Dr. Edward Garvey, Louis Berger Group

Using Sediment Tracers to Identify Release
Events, Differentiate Sources, and Assess
Monitored Natural Recovery
Edward A. Garvey, PhD, PG
The Louis Berger Group, Inc.
Morristown, NJ
EBC Seminar Series
Part I: Advances in Sediment Site Characterization
September 23, 2011
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Session Outline
• Background on Sediments and Dating
• Time Clocks and Horizon Markers
• Tracer Examples
• Applications
• Current Conditions
• Historical Conditions
• Estimating Natural Recovery
• Conclusions
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Background on Sediments and Dating
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Nature of Sediment and Contamination
• Sediment is NOT wet dirt…
• It moves!
• Energy changes everything
• ocean vs. lake vs. estuary vs. river
Increasing energy
• deep water vs. shoreline
• Influence of water
• Solids transport
• Dissolved phase transport
• Partitioning and K D
• Diagenesis
• Understanding time of deposition
deconvolves impacts of energy
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Begin with a Good Core!
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How Do We Establish Time of Deposition?
(1)
• Established principals for geological dating can be
applied to recent deposition as well.
• Geologist’s Time Keepers (Clocks)
• Radioisotope Clocks (Isotope , half-life)
• Age of the universe (Th232, 10 10 yrs)
• Age of the earth (U-238, 10 9 yrs)
• Age of the dinosaurs (U/Pb, 10 8 yrs)
• Age of the ice ages (U-234, 10 5 yrs, Th-230, 10 4 yrs)
• Age of the Egyptians (C-14, 10 3 yrs)
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How Do We Establish Time of Deposition?
(2)
• Geological Marker Horizons
• Banded Iron Formations
Appearance
Disappearance
3,800 My
1,700 My
• Fossils (trilobites) (530-250 My)
Appearance
530 My
Disappearance
250 My
• Iridium maximum
End of the dinosaurs
65 My
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How Do We Establish Time of Deposition?
Environmental Geochemist’s Tools
• Radioisotope Time Clocks
• Be-7 (53 days)
• Pb-210 (Excess) (22 yrs)
• Horizon Markers
• Appearance of DDT (~1940)
• Bomb Radiocesium (Cs-137)
Appearance 1954
Maximum 1963
• Soda Can Tabs (1960-1975)
• Appearance of PBDEs (1970s)
• Appearance of Fluorinated Surfactants (PFOA/PFOS) -appearance 1950s,
max ~2000
• Appearance of Quaternary Ammonium Surfactant (ATMAC-22) ~1990
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Beryllium-7 as a Radiotracer
• Half life of 53 days
• Highly particle reactive
• Effective Partition Coefficient >10 4
• Tags recently deposited sediment
• Typically limited to upper 2 to 3 centimeters in
sediment
• Sediments containing Be-7 are considered very
recently deposited,

Atmospheric Production
Be-7
Tidal Transport
and Redeposition
Deposition
Particle Reactive
Be-7
Water Column
Upland Sources
Sediment
Resuspension
and new solids
entering the
system
Sediment Bed
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Radiocesium (Cs-137) as a Marker Horizon
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Depth
CESIUM-137 CORE DATING
Three Deposition Rate Formulas:
Cesium-137 (pCi/g)
Rate 1 = Depth of Cs137 Appearance
(Time of core collection – 1954)
2005, year of
collection
2
Ideally the
same rate
1963 Peak
1
Rate 2 = Depth of Cs137 Peak
(Time of core collection – 1963)
Ideally the
same rate
1954 Appearance
3
Rate 3 = Depth of Appearance –Depth of Peak
(1963– 1954)
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Cs-137 Dated Sediment Cores from the
Hudson River
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Chemical Marker Examples
• DDT first appearance circa 1940
• Fluorinated Surfactants (PFOA/PFOS)-appearance
1950s, max ~2000
• PBDE first appearance circa 1978, max 2000 to
present
• PBB first appearance circa 1970, max 1980, decline
to present
• Appearance of Quaternary Ammonium Surfactant
22 (ATMAC-22) ~1990
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Chemical Marker Examples
Poly Brominated Diphenyl Ethers
Poly Brominated Biphenyls
PBB-153
From Zhu, et al., 2005
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Quaternary Ammonium Surfactants
• ATMAC 22 provides an indicator of post 1990
deposition
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Depth
Year of collection
1 Year prior
1990
Concentration
Excess
Pb-210
Idealized
Dated Core
1978
1963
Cs-137
1954
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Limitations of Sediment Dating
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Use of Beryllium-7 to Identify Current Spatial Trends
Tidal Estuary Example
Dam
Tidal Currents
Major Tidal
Exchange
RM 0
17-mile long
RM 17
estuary
Inflow
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Use of Beryllium-7 to Identify Current Spatial Trends
Tidal Estuary Example
• Four studies of 2,3,7,8-TCDD and 4,4-DDE.
1995 0-6 inch sample
2008 0-6 inch sample
2009 0-6 inch sample
2008 0-1 inch sample
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2,3,7,8-TCDD Concentration (ng/kg)
2,3,7,8-TCDD vs. Distance along Estuary
100000
10000
1000
100
10
1
0.1
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0
River Mile
To the Sea
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4,4'-DDE Concentration (ug/kg)
4,4’-DDE vs. Distance along Estuary
1000
100
10
1
0.1
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0
River Mile
To the Sea
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4l
Cesium-137 Core Dating
Hudson River Example
Inflow
Tidal
Exchange
Tidal Currents
One directional
freshwater flow
Inflow
Approximately 200-mile long river
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Similar Recovery Rates Post 1980
Circa 1970 Peak Identified all the way to RM 0
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Cesium-137 Core Dating
Tidal Estuary Example
Dam
Major Tidal
Exchange
Tidal Currents
RM 0
17-mile long
RM 17
estuary
Inflow
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Cs-137 Profiles Permit Comparisons
across the Entire Length of the Estuary
Depth to Cs-137 Maximum
3 ft 7 ft 13 ft 2 ft 4 ft
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Approximate Year of Deposition
Approximate Year of Deposition
Approximate Year of Deposition
0.1 1 10
Historical Dioxin Levels were Extremely High
2007
. . . but Recent Levels are Declining Slowly at Best
2,3,7,8 - TCDD (ug/kg)
2005
0.001 0.01 0.1 1 10
2005
2000
1995
2000
1990
1985
2,3,7,8 - TCDD (ug/kg)
0.1 1 10
2005
2000
1995
RM 1.4
RM 2.2
RM 1.4
RM 7.8
RM 2.2
RM 7.8
RM 11
RM 11
RM 12.6
RM 12.6
Non-contiguous
core segment
1980
1975
1995
1990
1970
1985
1965
1960
1990
1980
1955
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1950
1975
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Depth (Represented by Year)
Approximate Year of Deposition
Dated Sediment Cores Permit Forensic Analysis
of Historical Deposition and Sources
2005
1995
1985
1975
1965
Ratio 2,3,7,8 - TCDD to Total TCDD
0.00 0.20 0.40 0.60 0.80 1.00 1.20
RM 1.4
RM 2.2
RM 7.8
RM 11
RM 12.6
But…Recent
release has
identifiably
different
signature..
Ratio
of ~0.7
1955
1945
1935
Dioxin ratios have changed
only marginally over time.
Original source material is
largely unchanged.
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Depth (represented by years)
Establishing The Current Rate of Recovery
Cesium-137 Core Dating
Total PCB Concentration (ug/kg))
4i
Decline in Total PCB Load
1970s-Present
Peak Total PCB
Load 1960s
Rate of recovery is
equivalent to a 25
year half life.
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Conclusions
• Sediments are a complex media in an energetic
environment.
• Sufficient tracers are available to establish time of
deposition for the last 50 to 100 years, with a resolution of
10 years or less.
• Establishing time of deposition permits comparisons across
large spatial scales and avoids natural “noise.”
• Particle-bound contaminant histories are recorded in the
sediment and can be readily established.
• Current conditions can be easily and inexpensively
established using the right tracers and sampling techniques.
• The contaminant record provides a basis for forensic
analysis and can be used to establish the current rates of
recovery.
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