenic signals entwined with the variety of organic signatures that exist in aquatic environments. However, methods for non‐targeted analysis of natural metabolites are not always well suited for the analysis of pollutants. Here, we report the reassessment of styrene‐divinylbenzene polymer‐based Priority PolLutant (PPL) solid‐phase extraction (PPL‐SPE), which is typically used to extract marine dissolved organic matter (DOM) for biogeochemical studies, to analyze a set of xenobiotics commonly observed in coastal North Pacific seawater. After PPL extraction and analysis by nontargeted liquid chromatography tandem mass spectrometry (LC–MS/MS), we successfully detected 23 out of 25 selected pharmaceuticals, personal care products, biocides, perfluorocarbons, and polymer additives in a complex marine DOM sample using positive and negative electrospray ionization. We tested two pH conditions to mimic typical marine DOM extraction studies and found mean recovery rates of xenobiotics were approximately 10% higher in seawater pH (pH ~ 8) than in acidified samples (pH ~ 2) for both negative and positive modes, although overall, mean recovery rates were 10% lower in negative mode. Our results indicate that PPL‐SPE in combination with non‐targeted LC–MS/MS is capable of capturing the tested set of xenobiotics, thus allowing the repurposing of biogeochemical sampling strategies as well as existing DOM samples and MS data for the subsequent assessment of anthropogenic impacts in marine environments.
Most of the Earth's surface is paved by oceanic crust formed along mid-ocean ridges, a ~ 65,000 km long volcanic chain, and one of the most prominent morphologic features on the planet. Seafloor morphology is thus shaped, at large spatial scales (tens to hundreds of km) by the overall ridge geometry, and in particular by both transform faults and non-transform discontinuities that dissect the ridge axis, defining ridge segments, and leave off-axis wakes in seafloor morphology. At smaller scales (tens of km and less) morphological variability is primarily controlled by the relative importance of tectonic and volcanic processes on-axis, in addition to hydrothermal activity on very local scales. While spreading rate is classically invoked as a primary control on ridge segmentation and seafloor morphology, the strongest controls are in fact melt supply to the ridge axis and on-axis lithospheric thickness. Fast-spreading ridges (> 60 mm/year) show relatively consistent and homogeneous morphologies, dominated by volcanism with limited tectonic reshaping by normal faults. With decreasing spreading rate, the variability in seafloor morphology increases, and encompasses seafloor similar to that formed at fast-spreading ridges wherever magma supply is important, and amagmatic spreading dominated by faulting, while also displaying significant variations at the scale of individual ridge segments. In all cases, tectonic deformation is pervasive, and fault-bounded abyssal hills formed on-axis are ubiquitous throughout the seafloor. Seafloor relief is also modified by mass wasting, which is particularly active along tectonic scarps (e.g., normal faults, walls of rift and transform valleys), and by sedimentation of pelagic or continental origin. This article provides an overview of seascapes formed at mid-ocean ridges and interprets them as the interaction of relief-creating and relief-reworking processes on a range of scales.
We report the first successful use of chemical sensors integrated on to an underwater vehicle to locate, map and estimate flux from a controlled sub-seabed CO2 release, analogous to a leak from a Carbon Capture and Storage (CCS) reservoir. This has global implications for the efficacy and cost of monitoring of offshore CCS sites and hence public and regulatory confidence as this tool for addressing climate change is considered and rolled out. A remotely operated vehicle (ROV) equipped with three different pH sensors was deployed to determine the spatial extent of the controlled release. The sensors each operated on a different principle (spectrophotometric, fluorescence, and electrochemical) and the strengths and weaknesses of each sensor are discussed. The sensor data demonstrated that evidence of the plume was limited to within 3 m of the seafloor, as predicted by previous modelling work. The data were then utilised to develop a model of the plume, to extend the spatial coverage of the data. This comparison of the three sensors and the insight into plume dynamics provided by the model would assist in the planning of future plume surveys to ensure the sensor and vehicle combination can resolve the plume of interest.
The deep sea - an oceanic layer below 200 m depths – has important global biogeochemical and nutrient cycling functions. It also receives organic pollutants from anthropogenic sources, which threatens the ecological function of the deep sea. In this Review, critically examined data on the distribution of organic pollutants in the deep sea to outline the role of biogeochemical and geophysical factors on the global distribution and regional chemodynamics of organic pollutants in the deep sea. We found that the contribution of deep water formation to the influx of perfluorinated compounds reached a maximum, following peak emission, faster in young deep waters (<10 years) compared to older deep waters (>100 years). For example, perfluorinated compounds had low concentrations (<10 pg L⁻¹) and vertical variations in the South Pacific Ocean where the ocean currents are old (<1000 years). Steep geomorphologies of submarine canyons, ridges, and valleys facilitated the transport of sediments and associated organic pollutants by oceanic currents from the continental shelf to remote deep seas. In addition, we found that, even though an estimated 1.2-4.2 million metric tons of plastic debris enter the ocean through riverine discharge annually, the role of microplastics as vectors of organic pollutants (e.g., plastic monomers, additives, and attached organic pollutants) in the deep sea is often overlooked. Finally, we recommend assessing the biological effects of organic pollutants in deep sea biota, large-scale monitoring of organic pollutants, reconstructing historical emissions using sediment cores, and assessing the impact of deep-sea mining on the ecosystem.
Global warming increases a chance of eutrophication, and such fact offers that unhygienic organic waste materials (OWMs) in water must be treated. Hence, this study laid emphasis on the thermal-chemical (pyrolysis) process to establish a rapid valorization platform for OWMs. Indeed, OWMs were collected from the eutrophication site, and OWMs were mainly comprised of lignocellulosic biomass, microalgae (cyanobacteria) and the diverse types of bacteria (commonly observed from livestock waste). In an attempt to offer more sustainable valorization route for OWMs, CO2 was used as a raw material in pyrolysis process. From the CO2-assisted pyrolysis, the conversion of CO2 and OWMs into gaseous fuel (CO) was observed. A cheap Ni-based catalyst was used in pyrolysis of OWMs as a strategic practice to promote conversion of CO2 into CO. Indeed, syngas production (38 %) was enhanced from catalytic pyrolysis over Ni/SiO2 under CO2 condition as compared to inert condition (N2).
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Non-targeted GC×GC-TOF/MS analysis of blubber from 8 common bottlenose dolphins (Tursiops truncatus) inhabiting the Southern California Bight was performed to identify novel, bioaccumulative DDT-related compounds, and to determine their abundance relative to the commonly-studied DDT-related compounds. We identified 45 bioaccumulative DDT-related compounds of which the majority (80%) are not typically monitored in environmental media. Identified compounds include transformation products, technical mixture impurities such as tris(chlorophenyl)methane (TCPM), the presumed TCPM metabolite tris(chlorophenyl)methanol (TCPMOH), and structurally-related compounds with unknown sources, such as hexa- to octa-chlorinated diphenylethene. To investigate impurities in pesticide mixtures as possible sources of these compounds, we analyzed technical DDT, the primary source of historical contamination in the region, and technical Dicofol, a current use pesticide that contains DDT-related compounds. The technical mixtures contained only 33% of the compounds identified in the blubber, suggesting that transformation products contribute to the majority of the load of DDT-related contaminants in these sentinels of ocean health. Quantitative analysis revealed that TCPM was the second most abundant compound class detected in the blubber, following DDE, and TCPMOH loads were greater than DDT. QSPR estimates verified 4,4’,4’’-TCPM and 4,4’4,’’-TCPMOH are persistent and bioaccumulative.
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The Southern California Bight (SCB) is a unique ecological and economic resource, home to some of the most productive coastal ecosystems, but also some of largest pollutant inputs in the United States. Historically, environmental monitoring of the coastal environment has been temporally intensive, but spatially focused on narrow areas closest to regulated discharges, providing a potentially biased perspective of overall coastal sediment quality. Beginning in 1994 and conducted approximately every five years thereafter, nearly 100 regulated, regulatory, non-governmental or academic organizations join forces to implement the SCB Regional Marine Monitoring Program (the Bight Program). The most recent Bight program sampled nearly 400 locations, from the head of tide in coastal estuaries to offshore basins 1000 m in depth, using a probabilistic survey design and measuring multiple indicators of sediment quality including chemistry, toxicity, and infauna. The three indicators were scored using regionally-developed assessment tools, and then combined for an integrated assessment of sediment quality. Results showed that the vast majority of SCB sediments do not have impacted sediment quality, but that not all habitats are in equally good condition. Most of the continental shelf is not impacted, despite the discharge of very large volumes (10. 9 L/day) of treated wastewater discharges. In contrast, up to 50% of the area in estuaries and 45% of the area in marinas have impacted sediment quality. These generally quiescent waterbodies receive pollutant inputs from the region's extensively urbanized watersheds and high density of boating activities. Despite the relatively large extent of impacted sediment quality in embayments, sediment quality has been steadily improving in this habitat over the last decade based on surveys dating back to the 1998. The Bight Program has affected management actions in the region by focusing current efforts in habitats most impacted by poor sediment quality, and highlighting the improvements from previous management actions.
For nearly two and a half decades following World War II, production wastes from the world's largest manufacturer of technical DDT (1-chloro-4-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene) were discharged into sewers of Los Angeles County. Following treatment, the wastes were released via a submarine outfall system to nearshore coastal waters where a portion accumulated in shallow sediments of the Palos Verdes Shelf (PVS). An investigation of the pore-water geochemistry of DDT-related compounds (DDX) was undertaken in an effort to understand factors controlling the rate of reductive dechlorination (RDC) of the major DDT degradate, 4,4′-DDE (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene). Equilibrium matrix-solid phase microextraction (matrix-SPMEeq) combined with automated thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) was used to determine freely dissolved concentrations of ten DDX analytes in sediment cores collected from three locations on the PVS (stations 3C, 6C, 8C, which are 7 km, 2 km, and 0 km, respectively, downcurrent from the outfall system). Pore-water concentrations (pM) of the principal DDX compounds involved in RDC were: 3C-DDE: 6.0–24, DDMU (1-chloro-4-[2-chloro-1-(4-chlorophenyl)ethenyl]benzene): 11–160, DDNU (1-chloro-4-[1-(4-chlorophenyl)ethenyl]benzene): 1.8–68; 6C-DDE: 5.6–170, DDMU: 5.6–177, DDNU: 1.7–87; 8C-DDE: 27–212, DDMU: 31–403, DDNU: 5.5–89. Variations in the spatial distribution of DDX analytes in pore water reflect several factors including proximity to the outfalls, RDC reaction rates, and natural variability in sedimentation and post-depositional transport processes. A comparison of pore-water data produced using matrix-SPMEeq/TD-GC/MS and whole-core squeezing/solvent extraction/liquid injection-GC/MS indicates that the majority of the DDE in the upper sediment column (≤about 10 cm) is associated with dissolved/colloidal organic matter. Below that depth, freely-dissolved DDE predominates. The principal organic geochemical phase controlling sorption of DDE in PVS sediments are residual hydrocarbons, the vast majority of which originated from petroleum refinery wastes. Organic carbon-normalized sediment-water distribution coefficients (KOC) were calculated from solid-phase and pore-water concentrations of DDX and organic carbon. Log KOC values (L/kg) were relatively invariant across the shelf and with depth in the sediment column. Shelf-wide compound-specific coefficients (log KOC) were: DDE: 7.5 ± 0.11, DDMU: 6.92 ± 0.13, DDNU: 6.37 ± 0.19. The spatial uniformity of KOC means that biological exposure and availability of the DDX compounds can, in principle, be estimated from solid-phase chemical measurements.
Benthic accumulations of filamentous, mat-forming bacteria occur throughout the oceans where bisulfide mingles with oxygen or nitrate, providing key but poorly quantified linkages between elemental cycles of carbon, nitrogen and sulfur. Here we used the autonomous underwater vehicle Sentry to conduct a contiguous, 12.5 km photo-imaging survey of sea-floor colonies of filamentous bacteria between 80 and 579 m water depth, spanning the continental shelf to the deep suboxic waters of the Santa Barbara Basin (SBB). The survey provided >31,000 images and revealed contiguous, white-colored bacterial colonization coating >~80% of the ocean floor and spanning over 1.6 km, between 487 and 523 m water depth. Based on their localization within the stratified waters of the SBB we hypothesize a dynamic and annular biogeochemical zonation by which the bacteria capitalize on periodic flushing events to accumulate and utilize nitrate. Oceanographic time series data bracket the imaging survey and indicate rapid and contemporaneous nitrate loss, while autonomous capture of microbial communities from the benthic boundary layer concurrent with imaging provides possible identities for the responsible bacteria. Based on these observations we explore the ecological context of such mats and their possible importance in the nitrogen cycle of the SBB.
In this article, we examine the decisions made by corporate executives and government officials that led to the discharge with minimal treatment of hundreds of metric tons of dichloro-diphenyl-trichloroethane (DDT) waste into the Pacific Ocean over several decades. After World War II, Montrose Chemical Corporation of California's Los Angeles plant began making the new wonder pesticide, and Montrose executives worked with local officials to develop a waste disposal system that funneled the plant's process wastes into the county sewer system and ultimately into the ocean. Faced with increasing scientific concern about pesticides and a changed political climate in the 1960s, Montrose vigorously defended DDT and relied increasingly on exports to remain profitable. Years after the plant closed, a federal suit forced Montrose and related companies to pay the costs of environmental cleanup.
This chapter describes the use of manned submersibles in the study of ocean waste disposal. The economics of delivering wastes to the marine environment are primarily affected by the distance of the discharge or release site from a port or coastal facility. Thus, those responsible for waste disposal prefer sites as close to shore as possible. Some smaller municipal sewage-treatment plants discharge into shallow waters only tens of meters offshore. In such cases, SCUBA techniques are appropriate for line inspection and maintenance, but for sites or installations deeper than several tens of meters, it may prove more economical to employ a small submersible for periodic surveys of pipe integrity and discharge effects. To illustrate the utility of manned submersibles in waste-disposal studies, this chapter presents different case histories describing various technical methods and results of operations at specific dumpsites. The chapter presents a partial listing of the advantages and disadvantages of employing divers vs. submersibles. For extended missions at depths as shallow as 20 m, it is demonstrated that a dry submersible offers the most economical approach to surveying.
Because of their preponderant use as fuel in marine vessels, marine residual fuels are often the focus of maritime oil spill investigations. Residual fuels, often referred to generically as heavy fuel oil or HFO, pose a variety of challenges to oil spill investigators. Variability in the composition of modern heavy marine fuels provides unique opportunities for chemical "fingerprinting" of HFOs in the environment. This chapter focuses on the forensic chemistry of HFO-the most widely used of the commercial marine fuel oils-and chemical features of these fuels pertinent to oil spill investigations. Two most popular groups of heavy fuel oils, IFO 180 and IFO 380, differ largely in their blending formulas. From a forensic chemistry standpoint, it is the combination of the refining and blending processes that impose unique chemical "fingerprints" on IFO 380 HFOs, which oil spill investigators can use to identify and track spilled fuel in the environment. Gas chromatographic analysis of petroleum fuels reveals the distinctive boiling point distribution of the chromatographable hydrocarbons that compose the fuels.
Amounts plus physical and chemical properties of industrial and sewage wastes are discussed. Abundances of toxic metallic elements in these wastes varied by orders of magnitude when compared on an element-to-element basis. Fly ash and sewage sludge have the highest concentrations of elements of environmental concern. The distribution and fate of an ocean-dumped waste in the sea are complicated, depending on (1) the physical processes of dispersion, advection, and sedimentation; (2) chemical processes such as volatilization, neutralization, precipitation, flocculation, adsorption, desorption, dissolution, oxidation, and reduction; and (3) biological processes involving responses of marine organisms to waste materials, incorporation of these materials within the organism, and modification of waste substances by organisms.