A Bioaccumulation Model of the
Effects of DDTs and PCBs at the Palos
Verdes Shelf: A Tool to Determine
Risk and in Support of Remediation.
Earl Byron, Christine Arenal.
1
Historical Contamination of a Significant
Area of the Southern California Coast
The Palos Verdes Peninsula
2
Why is there a Problem?
Montrose DDT Plant
LACSD outfalls
3
Palos Verdes Shelf
Continental shelf
Continental slope
4
Human Health as well as Ecological Risk
Sealions, pelicans, and people…all eat fish!
5
tDDT Sediment Contours (1992 - 2003)
6
PCB Sediment Contours (1992, 1998)
7
8
Basic Conceptual Site Model
Major DDT & PCB
Transfer
Pathways
DDT
PCBs
9
Conceptual Site Model for Ecological Risk
Source
Release/Transfer
Mechanisms
Exposure
Media
Receptors
Water Column
Invertebrates
DDT drives Eco Risk
Water
Biota
Diffusive
Flux
Mammals
Water Column
Fish
Suspended
Sediments
Raptors
Piscivorous
Birds
Bioaccumulation
Benthic
Fish
Surface
Sediments
Surface
Sediments
Erosion &
Resuspension
Benthic
Invertebrates
Bioturbation
Deep
Sediments
Deep
Sediments
10
Sediment Characterization: Routine
Monitoring and Special Studies
Vibracores
Box Cores
= Volumes of Data!
11
Fish Tissue: Routine Monitoring and
Special Studies
Trawling for Turbot
12
Evaluating Ecological Risks from
DDTs and PCBs
 Evaluating risks to marine invertebrates and
fish from sediment, water, and diet: PVS area.
 Evaluating risks to marine mammals and
seabirds from dietary exposure: Greater SCB.
 Bulk sediment, porewater, water-column, and
fish tissue concentrations of organochlorine
contaminants derived from sediment sources.
 Consumer tissue concentrations derived from
mechanistic modeling.
13
The Bight vs. the PV Shelf Study Area
14
Exposure and Risk: Invertebrates
Weight of Evidence
 Marine invertebrate communities were most degraded
near the outfall.
 Sediments were toxic to bioassay organisms in many
areas of PVS, particularly near the outfall area.
 Porewater concentrations exceeded aquatic toxicity
values for exposure to marine invertebrates (0.0072
ppb)(applying acute/chronic ratio of 18 to acute value).
 Bulk sediment concentrations up to 30 cm deep
exceeded potentially toxic concentrations, particularly in
the areas nearest the outfalls (2 ppm @1%TOC).
15
Assessment Endpoints and Measures of
Exposure and Effects: Fish Community
Assessment Endpoints
Attribute
Community
structure and
function
Support of fish and
wildlife species (i.e., as a
food source)
Level
Community,
Population
Measures of Exposure and Effects
Sediment
DDT and PCB concentrations
Water column concentrations (very limited
data)
Measured concentrations in fish tissue
(limited whole-body, fillet)
Literature-based benchmarks
–Whole-body
–Water quality criteria
Site-specific
reproduction and population
studies
Receptors: White Croaker, Kelp Bass, Sanddabs
16
17
18
Food Chain Model to Evaluate Response
Actions
 Incorporate new fish tissue data (MSRP/EPA sampling and analysis
results)
 Updated Eco and Human Health Risk determinations
 Use of the model to predict changes in risk associated with
response actions
19
Information Needed for EcoRisk Modeling
 List of appropriate receptors
 Food chain information
 Strong sediment quality and fish tissue
databases
 GIS database for fish, sediment, and all
receptor foraging ranges
 Knowledge of receptor home ranges and food
habits
 Literature information on organochlorine
partitioning and metabolism (mechanistic
model components)
20
Comparing the Need for BSAF vs.
a Mechanistic Foodweb Model
 Data density and availability is key.
 BSAF: Good sediment and GIS data
coverage and knowledge of receptor home
range.
 BSAF at PVS: Estimated fish home ranges
and continuous sediment coverage. All tied
to sediment using GIS.
 Mechanistic Model at PVS: Only as needed to
translate dietary uptake to tissue
concentrations of higher consumers.
21
BSAF Challenges for PVS
 Deciding on boundaries for assessment
 GIS challenges: contouring, subareas
 Determining fish home ranges
 Choosing appropriate surrogate species
 Assigning surrogate species to receptor diets
 Determining foraging ranges of marine
mammals and birds
22
23
Fish tissue concentration (Log mg/kg DDT WW)
Predicted Fish Tissue Concentrations Based on BSAFs
White Croaker, BSAF model
2.5
2
1.5
1
.5
0
-.5
-1
-1.5
-2
-2.5
-3
-3.5
-3
-2.5
-2
-1.5
-1
-.5
0
.5
1
Y = .214 + .75 * X; R^2 = .766
Average sediment concentration (Log mg/kg DDT DW)
2 - 10 km home range
Also, fillets converted to whole-body concentrations.
24
California Sea Lion Distribution
25
Exposure Analysis
Goal: Combine spatial distribution of tDDT and
tPCB contamination with the home ranges of bird
and mammal receptors to predict exposure
• Oral Exposure (dietary)
– sediment to fish regression
(BSAF); allows calculation of
fish or sediment
concentrations where actual
data not available
• Target Organ Exposure
– Empirical (site-specific
measured data - egg and
blubber)
26
Data Required for Exposure Analysis
 Sediment contaminant data
 Contaminant data for dietary items (fish, birds,
mammals)
 Measured concentrations in receptor tissues/target
organs
 Locations of tissue samples for each receptor
 Identification of SCB locations used by each receptor
 Seasonality (percent time receptor spends in SCB)
 Foraging ranges from breeding, nesting or resting areas
 Foraging depths
 Diet composition (development of surrogate diet)
 The importance of pelagic versus benthic dietary items
 Literature-derived body weights and food ingestion rates
for receptors
27
Adult Female Sea Lion:
Oral dosage – Summer range
*
28
Bald Eagle:
tDDT oral
dosage.
#
#
29
Ecological Risk Conclusions

Measured and modeled results
of invertebrates, fish, bird, and
sea lion exposure levels
throughout SCB indicate link to
contaminated sediments at
PVS.
 Risks are small in some areas, but
measurable at locations throughout
the SCB.
 The choice or receptors and area for
evaluation influences the strength of
the link to PVS sediments.
30
Using Food Web Model to Evaluate
Remedial Actions: Important considerations.
 PVS study area versus SCB
 Choice of receptors: Demersal fish; and a coastal,
piscivorous bird.
 Receptors closely tied to PVS.
 Human health vs. Eco drivers
 Short vs. long-term effects
31
PVS Bioaccumulation Model: Baseline Results
 Oral dosages from the model were compared to primary and
secondary literature values for NOECs and LOECs for tDDT and
PCBs.
 Risk was demonstrated as usually greatest for species foraging at
the PVS area. Species at risk, and their modeled diet included:
–
–
–
–
–
Brown Pelican (fish)
Double Crested Cormorant (fish)
Peregrine Falcon (gulls)
Bald Eagle (fish, gulls, sea lion carcasses)
California sea lion (fish)
•
Nursing pups
32
Future remediation? An ability to evaluate the
effects of sediment changes using high site-fidelity
species and to project risks for far-ranging receptors
[as verified by continued monitoring]
Palos Verdes, experimental capping photos
33