The Louis Berger Group, Inc. L B G 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 Using Sediment Tracers to Identify Release Events, Differentiate Sources, and Assess Monitored Natural Recovery
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The Louis Berger Group, Inc.
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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
Using Sediment Tracers to Identify Release
Events, Differentiate Sources, and Assess
Monitored Natural Recovery
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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
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Increasing energy
Sediment is NOT wet dirt…
• It moves!
Energy changes everything
• ocean vs. lake vs. estuary vs. river
• deep water vs. shoreline
Influence of water
Solids transport
Dissolved phase transport
Partitioning and KD
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)
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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, 1010 yrs)
Age of the earth (U-238, 109 yrs)
Age of the dinosaurs (U/Pb, 108 yrs)
Age of the ice ages (U-234, 105 yrs, Th-230, 104 yrs)
Age of the Egyptians (C-14, 103 yrs)
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How Do We Establish Time of Deposition?
(2) Geological Marker Horizons
• Banded Iron Formations
Appearance 3,800 My
Disappearance 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 >104
Tags recently deposited sediment
Typically limited to upper 2 to 3 centimeters in
sediment
Sediments containing Be-7 are considered very
recently deposited, <1 year.
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Atmospheric Production
Be-7
Sediment
Resuspension
and new solids
entering the
system
Be-7 Tidal Transport
and Redeposition
Particle Reactive
Sediment Bed
Water Column
Upland Sources
Deposition
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Radiocesium (Cs-137) as a Marker Horizon
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CESIUM-137 CORE DATING
Three Deposition Rate Formulas:
Dep
th
1963 Peak
1954 Appearance
Cesium-137 (pCi/g)
2005, year of
collection
Rate 3 = Depth of Appearance –Depth of Peak
(1963– 1954)
3
Ideally the
same rate
Ideally the
same rate
Rate 2 = Depth of Cs137 Peak
(Time of core collection – 1963)
2
Rate 1 = Depth of Cs137 Appearance
(Time of core collection – 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