uses
science for a changing world
Prepared in cooperation with the U.S. Environmental Protection Agency
Measurement and Monitoring for the 21st Century Initiative
User's Guide to the Collection and Analysis of Tree
Cores to Assess the Distribution of Subsurface
Volatile Organic Compounds
Scientific Investigations Report 2008-5088
U.S. Department of the Interior
U.S. Geological Survey
-------
Cower, U.S. Geological Survey hydrologist using an increment borer to obtain a tree core (digitally modified photograph taken
by Allison Vroblesky).
-------
to the and
of to the of
By Don A. Vroblesky
Prepared in cooperation with the U.S. Environmental Protection Agency
Measurement and Monitoring for the 21st Century Initiative
Scientific Investigations Report 2008-5088
U.S. of the Interior
U.S. Sureef
-------
U.S.
DIRK KEMPTHORNE, Secretary
U.S.
Mark D. Myers, Director
U.S. Geological Survey, Reston, Virginia: 2008
For product and ordering information:
World Wide Web: http://www.usgs.gov/pubprod
Telephone: 1-888-ASK-USGS
For more information on the USGS—the Federal source for science about the Earth, its natural and living resources,
natural hazards, and the environment:
World Wide Web: http://www.usgs.gov
Telephone: 1-888-ASK-USGS
Suggested citation:
Vroblesky, D.A., 2008, User's guide to the collection and analysis of tree cores to assess the distribution of subsurface
volatile organic compounds: U.S. Geological Survey Scientific Investigations Report 2008-5088, 59 p.
(available online at http://pubs.waterusgs.gov/sir2008~5088)
-------
Hi
Contents
Abstract 1
Introduction 1
Advantages of Tree Coring as a Tool to Examine Subsurface Volatile Organic Compound
Concentrations 2
Limitations of Tree Coring as a Tool to Examine Subsurface Volatile Organic Compound
Concentrations 2
Acknowledgments 3
Part 1. Methodology for Collection and Analysis of Tree Cores 3
Tree-Core Collection 3
Tree-Core Analysis 7
Quality Control and Assurance 8
Part 2. Historical Perspectives and Technical Considerations 8
Historical Perspectives 8
Technical Rationale for Methodology 9
Tree-Core Collection 9
Tree-Core Transferto Sample Vials and Storage 10
Tree-Core Equilibration Time 11
Tree-Core Analysis 13
Quality Control and Assurance 14
Factors Influencing Volatile Organic Compound Concentrations in Tree Cores 15
Types of Volatile Organic Compounds 15
Subsurface Volatile Organic Compound Concentrations 16
Differences Among Tree Species 18
Rooting Depth and Depth to the Contaminated Horizon 18
Subsurface Lithology 19
Concentration Differences Around the Tree Trunk 19
Volatilization Losses from the Tree Trunk 20
Rainfall Infiltration as a Dilution Mechanism 20
Seasonal Influences 21
Sorption 21
Within-Tree Volatile Organic Compound Degradation 22
Summary 22
References Cited 23
Appendix 1. Case Studies 29
Case Study 1: Chlorinated Ethenes from Ground Water in Tree Trunks
(Summarized from D.A. Vroblesky, C.T. Nietch, and J.T. Morris) 29
Case Study 2: Tree Coring as a Guide to Well Placement, Solid Waste
Management Unit 17, Naval Weapons Station Charleston, South Carolina,
2002 (by D.A. Vroblesky and C.C. Casey) 32
Case Study 3: Operable Unit 4, Riverfront Superfund Site, Franklin County, Missouri
(by J. Schumacher) 34
Case Study 4: MTBE and BTEX in Trees above Gasoline-Contaminated Ground Water
(by J.E. Landmeyer, D.A. Vroblesky, and P.M. Bradley) 38
Appendix 2: Air Sample Analysis for Volatile Organic Compounds (by S. Clifford) 43
-------
IV
Figures
1-4. Photographs showing:
1, Typical tree-coring tool 3
2, Comparison of nonporous, diffuse-porous, and ring-porous wood 5
3. Crimping tool, 20-milliliter crimp-top serum vial, and 40-millilliter volatile
organic analysis fVQA} vial used for collecting tree cores 6
4, Crimp-top serum vial containing tree core 6
5-8. Graphs showing:
5, Loss of trichloroethene overtime from uncapped 20-milliliter serum vials,
Naval Weapons Station Charleston, South Carolina, 2006 10
6, Headspace trichloroethene concentrations at 24 hours and 19 days
of storage in sealed serum vials containing tree cores from a
trichloroethene-contaminated site showing generally slight concentration
increases in most cores and no evidence of volatilization loss overtime 11
7, Trichloroethene concentrations over time in unheated and heated
sealed serum vials containing loblolly pine tree cores from a
trichloroethene-contaminated site showing little concentration change in
cores from some trees after 5 to 6 minutes and an increase in sensitivity
by field heating and analyzing the cores, Solid Waste Management Unit 17,
Charleston, South Carolina 12
8, Field-heated and unheated (A) trichloroethene and (B) tetrachloroethene
concentrations in 20-milliliter serum vials containing cores from
trees growing over ground-water contamination showing that field
heating the sample vials can produce VOC concentrations that are in the
range of or higher than concentrations obtained by allowing the samples
to equilibrate at room temperature overnight 13
9-10. Maps showing:
9, Trees cored at the Nyanza Chemical Waste Dump Superfund Site, Ashland,
Massachusetts, August 2006, showing proximity to wells and to buildings
where vapor-intrusion investigations were conducted in 2004 17
10, 1,1,1-Trichloroethane concentrations in tree cores in 2006 showing
correspondence to the combined results of 2003 and 2006 soil-gas
investigations at the Merriam Manufacturing Company property,
Durham Meadows Superfund Site, Connecticut 17
11. Graph showing trichloroethene removal from the rhizosphere of bald cypress
seedlings as (A) nanomoles per minute through the above-ground part
of the plant and (B) fractional trichloroethene loss from carboy water
during the summer and winter 21
Tables
1. Examples of nonporous, diffuse-porous, and ring-porous trees 5
2. Field data to be collected during tree-coring investigation 7
3. Trichloroethene concentrations in tree cores collected within about 5 minutes
of each other, using the same core barrel with no decontamination between
cores, showing no carryover between core collections 14
4. Chemical formula, Henry's Law constant, and log octanol-water partition
coefficients for selected volatile organic compounds reported in tree-coring
investigations 15
-------
Conversion Factors and Datums
Multiply
inch (in.)
inch (in.)
foot (ft)
mile (mi)
square foot (ft2)
square mile (mi2)
gallon (gal)
cubic inch (in3)
cubic yard (yd3)
foot per day (ft/d)
foot per year (ft/yr)
gallon per minute (gal/min)
gallon per day (gal/d)
inch per year (in/yr)
foot per mile (ft/mi)
By
Length
2.54
25.4
0.3048
1.609
Area
0.09290
2.590
Volume
3.785
16.39
0.7646
Flow rate
0.3048
0.3048
0.06309
0.003785
25.4
Hydraulic gradient
0.1894
To obtain
centimeter (cm)
millimeter (mm)
meter (m)
kilometer (km)
square meter (m2)
square kilometer (km2)
liter (L)
cubic centimeter (cm3)
cubic meter (m3)
meter per day (m/d)
meter per year (m/yr)
liter per second (L/s)
cubic meter per day (m3/d)
millimeter per year (mm/yr)
meter per kilometer (m/km)
Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:
°F=(1.8x°C)+32
Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:
°C=(°F-32)/1.8
Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).
Altitude, as used in this report, refers to distance above the vertical datum.
Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or
micrograms per liter (ug/L).
-------
VI
in this
BTEX benzene, toluene, ethylbenzene, and xylene
cDCE cis-1,2-dichloroethene
cni/yr centimeter per year
DNAPL dense non-aqueous phase liquid
BCD electron-capture detector
GC gas chromatograph
GC/MS gas chromatograph/mass spectrometry
g/L grani per liter
HSA headspace analysis
kg kilogram
Kmv octanol-water partition coefficient
Kwmd equilibrium distribution of compounds between tree tissue and water
L/d liter per day
L/nr/yr liter per square meter per year
mg/g milligram per gram
mL milliliter
rnpfa miles per hour
MTBE methyl tot-butyl ether
OS WER Office of Solid Waste and Emergency Response
OU operable unit
PC A 1,1,2,2-tetrachloroethane
PCE tetrachloroethene
P1D photoionization detection
ppbv parts per billion by volume
ppmv parts per million by volume
PRG preliminary remediation goal
PT purge-and-trap analysis
PVC polyvinyl chloride
RCF root concentration factor
SWMU Solid Waste Management Unit
TC A 1,1,1 -trichloroethane
TCE trichloroethene
1MB trimethylbenzene
TSCF transpiration stream concentration factor
|!g-h/kg microgram in headspace per kilogram of wet core
|ig/kg microgram per kilogram
|,ig/L microgram per liter
|iL microliter
USEPA U.S. Environmental Protection Agency
USGS U.S. Geological Survey
VC vinyl chloride
VOA volatile organic analysis
VOC volatile organic compound
-------
¥11
and of in this
Common name
Alder
Apple, pear
Ash
Aspen, cottonwood
Bald cypress
Beech
Birch
Blue beech
Buckeye
Cedar
Coffee tree
Cottonwood. Eastern
Cottonwood. Fremont
Cottonwood. narrow leaf
Dogwood
Douglas fir
Him, American
Elm, Cedar
Elm, Chinese
Eucalyptus
False cypress
Fig, laurel
Fir
Ginkgo
Gum
Hackbcrry, Southern
Hemlock
Holly
Scientific name
Alnus sp.
Primus sp.
Fraxinus sp.
Populus sp.
Taxodium sp.
Fagus sp.
B etui a sp.
Carpinus sp.
Aesculus sp.
Thuja sp.
Gymnocladus dioicus
Populus deltoides
Populus fremontii
Populus angustifolia James
Cornus sp.
Psendotsuga sp.
Ulmus ainericana
Ulinus crassifolia
Ulmus parvifolia
Eucalyptus sp.
Chamaecyparis sp.
Ficus microcarpa
Abies sp.
Ginkgo sp.
Nyssa sp.
Celtis laevigata
Tsuga sp.
Ilex sp.
Common name
Iloneylocust
Juniper
Juniper, Ashc
Larch
Locust
Magnolia
Maple
Maple, box elder
Mulberry
Oak
Oak. Texas live
Oak. White shin
Osage orange
Paulownia
Pine
Pine, loblolly
Poplar, hybrid
Redwood
Rosewood
Russian olive
Sassafras
Spruce
Sunflower
Sweetgum
Sycamore
Willow
Willow, Goodding's
Scientific name
Gleditsia sp.
Juniperus sp.
Juniperus ashei
Larix sp.
Robinia sp.
Magnolia sp.
Acer sp.
Acer negundo
Morns sp.
Quercus sp.
Quercusfiisiforniis
Quercus sinuata
Madura potnifera
Paulownia sp.
Finns sp.
Pinus taeda
Populus dell aides x Populus
trichocarpa
Sequoia sp.
Dalbergia sissoo
Elaeagnus angustifolia
Sassafras sp.
Picea sp.
Helianthus annuus
Liquidambar sp.
Platanus sp.
Salix sp.
Salix gooddingii
-------
-------
to the and of
to the of
By Don A. Vroblesky
Abstract
Analysis of the volatile organic compound content of tree
cores is an inexpensive, rapid, simple approach to examining
the distribution of subsurface volatile organic compound
contaminants. The method has been shown to detect several
volatile petroleum hydrocarbons and chlorinated aliphatic
compounds associated with vapor intrusion and ground-water
contamination. Tree cores, which are approximately 3 inches
long, are obtained by using an increment borer. The cores
are placed in vials and sealed. After a period of equilibration,
the cores can be analyzed by headspace analysis gas chroma-
tography. Because the roots are exposed to volatile organic
compound contamination in the unsaturated zone or shallow
ground water, the volatile organic compound concentrations in
the tree cores arc an indication of the presence of subsurface
volatile organic compound contamination. Thus, tree coring
can be used to detect and map subsurface volatile organic
compound contamination. For comparison of tree-core data at
a particular site, it is important to maintain consistent methods
for all aspects of tree-core collection, handling, and analysis.
Factors affecting the volatile organic compound concentrations
in tree cores include the type of volatile organic compound,
the tree species, the rooting depth, ground-water chemistry,
the depth to the contaminated horizon, concentration differ-
ences around the trunk related to variations in the distribution
of subsurface volatile organic compounds, concentration
differences with depth of coring related to volatilization loss
through the bark and possibly other unknown factors, dilution
by rain, seasonal influences, sorption, vapor-exchange rates,
and wilhin-lree volatile organic compound degradation.
Introduction
Tree roots absorb water and chemicals from the soil and
transport them up the tree trunk. Thus, the chemical content of
tree cores can be useful indicators of subsurface contamination
(Vroblesky and Yanosky, 1990; Vroblesky and others, 1992,
1999; Yanosky and Vroblesky, 1992, 1995; Yanosky and
others, 2001). A variety of volatile organic compounds
(VOCs) from subsurface contamination are known to be
taken up by plant roots into the trunks of trees. These
compounds include benzene, toluene, elhylbenzene,
xylcnc isomcrs, trimcthyl benzene, methyl tert-butyl ether
(MTBE), 1,1,2,2-tetrachloroethane, trichloroethene (TCE),
tetrachloroethene (PCE), 1,1,1-trichloroethane (TCA), vinyl
chloride (VC), and ris-l,2-dichlorocthene (cDCE) (Burkcn,
2001; Burken and Schnoor, 1998; Ilirsh and others, 2003;
Landmeyer and others, 2000; Newman and others, 1997;
Nietch and others, 1999; Trapp and others, 2007; Vroblesky
and others, 1999, 2006). The presence of VOCs in tree trunks
can allow a reconnaissance-level mapping of the ground-water
plume by simple analysis of tree cores (Vroblesky and others,
1999, 2001, 2004). Determining the presence of subsurface
VOCs is useful for evaluating the potential ingestion risks to
human health from ground water and the potential for respira-
tion risks from vapor intrusion
into buildings.
The purpose of this report is to provide a guide to the
use of tree coring as a tool to examine subsurface VOCs. To
that end, the report is divided into two major parts. The first
part of the report presents basic guidelines for a tree-coring
investigation to examine subsurface VOCs. The second pail of
the report examines historical and technical issues related to
tree coring as a tool to examine subsurface contamination.
The technical considerations include rationale for various
aspects of the methodology and a discussion of factors influ-
encing VOC concentrations in tree cores. An understanding
of the factors influencing VOC concentrations in tree cores is
necessary to better plan field investigations and to understand
the meaning of the results of the investigation. In addition,
two appendixes are attached. Appendix 1 is a collection of
case studies. Appendix 2 is a protocol by the U.S. Environ-
mental Protection Agency (USEPA) for conducting air-sample
analysis of VOCs using two different types of gas chromato-
graphs. The analytical method reported in Appendix 2 has
been tested only for selected VOCs (listed in Appendix 2).
Additional testing would be required to determine the
appropriateness of this method for the other VOCs
discussed in the report.
-------
User's Guide to the Collection and Analysis of Tree Cores to the Distribution of Subsurface Volatile Organic Compounds
Funding for this guide was provided by the USEPA's
Office of Solid Waste and Emergency Response (OSWER)
through its Measurement and Monitoring Technologies for
the 21st Century Initiative http://clu-in.org/progratns/21M2/.
This initiative seeks to identify and disseminate information
on promising measurement and monitoring technologies in
response to waste management and cleanup needs. Methodolo-
gies described in this guide arc also fully compatible with
USEPA's Triad strategy to manage hazardous waste site
decisionmaking uncertainty through systematic planning,
dynamic work strategies, and real-time measurement technolo-
gies. More information on the Triad approach can be found at
http://www.triadcentral.org/.
Tree coring to examine subsurface VOCs has several
advantages and limitations over more invasive approaches to
site investigations, such as well drilling. The advantages and
limitations are listed below.
of Coring as a Tool to
Concentrations
1. Tree coring allows examination of unsaturated-zone
and ground-water contamination in areas where cultural
influences, vegetation cover, or concerns of landown-
ers limit the ability lo use more invasive reconnaissance
approaches to site characterization using large mechanical
equipment.
2. The method is applicable to a variety of VOCs commonly
associated with vapor intrusion and ground-water con-
tamination, including chlorinated solvents and petroleum
hydrocarbons.
3. The presence of VOCs in tree cores is a strong indicator
of subsurface VOC contamination. The relative concen-
trations of VOCs among tree cores from a particular site
often can provide general information on the relative
distribution of VOC concentrations in the subsurface.
4. Under some conditions, tree coring can be used to detect
VOCs in soil gas (Struckhoff, 2003; Schumacher and
others, 2004; Struckhoff and others, 2005b), providing a
potentially useful tool for examining soil-vapor concen-
trations. Thus, tree coring for VOCs may be an effective
approach for determining areas that have relatively high
vapor-intrusion potential.
5. Tree coring can detect chlorinated solvents at relatively
low concentrations. Schumacher and others (2004)
determined that analysis of tree-core samples can be used
to detect PCE contamination in soils at concentrations
of several hundreds of micrograms per kilogram or less
and PCE concentrations as low as 8 micrograms per liter
(|ig/L) in ground water in direct contact with the roots.
6. The method is rapid and uncomplicated. A tree core can
be collected in less than 5 minutes. No decontamination
of the core barrel is required, other than inspection to
ensure that there is no paniculate carryover, such as sec-
tions of tree core, remaining in the core barrel. The cores
can be analyzed by the relatively simple gas chromatog-
raphy.
7. The samples can be analyzed for preliminary results in
the field after equilibrating for 5 minutes or longer or by
heating to assist in directing the tree-coring effort, or can
be transported back to a laboratory for later analysis.
8. If the samples are to be analyzed within a few days of col-
lection, the cores can be stored without refrigeration.
9. The method is inexpensive. Increment borers can be
purchased for a few hundred dollars and can be re-used
for years with proper care. By contrast, well sampling is
time consuming, and well sampling equipment can cost
thousands of dollars. In the time it takes to sample a well,
several tree cores can be collected.
10. A minimal amount of field equipment is required. A large
number of tree cores can be collected rapidly with an
increment borer and sample containers.
11. There is evidence that parts of the aquifer where there is
preferential, chlorinated-solvent dechlorinalion sometimes
can be delineated by comparing parent/daughter ratios in
tree cores (Vroblesky and others, 2004). Areas where the
tree-core data indicate a low parent/daughter ratio, such as
TCE/cDCE, relative lo other areas of the site may be loca-
tions of enhanced subsurface dechlorination.
12. Because trees collect water from the subsurface over the
lateral and vertical extent of their root system, trees pro-
vide information over a substantially larger volume than
a well or soil sample. Tree coring targets contaminants in
shallow horizons, such as the uppermost ground water, the
capillary zone, and the unsaturated zone.
of as a Tool to
Concentrations
1. Because there are a number of influences on tree-core
VOC concentrations, the absence of VOCs in a tree core
cannot be used to definitively show that VOC contamina-
tion is not present. It is possible that at the site in ques-
tion, the tree roots do not extend to the contamination
because the tree can obtain adequate water supplies from
a source shallower than the contamination, or because the
contamination is otherwise inaccessible to the tree.
2. The variety of influences on tree-core VOC concen-
trations renders it improbable that tree-core VOC
-------
Parti. Methodology for Collection and Analysis of Tree Cores
concentrations can be used in a quantitative way to deduce
specific subsurface VOC concentrations. Instead, tree-
core concentrations reflect the generalized distribution of
high and low subsurface VOC concentrations.
3. While the proper collection of several cores from a single
large tree typically does not result in lasting damage to
the tree, care should be taken to avoid excess coring of
individual trees to minimize stress to the tree.
4. Because incorporation of infiltrating rainwater into the
transpiration stream can dilute in-tree VOC concentra-
tions, higher tree-core VOC concentrations probably will
be obtained if the cores are collected during a relatively
dry period rather than immediately after a rain event.
Cores collected during the dormant-growth season may
contain lower VOC concentrations than cores collected
during the summer, although multiple field studies found
that the VOC content of tree cores still can be useful
indicators of subsurface VOC contamination even during
the dormant-growth season (Vroblesky and others, 1999,
2006; Richard Willey, U.S. Environmental Protection
Agency, written commun., 2008).
5. When using headspace gas chromatographic analysis of
tree cores on a typical field gas chromatograph (GC), a
number of tree-related volatile compounds elute at about
the same time as VC, potentially complicating identifica-
tion of that compound.
Tree-Core Collection
Tree cores are collected by using a tree-coring tool
(fig. 1). The tree-coring tool consists of an increment borer
and a core extractor. The core extractor is a component that
easily can be misplaced in a forest because of its thin elon-
gated shape. A practical approach is to tie a brightly colored
plastic tape or cloth to the extractor (fig. 1).
1. Choosing a tree-coring tool: Increment borers are avail-
able in various lengths from 4 in. (inches) to 28 in., and
in three diameters (0.169, 0.2, and 0.5 in.). Considering
that most tree coring for VOCs involves coring to a depth
of only about 3 in., increment borers from 8 to 10 in. long
allow hands to be far enough from the tree so as not to
scrape bark or come into contact with poison ivy vines
yet not be so long as to become unwieldy. The smallest
borer diameter is commonly used for general forestry
applications, and the largest diameter is used when large
amounts of wood are required for chemical analysis. Most
of the investigations using increment borers to examine
VOC concentrations in tree cores have used either 0.169-
or 0.2-in. diameter borers. Increment borers also can be
obtained in a two-thread or three-thread design. Three-
thread designs typically advance farther per revolution
than two-thread designs but can be more difficult to turn
and to initially engage the wood than a two-thread design.
Thus, two-thread designs are more suited to hardwoods,
and three-thread designs are more suited to softwoods.
Acknowledgments
Several people outside of the U.S. Geological Survey
(USGS) made important contributions to this publication.
Richard Willey (USEPA) functioned as project manager and
invested many hours in reviews, suggestions, and creative
input. Manuscript reviewers from the USEPA included Scott
Clifford, Charles Porfert, Anni Loughlin, Kathy Davies,
Michael Adam, and Robert Alvey. Judy Canova from the
South Carolina Department of Health and Environmental
Control also provided review comments. Joel Burken of the
University of Missouri-Rolla provided a colleague review of
the manuscript. James Landmeyer provided a colleague review
within the USGS. The suggestions and comments from these
reviewers were invaluable and, in some cases, changed the
direction of the manuscript.
Parti. Methodology for Collection
and Analysis of Tree Cores
Tree coring involves collecting a core from a tree and
transferring the core to sample vials. The samples can be
stored for a few days at room temperature prior to analysis. If
longer storage is required, the samples should be refrigerated.
Core extractor
with attached flagging
Increment borer
3 inches
111111111 i
012345 centimeters
Figure 1. Typical tree-coring tool.
-------
User's Guide to the Collection and Analysis of Tree Cores to the Distribution of Subsurface Volatile Organic Compounds
2. Core-barrel sharpening: Increment borers should be
sharp enough to easily engage the wood. The borer needs
sharpening when engaging the wood is difficult, when the
borer cuts a rough core, when the edge feels dull to the
touch, or whet) the extractor consistently fails to recover
the core. It should not be assumed that a new borer is
sharp; sharpening methods for increment borers can be
found in Maeglin (1979) and Grissino-Mayer (2003).
3. Core-barrel cleaning: New increment borers should be
cleaned prior to use in examining tree-core VOC concen-
trations because the new borers some limes are coated with
a thin layer of oil. In addition, researchers involved in tree
coring for the use of dendrochronology often lubricate the
interior of the core barrels. Such lubrication, however, is
inappropriate for the use of tree cores to examine VOCs.
Borers can be cleaned with soap and water. For increment
borers with a diameter of 0.2 in., rifle-cleaning rods with
an attached soft cloth are effective for cleaning inside
the barrel. A clean cloth can be pushed through the core
barrel, sealed in a vial, allowed to equilibrate with the
headspace, and analyzed by headspace chromatography to
verify that the cleaning removed potential interferences.
4. Initiating coring: The most difficult part about tree cor-
ing is initiating the coring. The boring should be started
slowly and carefully to avoid sideways slippage of the bit
against the tree trunk. One approach is to hold the borer
shaft near the threaded bit with one hand while apply-
ing pressure toward the Iree and turning the borer with
the other hand. Folding chest plates and straps that wrap
around the trunk also are commercially available as tools
to assist in starling the bit into the tree. The coring should
be approximately perpendicular to the tree trunk. Once the
bit has begun drilling into the tree, both hands can be used
to advance the borer. Increment borer drill chucks are
available for use with a drill; however, standard 19-volt
or less portable drills are not always powerful enough to
collect a complete length of core.
5. Core-collection location: When conducting a tree-coring
survey to examine the areal distribution of VOCs at a site,
the cores should be collected from the trees at about the
same height. A core collected near the ground usually
provides higher VOC concentrations than a core collected
higher up the trunk; however, for ease of core collection
in typical applications, a simple approach is to use mean
breast height, a commonly used forestry term meaning
about 4.3 feet (ft) above land surface. In general, the core
should be collected from the side of the tree suspected
to be closest to the target contamination body. Dead or
damaged parts of the tree should be avoided. Refer to the
technical considerations section of this report for a more
complete discussion of concentration variations with
height above the ground and with azimuthal direction.
6. Core length: The length of the core should be consistent
among the cored trees and should include the outermost
growth ring. A core of the outermost 3 in. (not includ-
ing the bark) is sufficient to identify the contaminants. A
simple approach is to mark the core barrel at a distance
from the bit equivalent to the length of a serum vial
(approximately 3 in., not including the bark). By advanc-
ing the borer until the mark is at the inner edge of the
bark, xylem cores of uniform length can be obtained that
fit into the sampling vials. If necessary, the cores can be
broken to make the vials easier to seal.
7. Core removal: The core is removed from the borer by
means of an extractor (fig. 1). After the increment borer
has been advanced into the tree to the desired depth, the
extractor is fully inserted into the borer. The extractor
should be inserted with the concave side of the extractor
facing down. In typical forestry applications, the borer is
then rotated one half turn counter clockwise to break the
core, and the core is removed from the borer by pulling
on the extractor. Often, this procedure will remove the
entire core from the borer. In some cases, however, pan
of the core will remain in the borer because extractors
sometimes lose their ability to adequately grip the core or
because part of the core becomes wedged in the bit. Prob-
able causes of a jammed core in the core barrel include
a dull core-barrel bit and a dirty core barrel. To facilitate
comparison of tree-core VOC concentrations, it is prefer-
able to maintain uniform lengths of core samples and to
seal the entire length of required core in sampling vials
as soon as possible. Therefore, if the extractor begins to
fail to recover the entire core from the barrel, an alternate
approach should be used. The alternate approach is to
insert the extractor fully into the borer once the depth of
penetration has been reached, rapidly remove the borer
from the tree, insert an unpainted golf tee into the end of
the bit, and press it against the tree while removing the
extractor and tree core. In most cases, this gently removes
the entire core without damaging the cutting edge of
the bit.
8. Parts of the tree core to be included: Because the bark
is not involved in transpiration, inclusion of the bark
in the sample is not necessary. If the bark is removed,
however, care should be taken to avoid accidental removal
of the outermost xylem growth ring in ring-porous trees
(table 1; fig. 2) because the outermost ring is the domi-
nant path for water transport through the trunk (Ellmore
and Ewers, 1986). A more detailed discussion can be
found in the section on technical rational for methodol-
ogy. Inclusion of the inner part of the bark as part of the
sample probably does not produce a substantial adverse
effect on VOC headspace concentrations when the values
are reported as parts per million by volume (ppmv) of
headspace.
-------
Part 1. Methodology for Collection and Analysis of Tree Cores
Table 1. Examples of nonporous, diffuse-porous, and ring-porous trees.
Nonporous
Diffuse porous
Ring porous
Bald cypress (Taxodium sp.)
Cedar (Thuja sp.)
Douglas fir (Pseudotsuga sp.)
False cypress (Chamaecyparis sp.)
Fir (Abies sp.)
Ginkgo (Ginkgo sp.)
Hemlock (Tsuga sp.)
Juniper (Juniperus sp.)
Larch (Lam sp.)
Pine (Pinus sp.)
Redwood (Sequoia sp.)
Spruce (Picea sp.)
Alder (Alnus sp.)
Apple, pear (Prunus sp.)
Aspen, cottonwood (Populus sp.)
Beech (Fagus sp.)
Birch (Betula sp.)
Blue beech (Carpinus sp.)
Buckeye (Aesculus sp.)
Dogwood (Cornus sp.)
Eucalyptus (Eucalyptus sp.)
Gum (Nyssa sp.)
Holly (Ilex sp.)
Magnolia (Magnolia sp.)
Maple (Acer sp.)
Sweetgum (Liquidambar sp.)
Sycamore (Platanus sp.)
Willow (Salix sp.)
Ash (Fraxinus sp.)
Coffee tree (Gymnocladus dioicus)
Honeylocust (Gleditsia sp.)
Locust (Robinia sp.)
Mulberry (Moms sp.)
Oak (Quercus sp.)
Osage orange (Madura pomifera)
Paulownia (Paulownia sp.)
Sassafras (Sassafras sp.)
A. Nonporous wood
B. Diffuse-porous wood C. Ring-porous wood
Figure 2. Comparison of nonporous, diffuse-porous, and ring-porous
wood (reprinted with permission from Chaney, 2000).
9. Timing of tree-core transfer to sample vials: Tree
cores should be sealed in vials immediately upon recovery
from the tree. Volatilization loss begins immediately upon
removal of the core from the tree. If the core is not sealed
in a vial within several seconds of collection, it should be
discarded, and a new core should be collected.
10. Type of sample vial: Either 20-milliliter (mL) glass
serum vials or 40-mL volatile organic analysis (VOA)
vials can been used for collecting tree cores for head-
space analysis (figs. 3 and 4). Consistency should be
maintained within an individual study area. The VOA
vials have an advantage in that they do not require the
use of a crimping tool; however, the crimp-top serum-vial
cap provides a better seal than the VOA-vial cap because
the VOA-vial seal is designed for use with water samples
rather than air samples. In addition, for a given mass of
TCE in a tree core, higher headspace TCE concentrations
are found in the 20-mL vials as compared to the 40-mL
vials because of dilution. Therefore, if the expected
concentrations are relatively low, the vials are going to be
stored for several days prior to analysis, or the vials will
be heated, the 20-mL crimp-top serum vials offer a greater
margin of confidence.
11. Sample storage: In general, TCE concentrations appear
to be fairly stable for several days in sealed sampling vials
containing tree cores; however, it is prudent to analyze
the cores within a few days of collection. The samples
should be stored in the dark because of the potential for
photodegradation of the VOCs. If the tree-core samples
will be analyzed within a few days of sample collection,
the samples can be stored at room temperature prior to
analysis to facilitate equilibration of the headspace in the
vials with the VOCs in the enclosed tree core. If a longer
period of time before analysis is anticipated, then refriger-
ating the cores will reduce the potential for vapor loss and
decay. Refrigerated cores should be allowed to equilibrate
for at least a few hours at room temperature or for a few
minutes by heating prior to analysis.
12. Map the location and mark the tree: It is important to
preserve a record of the location of cored trees so that the
analytical results can accurately be related to the site. An
-------
User's Guide to the Collection and Analysis of Tree Cores to Assess the Distribution of Subsurface Volatile Organic Compounds
6 inches
TT IT
n i
10 centimeters
Crimping
tool
Crimp cap
Teflon-lined
seal
20-milliliter
serum vial
Vial cap with
Teflon-coated seal
40-milliliter
VOAvial
Figure 3. Crimping tool, 20-milliliter crimp-top serum vial, and 40-millilliter volatile
organic analysis (VOA) vial used for collecting tree cores.
Figure 4. Crimp-top serum vial containing
tree core.
effort should be made to mark the approximate location of
each cored tree on a site map. If necessary, the tree loca-
tions can be precisely mapped by surveying at a later date.
The cored trees should be marked in some way to facili-
tate returning to the site to follow up on the investigation.
A variety of tree-marking methods are available. The
most long-term marking method involves "engraving"
the tree identification number on an aluminum tag with a
ball-point pen and nailing the tag to the tree. Depending
on esthetic issues and how long the tree-tag needs to last,
other means of marking the tree with an identification
number include tree paint, marked wooden stakes driven
into the ground adjacent to the tree, or colorful flagging
with the identification number written on the flag tied
around the tree.
13. Tree-coring damage: Although tree coring can impart
local damage to tree trunks, most trees are capable of
compartmentalizing the damage and healing within 2-3
years with no adverse effects. Trees that have a more dif-
ficult time recovering are generally those that are short-
lived species or suppressed individuals. Sealing the core-
hole does not appear to accelerate the repair and probably
is not necessary. A more detailed discussion is available in
the section of this report titled "Tree-Core Collection" in
the "Technical Rationale fore Methodology" section.
14. Supportive data to be collected: A variety of data
should be collected in conjunction with tree coring to
assist in interpretation of the results. The data are summa-
rized in table 2.
-------
Part 1. Methodology for Collection and Analysis of Tree Cores
Table 2. Field data to be collected during tree-coring investigation.
Location information:
Date/time.
Site location.
Unique tree identifier.
Location of tree in study area.
Note unusual geographic issues, such as if the tree is in an island in a parking lot where rainfall infiltration
may be limited, on the edge of a cliff where depth to ground water may be large, on a stream bank where
bank storage may constitute part of the tree's water supply, or other factors of potential interest.
Temperature and weather conditions at the time of collection and for approximately 3 days prior to the sam-
pling, based on the nearest weather station.
Tree characteristics:
Species.
Indications of tree stress (damaged bark, dead branches, etc.).
Whether or not there are leaves on the tree
'Free diameter (can be rneasuiod vulh hoc diamcloi tape moasmcl
Note whether or not the hoc IN oomideied to lopiosont haokgiound conditions
Core-collection information:
Height of tree core.
Side of the tree from which the core was collected.
Note whether duplicate samples were collected.
Note whether an air blank was collected at the tree.
Note any unusual core characteristics, such as a hollow or rotten interior of the tree.
Tree-Core
Analysis of the tree-core samples involves allowing an
initial equilibration period for the VOCs in the tree core to
partition into the sampling media, typically headspace air. The
media is then analyzed by gas chromatography.
1. Sample equilibration time: Once the tree cores are
sealed in the sample vials, the VOCs associated with the
tree core begin to volatilize into the vial headspace. The
volatilization is fast enough so that detectable quantities
of TCE can accumulate within the vial within minutes.
In a field test for this investigation where the ambient
air temperature was about 21 °C, analysis of the samples
about 5 to 6 minutes after capping the vials was adequate
to detect subsurface VOC contamination. In some cases,
however, VOC concentrations in the tree-core vials can
increase substantially by allowing the cores to equilibrate
at room temperature overnight. Variations in equilibration
time can be caused by differences in ambient temperature,
differences in heating of the core by friction during cor-
ing, and other unidentified factors. If an important part of
the investigation is to compare concentrations among tree
cores at a particular site, then allow enough equilibration
time so that the VOC concentrations are less sensitive to
factors related to core collection. Overnight equilibra-
tion at room temperature is a commonly used approach.
Alternatively, heating the vials can transfer larger amounts
of the VOCs into the headspace, resulting in an increased
sensitivity. A simple block heater or water bath can be
used in the field with a power inverter connected to a car
battery to heat the cores in sealed vials at 60-70 °C for a
few minutes. An advantage of field analysis of tree cores
is that it can be used to direct the field sampling effort.
2, Sample analysis: In general, the simplest analyti-
cal approach for tree cores in vials is to use headspace
analysis (HSA) gas chromatography. The headspace can
be analyzed by purge-and trap (PT) or by direct injection
onto a GC column by syringe. The photoionization detec-
tors (PID) and the electron-capture detector (ECD) are
both useful gas chromatographic tools for tree-core analy-
sis. A protocol for HSA of VOCs is included as Appen-
dix 2 in this report. The protocol reported in Appendix 2
has not been tested for all analytes reported to have been
detected in tree cores in this report. Analytes not listed in
the Appendix should be tested to determine the applicabil-
ity of the method. A variety of VOC-conccntration report-
ing units have been used in tree-coring investigations, but
because semiquantitative data are typically sufficient, a
simple approach is to use a consistent sample-vial
volume, collect a consistent core size, and report the
results as the volume of the VOC per billion volumes of
ambient air.
-------
8 User's Guide to the Collection and Analysis of Tree Cores to the Distribution of Subsurface Volatile Organic Compounds
and
Four types of quality control and assurance samples
should be collected to maintain the integrity of the data.
The sample types are duplicate samples, air-blank samples,
background samples, and trip blanks.
1. Duplicate samples: Duplicate samples consist of two
core samples collected in separate vials. The samples
should be collected from the same tree with the second
core collected approximately 1 in. below the first core.
The cores should be of equal length. These samples pro-
vide information on the variability of VOC concentrations
caused by collection and analysis. The number of dupli-
cate samples collected should be about 10 percent of the
total number of trees cored.
2. Air-blank samples: Air-blank samples are collected
by rapidly waving an empty vial in the air in the vicinity
of the target tree. The vial then is capped, transported,
and analyzed in the same manner as the tree cores. This
measurement provides information on the influence of
air pollution on the sample quality. If TCE were present
in analysis of a tree core, for example, but not in the air
blank sample collected adjacent to the tree, then ambient
air can be eliminated as the source of the detected TCE,
demonstrating that the TCE is associated with the core.
Ambient air samples should be collected at various loca-
tions across the study area and whenever there is a suspi-
cion that airborne contaminants may provide interference,
as is sometimes the case near active gasoline stations
or dry-cleaning facilities. It also is possible that some
level of VOC concentration may be present in the air by
virtue of plant cvapotranspiration. In general, the dilution
factors and wind influences are large enough that VOC
concentrations in excess of air standards for gas-phase
contamination arc unlikely to be caused by phytovola-
tilization; however, at least one investigation found that
possible action-level exceedances might occur with highly
toxic substances, such as VC and carbon tetrachloride, if
they are present in ground water at levels above kilogram
amounts in a single plume of a few hectares, and released
by vigorously growing plants under hot, dry conditions
(Narayanan and others, 2004).
3. Background sample: A background sample for a par-
ticular tree species consists of a core of that species col-
lected from an uncontaminated area. Background samples
are used because trees can contain natural VOCs, such as
toluene, that can be detected during gas chromatographic
analysis of the cores. The background sample ensures that
target compounds detected in trees from a contaminated
area arc not a misinterpretation of naturally occurring
volatile compounds that elute on a gas chromatograph at
the same time as the target compounds. A background
sample should be analyzed for each tree species.
4. Trip blanks: Trip blanks are air-filled vials sealed in a
contaminant-free environment. The trip blanks are taken
to the field and are kept with the tree-core samples once
they are collected. The purpose of the trip blank is to
determine whether exposure to target compounds during
sample transportation could have resulted in false detec-
tions of contaminants.
Part 2 of this report provides an overview of historical
perspectives related to the use of tree coring with an emphasis
on application of the method to examining uptake of organic
contaminants. In addition, this section of the report provides
technical rationale for various aspects of the methodology
and examines factors influencing VOC concentrations in tree
cores.
Tree cores have been widely used for dendrochronology
and other environmental applications since the early part of the
20th century when an American astronomer, A.E. Douglass,
related tree-core widths to climatic wet and dry periods
(Douglass, 1919). Examination of plants as a mechanism to
remediate subsurface organic contaminants dates back at least
to the early 1960s (Castelfranco and others, 1961).
Early interest in the uptake of organic chemicals by
plants had an emphasis on agrochemicals (Shone and Wood,
1972, 1974). These authors used the transpiration stream
concentration factor (TSCF) to normalize the compound
concentration in the transpiration stream with respect to root-
zone bulk compound concentrations (Shone and Wood, 1974).
Briggs and others (1982) showed that TSCFs of nonvolatile
compounds were related to the properties of the chemical
being taken up by the plant, particularly, the degree to which
the compound was hydrophobic. Burken (1996) showed that
the same general factors control plant uptake of VOCs. Thus,
since the 1990s, it was clear mat VOCs could be taken up
into trees through the root system (Burken, 1996; Burken
and Schnoor, 1998; Complon and others, 1998; Davis and
others, 1998a; Newman and others, 1997; Vroblesky, 1998;
Vroblesky and others, 1999).
The first application of tree-core chemistry to map VOCs
in ground water was at the Savannah River Site in South
Carolina (Vroblesky, 1998; Vroblesky and others, 1999). This
investigation involved tracking a chlorinated solvent plume
beneath a flooded cypress swamp. Headspace analysis of cores
from 97 trees (6 species, predominantly bald cypress [Taxo-
diutn dixtichutn]) growing over ground-water contamination in
a forested flood plain of the Savannah River in South Carolina
showed that rDCE and TCE concentrations in tree cores
-------
Part 2. Historical Perspectives and Technical Considerations 9
reflected the configuration of the ground-water contamination
plume, despite the fact that most of the trees were growing in a
few feet of uncontaminated standing water from the Savannah
River.
Landmeyer and others (2000) extended the application
of tree cores from examining subsurface chlorinated solvents
to examining subsurface petroleum hydrocarbons. They
found MTBE and the conventional gasoline compounds
benzene, toluene, ethylbenzene, and the isomers of xylenes
and trimethylbenzene in cores from oak trees (Quercus sp.)
growing above petroleum-hydrocarbon contaminated ground
water. Additional evidence of MTBE uptake by trees was seen
in other investigations by examining biomass of trees (Brown
and others, 2001), transpiration gasses (Parfitt and others,
2000), and bioreactor experiments (Hong and others, 2001;
Ramaswami and Rubin, 2001).
VOCs in tree cores have been used to delineate ground-
water contamination plumes in a variety of locations. Field
tests have been conducted in Colorado (Vroblesky and
others, 2004), Florida (Doucette and others, 2003), Maryland
(Bui-ken, 2001; Weishaar and Burken, 2005), Missouri (Schu-
macher and others, 2004), South Carolina (Vroblesky and
others, 2004), Texas (Vroblesky and others, 2004), and Utah
(Doucette and others, 2003; Lewis and others, 2001). Trapp
and others (2007) investigated tree coring as a tool for screen-
ing subsurface pollution in Europe and published a concise
guide to field sampling. At least one study examined chloride
concentrations in tree rings to estimate the onset of chlorinated
hydrocarbon contamination (Yanosky and others, 2001). VOC
analysis of tree cores has been used to detect subsurface VOC
contamination and to direct subsequent drilling efforts in areas
where there were little or no pre-existing characterization data
(Schumacher and others, 2004; Vroblesky and Casey, 2004;
Sorek and others, 2008).
VOC analysis of tree cores has been used to monitor
ground-water plumes (Gopalakrishnan and others, 2005).
Tree cores have been used to show that some of the trees
at the leading edge of a ground-water TCE contamination
plume began to take up TCE in increasing amounts over time
as the plume approached (Vroblesky and others, 2004). The
variety of applications and successful field tests indicate that
tree coring can be a viable reconnaissance tool for examining
subsurface VOCs.
In some cases, analysis of stems and branches has been
shown to be a less intrusive approach to tracking subsurface
VOCs than collection and analysis of tree cores (Vroblesky
and others, 2004; Gopalakrishnan and others, 2007). In
general, however, the VOC concentrations in stems appear to
be lower than the VOC concentrations in tree cores, sometimes
resulting in stem analyses mat produce false negatives
(Vroblesky and others, 2004). A recent modification of the
tree-coring approach involves inserting activated carbon
into the core hole, followed by recovery and analysis of the
activated carbon (Sheehan and others, 2007). In most cases,
simple HS A of tree cores is an adequate approach to locating
and mapping subsurface VOCs; however, the activated-carbon
approach has the potential to detect VOCs at lower levels than
HSA in situations where such sensitivity is needed. In areas of
high chlorinated VOC concentrations (greater than 1 pail per
million by volume [ppmvj in tree-core headspace vials) where
relatively little sensitivity is needed, simple field colorimetric
tubes have been used to detect the contaminants in tree cores
(Vroblesky and others, 2007b).
for
In lhis section of the report, technical rationale is
provided for various aspects of the tree coring methodology.
In particular, this section includes discussions of parts of the
trunk to be sampled, maintenance of the core hole after core
collection, limes involved in core transfer to sample vials,
VOC stability in the sample vials, equilibration times, quality-
control issues, and alternative approaches to collection and
analysis of tree cores for VOC analysis.
Tree-Core Collection
The depth of coring depends on the length of core
desired. In most cases, il is not necessary to core deeply into
the trunk to obtain VOC concentrations. This is primarily
because most of the water flow during transpiration is in the
outer part of the trunk. In ring-porous trees (table 1), over
90 percent of water transported through the xylem is in the
outermost growth ring (Ellmore and Ewers, 1986). Thus,
inclusion of the outermost growth ring is particularly impor-
tant in ring-porous trees. In diffuse-porous and nonporous
trees, multiple growth rings conduct water. The preferential
conductance of water in the outer part of the tree does not
necessarily mean that the highest VOC concentrations are
always in the outermost part of the trunk. Often, the VOC con-
centrations decrease from the inner to outer parts of the trunk
(xylem), possibly related to volatilization loss through the
bark (Ma and Burken. 2003). The inner part, or heartwood, of
some trees is known to provide a waste repository for excess
concentrations of some constituents (Tout and others, 1977;
Vroblesky and others, 1992), although this issue has not been
investigated for VOCs. Because increased concentrations of
VOCs sometimes can be found in the inner relative to the outer
part of the trunk, there may be instances where coring more
deeply into the trunk can result in higher detection potential of
VOCs in the tree cores. Field investigations, however, indicate
that a core of the outermost 3 in. (not including the bark)
can be sufficient to identify subsurface VOC contamination
(Vroblesky and others, 1999, 2004)
Research indicates that sealing the tree core hole prob-
ably is not needed and sometimes can be harmful. Although
il is clear thai open boreholes can allow decay and disease
(Took and Gammage, 1959; Hart and Wargo, 1965; Shigo,
1967) and that tree wounds from increment borers can be
associated with long streaks of discolored and decayed wood
(Shigo, 1983), plugging the core holes does little to reduce
-------
10 User's Guide to the Collection and Analysis of Tree Coresto Assess the Distribution of Subsurface Volatile Organic Compounds
discoloration or decay (Meyer and Hayward, 1936; Lorenz,
1944; Hepting and others, 1949). In some cases, the swelling
of dowel plugs inserted in the core hole has caused splits in
the trunk near the entry hole (Hepting and others, 1949). In
addition, wounds treated with wound dressing often form large
callus ribs that turn inward to form "ram's horns," and there
are no data to show that wound dressings stop decay (Shigo,
1983). In general, healthy dominant and co-dominant trees
respond well to tree coring both by creating a chemical barrier
to inhibit microbial invasion and by compartmentalizing
infected wood when microorganisms bypass the chemical
barrier (Shigo, 1974). Conifer species appear to be particularly
resilient to coring (Meyer and Hayward, 1936; Shigo, 1985).
A summary of the effects of coring on differing species can be
found in Grissino-Mayer (2003). Core-damage studies showed
that more than half of the core holes healed within 2-3 years,
with most of the poorly healing trees being short-lived species
or suppressed individuals (Meyer and Hayward, 1936, Lorenz,
1944; Hepting and others, 1949; Toole and Gammage, 1959).
Further, several studies reported no evidence of tree mortality
after increment coring (Meyer and Hayward, 1936; Lorenz,
1944; Hepting and others, 1949; Toole and Gamage, 1959;
Hart and Wargo, 1965; Eckstein and Dujesiefken, 1999; van
Mantgem and Stephenson, 2004) and little effect on tree
mortality when stem wedge sections were removed using a
chainsaw (Heyerdahl and McKay, 2001). Therefore, a practi-
cal approach is to leave the borehole unsealed. The open hole
allows the borehole to dry, and the water and sap flow from
the hole may cleanse the wound and discourage infection (Neil
Pederson, Eastern Kentucky University, written commun.,
2007). Some researchers use antiseptic approaches to mini-
mize introduction of microorganisms to the core hole by either
dipping the increment borer in alcohol between trees (Neil
Pederson, Eastern Kentucky University, written commun.,
2007) or by squirting antiseptic soap into the core hole (Lee
Newman, University of South Carolina, oral commun., 2007).
The effectiveness of these antiseptic approaches, however, has
not been determined. To reduce stress to the tree, excessive
coring of the same tree should be avoided.
Tree-Core Transfer to Sample Vials and Storage
Tree cores should be transferred to sealed vials as rapidly
as possible because volatilization loss from the tree cores
is rapid. A field test allowing the cores to remain in open
vials for several minutes prior to sealing showed that TCE
concentrations decreased by about 40 percent over a period of
5 minutes (fig. 5).
Other approaches to collect tree cores for analysis also
have been used. Schumacher and others (2004) collected
replicate cores in vials containing 5 mL of organic-free water
and stored them upside down to limit volatilization loss
through the septa. Rather than preventing VOC loss, however,
the added water reduced the amount of detectable PCE. Up to
55 percent less PCE was detected in the samples containing
water than in replicate samples not containing water. The
® 2,500
> 2,000
.c c
o.o 1,500
o =
.y Q.
_
CD
Q.
1,000
500
Loblolly pine
0 2 4 6 8 10 12
Minutes vials containing
tree cores were left uncapped
Figure 5. Loss of trichloroethene over time from
uncapped 20-milliliter serum vials, Naval Weapons Station
Charleston, South Carolina, 2006.
authors attributed the difference to a combination of PCE
partitioning into the water phase and slightly longer time
required to avoid spilling water from the vials while adding
the core samples. Thereafter, the authors discontinued addition
of water to the vials.
Methanol extraction also has been used for chemical
analysis of tree cores (Landmeyer and others, 2000; Lewis and
others, 2001). In the Landmeyer investigation, the cores were
sealed in vials containing 5 mL of reagent-grade methanol.
Methanol extraction used in combination with PT analysis can
be an effective approach to confirm the identity of the detected
compound by mass spectrometry.
An additional approach to collecting tree cores that has
been reported is chilling the cores upon collection, transport-
ing them back to the laboratory, freezing them until analysis,
and then crushing the cores prior to analysis (Sorek and others,
2008). In the laboratory, the crushed cores were heated prior to
analysis.
Changes in VOC concentrations can take place in the
tree-core sampling vial over time. Sometimes these changes
can be seen as changes in the amplitude of early-eluting
chromatographic peaks typically not associated with ground-
water contamination. To test the length of time that the tree
cores for TCE analysis can be stored in sample vials prior to
analysis, repeated sampling was done with a series of vials
stored at room temperature, containing cores from a tree
growing above contaminated ground water. Most vials showed
no TCE volatilization loss from 24 hours to 19 days of storage
(fig. 6). These data indicate that the vials can be stored for
at least a few days prior to analysis. It should be cautioned,
however, that it is prudent to analyze the samples within a
few days of collection rather than waiting 19 days to avoid
potential transformations or volatilization losses not evident in
this investigation.
-------
Part2. Historical Perspectives and Technical Considerations 11
CO ®
Q. E
— "o
c" i
0) -Q
£ C
"CD o
o =
o
0)
10,000
123456789
Vial number
Figure 6. Headspace trichloroethene concentrations at 24 hours and 19 days of storage in sealed serum vials
containing tree cores from a trichloroethene-contaminated site showing generally slight concentration increases
in most cores and no evidence of volatilization loss overtime.
Tree-Core Equilibration Time
VOCs begin to de-gas from tree cores immediately upon
removal from the tree. In field investigations conducted for
this user's guide, sufficient TCE concentrations to indicate the
presence of subsurface contamination accumulated in crimp-
capped serum vials containing tree cores within 5 minutes
of collection. In tests where repeated vapor extractions were
taken from the same tree-core vial over time, several vials
showed that the TCE concentration in the vial headspace
after 5 minutes of equilibration was approximately the same
as allowing the vials to equilibrate overnight (fig. 7A, B,
C, D). In other tree-core vials and on other sampling dates,
however, TCE concentrations in the vial headspace increased
by a factor of 2 or more after equilibrating overnight (fig. 7E).
The factors controlling equilibration time probably include
ambient air temperature, differences in heating of the core
barrel by friction during coring, and other unidentified factors.
The influences of these factors are not yet well understood.
Thus, in general, it appears that analysis of tree cores within
5 minutes of core collection can be a useful indicator of
subsurface TCE contamination. If the intent, however, is to
compare VOC concentrations among several trees at the site,
a prudent approach, until the factors that control equilibrium
time are more thoroughly studied, is to treat all of the cores
the same way and allow them to equilibrate approximately
24 hours or more (Landmeyer and others, 2000; Schumacher
and others, 2004; Vroblesky and others, 2004). A comparison
of cores allowed to equilibrate for 24 hours relative to 19 days
shows that only slight concentration increases took place after
24 hours and there was no evidence of VOC loss (fig. 6).
An alternate field approach is to analyze the tree cores
in the field after heating the cores in crimp-capped serum
vials for about 5 to!5 minutes. Field tests for development of
this guide showed that field heating the cores produced TCE
concentrations higher than in unheated cores or cores allowed
to equilibrate at ambient temperature for 24 hours (fig. 7D).
A similar relation was seen in field-heated cores with a
reanalysis of the core after about 24 to 28 hours of equilibra-
tion at ambient temperature following heating (fig. 7F, G, H).
Although it is possible that the lower TCE concentrations
in the corresponding unheated sample the next day could
represent volatilization loss during the previous heating, such
loss probably is minor because similar TCE-concentration
declines between the 5-minute time step and the unheated
analysis the following day were seen whether the samples
were heated for 40 minutes or for only 5 minutes (fig. 7G, H).
Tests have not yet been done to determine the upper range of
acceptable heating, but it is logical that some level of volatil-
ization loss or thermal destruction could occur with excessive
heating. Therefore, core heating should be maintained within
the ranges cited above or should be tested.
In additional investigations of field heating conducted
for this guide, duplicate cores were collected 0.75 in. apart
from trees at Solid Waste Management Unit (SWMU) 17,
Naval Weapons Station Charleston, South Carolina, in June
2006 and at the Durham Meadows Superfund Sites, Durham,
Connecticut, in August 2006. At each site, one of the cores
was heated for 5 minutes at 60-70 °C and analyzed in the
field within 10 minutes of collection. Comparison of VOC
concentrations in vials containing tree cores shows that field
heating the cores, in most cases, produced concentrations that
were in the range of, or higher than, concentrations obtained
after allowing the vials to equilibrate 24 to 30 hours at room
temperature (fig. 8A). Although only two trees were tested for
PCE, the limited data set implies that a similar correspondence
applies to PCE (fig. 8B).
-------
12 User's Guide to the Collection and Analysis of Tree Coresto Assess the Distribution of Subsurface Volatile Organic Compounds
C
0) O
5r — Q)
•= -P >
500
400
200
100
0
A. Tree T1 6,
10/15/2007
in in in in in in in
CD CD CD CD bi ±i ±i
4-> 4-> 4-> 4-> =5 =5 =5
3 3 3 3 O O O
C C C C .C .C .C
E E E E f ••- °°
= = = = £ " "
T- i- CN 4-> =5
=5 =5 0
500
400
300
200
100
0
C. TreeT16,
10/15/2007
zi
=5 O
E E
in i-
co
CN
D. Tree T100,
Heated at 70°C, 5/3/2007
H C
2,500
2,000
1,500
1,000
500
n
E. TreeTI,
4/16/2006
— I
— |
-
-
-
-
-
ininaiaiininininai
E E E E E E
CD CD 00 10 M- ^T
=5 =5
o o
in in
,_j CM
=5
o
F. TreeT16,
Heated at 70 °C
G. TreeT16,
Heated at 50 °C, 10/15/2007
500
H. TreeT16,
Heated at 50 °C, 10/15/2007
500
400 -
200 -
100 -
(/)(/)(/)(/)(/)(/)(/)(/)(/)
QJQJQJQJQJQJQJQJ1—
EEEEEEEE°>
inocD-^-inoino
T- i- CN CN CO CO M-
Time since tree-core collection
EXPLANATION
Heated prior to analysis
Unheated following the last heated analysis
i i Unheated
(A) Core identifier
Each graph represents multiple analyses of the
same core, with the exception of graph D.
Figure 7. Trichloroethene concentrations over time in unheated and heated sealed serum vials containing
loblolly pine tree cores from a trichloroethene-contaminated site showing little concentration change in cores
from some trees after 5 to 6 minutes and an increase in sensitivity by field heating and analyzing the cores. Solid
Waste Management Unit 17, Charleston, South Carolina.
-------
Part 2. Historical Perspectives and Technical Considerations 13
"5.2
Efl)
t!— Q)
co a E
10,000
o 1,000
£ N C
-t= .>> O
C CD =
CD CD w
•fc= T3 t
C CD CD
Sro ^
c
-------
14 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
that although the methanol extraction produced higher TCE
concentrations than the HSA, there are costs and analytical
complications associated with the methanol extraction
analyses mat make HSA a preferable alternative.
Where increased sensitivity is needed relative to HSA,
activated carbon has been inserted into a tree-core hole,
followed by recovery and analysis of the activated carbon
(Sheehan and others, 2007). This approach utilizes the
tree-core hole rather than the tree core.
In a highly contaminated area where relatively little
sensitivity is needed, field colorimetiic gas-detector tubes
(GasTec 133LL) have been used to rapidly and inexpensively
detect VOCs in tree cores (Vroblesky and others, 2007b).
This approach was used as part of the development of this
field guide and utilized a simple modification of the Color Tec
screening method (Kelso, 2005) to employ vials containing
tree cores in air rather than the recommended vials containing
water or sediment in water. The relative concentrations of total
chlorinated VOCs obtained by the colorimetric method com-
pared favorably to the quantitative analysis of total chlorinated
VOCs obtained by gas chromatography at concentrations
greater than 1 pprnv (r2 = 0.05). Below total chlorinated VOC
concentrations of 1 ppmv, the colorimetric method sometimes
detected VOCs and sometimes did not. Below total chlorinated
VOC concentrations of 0.7 ppmv, the colorimetric method
failed to detect VOCs. The gas chromatographic method
remained useful for detecting total chlorinated VOCs down to
at least 10 ppbv.
Comparison of the colorimetric method to the gas
chromatographic approach of field analyzing tree cores for
chlorinated VOC content shows that both methods can provide
effective detection of subsurface chlorinated VOCs at high
concentrations (greater than 1 ppmv). At some sites, such as
the Carswell Golf Course in Fort Worth, Texas, this level of
detection is inadequate to detect the ground-water contamina-
tion (Vroblesky and others, 2004). At other sites, however,
such as Solid Waste Management Unit 12 (tree-core TCE
concentrations up to 10.19 ppmv) and Solid Waste Manage-
ment Unit 17 (tree-core TCE concentrations up to 85 ppmv) at
the Naval Weapons Station Charleston in South Carolina and
at Air Force Plant PJKS in Colorado (tree-core TCE concen-
trations up to 2.191 ppmv) (Vroblesky and others, 2004), field
analysis by using either gas chromatography or colorimetric
method would be a viable means of locating the plume.
Disadvantages of the colorimetric approach are that (1) it is
substantially less sensitive than the field gas chromatograph
and may miss pails or all of ground-water contamination
plumes that are not reflected by relatively high ttee-core VOC
concentrations, and (2) the colorimetric approach is sensitive
only to chlorinated VOCs with a larger influence of chlori-
nated alkenes relative to chlorinated alkanes. An advantage
is that the colorimetric approach is simple to use, easily field
portable, and inexpensive (less than about S10 per sample).
At sites with sufficient concentrations of tee-core chlorinated
VOCs, the colorimetric approach can be a viable, inexpensive
reconnaissance tool without the need for a field GC.
Quality Control and Assurance
A field test conducted for this investigation in October
2005 to determine whether decontamination of core barrels
was required between collecting cores from different trees
showed that the decontamination was unnecessary for
investigating TCE in tree cores. The test involved collecting
a core from the trunk of a loblolly pine known from previous
work to contain high concentrations of TCE. The core was
immediately sealed in an empty 20-mL crimp-top vial. The
core barrel was not cleaned following collection of the core.
Within 6 minutes of collecting the core from the contaminated
tree, a core was collected from a loblolly pine of similar
diameter in a background area. This sequence was repeated
two more times so that a total of three cores were collected
from the contaminated tee and three from the uncontaminated
tree. At no time during the coring was the core barrel cleaned.
The cores were allowed to equilibrate with the headspace of
the sample vials for approximately 24 hours at approximately
25 °C and then were analyzed by HSA using photoionization
gas chromatography.
TCE concentrations in the contaminated tree ranged from
5,000 to greater than 10,000 ppbv (table 3). TCE was not
detected in cores from the background tree at a detection limit
of about 15 ppbv. Thus, the core barrel showed no evidence of
TCE carryover from the contaminated to the uncontaminated
cores. The data indicated that decontamination of the core
ban-el prior to sampling the background tee was unnecessary
when investigating TCE. The probable reasons for the lack of
carryover include the low sorption potential of VOCs to metal,
the heat generated during the coring, and the volatility of the
compounds. It should be cautioned, however, that the core
ban-el should be inspected to ensure that mere is no paniculate
carryover, such as sections of tree core, remaining in the core
Table 3. Trichloroethene concentrations in tree cores
collected within about 5 minutes of each other, using the same
core barrel with no decontamination between cores, showing
no carryover between core collections.
[ND. not detected at 15 parts per billion by volume; >, greater than]
Tree
Background tree
Contaminated tree
Background tree
Contaminated tree
Background tree
Contaminated tree
Background tree
Air sample near contaminated tree
Air sample near background tree
Collection
time,
in hours:
minutes
13:55
14:00
14:04
14:09
14:14
15:10
15:19
15:10
15:19
Trichloro-
ethene,
in parts per
billion by
¥olume
ND
7,649
ND
5,000
ND
> 10,000
ND
ND
ND
-------
Part 2. Historical Perspecti¥es and Technical Considerations 15
barrel that could adversely impact subsequent samples. In
addition, TCE was the only compound examined during this
test of potential carryover. Although the results technically
apply only to TCE, they probably are applicable to other
chlorinated solvents, based on their chemical similarity
to TCE.
in
A variety of factors influence the ability of plants to be
useful indictors of ground-water VOC contamination. These
factors include the type of VOC, the tree species, the rooting
depth, aqueous concentrations, the depth to the contaminated
horizon, concentration differences around the trunk related
to different sources of subsurface VOCs, concentration
differences with depth of coring related to volatilization loss
through the bark and possibly other unknown factors, dilution
by rain, seasonal and climatic influences, sorption, and
within-tree VOC degradation. The following sections discuss
these factors in greater detail.
Types of Volatile Organic Compounds
Various VOCs are known to be taken up by plant roots
into the trunks of trees and are, therefore, probable candidates
for tree-coring investigations. VOCs that have been found
in tree-coring investigations include benzene, toluene,
ethylbenzene, xylene isomers, trimethylbenzene, MTBE,
1,1,-2-2-tetrachloroethane (PCA) (Hirsh and others, 2003),
1,1,1-trichloroethane, 1,1-dichloroethene, carbon tetrachloride
(Sorek and others, 2008), VC (Trapp and others, 2007), TCE,
PCE, and cDCE (Burken and Schnoor, 1998; Nietch and
others, 1999; Vroblesky and others, 1999; Landmeyer and
others, 2000; Burken, 2001; Davis and others, 2003). Sorek
and others (2008) found that 1,1-dichloroethene appeared
to be rarely detected in tree cores despite relatively high
concentrations in the subsurface, possibly due to being lost by
volatilization from the trunk and sampled tree cores.
Direct uptake of contaminants is controlled by a variety
of factors, but in general, moderately hydrophobic organic
compounds (octanol-water coefficient, log Kow= 0.5-3), such
as TCE and cDCE, readily enter the vegetation transpiration
streams (Briggs and others, 1982, 1983; Schnoor and others,
1995). Hydrophobic chemicals (log Km greater than 3.5) are
too strongly bound to roots and soil to be translocated within
plants (Briggs and others, 1982; Schnoor and others, 1995).
Early work considered very water soluble chemicals (log Kow
less than 0.5) to be neither sufficiently sorbed to roots nor
passively transported through plant membranes (Briggs and
others, 1982; Schnoor and others, 1995); however, a more
recent investigation provides evidence that soluble, highly
polar compounds (such as sulfolene with a log Kmof -0.77)
can be readily taken up by plant root systems (Dettenmaier
and others, 2008). Thus, log Kow (table 4) is an important
factor influencing the ability of a compound to be translocated
up the tree trunk.
Table 4. Chemical formula, Henry's Law constant, and log octanol-water partition coefficients for selected
volatile organic compounds reported in tree-coring investigations,
[atm nr'/mol, atmosphere cubic meter per mole]
Compound
Tetrachloroethene
Trichloroethene
1 , 1 -Dichlorocthcnc
cis- 1 ,2-Dichloroethene
Vinyl chloride
1.1. 1 -Trichlorethane
1 . 1 -Dichloroe thane
Carbon tetrachloride
Benzene
Toluene
Ethyl benzene
Xylene isomers
/M-xylene
p -xylene
Methyl ferf-butyl ether
Formula
C2C14
C2HCL,
C2H2C12
C,H2CL,
C2H,C1
C2H3C13
C2H,C12
CC14
C6I-I6
C7HS
CSHK,
C8H!0
<'8H10
C8H!0
C5H12°
Henry's Law constant
(atm m3/mol)
1.53xlO-2
9.10x10-3
l.SxlO-2
3.37x10 3
1.22x10-'-°°
1.62xl02
5.42x10-3
2.40xlO-2
5.40x10-3
6.70x10 3
6.60x10-3
5. 27x10- to 7. IxlO-3
7.00x10-3
7.10x10-3
5.4xlO-4
log octanol-water
coefficient
2.60
2.03
1.84
1.86
0.60
2.18
1.79
2.78
2.12
2.65
3.13
2.95 to 3.2
3.20
3.18
1.24
-------
16 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
In general, the log K^ con-elates well with the root
concentration factor (RCF) and the transpiration stream
concentration factor (TSCF). The RCF describes the efficiency
of solute movement from an external solution into the root
system and is defined by Shone and Wood (1974) as:
RCF = (Concentration in roots) / (Concentration (1)
in external solution).
The TSCF is defined by Shone and Wood (1974) as:
TSCF = (Concentration in the transpiration stream) / (2)
(Concentration in external solution).
TSCF values have been measured for a number of compounds
(Briggs and others, 1982; Burken and Schnoor, 1998; Davis
and others, 1998b; Inoue and others, 1998). A TSCF of 1.0
indicates unrestricted passive uptake. A TSCF of less than 1.0
indicates some degree of exclusion by the plant, and a TSCF
of greater than 1.0 indicates active uptake by the plant.
Various TSCF values for TCE have been reported. Davis
and others (1996) reported a TSCF of 0.67 (at 1.5 grams
per liter [g/L]) for TCE. Orchard and others (2000) found
TSCF values of 0.02 to 0.22 with an average of 0.12 for TCE.
Lockheed Martin (2000) used a TSCF value of 0.79 for TCE.
The wide range of TSCF values probably reflects different
experimental setups, such as hydroponic rather than soil
growth or flowthrough chamber rather than static chambers,
leaks, and other factors.
Doucettc and others (2003) found that depending on the
climate, 200 to 1,400 liters per square meter per year (L/m2/yr)
probably represents a reasonable range of annual transpiration
values, and Wullschleger and others (1998) reported that
90 percent of the observations for maximum rates of daily
water use were between 10 and 200 liters per day (L/d) for
individual trees that averaged 70 ft in height. The authors
concluded that reasonable values for yearly TCE plant uptake
from a ground-water TCE concentration of 1 mg/L are 2.4-
84 milligrams per square meter per year (mg/m2/yr) (TSCF
value of 0.12) to 525 mg/nf/yr (TSCF value of 0.75) depend-
ing on the choice of TSCF values (Orchard and others, 2000).
The mass of TCE removed by plant uptake can be
modeled by
Mass = (TSCF) (CTCE) (T) (f) (Doucette and others, 2003), (3)
where TSCF is assumed to be constant, CTCE is the average
ground-water concentration of TCE in milligrams per liter, T
is the cumulative volume of water transpired per unit area per
year in liters per square meter per year, and / is the fraction
of the plant-water needs met by contaminated ground water.
It should be cautioned, however, that TSCF does not include a
vapor-transport term for uptake or loss and, thus, may provide
misleading conclusions in situations where vapor transport is
significant.
The / factor is difficult to measure at most phytoremedia-
tion sites described in the literature because ground-water
use by plants tends to decrease as the availability of surface
water increases (Nilsen and Orcutt, 1996). Doucette and others
(2003) suggest that a range / from 0.1 to 0.5 is probably
reasonable for climates with more than 16 in. of annual rain.
Although the equations based on log Kow provide a
generally useful predictive tool for examining uptake of
organic compounds by plants, numerous exceptions exist
(Burken and Schnoor, 1998). There are classes of compounds
(such as nitroaromatics, phenols, and aromatic amines) that are
more tightly bound to roots than predicted by the RCF because
the sorption is related to biochemical bonding rather man to
hydrophobic partitioning behavior. Binding to the roots for
these compounds, such as aniline, nitrobenzene, catechol, and
chlorobenzene, is irreversible (Dietz and Schnoor, 2001).
Subsurface Volatile Organic Compound
Concentrations
Field investigations (Vroblesky and others, 1999, 2004;
Schumacher and others, 2004) showed that the highest
VOC concentrations in tree cores usually were found in
trees growing above the highest ground-water or soil VOC
concentrations, as indicated by samples from ground-water
wells or soil-vapor surveys. Additional evidence for the
correspondence between environmental VOC and tree-core
VOC concentrations was shown in laboratory studies (Ma and
Burken, 2002, 2003). Thus, it is clear that subsurface VOC
concentrations can directly influence VOC concentrations in
tree vascular tissues.
In one study, comparison of PCE concentrations in a
number of tree-core samples and sediment samples 12 ft deep
showed a linear relation for soil-PCE concentrations greater
than 60 micrograms per kilogram (ug/kg) (Schumacher and
others, 2004). Therefore, the PCE concentration in tree cores
was found to be a good predictor of PCE concentrations in soil
at 12 ft deep. In general, however, predictions of subsurface
VOC concentrations based on tree-core results should be
considered as a qualitative rather than quantitative relation and
indicative of minimum concentrations.
In some cases, VOC concentrations in tree cores appear
to correspond more closely to soil-gas VOC concentrations
than to ground-water VOC concentrations (Schumacher and
others, 2004). This finding raises the possibility that tree-core
analysis may be useful as a rapid, inexpensive, relatively
low-profile, non-intrusive reconnaissance tool to identify areas
of potential vapor intrusion to be targeted by more definitive
and cumbersome investigative approaches. In a limited study
at the Nyanza Chemical Waste Dump Superfund Site, Mas-
sachusetts, tree cores were examined as a possible indicator
of vapor intrusion (Vroblesky and others, 2006) (fig. 9). Trees
N3, N5, and N8 contained TCE and were adjacent to buildings
in which vapor intrusion by TCE had been identified.
In a separate study at the Durham Meadows Superfund
Site, Connecticut (Vroblesky and others, 2008), TCA in tree
trunks corresponded to TCA in soil gas, although the two stud-
ies were done 3 years apart (fig. 10). Thus, multiple studies
-------
Part 2. Historical Perspectives and Technical Considerations 17
\,
PLEASANT STREET JM9
§
MW-302
EXPLANATION
Monitoring well and label
Tree-coring location and label. Blackfill
indicates positive detection of vapor
intrusion, gray indicates no detection.
I 1 Building. Blackfill indicates positive
detection of vapor intrusion, gray indicates
no detection, white indicates no data.
400 FEET
Figure 9. Trees cored at the Nyanza Chemical Waste Dump Superfund Site, Ashland,
Massachusetts, August 2006 (modified from Vroblesky and others, 2006), showing proximity
to wells and to buildings where vapor-intrusion investigations were conducted in 2004 (ICF
Consulting, 2005).
Existing
'0—DM7 \ buildin9
MERRIAM MANUFACTURING
COMPANY PROPERTY
25 50 75
0 5 10 15 20 25METERS
Basemap modified from Metcalf & Eddy, Inc. (2006)
EXPLANATION
1,1,1-Trichlorethane in soil vapor, in parts per billion by volume .combination
of soil gas surveys in 2003 and 2006 (Anni Loughlin, U.S. Environmental Protection
Agency, written commun., February 2007)
/ \ Tree containing less than 1.6 parts per billion by volume of 1,1,1-trichloroethane
DM5 / \ Tree containing 5.6 parts per billion by volume of 1,1,1-trichloroethane
DM7 ^^ Tree containing 24 parts per billion by volume of 1,1,1-trichloroethane
I I Former areas of liquid storage in tanks and former paint booths
o14 Soil-gas sampling point. Black indicates 2003 and open indicates 2006 sampling.
Figure 10. 1,1,1-Trichloroethane
concentrations in tree cores in
2006 showing correspondence to
the combined results of 2003 and
2006 soil-gas investigations at the
Merriam Manufacturing Company
property, Durham Meadows
Superfund Site, Connecticut.
-------
18 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
indicate that tree coring is a potential reconnaissance tool to
identify areas of soil-gas and vapor-intrusion hazard.
Differences Among Tree Species
Plant utilization of ground water is partly dependent
on plant species (Smith and others, 1991; Busch and others,
1992; Thorburn and Walker, 1994; Kolb and others, 1997).
Studies also have shown that the degradation and bioavail-
ability of contaminants in soil systems can vary with plant
species (Shann and Boyle, 1994). In addition, comparisons of
increment cores from trees of differing species growing near
each other sometimes show VOC concentration differences
that appear to be species-related. In a study in South Carolina
(Vroblesky and others, 1999), oaks consistently contained less
TCK than adjacent bald cypress or loblolly pines. In the same
study, however, adjacent bald cypress and tupelo trees (Nyssa
sp.) showed no significant differences in TCE concentrations
from increment cores, indicating similar uptake of TCE. A
possible contributing factor to the differences among some
species is that conifers, such as bald cypress and loblolly pine,
conduct water through more than the outermost growth ring,
whereas in ring-porous trees (table 1), nearly all of the water
is conducted through the outermost growth ring (Kozlowski
and others, 1966; Ellmore and Ewers, 1986). Thus, the higher
concentrations detected in conifers relative to the oaks may
be because the cores, being of approximately equal length,
incorporated more of the transpiration stream in conifers than
in ring-porous trees. In another study, similar TCE concentra-
tions were observed in increment cores in 1998 and 2000
from a willow (Salix sp.) and an eastern cottonwood (Populus
delta ides) growing directly adjacent to each other (Vroblesky
and others, 2004). Sorek and others (2008) found order of
magnitude differences in TCE concentrations in a rosewood
(Dalbergia sissoo) and laurel fig (Ficus microcarpa), despite
comparatively small TCE concentration differences in the
subsurface.
In one set of trees spaced within 30 ft of each other,
Lewis (2001) found that the relative amount of TCE uptake
among tested species appeared to follow the trend cottonwood
(Populus delta ides) > Russian olive (Elaeagnus angustifo-
/za)> poplar species (Populus sp.). There is some uncertainty
with this conclusion, however, because of data limitations,
such as the fact that only one of each species was compared,
there were tree-diameter differences, and there were potential
subsurface influences and spatial variations.
Rooting Depth and Depth to the
Contaminated Horizon
Rooting depth, or the proximity of the roots to the
contaminated horizon, is a factor that potentially can influ-
ence VOC uptake in trees. To some extent, rooting depth is
species-dependent. Trees of different species (Ehleringer and
others, 1991) and even different size trees of the same species
(Dawson and Pate, 1996) can obtain water from different
sources. Some species, such as poplars, and willows, are
genetically predisposed to develop roots extending to the
water table or capillary fringe at depths ranging from 3 to
40 ft (Negri and others, 2003). In general, however, trees
with the capability to root deeply will do so only if mere is
a hydrologic need to do so. In rainy climates where mere is
adequate water available for the plants from the soil zone,
rooting depth will be limited. In some cases, where the depth
to ground water increases, there is a corresponding increase in
rooting depth and decrease in the ground-water contribution to
the plant water use (Sepaskhah and Karimi-Goghari, 2005).
Few studies have rigorously examined rooting depth
because of the difficulty in uncovering roots. Descriptions of
rooting depths vary widely. A study in the United Kingdom
of five willows and five poplar clones in differing soil types
showed that although the rooting depths were more than 4 ft,
75 to 95 percent of the roots were in the top 14 in. (Keller and
others, 2003). A study in central Texas used DNA sequencing
of roots in caves 16 to 213 ft deep to examine the rooting
depth of various species (Jackson and others, 1999). The
tested species were southern hackberry (Celtsi laevigata), ash
juniper (Junlperus ashei), white shin oak (Quercus sinuata),
Texas live oak (Quercus fusiformis), American elm (Ulmus
americana), and cedar elm (Ulmus crassifolia), and represent
approximately three-fourths of the woody plants comprising
the studied ecosystem. At least six tree species grew roots
deeper than 16 ft, but only Texas live oak was found below
32 ft. The maximum rooting depth for mat ecosystem was
about 82 ft. The oxygen 18 (1SO) isotopic signature for stem
water from a live oak confirmed water uptake from a depth of
59 ft.
The degree to which the roots are in intimate contact with
the contaminated horizon appears to be an important control
on the amount of contaminant uptake. A study was conducted
in Colorado to examine eastern cottonwood trees that were
about the same diameter (Vroblesky and others, 2004).
Vroblesky and others (2004) found that a core from an eastern
cottonwood where the depth to TCE-contaminated ground
water (200 ug/L TCE) was about 24 ft contained 99 ppbv of
TCE. In contrast, the TCE concentrations were substantially
higher (2,191 and 552 ppbv) in cores from two eastern cot-
tonwoods growing at the bottom of a creek erosional channel
where the ground water was less than 3 ft deep, despite the
presence of only 29 to 39 ug/L TCE in the ground water. The
data strongly imply that the percentage of transpiration uptake
composed of contaminated water was higher in trees in the
drainage ditch where the roots were in more close contact with
the contaminated ground water than in the upland trees where
the depth to water was about 24 ft.
Tree coring has been used in field investigations to
successfully detect subsurface VOCs in areas where the
ground water was 20 to 25 ft deep (Schumacher and others,
2004; Vroblesky and others, 2004) and 59 to 65 ft deep (Sorek
and others, 2008). In some studies, however, poor quantitation
between tree VOCs and ground-water VOCs was attributed to
-------
Part 2. Historical Perspeeti¥es and Technical Considerations 19
a relatively large depth to water (Cox, 2002; Schumacher and
others, 2004). The probable causes for the poor correlation
in areas of large depth to water include the lack of intimate
contact between the contaminated ground water and the tree
roots, the potential for tree roots to obtain soil water from
shallower horizons when it is available (Mensforth and others,
1994; Thorburn and Walker, 1994; Dawson and Pate, 1996;
Jolly and Walker, 1996), and the diffusion of VOCs out of
the roots during upward transport (Struckhoff, 2003). The
decrease in TCE concentration with increasing depth to water
is consistent with predictions from ground-water modeling
(Wise, 1997) and from observations that ground water can
provide less of a contribution to plant-water use when it is
deep or when shallower soil moisture is available (Zencich and
others, 2002; Sepaskhah and Karimi-Goghari, 2005).
Perhaps a more meaningful conceptualization of rooting
depth is the depth of hydraulic influence of the roots. An
example is the engineered phytoremediation site using hybrid
poplar (Populus deltiodes x Populus trichocarpa) at Aberdeen
Proving Ground, Maryland, where the depth to the water
table is 5 to 15 ft (Hirsh and others, 2003). A ground-water
study at the site showed mat water use by the poplar trees
induced upward ground-water hydraulic gradients toward the
roots, with the depth of hydraulic influence extending to 25 ft
(Schneider and others, 2002). Thus, in some environments,
trees can induce movement of water and the associated
dissolved contaminants upward to the roots from areas beyond
the physical extent of the roots.
It should also be noted that sites that have ground water
at a depth that appears to be beyond the reach of the tree roots
still may be viable candidates for use of tree coring as a tool to
investigate subsurface VOCs. Studies have shown that soil gas
can be an effective transport mechanism of VOCs to tree roots
(Struckhoff, 2003; Schumacher and others, 2004; Struckhoff
and others 2005a, b) and may explain some of the VOC detec-
tions in tree cores where a relatively large depth to water was
reported. Sorek and others (2008) found chlorinated solvents
in tree cores where the depth to the contaminated ground water
was 59-65 ft, and where the same chlorinated solvents were
present as soil gas in the vadose zone. In addition, hydraulic
lift has the potential to transport contaminants from deeper
to shallower parts of the soil where the water and solutes can
be accessed by shallower rooted species. Hydraulic lift is a
process by which differences in water potential allow trees
to derive water from deep, wet roots and lose water through
shallow dry roots. (Richards and Caldwell, 1987; Caldwell
and others, 1998). Finally, tree roots tap the ground water
indirectly by extending into the capillary fringe. Thus, in
areas where the capillary fringe is large, tree roots can derive
water from the ground water even when they appear to be too
shallow to access it.
Subsurface Lithology
The subsurface lithology can have an influence on the
ability of trees to be useful tools for examining VOCs in
ground-water contamination. In general, tree roots extend to
the depth necessary to maintain a water supply adequate for
growth. If a confined contaminated aquifer is overlain by an
unconfined uncontaminated aquifer, then it is unlikely that the
trees will be useful indicators of the contamination because
sufficient water can be obtained from a shallower source. If
the confining layer is absent, however, men it is possible that
the trees can sample the contaminated ground water, despite
the fact that the contaminated ground water is overlain by a
veneer of uncontaminated ground water. Field investigations
found mat roots from poplar trees induced upward hydraulic
gradients toward the roots (Schneider and others, 2002; Hirsh
and others, 2003).
The presence of a confining layer does not neces-
sarily limit the use of tree coring as a tool for examining
subsurface VOCs. A study in South Carolina examined the
TCE concentrations in tree cores growing above a confined
TCE-contaminated aquifer where a 9- to 10-ft-thick tight
clay confining layer extended to land surface. In mis case,
the availability of shallow ground water for use by the trees
was limited by presence of the clay. The roots of the trees
in this area extended to the aquifer below the clay in order
to maintain adequate water supply, as evidenced by the
presence of live roots in multiple sediment cores below the
clay (Vroblesky and others, 2007a). Despite the fact that
the contaminated aquifer was confined beneath about 9 to
10 ft of tight clay, the distribution of trees containing TCE in
tree cores closely matched the distribution of ground-water
contamination (Vroblesky and others, 2004). The concept
of tree roots seeking out sources of adequate water supply
indicates that in fractured-rock environments where there is
little saturated overburden, tree roots will preferentially sample
the water-bearing fracture zones, potentially optimizing their
use as indicators of shallow ground-water contamination in
this hydraulically complex setting.
Concentration Differences Around the Tree Trunk
Studies have reported VOC concentration variations
from cores collected on different sides of the same tree trunk
(Vroblesky and others, 1999, 2004; Lewis, 2001; Schumacher
and others, 2004; Sorek and others, 2008). Vroblesky and oth-
ers (1999) found concentration differences ranging from 44 to
92 percent for TCE and from 6 to 90 percent for cDCE in
cypress trees. The same trees, however, showed relatively good
replication for cores collected 1 in. (approximately 25 mil-
limeters (mm) apart (15.5 percent for TCE and 2.5 percent for
c'DCE), indicating mat the coring approach did not contribute
significant inconsistencies to the data. Schumacher and others
(2004) found three- to five-fold differences in PCE concentra-
tions around some tree trunks. Sorek and others (2008) found
VOC concentration variations up to a factor of about 5 from
differing sides of the same tree at the same height.
A variety of factors potentially can contribute to such
directional variations, including injuries (Scholander and
others, 1957), disease and insect damage (Kozlowski and
-------
20 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Paiiardy, 1997), gas embolisms (Clark and Gibbs, 1957), and
spiral transport up the trunk (Kozlowski and others, 1967;
Schumacher and others, 2004). In some situations, however,
directional differences in tree-core VOC concentrations are
caused by variations in subsurface VOC concentrations taken
up by root systems on differing sides of the tree (Vroblesky
and others, 1999). A study of loblolly pines (Pinus taeda)
showed that TCE concentrations in cores from a tree near
the edge of a ground-water contamination plume were 61 to
68 percent lower on the sides of the tree facing away from
the axis of contamination than on the sides of the tree facing
toward the axis of contamination (Vroblesky and others,
2004). The data indicate that in some cases, the direction
of the highest VOC concentration in a tree trunk may be
an indicator of the direction toward the greatest subsurface
VOC concentrations. Caution should be exercised with this
approach, however, because of the potential for spiral transport
up the trunk and other influences cited above (Kozlowski and
others, 1967; Schumacher and others, 2004).
Volatilization Losses from the Tree Trunk
VOC concentration decreases up the trunk of a tree have
been observed in some studies (Vroblesky and others, 1999;
Schumacher and others, 2004). These changes may be caused
by a variety of factors. In the first investigation using tree
coring as a tool to examine ground-water VOC concentrations,
a decrease in TCE concentration with height up a tree trunk
was observed and hypothesized to be caused by volatilization
loss through the bark (Vroblesky and others, 1999). Subse-
quently, laboratory and field investigations confirmed that
volatilization loss through the bark can be a major mechanism
for transfer of VOCs to the atmosphere (Davis and others,
1999; Burken, 2001; Ma and Burken, 2003), and upward
decreases in concentration also were observed in an additional
field investigation (Hirsh and others, 2003). One laboratory
experiment utilized diffusion traps to capture VOCs leaking
from stems and found that TCE leaked through the stems and
in all cases, the amount of TCE in the uppermost traps was
less than in the lowermost traps, indicating TCE loss up the
trunk (Ma and Burken, 2003). VOC loss also can occur from
the roots (Struckhoff, 2003). An additional effect of volatiliza-
tion loss from the tree trunk is that VOC concentrations in the
trunk sometimes decrease from the inner to the outer part of
the trunk (Ma and Burken, 2003). Thus, in some cases, higher
VOC concentrations may be obtained by coring deep into the
tree rather than by collecting only the outermost rings.
The rate of diffusive loss from tree trunks may be
influenced by the diameter of the trunk. Struckhoff (2003)
found that a 0.5-in.-diameter poplar cutting planted in con-
taminated soil or water has a 24-percent concentration loss in
5 in. of height, whereas a 6.5-in.-diameter Chinese elm (Ulmus
parvifolia) showed the same percent loss in 5 ft of height. The
author concluded that the greater surface area to volume ratio
in a smaller diameter section of tree will more quickly deplete
the reservoir of PCE in the trunk. In support of this conclusion,
Schumacher and others (2004) found that diffusion loss of
PCE in small (0.5-in. diameter) trees occurred at a rate more
than 10 times higher man in trees 6.5 in. in diameter.
Decreases in the VOC content of tree cores with increas-
ing height up the trunk have not been observed at all sites
(Vroblesky and others, 2004; Sorek and others, 2008). At a
site in Texas, an upward increase in tree-core TCE concentra-
tions was observed following a heavy rain (Vroblesky
and others, 2004). The concentration increases up the tree
appeared to represent a time series of water movement, with
the lowest pail of the trunk representing TCE-contaminated
ground water diluted with infiltrating rainwater, and the upper-
parts of the tree representing pre-rain undiluted ground water.
Thus, concentration changes up the trunk may be caused by
a variety of factors. Consequently, a prudent approach when
conducting a site survey to examine area! distribution of VOCs
in tree cores is to collect all cores from the same height.
Rainfall Infiltration as a Dilution Mechanism
Plant utilization of ground water and uptake of ground-
water contaminants depends partly on the reliability of
rainfall. In areas where rainfall is unreliable, riparian trees may
develop roots primarily in the capillary fringe and phreatic
zone rather man throughout the soil profile (Ehleringer and
Dawson, 1992), thus primarily utilizing ground water. Fremont
cottonwood (Populus fretnontii) and Goodding's willow
(Salix gooddingii) growing along streams in western Arizona
used ground water throughout the growing season regardless
of the depth to water (Busch and others, 1992). Plants with
roots disseminated in multiple soil zones may use various
combinations of ground water, rainfall infiltrate, and stream
water, sometimes responding opportunistically to rainfall
events (Mensforth and others, 1994; Thorburn and Walker,
1994; Dawson and Pate, 1996; Jolly and Walker, 1996). Trees
near a perennial stream in California used shallow soil water
early in the growing season and then primarily used ground
water in the later part of the season when the soil dried (Smith
and others, 1991). Mature box elder (Acer negundo) trees used
only ground water and did not seem to use perennial stream
water or shallow soil water in northern Utah (Dawson and
Ehleringer, 1991), but they did use soil water from precipita-
tion at ephemeral and perennial stream reaches in Arizona
(Kolb and others, 1997).
The potential for source water to trees to be affected
by rainfall infiltration indicates that the VOC concentrations
detected in cores from trees growing above contaminated
ground water also may be affected by mixing with various
water sources. For example, Doucette and others (2003)
reported that TCE concentrations in plant tissue at Hill Air
Force Base, Utah, where the climate is arid, were 10 to 100
tunes higher than at Cape Canaveral Air Station, Florida,
where the climate is humid and rainy, despite similar TCE
ground-water concentrations at both sites. The authors
hypothesized that the TCE concentration difference in tree
cores between the two sites was due to greater dilution effects
-------
Part 2. Historical Perspectives and Technical Considerations 21
from rainfall at the Florida site than at the Utah site. It also is
possible, however, that the difference could be due to the dif-
ference in sample-collection methods and analytical variabil-
ity. Methanol extraction coupled with PT gas chromatography
was used to analyze the Florida plant tissue, whereas HAS gas
chromatography was used to analyze Utah plant tissue.
To determine the influence on VOC concentrations in
tree cores of rainfall incorporation into transpiration stream,
a field test was conducted using artificial irrigation of a
mature cottonwood tree in Texas (Clinton and others, 2004;
Vroblesky and others, 2004). The test involved measuring
transpiration and tree-core TCE concentrations before and
after irrigating the tree. The results showed rapid TCE
concentration decreases and maximum transpiration value
increases following the artificial irrigation. These data indicate
that the uptake of irrigation water resulted in a rapid dilution
of TCE concentrations in the trunk. Thus, VOC concentrations
in tree cores collected after a rainfall may be less than before
the rainfall. A possible exception to this may occur if the
rainfall mobilizes contamination in the unsaturated zone. j
I
Seasonal Influences
Clear seasonal trends in VOC concentration of
tree cores has been observed in recent studies (Trapp
and others, 2007; Sorek and others, 2008). Much
higher TCE concentrations in the trees were recorded
in the dry hot season than in the wet cold season. Other
tree-coring investigations have shown concentration
changes possibly related to seasonal influences. The TCE
concentrations in bald cypress trees in South Carolina
decreased from July to September to January (Vroblesky
and others, 1999). Lewis (2001) reported that tree cores
from cottonwoods and Russian olive trees contained
significantly higher TCE in June 2000 and June 2001
than in the winter or even in May or late June to July of
the same years. Thus, it appears that in some cases there
are seasonal VOC concentration differences in trees with
higher concentrations during the summer than the winter.
Controlled mesocosm experiments have shown
that TCE flux to the atmosphere by transpiration of bald
cypress seedlings is influenced diurnally and seasonally
(Nietch and others, 1999). The flux decreased from day
to night, probably because the stomata are closed at
night (fig. 11). TCE flux also decreased from June to
December as transpirative water use seasonally decreased
(fig. 11). Interestingly, the study found that although the
winter TCE flux was reduced relative to the summer flux,
there was still significant TCE flux in the winter, imply-
ing that trees do not need to be conducting substantial
amounts of water to remove TCE from the ground water.
Although seasonal variations in tree-core VOC con-
centrations sometimes are present, the seasonal variations
do not appear to prevent the use of the tree coring as a tool
to investigate subsurface VOC concentrations during winter
months. The TCE concentrations in cores from a pine and
an oak tree in Ashland, Massachusetts, were 17 ppbv in late
August 2006 (Vroblesky and others, 2006), and approximately
the same amount (14 and 18 ppbv, respectively) at the end of
November 2006, after the leaves had fallen (Scott Clifford,
U.S. Environmental Protection Agency, written commun.,
2006). In addition, winter (February) tree cores provided
the data that were successfully used in the first study to use
tree cores as a tool to map subsurface VOCs (Vroblesky and
others, 1999). Additional work is needed to fully understand
the seasonal influences on tree-core sampling for VOCs.
Sorption
Organic compounds such as TCE have a tendency to sorb
to plant tissue (Davis and others, 1998a). Newman and others
(1997) found that a small percentage (3 to 4 percent) of TCE
remained as an insoluble residue in poplar tree cells. Other
LU I-
CO Z>
55
OS
£<*
"- UJ
X CL
i <
O^
on z
2-
o
on
70
60
50
40
30
20
10
A.
DAY
NIGHT
AUG
OCT
NOV
DEC
MONTH
on
s
0.08
0.06
±: 0.04
.
LJJ
I
tJ
O
on
2
o
on
0.02
0.00
B.
Day
Night
SUMMER
WINTER
Figure 11. Trichloroethene removal from the rhizosphere of bald
cypress seedlings as (A) nanomoles per minute through the above-
ground part of the plant and (B) fractional trichloroethene loss from
carboy water during the summer and winter (modified from Nietch
and others, 1999).
-------
22 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
investigations found that the predominant mass of VOCs in
tree trunks may reside in the wood tissue (Ma and Burken,
2002, 2003; Struckhoff, 2003; Schumacher and others,
2004) with a greater amount of sorption in more lignified
tissues, such as poplar trees, relative to young sunflower
plants (Helianthus annuus) (Davis and others, 1998b). Thus,
soiption of VOCs to the wood of the tree may be an important
influence on tree-core VOC concentrations (Schumacher and
others, 2004).
Sorption of VOCs onto wood is related to the compound
Henry's Law constant and vapor pressure (Ma and Burken,
2002) and to the lipophilicity of the compounds, expressed
as log Kow (Trapp and others, 2001). In general, chlorinated
hydrocarbons tend to be partly excluded or sorbed within
plants, ethers are only slightly excluded or sorbed, and less
polar gasoline constituents are more strongly excluded or
sorbed man TCE (Burken, 1996; Makepeace and others, 1996;
Davis and others, 1998a). The soiption of TCE is considerably
stronger than that of TCA despite the greater log Kow of TCA
(Davis and others, 1998b). Chloroform and dichloromethane
tend to be weakly sorbing compounds (Davis and others,
1998a).
Approaches to quantifying sorption of VOCs onto wood
include examining the equilibrium distribution of VOCs
between tree tissue and water (KwoiJ. Higher KwooJ values
indicate higher potential for sorption. Mackay and Gschwend
(2000) measured soiption of benzene, toluene, and o-xylene to
wood and found that the Km>od coefficients were between 6.6
and 28 milligrams per gram (mg/g) of dry wood to milligrams
per milliliter of water, indicating a relatively high sorption
capacity of wood. They also found that the soiption is linear
and reversible.
Within-Tree Volatile Organic
Compound Degradation
Phytodegradalion, or the breakdown of organic
contaminants within tree tissue, can take place inside the
plant or within the rhizospere of the plant (Newman and
Reynolds, 2004; Vroblesky and others, 2004). A study of
willow and poplar trees used as a polishing step for mitigating
a chlorinated solvent plume showed the presence in tree
tissue of parent chlorinated ethenes and chloroacetic acids
(oxidative transformation products), indicating the uptake
and phytodegradalion of the contaminants (Nzengung, 2005).
Intermediate stable metabolites, apparently from the break-
down of chlorinated solvents, have been reported in various
tree species growing above contaminated soils (Newman and
others, 1997; Complon and others, 1998; Doucetie and others,
1998; Gordon and others, 1998). The presence of intermediate
degradation products and mass-balance considerations suggest
that MTBE degradation may take place in mature trees (Rubin,
2007). Newman and others (1997) found that cells from
poplar trees are capable of transforming and mineralizing TCE
without the involvement of microbial metabolism. Vroblesky
and others (2004) found that the tree-core TCE and cDCE
distribution between the inner and outer parts of the trunk of a
narrow-leaf cottonwood (Populus angustifolia James) tree core
from Colorado was consistent with microbial dehalogenation
of TCE within the apparently methanogenic conditions of the
wetwood of the inner trunk. Wetwood conditions are caused
by an infestation in the tree of methanogenic and other bacte-
ria in the tree heartwood (Stankewich and others, 1971; Zeikus
and Ward, 1974). Methanogenic conditions are associated with
efficient dehalogenation of TCE to cDCE (Parsons and others,
1984, 1985; Kloepfer and others, 1985; Wilson and others,
1986). The data from a variety of investigations indicate that
some level of VOC degradation can take place within the
tree or rhizosphere. Phytodegradation that takes place in the
rhizosphere, roots, or trunks of trees has the potential to reduce
or alter the VOC concentrations detected in tree cores.
This manual provides a guide to the use of tree coring as
a tool to examine subsurface VOCs. It examines some of the
factors influencing the use of tree coring for that purpose and
summarizes some case studies in which tree coring has been
used to examine subsurface VOCs. Typical VOCs thai have
been detected in tree cores include benzene, toluene, ethylben-
zene, xylene isomers, trimethyl benzene, MTBE, TCE, PCE,
and cDCE. The method is inexpensive, portable, rapid, and
uncomplicated. The presence of VOCs in tree cores is a strong
indicator of subsurface VOC contamination; however, the
lack of VOC detection does not necessarily mean that VOC
contamination is not present.
Tree cores are obtained by use of a clean and sharp incre-
ment borer. The boring should be started slowly and carefully
to avoid sideways slippage of the bit against the tree trunk. The
core is removed from the borer by means of an extractor. The
core should be transferred to a vial and sealed immediately
upon recovery from the tree. The hcadspacc in the vials should
be given enough time to equilibrate with the VOCs in the tree
core prior to analysis, typically about 24 hours for storage at
room temperature to about 5 to 15 minutes for field-healed
cores. Diffusion of TCE from the tree cores to the hcadspacc
in sample vials is fast enough, however, that analysis of
unhealed cores after 5 minutes can contain sufficient TCE to
indicate the presence of TCE contamination. Core analysis
can be performed using a variety of approaches, but IIS A by
gas chromatography often is the simplest approach. Quality
control and assurance samples should be collected to ensure
the integrity of the data.
A variety of factors influence the ability of plants to
be useful indictors of ground-water VOC contamination.
These factors include the type of VOC, the tree species, the
rooting depth, aqueous concentrations, the depth to water,
concentration differences around the trunk related to different
sources of subsurface VOCs, concentration differences with
-------
References Cited 23
depth of coring related to volatilization loss through the bark
and possibly other unknown factors, dilution by rain, seasonal
influences, soiption, and within-tree VOC degradation.
Azevedo, J.I,., Maccheroni, Walter. Jr., Pereira, J.O., and de
Araujo, W.L., 2000, Ednophytic microorganisms—A review
on insect control and recent advances on tropical plants:
Environmental Biotechnology, v. 3. no. 1, accessed
January 12, 2006, ai http://www.ejbiote.chnology.info/
content/vo13/issuel/fuU/4/index.hlml
Briggs, G.G., Bromilow, R.IL, and Evans, A.A., 1982, Rela-
tionships between lipophicity and root uptake and transloca-
lion of non-ionized chemicals by barley: Pesticide Science,
v. 13, p. 495-504.
Briggs, G.G., Bromilow, R.H., Evans, A.A., and Williams, ML,
1983, Relationships between lipophilicity and the distribu-
tion of non-ionized chemicals in barley shoots following
uptake by the roots: Pesticide Science, v. 14, p. 492-500.
Brown, K., Tyner, L., Grainger, 13., and Perina, T., 2001,
Impact of natural attenuation and phyloremedialion on
MTBE and fuel, in Magar, V., Gibbs, J.T., O'Reilly, K.T.,
Ilyman, M.R., and Leeson, A., eds., Bioremediation of
MTBE, alcohols, and ether, Sixth International In Situ and
On-Site Bioremedialion Symposium, June 4-7, 2001, San
Diego, California: Columbus, Ohio, Battellc Press.
Burken, J.G., 1996, Uptake and fate of organic contaminants
by poplar trees: Iowa City, Iowa, University of Iowa, Ph. I).
dissertation, 215 p.
Burken, J.G., 2001, Uptake and volatilization of chlorinated
solvents by poplars at field scale, in Leeson, A., Foote,
E.A., Banks, M.K., and Magar, V.S., eds., Phytoremedia-
tion, wetlands and sediments: Columbus, Ohio, Batelle
Press, p. 113-120.
Burken, J.G., and Schnoor, J.L., 1998, Predictive relation-
ships for uptake of organic contaminants by hybrid pop-
lar trees: Environmental Science and Technology, v. 32,
p. 3379-3385.
Busch, D.E., Ingraham, N.L., and Smith, S.D., 1992, Water
uptake in woody riparian phreatophytes of the southwestern
United States—A stable isotope study: Ecological Applica-
tions, v. 2, p. 450-459.
Caldwell, M.M., Dawson, T.E, and Richards, J.H., 1998,
Hydraulic lift—Consequences of water efflux for the roots
of plants, Oecologia, v. 113, p. 151-161.
Castelfranco, P., Foy, C.L., and Deutsch, D.B., 1961, Non-
enzymatic detoxification of 2-chloro-4,6-bis(ethylamino)-
s-triazine (simazine) by extracts of Zea Mays: Weeds, v. 9,
p. 580-591.
Chancy, W.R., 2000, Water and chemical movement beneath
the bark: The Woodland Steward, Spring 2000, v. 9, no. 1,
downloaded from http://www.fnr.purdue. edu/inwood/
past%20issues/WATERANDCHEMICAL.htm (accessed on
November 1,2007).
Clark, J., and Gibbs, R.D., 1957, Studies in tree physiology,
IV, Further investigations of seasonal changes in moisture
content of certain Canadian forest trees: Canadian Journal
of Botany, v. 35, p. 219-253.
Clinton, B.D., Vose, J.M., Vroblesky, D.A., and Harvey, G.J.,
2004, Determination of the relative uptake of ground vs.
surface water by Populus deltoides during phytoremedia-
tion: International Journal of Phytoremediation, v. 6, no. 3,
p. 239-252.
Compton, II.R., Ilaroski, D.M., Ilirsh, S.R., and Wrobel, J.G.,
1998, Pilot-scale use of trees to address VOC contamina-
tion, in Wickramanayake, G.B., and Hinchee, R.E., eds.,
Bioremediation and Phytoremediation, First International
Conference on Remediation of Chlorinated and Recalci-
trant Compounds, May 18-21, 1998, Monterey, California:
Columbus, Ohio, Battelle Press, p. 245-249.
Cox, S.E., 2002, Preliminary assessment of using tree-tissue
analysis and passive-diffusion samplers to evaluate trichlo-
roethene contamination of ground water at Site SS-34N,
McChord Air Force Base, Washington, 2001: U.S. Geologi-
cal Survey Water-Resources Investigations Report 02-4274,
13 p.
Davis, L.C., Banks, M.K., Schwab, A.P., Muralidharan, N.,
Erickson, L.E., and Tracy, J.C., 1996, Plant based biore-
mediation, in Sikdar, S.K., and Irvine, R.L., eds., Bioreme-
diation: Lancaster, Pennsylvania, Technomics Publishing
Company.
Davis, L.C., Erickson, L.E., Narayanan, M., and Zhang,
Q., 2003, Modeling and design of phytoremediation, in
McCulheon, S.C., and Schnoor, J.L., eds., Phytoremedia-
tion—Transformation and control of contaminants: Hobo-
ken, New Jersey, John Wiley and Sons, Inc., p. 663-694.
Davis, L.C., Lupher, D., Hu, J., and Erickson, L.E., 1999,
Transport of trichloroethylene through living plant tis-
sues, in Proceedings of the 1999 Conference on Hazardous
Waste Research, St. Louis, Missouri, May 24-27, 1999,
p. 203-209.
-------
24 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Davis, L.C., Vanderhoof, S., Dana, J., Selk, K., Smith, K.,
Goplen, B., andErickson, L.E., 1998b, Chlorinated solvent
movement through plants monitored by Fourier transform
infrared (FT-IR) spectroscopy: Journal of Hazardous Sub-
stances Research, v. 1, no. 4, p. 1-26.
Davis, L.C., Vanderhoof, S., and Lupher, D., 1998a, Sorption
of irichloroelhylene (TCE) and olher halogenaled aliphalics
on plant materials, in Ericksoti, L.E., and Rankin, M.M.,
eds., Proceedings of the 1998 Conference on Hazardous
Waste Research, Kansas State University, Manhattan, Kan-
sas,?. 319-325.
Dawson, T.E., and Ehleringer, J.R., 1991, Streamside trees that
do not use stream water: Nature, v. 350, p. 335-337.
Dawson, T.E., and Pate, J.S., 1996, Seasonal water uptake
and movement in root systems of phreatophytic plants of
dimorphic root morphology—A stable isotope investigation:
Oecologia, v. 107, p. 13-20.
Dcttcnmaicr, E.M., Doucettc, W.J., Bugbcc, B., and Hall, A.,
2008, Reexamining the relationship between plant uptake of
organic chemicals and octanol water partition coefficients,
in Platform Abstracts of the Sixth International Conference
on Remediation of Chlorinated and Recalcitrant Com-
pounds, May 19-22, 2008, Monterey, California: Columbus,
Ohio, Battelle Press, session B6.
Dietz, A.C., and Schnoor, J.L., 2001, Advances in bioremedia-
tion: Environmental Health Perspectives, v. 109, supple-
ment 1, p. 163-168.
Doucette, W.J., Bugbee, B., Hayhurst, S., Plaehn, W., Downey,
D., Taffinder, A., and Edwards, R., 1998, Phytoremediation
of dissolved-phase trichloroethylene using mature vegeta-
tion, in Wickramanayake, G.B., and Hinchee, R.E., eds.,
Bioremediation and Phytoremediation, First International
Conference on Remediation and Recalcitrant Compounds,
May 18-21,1998, Monterey, California: Columbus, Ohio,
Battelle Press, p. 251-256.
Doucette, W.J., Bugbcc, G.B., Smith, S.C., Pajak, C.J., and
Ginn, J.S., 2003, Uptake, metabolism, and phytovolatiliza-
tion of trichloroethylene by indigenous vegetation—Impact
of precipitation, in McCutcheon, S.C., and Schnoor, J.L.,
eds., Phytoremediation—Transformation and control of
contaminants: Iloboken, New Jersey, John Wiley and Sons.
Inc., p. 561-588.
Douglass, A.E., 1919, Climatic cycles and tree growth: Carn-
egie Institute of Washington Publication Number 289, v. 1,
127 p.
Eckstein, D., and Dujesiefken, D., 1999, Long-term effects
in trees due to increment borings.: Dendrochronologia,
v. 16-17, p. 205-211.
Ehleringer, J.R., and Dawson, T.E., 1992, Water uptake by
plants—Perspectives from stable isotope composition:
Plant, Cell, and Environment, v. 15, p. 1073-1082.
Ehleringer, J.R., Philips, S.L., Schuster, W.F.S., and Sandquist,
D.R., 1991, Differential utilization of summer rains by des-
ert plants: Oecologia, v. 88, p. 430-434.
Ellmore, G.S., and Ewers, F.W., 1986, Fluid flow in the
outermost xylem increment of a ring-porous tree, Ulmus
atnericana: American Journal of Botany, v. 73, no. 12,
p. 1771-1774.
Gopalakrishnan, Gayathri, Negri, M.C., Minsker, B.S., and
Werth, C.J., 2005, Monitoring soil and ground water plumes
using trees in an existing phytoremediation system: Pre-
sented at the 3rd International Phytotechnologies Confer-
ence, April 19-22, 2005, sponsored by The U.S. Environ-
mental Protection Agency and the Midwest Hazardous
Substance Research Center, Atlanta, Georgia.
Gopalakrishnan, Gayathri, Negri, M.C., Minsker, B.S., and
Werth, C.J., 2007, Monitoring subsurface contamination
using tree branches: Ground Water Monitoring and Reme-
diation, v. 27, no. 1, p. 65-74.
Gordon, M., Choe, N., Duffy, J., Ekuan, G., Heilman, P.,
Muiznieks, I., Ruszaj, M., Shurtleff, B., Strand, S., Wilmot,
J., and Newman, L., 1998, Phytoremediation of trichloroeth-
ylene with hybrid poplars: Environmental Health Perspec-
tive, v. 106, no. 4, p. 1001-1004.
Grissino-Mayer, Henri, 2003, A manual and tutorial for the
proper use of an increment borer: Tree-Ring Research,
v. 59, no. 2, p. 63-79.
Hart, J.H., and Wargo, P.M., 1965, Increment borer wounds—
penetration points for Ceralocyslis fagacearum: Journal of
Forestry, v. 63, no. 1, p. 38-39.
Hepting, G.H., Roth, E.R., and Sleeth, B., 1949, Discoloration
and decay from increment borings: Journal of Forestry,
v. 47, p. 366-370.
Heyerdahl, E.K., and McKay, S.J., 2001, Condition of live
fire-scarred ponderosa pine trees six years after remov-
ing partial cross sections: Tree-Ring Research, v. 57,
p/131-139.
Hirsh, S.R., Compton, H.R., Matey, D.H., Wrobel, J.G., and
Schneider, W.H., 2003, Five-year pilot study, Aberdeen
Proving Ground, Maryland, in McCutheon, S.C., and
Schnoor. J.L., eds., Phytoremediation—Transformation and
control of contaminants: Hoboken, New Jersey, John Wiley
and Sons, Inc., p. 635-659.
Hong, M.S., Rarmayan, W.F., Dortch, I.J., and Chiang, C.Y.,
2001, Phytoremediation of MTBE from a groundwater
plume: Environmental Science and Technology, v. 35, no. 6,
p. 1231-1239.
-------
References Cited 25
ICF Consulting, 2005, Indoor air human health risk assess-
ment, Nyanza Chemical Waste Dump Superfund Site Oper-
able Unit II, Ashland, Massachusetts: Consultant's report to
the U.S. Army Corps of Engineers, New England District,
October 25, 2005 [variously paged].
Inoue, J., Chamberlain, K., and Vromilow, R.H., 1998,
Physiochemical factors affecting the uptake by roots and
translocation to shoots of arnine bases in barley: Pesticide
Science, v. 54, p. 8-21.
Jackson, R.B., Moore, L.A., Hoffmann, W.A., Pockman, W.T.,
and Linder, C.R., 1999, Ecosystem rooting depth deter-
mined with caves and DNA: Proceedings of the National
Academy of Sciences of the United States of America,
v. 96, p. 11387-11392.
Jolly, I.D, and Walker, G.R., 1996, Is the field water use of
Eucalyptus largiflorens F. Meull affected by short-term
flooding?: Australian Journal of Ecology, v. 21, p. 173-183.
Keller, C., Hammer, D., Kayscr, A., Richneer, W., Brodbcck,
M., and Sennhauser, M., 2003, Root development and heavy
metal phytoextraction efficiency—Comparison of different
plant species in the field: Plant Soil, v. 249, p. 67.
Kelso, P.W., 2005, An innovative field-based analytical
method for low-level detection of chlorinated compounds
in groundwater and soil samples (The Color-Tec Method);
accessed June 13, 2008, at http://www.clu-in.org/conf/tio/
pasifcolortec___description.pdf
Kloepfer, R.D., Easley, B.B., Haas, B.B., Jr., Deihl, T.G.,
Jackson, D.E., and Wurrey, C.J., 1985, Anaerobic degrada-
tion of trichloroethylene in soil: Environmental Science and
Technology, v. 19, no. 3, p. 277-280.
Kolb, T.E., Hart, S.C., and Amundson, R., 1997, Boxelder
water source and physiology at perennial and ephemeral
stream sites in Arizona: Tree Physiology, v. 17, p. 151-160.
Kozlowski, T.T., Hughes, J.F., and Leyton, L., 1966, Patterns
of water movement in dormant gymnosperm seedlings:
Biorheology, v. 3, p. 77-85.
Kozlowski, T.T., Hughes, J.F., and Leyton, L., 1967, Dye
movement in gynmosperms in relation to tracheid align-
ment: Forestry, v. 40, p. 209-227.
Kozlowski, T.T., and Pallardy, S.G., 1997, Physiology of
woody plants (2d ed.): San Diego, California, Academic
Press, 411 p.
Landmeyer, J.E., Bradley, P.M., and Vroblesky, D.A., 2000,
MTBE in trees transpiring gasoline-contaminated ground
water, presented at the Second International Conference on
Remediation of Chlorinated and Recalcitrant Compounds,
May 22-25, 2000, Monterey, California: Columbus, Ohio,
Battelle Pi-ess.
Lewis, Kerry, 2001, The relationship between tree-core and
groundwater trichloroethylene concentrations for ground-
water plume delineation: Logan, Utah, Utah State Univer-
sity, Department of Environmental Engineering, M.S. thesis,
188 p.
Lewis, K., Doucette, W., Bugbee, B., and Ginn, J., 2001,
Relationship between irichloroelhylene concentrations in
tree cores and ground water for plume delineation, in Pro-
ceedings of the Society of Toxicology and Environmental
Chemistry (SETAC) 22"d Annual Meeting Abstract Book,
November 11-15, 2001, Baltimore, Maryland.
Lockheed Martin, 2000, J-Field phytoremediation project—
Field events and activities through July 31, 2000, Aberdeen
Proving Ground, Edgewood, Maryland, August 31, 2000:
Consultant's report to the U.S. Environmental Protection
Agency, 28 p.
Lorenz, R.C., 1944, Discoloration and decay resulting from
increment borings in hardwoods: Journal of Forestry, v. 42,
p. 37-43.
Ma, X., and Burken, J.G., 2002, VOCs fate and partitioning
in vegetation—Use of tree cores in groundwater analysis:
Environmental Science and Technology, v. 36, no. 21,
p. 4663-4668.
Ma, X., and Burken, J.G., 2003, TCE diffusion to the atmo-
sphere in phytoremediation applications: Environmental
Science and Technology, v. 37, p. 2534-2539.
Mackay, A. A., and Gschwend, P.M., 2000, Soiption of mono-
aromatic hydrocarbons to wood: Environmental Science and
Technology, v. 34, no. 5, p. 839-845.
Maeglin, R.R., 1979, Increment cores, how to collect, handle,
and use them: Madison. Wisconsin, U.S. Department of
Agriculture, Forest Service General Technical Report
FPL 25,18 p.
Makepeace, V.D., Davis, L.C., Dana, J., Selk, K, Smith, K.,
Hammaker, R.M., Fateley, W.G., and Erickson, L.E., 1996,
Measuring contaminant flux through plants by fourier
transform infrared (FT-IR) spectrometry, in Proceedings of
the HSRC/WERC Joint Conference on the Environment,
May 21-23,1996, Albuquerque, New Mexico: Manhattan
Kansas, Kansas State University, p. 577-582.
Mensforth, L.J., Thorburn, P.J., Tyerman, S.D., and Walker,
G.R., 1994, Sources of water used by riparian Eucalyptus
catnaldulensis overlying highly saline ground water: Oeco-
logia, v. 100, p. 21-28.
Melcalf & Eddy, Inc.. 2006. Technical memorandum for
site-wide shallow groundwater investigation, final, Durham
Meadows Superfund Site, Durham, Connecticut: Consul-
tant's report to the U.S. Environmental Protection Agency,
November 2006 [variously paged!.
-------
26 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Meyer, W.H., and Hayward S.B., 1936, Effect of incre-
ment coring on Douglas-fir: Journal of Forestry, v. 34,
p. 867-869.
Narayanan, M.N., Erickson, L.E., and Davis, L.C., 2004, Sim-
ple plant-based design strategies for volatile organic pollut-
ants: Environmental Progress, v. 18, no. 4, p. 231-242.
Negri, M.C., Gatliff, E.G., Quinn, J.J., and Hinchman,
R.R., 2003, Root development and rooting at depths, in
McCutheon, S.C., and Schnoor, J.L., eds., Phytoremedia-
tion—Transformation and control of contaminants: Hobo-
ken, New Jersey, John Wiley and Sons, Inc., p. 233-262.
Newman, L.A., and Reynolds, C.M., 2004, Phytodegradation
of organic compounds: Current Opinion in Biotechnology,
v. 1, no. 3, p. 225-230.
Newman, L.A.. Strand, S.E., Duffy. J., Choe, Nami, Ekuan,
G., Ruszaj, M., Shurtleff, B.B., Wilmoth, J., Heilman, P.,
and Gordon, M.P., 1997, Uptake and biolransformalion of
trichlorocthylene by hybrid poplars: Environmental Science
and Technology, v. 31, no. 4, p. 1062-1067.
Nietch, C.T., Morris, J.T., and Vroblesky, D.A., 1999, Bio-
physical mechanisms of trichloroethene uptake and loss
in bald cypress growing in shallow contaminated ground
water: Environmental Science and Technology, v. 33,
no. 17, p. 2899-2904.
Nilsen, E.T., and Orcutt, D.M., 1996, Physiology of plants
under stress: New York, New York, John Wiley and Sons,
704 p.
Nzcngung, V.A., 2005, Case studies of phytoremcdiation
of petrochemicals and chlorinated solvents in soil and
ground water, in Hatcher, K.J., ed., Proceedings of the 2005
Georgia Water Resources Conference, April 25-27, 2005,
Athens, Georgia.
Orchard, B.J., Doucette, W.J., Chard, J.K., and Bugbee,
B., 2000, Uptake of trichloroethylene by hybrid poplar
trees grown hydroponically in flow-through plant cham-
bers: Environmental Toxicology and Chemistry, v. 19,
p. 895-903.
Parfitt, D.G., Arnold, C., and Kaltreider, M, 2000, Root
uptake and transpiration of gasoline oxygenates by Pinus
radiata [abst.]: Tenth Annual West Coast Conference on
Contaminated Soils and Groundwater, March 20-23, 2000,
San Diego, California.
Parsons, E, Lage, G.B., and Rice, R.. 1985. Biotransformation
of chlorinated organic solvents in static microcosms: Envi-
ronmental. Toxicology and Chemistry, v. 4, p. 739-742.
Parsons, E, Wood, P.R., and DeMarco, J., 1984, Transforma-
tion of tetrachloroethene and trichloroethene in microcosms
and ground water: Journal of the American Water Works
Association, v. 72, no. 2, p. 56-59.
Ramaswami, A., and Rubin, A., 2001, Measuring phytoreme-
diation parameters for volatile organic compounds—Focus
on MTBE: Practice Periodical of Hazardous, Toxic, and
Radioactive Waste Management, July 2001, p. 123-129.
Richards, J.IL, and Caldwell, M.M., 1987, Hydraulic lift-
Substantial nocturnal water transport between soil layers by
Arlemesia tridentate roots: Oecologia, v. 73, p. 486-489.
Roy F. Weston, Inc., 2000, Electronic map of Nyanza Chemi-
cal Waste Dump Superfund Site, Ashland, Massachusetts,
filename MAPPH.DWG, November 2005.
Rubin, E.G., 2007, Evidence for phytodegradation of MTBE
from coupled bench-scale and intermediate-scale tests:
Journal of Environmental Engineering, v. 133, no. 4,
p. 389-396.
Schneider, W.IL, Ilirsh, S.R., Compton, II.R., Burgess,
A.E., and Wrobel, J.G., 2002, Analysis of hydrologic
data lo evaluate phyloremedialion system performance, in
Gavaskar, A.R., and Chen, A.S.C., eds., Proceedings of the
Conference on Remediation of Chlorinated and Recalci-
trant Compounds—Third International Conference, March
20-23, 2002, Monterey, California: Columbus, Ohio, Bat-
tellc Press, 2B-26.
Schnoor, J.L., Licht, L.A., McCutcheon, S.C., Wolf, N.L., and
Carreira, L.H., 1995, Phytoremediation of organic and nutri-
ent contaminants: Environmental Science and Technology,
v. 29, no. 7, p. 318A-323A.
Scholander, P.F, Ruud, B., and Leivestad, H., 1957, The rise of
sap in a tropical liana: Plant Physiology, v. 32, p. 1-6.
Schumacher, J.G., Struckhoff, G.C., and Burken, J.G., 2004,
Assessment of subsurface chlorinated solvent contamina-
tion using tree cores at the Front Street Site and a former
dry cleaning facility at the Riverfront Superfund Site, New
Haven, Missouri, 1999-2003: U.S. Geological Survey Sci-
entific Investigations Report 2004-5049, 35 p.
Sepaskhah, A.R., and Karimi-Goghari, Sh., 2005, Shallow
ground-water contribution to pistachio water use: Agricul-
tural water Management, v. 72, p. 69-80.
Shann, J.R., and Boyle, J.J., 1994, Influence of plant spe-
cies on in situ rhizosphere degradation, in Anderson, T.A.,
and Coats, J.R., eds., Bioremediation through rhizosphere
technology: American Chemical Society, Washington DC,
p. 71-81.
Sheehan, E.M., Burken, J.G., Karlson, II., Mayer, P., and
Legind, C., 2007, Plant sampling for ground-water investi-
gations fabsl.l: Fourth International Phylotechnologies Con-
ference, September 24—26, 2007, Denver, Colorado, p. 43.
Shigo, A.L., 1967, Successions of organisms in discolor-
ation and decay of wood: International Review of Forestry
Research: v. 2, p. 237-239.
-------
References Cited 27
Shigo, A.L., 1974, A tree hurts too: Broomall, Pennsylvania,
Forest Service, Northeastern Forest Experiment Station,
Report NE-INF-16-73, 28 p.
Shigo, A.L., 1983, Tree defects—A photo guide: Broomall,
Pennsylvania, Forest Service, Northeastern Forest Experi-
ment Station, General Technical Rep NE-82, 167 p.
Shigo, A.L., 1985, Compaflmentalization of decay in trees:
Scientific American, v. 252, no. 4, p. 96-103.
Shone, M.G.T., and Wood, A.V., 1972, Factors affecting
absorption and translocation of simazine in barley: Journal
of Exploratory Botany, v. 23, no. 74, p. 141-151.
Shone, M.G.T., and Wood, A.V., 1974, A comparison of the
uptake and translocalion of some organic herbicides and
a systemic fungicide by barley: Journal of Experimental
Botany, v. 25, p. 390-400.
Smith, S.D., Wellington, A.B., Nachlinger, J.A., and Fox,
C.A., 1991, Functional responses of riparian vegetation to
streamflow diversions in the eastern Sierra Nevada: Eco-
logical Applications, v. 1, p. 89-97.
Sorek, A., Atzmon, N., Dalian, O., Gerstl, Z., Kushisin, L.,
Laor, Y., Mingelgrin, U., Nasser, A., Ronen, D., Tsechan-
sky, L., Weisbrod, N., and Graber, E.R., 2008, Phytoscreen-
ing—The use of trees for discovering subsurface contamina-
tion by VOCs: Environmental Science and Technology, v.
42, p. 536-542.
Stankewich, J.P., Cosenza, G.J., and Shigo, A.L., 1971,
Closlridum quercicolum sp. N., isolated from discolored tis-
sues in living oak trees: Antonie van Lecuwenhock Journal
of Microbiology and Serology. v. 37, p. 299-302.
Struckhoff, G.C., 2003, Uptake of PCE vapor by plant-
Impacts for phytore-mediation: Rolla, Missouri, University
of Missouri, Department of Environmental Engineering,
unpublished M.S. thesis, 57 p.
Struckhoff, G.C., Burken, J., and Schumacher, J., 2005a,
Vadose zone PCE—An important source and fate in planted
systems: Presented at the 3rd International Phytotechnolo-
gies Conference, April 19-22, 2005, sponsored by The U.S.
Environmental Protection Agency and the Midwest Hazard-
ous Substance Research Center, Atlanta, Georgia.
Struckhoff, G.C., Burken, J., and Schumacher, J., 2005b,
Vapor-phase- exchange of perchloroelhene between soil
and plants: Environmental Science and Technology, v. 39,
p. 1563-1568.
Thorburn, P.J., and Walker, G.R., 1994, Variations in stream
water uptake- by Eucalyptus camaldulensis with differ-
ing access to stream water: Oecologia, v. 100, no. 3,
p. 293-301.
Took, E.R., and Gammage, J.L., 1959, Damage from incre-
ment borings in bottomland hardwoods: Journal of Forestry,
v. 57, no. 12, p. 909-911.
Tout, R.E., Gilboy, W.B., and Spyrou, N.M., 1977, Neutron
activation studies of trace elements in tree rings: Journal of
Radioanalytical Chemistry, v. 37, p. 715.
Trapp, Stefan, Larse-n, Morten, Legind, C.N., Burken, Joel,
Machackova, Jinna, and Karlson, U.G., 2007, A guide- to
vegetation sampling for screening of subsurface pollution;
accessed April 9, 2008, at vww2.er.dtu.dk/Homepages/stt/
GuidetoVegetationSanipIing.pdf
Trapp, Stefan, Miglioranza, K.S.B., andMosbak, Hans, 2001,
Sorption of lipophilic organic compounds to wood and
implications for their environmental fate: Environmental
Science and Technology, v. 35, no. 8, p. 1561-1566.
U.S. Environmental Protection Agency, 2003, Method 5021 A,
Volatile organic compounds in various sample matrices
using equilibrium headspace analysis; accessed Decem-
ber 2, 2005, at http://Hrww.epa.gov/epaoswer/hazwaste/test/
pdfs/502 la _rl.pdf
van Mantgem, P.J., and Stephenson, N.L., 2004, Does coring
contribute to tree mortality?: Canadian Journal of Forestry
Research, v. 34, p. 2394-2398.
Vroblesky, D.A., 1998, Chlorinated e-thene uptake- and loss in
tree- trunks: U.S. Geological Survey Department of Defense
Environmental Conservation (DODEC) meeting, May 4-8,
1998, Tampa, Florida.
Vroblesky, D.A., and Casey, C.C., 2004, Tree coring as an
optimization tool for monitoring-well placement, Fourth
International Conference-on Remediation of Chlorinated
and Recalcitrant Compounds, May 24-27, 2004, Monterey,
California: Columbus, Ohio, Battellc Press.
Vroblesky, D.A., Casey, C.C., Harvey, G., Morris, J.T., and
Vose, J.M., 2001, TCE and DCE in tree trunks in diverse
environments, Sixth International In Situ and On-Site Blore-
mediation Symposium, June 5, 2001, San Die-go, California:
Columbus, Ohio, Battelle Press.
Vroblesky, D.A., Casey, C.C., Petkewich, M.D., Lowery,
M.A., Conlon, K.J., and Harrelson, E.G., 2007a, Inves-
tigation of ground-water contamination at Solid Waste
Management Unit 12, Naval Weapons Station, Charleston,
North Charleston, South Carolina: U.S. Geological Survey
Scientific Investigations Report 2006-5311, 81 p.
Vroblesky, D.A., Clinton, B.D., Vose, J.M., Casey, C.C., Har-
vey, G.J., and Bradley, P.M., 2004, Groundwaler chlorinated
ethcnes in tree trunks—Case studies, influence of recharge,
and potential degradation mechanism: Ground Water Moni-
toring and Remediation, v. 24, no. 3, p. 124-138.
-------
28 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Vroblesky, D.A., Nietch, C.T., and Morris, J.T., 1999, Chlo-
rinated ethenes from ground water in tree trunks: Environ-
mental Science and Technology, v. 33, no. 3, p. 510-515.
Vroblesky, D. A., Willey, R.E., Clifford, Scott, and Jenkins,
David, 2007b, Real-time mapping of ground-water VOC
contamination with tree cores: Fourth International Phyto-
lechnologies Conference, September 24-28, 2007, Denver,
Colorado.
Vroblesky, D.A., Willey, R., Clifford, S., and Murphy,.!.,
2006, Data from tree-coring investigation near the Nyanza
Chemical Waste Dump Superfund Site, Ashland, Mas-
sachusetts, August 30, 2006: U.S. Geological Survey Data
Series 218, 5 p.
Vroblesky, D.A., Willey, R.E., Clifford, Scott, and Murphy,
J.J., 2008, Real-time and delayed analysis of tree and shrub
cores as indicators of subsurface volatile organic compound
contamination, Durham Meadows Superfund Site, Durham,
Connecticut, August 29, 2006: U.S. Geological Survey
Scientific Investigations Report 2007-5212, 12 p.
Vroblesky, D.A., and Yanosky, T.M., 1990, Use of tree-ring
chemistry to document historical ground-water contamina-
tion events: Ground Water, v. 28, no. 5, p. 677-684.
Vroblesky, D.A., Yanosky, T.M., and Siegel, F.R., 1992,
Increased concentrations of potassium in heartwood of trees
in response to ground-water contamination: Environmental
Geology and Water Science, v. 19, no. 2, p. 71-74.
Weishaar, L, and Burken, J.G., 2005, Phyto-mapping to delin-
eate a chlorinated VOC plume at Aberdeen Proving Ground,
Maryland: Presented at the 3rd International Phytotechnolo-
gies Conference, April 19-22, 2005, sponsored by The U.S.
Environmental Protection Agency and the Midwest Hazard-
ous Substance Research Center, Atlanta, Georgia.
Wilson, B.H, Smith, G.B, and Rees, J.F., 1986, Biotransfor-
mations of selected alkylbenzenes and halogenated aliphatic
hydrocarbons in methanogenic aquifer material—A micro-
cosm study: Environmental Science and Technology, v. 20,
no. 10, p. 997-1002.
Wise, D.P., 1997, Modeling the uptake and transpiration of
TCE using phrealophy tic trees: Wright-Patterson Air Force
Base, Ohio, Air Force Institute of Technology, M.S. thesis,
31.8 p.
Wullschleger, S., Meinzer, E, and Vertessy, R.A., 1998, A
review of whole-plant water use studies in trees: Tree Physi-
ology, v. 18, p. 499-512.
Yanosky, T.M., Hansen, B.P., and Schening, M.R., 2001, Use
of tree rings to investigate the onset of contamination of a
shallow aquifer by chlorinated hydrocarbons: Journal of
Contaminant Hydrology, v. 50, p. 159-173.
Yanosky, T.M., and Vroblesky, D.A., 1992, Relation of nickel
concentrations in tree rings to ground-water contamination:
Water Resources Research, v. 28, no. 8, p. 2077-2083.
Yanosky, T.M., and Vroblesky, D.A., 1995, Element analy-
sis of tree rings in ground-water contamination studies,
in Lewis, T.E., ed., Tree rings as indicators of ecosystem
health: Boca Raton, Florida^ CRC Press, Inc., p. 177-208.
Zeikus, J.G., and Ward, J.C., 1974, Methane formation
in living trees—A microbial origin: Science, v. 184,
p. 1181-1183.
Zencich, S.J., Froend, R.H., Turner, J.V., and Gaililis, Vit,
2002, Influence of ground-water depth on the seasonal
sources of water accessed by Banksia tree species on a shal-
low, sandy coastal aquifer: Oecologia, v. 131, no. 1, p. 8-10.
-------
Appendixl. Case Studies 29
Appendix 1. Case Studies
This section contains four case studies investigating volatile organic compounds in ground water using tree cores. The case
studies are of varying length and detail because of differences among the copyrights associated with the original publication
sources. Case Study 1 was the first investigation demonstrating that tree-core analysis could be used to delineate shallow
ground-water contamination by chlorinated ethenes. Case Studies 2 and 3 are previously unpublished investigations. Case
Study 2 examines a site where data from tree coring provided a reconnaissance-level understanding of the plume distribution and
allowed optimization of well placement. In Case Study 3, the search for a public-supply-well contaminant source encompassed
much of the city of New Haven, Missouri, but tree coring allowed the investigation to be narrowed to a 1-acre area. Although
much of the work involving tree coring has been directed toward chlorinated solvents, Case Study 4 shows that tree coring also
can be used to detect subsurface petroleum hydrocarbons and methyl tert-butyl ether (MTBE).
Case Study 1: Chlorinated Ethenes from Ground Water in Tree Trunks
Summarized from: Vroblesky, DA,1 Nietch, C.T.,2 and Morris, J.T.,21999, Chlorinated ethenes from ground
water in tree trunks: Environmental Science and Technology, v. 33, no. 3, p. 510-515.
This was the first investigation showing that tree-core
analysis could be used to delineate shallow ground-water
contamination by chlorinated ethenes. Headspace analysis of
cores from 97 trees (6 species, predominantly bald cypress)
growing over ground-water contamination in a forested flood
plain of the Savannah River near the TNX Area, Savannah
River Site, South Carolina (figs. 1.1 and 1.2), showed that
cw-l,2-dichloroethene (cDCE) (fig. 1.2) and trichloroethene
(TCE) (fig. 1.3) concentrations in tree cores reflected the
configuration of the ground-water contamination plume. The
distribution of bald cypress containing TCE was more wide-
spread than the distribution of bald cypress containing cDCE
and was found in trees farther south than the flow path from
the source area at the former seepage basin, indicating the
presence of a second plume of TCE in the aquifer (fig. 1.3).
Concentration variations around the tree trunks and a
TCE concentration decline of 30 to 70 percent with increasing
tree height up to 56 ft were observed. All tested tree species
were capable of taking up TCE. Some tree species, such as
tupelo and bald cypress, appeared to exhibit similar TCE or
cDCE uptake potential. Oaks, however, appeared to contain
less TCE than adjacent bald cypress or loblolly pines. Sweet-
gum also appeared to contain less TCE than loblolly pines.
Reference
Vroblesky, D.A., Nietch, C.T., and Morris, J.T., 1999, Chlo-
rinated ethenes from ground water in tree trunks: Environ-
mental Science and Technology, v. 33, no. 3, p. 510-515.
'U.S. Geological Survey, Columbia, South Carolina.
2University of South Carolina, Columbia, South Carolina.
Figure 1.1. Location of study area
[reprinted with permission from
Vroblesky and others (1999), copyright
(1999) American Chemical Society].
-------
30 User's Guide to the Collection and Analysis of Tree Coresto Assess the Distribution of Subsurface Volatile Organic Compounds
TNX Area
o
" 10 —
TCM3
227
V
134
*
EXPLANATION
BALDCYPRESS TREE SAMPLED FOR THIS INVESTIGATION
LINE OF EQUAL CIS 1,2-DICHLOROETHENE CONCEN-
TRATION IN TREE CORES, IN NANOMOLES OF GAS
PER LITER OF WATER IN CORE-Dashed where inferred.
Countour interval variable as shown.
OBSERVATION WELL AND IDENTIFIER AND CIS
1,2-DICHLOROETHENE CONCENTRATION IN GROUND
WATER, IN NANOMOLES PER LITER.
DITCH-BED PORE-WATER SAMPLING POINT AND CIS
1,2-DICHLOROETHENE PORE-WATER
CONCENTRATION, IN NANOMOLES PER LITER
V
TNX26D
not done
•v
0
0
100
200
300 FEET
SO METERS
Figure 1.2. c/s-1,2-Dichloroethene concentrations in bald cypress trunks in January and February 1998 and in ground water
during August 1997 and ground-water flow, TNX flood plain. Savannah River Site, SC [modified and reprinted with permission
from Vroblesky and others (1999), copyright (1999) American Chemical Society].
-------
Appendixl. Case Studies 31
Former
TNX Area
o
— 10
TNX15D
180
V
822
EXPLANATION
BALDCYPRESS TREE SAMPLED FOR THIS INVESTIGATION
LINE OF EQUALTRICHLOROETHENE CONCENTRATION
IN TREE CORES, IN NANOMOLES OF GAS PER LITER
OF WATER IN CORE-Dashed where inferred. Countour
interval variable as shown.
OBSERVATION WELL AND IDENTIFIER AND
TRICHLOROETHENE CONCENTRATION IN GROUND
WATER, IN NANOMOLES PER LITER.
DITCH-BED PORE-WATER SAMPLING POINT AND
TRICHLOROETHENE PORE-WATER CONCENTRATION,
IN NANOMOLES PER LITER.
TNX26D\
41-84 in 1996
\
\
0
0
100
200 300 FEET
50 METERS
Figure 1.3. Trichloroethene concentrations in bald cypress trunks in January and February 1998 and in ground water during
August 1997 and ground-water flow, TNX flood plain. Savannah River Site, SC [modified and reprinted with permission from
Vroblesky and others (1999), copyright (1999) American Chemical Society].
-------
32 User's Guide to the Collection and Analysis of Tree Coresto Assess the Distribution of Subsurface Volatile Organic Compounds
Case Study 2: Tree Coring as a Guide to Well Placement, Solid Waste Management Unit 17,
Naval Weapons Station Charleston, South Carolina, 2002
By Don A. Vroblesky1 and Clifton C. Casey2
Abstract
Several tree cores were collected from Solid Waste Man-
agement Unit (SWMU) 17, Naval Weapons Station Charles-
ton, South Carolina, as part of an effort to characterize the
site and to direct monitoring-well placement. Analysis of the
tree cores showed the presence of two distinct ground-water
plumes. One of the plumes was composed predominantly of
tetrachloroethene and the other was composed predominantly
of trichloroethene. The data allowed optimization of well
placement, and the subsequent well-sample analysis confirmed
the tree-core data.
Introduction
Solid Waste Management Unit (SWMU) 17 at the
Naval Weapons Station Charleston, South Carolina, is a
flat-lying forested area in which the dominant tree species
is loblolly pine. Well sampling at the site in 2001 showed
61-190 micrograms per liter (\ig/L)
of tetrachloroethene (PCE) and
very low concentrations (less than
9 (ig/L) of trichloroethene (TCE)
in the shallow ground water (Tetra
Tech NUS, Inc., 2004). Sampling
of temporary wells in 2002,
however, showed that other parts of
the site contained 31,000 \ig/L of
TCE (Tetra Tech NUS, Inc., 2004)
(fig. 2.1). The data indicated a need
for additional monitoring wells to
map the ground-water contamina-
tion. Initial investigations by the
contractor, however, indicated that
tidal changes caused substantial
variations in ground-water-flow
direction, complicating the plan-
ning of future monitoring-well
placement (Tetra Tech NUS, Inc.,
2004). Naval Facilities Engineering
Command Southeast requested that
the U.S. Geological Survey (USGS) conduct a tree-core survey
as a reconnaissance tool to direct well placement. As part of
the investigation, the USGS and Naval Facilities Engineering
Command Southeast cored and analyzed 61 tree cores from
the site in September 2002 (fig. 2.2). The cored trees consisted
of 28 loblolly pines, 12 Chinese tallow (Sapium sebiferum L.),
6 sweet gum, 1 oak, and 12 trees of unknown species.
Tree cores were collected by use of an increment borer.
The cores were sealed in crimp-cap 20-milliliter serum vials
immediately upon recovery and analyzed by headspace
analysis gas chromatography the day after sample collection.
Comparison of duplicate cores showed a TCE concentration
difference of less than 5 percent in a tree containing greater
than 8,000 parts per billion by volume (ppbv) of TCE. Most
of the tree cores were collected during a single day (Septem-
ber 11, 2002) and analyzed the following day. The remaining
tree cores were collected 2 days later to expand on results
from the first survey.
'U.S. Geological Survey, Columbia,
South Carolina.
2Naval Facilities Engineering Com-
mand Southeast, North Charleston, South
Carolina.
O 1OO 2OO FEET
i l
O 25 5O METERS
/ "-• ^
/ SWMU17 -.^ WelM7MW03
Trenches ' \ TCE<5 |jg/L
| Well 17MW03S \ PCE<5 |jg/L
i TCE<9 |jg/L /
EXPLANATION
® Permanent well
sampled in 2001
x-x Temporary well
<> sampled in 2002
~ ~ "i Boundary of
i | SWMU17
ug/L is micrograms
per liter. "<" indicates
less than. "J"
indicates estimated
value
PCE=190ug/L /
; ®
| Well 17TW02S /
' TCE<5 ug/L / ®
/ PCE<5 ug/L ' Well 17MW02S
/ TCE=2ug/L(J)
/ Well17TW01S / PCE=61U9/L
' TCE=31, 000 ug/L /
,' PCE<5 ug/L
n ''
\ Basinl I \
1 ^ \ Well 17MW06S
\ \ TCE<5 ug/L
^ > PCE<5ug/L N
"- — 1 vJ uc
^ <8> ^
Figure 2.1. Locations of monitoring wells and concentrations of ground-water trichloroethene
(TCE) and tetrachloroethene (PCE), Solid Waste Management Unit (SWMU) 17, Naval Weapons
Station Charleston, South Carolina.
-------
A. Trichloroethene (TCE)
50 METERS
SWMU17
A
o
A
V
A
ppb/v i
EXPLANATION
Countour showing
ground-water TCE
concentration, in micro-
grams per liter (data from
Tetra Tech NUS, Inc., 2004).
Dashed where inferred.
Interval variable as shown.
Monitoring well
Temporary well, 2002
Temporary well, April 2003
Tree: >500 ppb/v TCE
Tree: 10-100 ppb/v TCE
Tree: TCE not detectable
is parts per billion by volume
Appendixl. Case Studies 33
B. Tetrachloroethene (PCE)
200 FEET
50 METERS
SWMU17
A
EXPLANATION
-20- Countour showing
ground-water PCE
concentration, in micro-
grams per liter (data from
Tetra Tech NUS, Inc., 2004).
Dashed where inferred.
Interval variable as shown.
® Monitoring well
® Temporary well, 2002
o Temporary well, April 2003
A Tree: 10-47 ppb/v PCE
A Tree: PCE not detectable
ppb/v is parts per billion by volume
Figure 2.2. (A) Trichloroethene (TCE) and (B) tetrachloroethene (PCE) concentrations in tree cores in 2002 and ground water
in 2002-2003 at Solid Waste Management Unit (SWMU) 17, Naval Weapons Station Charleston, South Carolina.
Analysis of the tree cores showed the presence of two
distinct areas of ground-water contamination. In the southern
part of SWMU17, trees contained TCE with no detectable
PCE concentrations. The highest TCE concentrations found
in the tree cores (860 to 85,160 ppbv) were from trees near
a shallow drainage basin (fig. 2.2A). In the northern part of
S WMU17, trees contained 10 to 47 ppbv of PCE, but no
detectable TCE (fig. 2.2). Trees between the north and south
sides of SWMU17 contained no detectable TCE or PCE.
Using the tree-coring results as a placement guide, the
consultant installed and sampled 21 temporary wells in April
2003 (fig. 2.2). Analysis of ground water from the temporary
wells, combined with historical data from earlier wells,
confirmed the presence of the two distinct contamination
plumes identified by the tree coring. As indicated by the tree
coring, the southern plume consisted primarily of TCE, with
the highest concentrations near the shallow drainage basin
(9,000-95,000 (ig/L) (Tetra Tech NUS, Inc., 2004). PCE
concentrations were less than 6 \ig/L. In the northern part of
SWMU17 near the sampled trees, PCE concentrations in the
ground water were 29 \ig/L in the 2003 temporary well and 61
to 190 (ig/L in previously tested wells, with TCE concentra-
tions less than 10 |ig/L (Tetra Tech NUS, Inc., 2004).
The distribution of volatile organic compounds (VOCs)
in trees at the site strongly indicated that the shallow basin
in the southern part of SWMU17 (fig. 2.1) was a source area
for TCE ground-water contamination. Subsequent drilling
and sampling of temporary wells confirmed that finding
(fig. 2.2A). The lack of VOC detections in trees in the central
part of SWMU17 strongly implied that the PCE contamination
in the northern part of SWMU17 was unrelated to the TCE
plume near the shallow basin. Again, subsequent drilling
and sampling of temporary wells confirmed that finding and
provided additional evidence indicating that the northern PCE
plume appeared to be coming from the direction of some
trenches across the road northwest of S WMU17 (fig. 2.2B).
Thus, tree coring provided a simple, rapid, inexpensive
reconnaissance tool and guide to optimize monitoring-well
placement.
Reference Cited
Tetra Tech NUS, Inc., 2004, RCRA Facility Investigation
documentation and data summary 2000-2003, for Old
Southside Landfill—SWMU 16 and Old Southside Missile
and Waste Oil Disposal Area—SWMU 17, Naval Weapons
Station Charleston, Charleston, South Carolina: Consul-
tant's report submitted to Southern Division Naval Facilities
Engineering Command, January 2004 [variously paged].
-------
34 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Unit 4,
By John Schumacher1
Abstract
Tree coring for volatile organic compounds was used
at a site in New Haven, Missouri, as a reconnaissance tool
to locate the source area for tetrachloroethene-contaminated
ground water that caused the abandonment of two public-
supply wells. The ability to rapidly and inexpensively collect
tree cores from a broad area throughout the town allowed the
tree coring to eliminate some suspected source areas, such
as transport through sanitary sewer lines, and eventually to
narrow the search down to a 1-acre area. Subsequent drilling
confirmed that the site identified by tree coring was a previ-
ously undetected, shallow source of tetrachloroethene and was
a likely source of the tetrachloroethene-contaminated ground
water.
Introduction
Ground-water contamination by tetrachloroethene (PCE)
detected in two 800-feet (ft)-deep public-supply wells (wells
Wl and W2) in 1986 in New Haven, Missouri, resulted in
closure of those wells. The contaminated area is referred to as
the Riverfront site, and consists of six operable units (OUs).
The tree cores indicated that the probable contaminant source
was OU4. Unlike the other OUs, however, there was no known
PCE use or disposal at OU4, and the area was designated as
an OU primarily because it was upgradient from contaminated
city wells Wl and W2. The investigation was conducted in a
scries of iterations, beginning at the known PCE contamina-
tion in city wells Wl and W2 and moving upgradient to the
south.
I, Tree-Core
Sampling
In 2001, a reconnaissance sampling of water from
streams (grab samples) and cores from 86 trees in OU4 and
the surrounding area identified 2 stream reaches contaminated
with PCE and 9 trees in the central part of OU4 containing
PCE concentrations ranging from 0.58 to 117 micrograms in
headspace per kilogram (jig-h/kg) of wet core (fig. 3.1). The
largest PCE concentrations detected in trees were in trees
JS106 (117 |ig-/h/kg), a 30-inch (in.)-diameler hedge apple
(Madura pomiferd) tree growing along an old fence row, and
JS112 (99.1 iig-h/kg), a 36-in.-diameter cottonwood tree about
HJ.S. Geological Survey, Rolla, Missouri.
80 ft southwest of tree JS106. A large number of trees upslope
from the contaminated stream reach in the east-central part of
OU4 were cored based on a rumor that drums of waste may
have been buried in that area; however, none of the trees cored
along this stream contained detectable concentrations of PCE
and a surface geophysical survey detected no buried metallic
objects.
In 2001, trace concentrations of PCE (0.24 to 1.3 micro-
grams per liter (|ig/L) in sanitary sewer lines mat drained
suspected source areas south of OU4 (U.S. Environmental
Protection Agency, 2003a) raised concerns that OU2 was
the source area and thai the contamination was transmitted
through the sanitary sewer and streams. Tree-core evidence,
however, did not support this hypothesis. Although PCE was
detected at concentrations between 5.0 and 14 iig-h/kg in three
trees (JS100, JS104, and JS114) in proximity to the sanitary-
sewer main crossing OU4, most trees cored along the sewer
main had no detectable PCE concentrations. More importantly,
trees JS106 and JS112, which had the highest PCE concentra-
tions, were several hundred feet from the sanitary sewer main.
The 2001 stream and tree-core reconnaissance sampling had
indicated that the PCE source in OU4 was local and shallow.
By 2003, the source for the PCE plume in the bedrock aquifer
was thought to reside within an 80-acre "suspect area" in the
central pal of OU4 (fig. 3.1) In mid-2003, PCE concentrations
as large as 2,300 \igfL were detected at 138 ft deep in monitor-
ing well cluster BW-10 that was installed downgradient (north)
from this suspect area (fig. 3.1).
2, Tree-Core
To refine the size of the 80-acre suspect area, during
the fall of 2003, an additional 62 trees were cored within
the suspect area, including several trees around the former
corporate guest house (fig. 3.1). PCE was detected above the
0.5 ug-h/kg detection threshold used for this study in only 5
of the 62 trees cored. Although 2 of the 16 trees cored at the
former corporate guest house contained low (0.51 to
3.9 |ig-h/kg) PCE concentrations, the largest PCE concentra-
tions detected (21.2 to 100 |ig/kg) were in 3 trees more than a
block south of the former corporate guest house. Two of these
trees [JS324 (PCE of 100 ug-h/kg) and tree JS340 (PCE of
74.9 (xg-h/kg)] were within 90 ft of two trees that previously
showed PCE contamination (trees JS106 and JS112) (fig. 3.2).
Tree JS324 was a small (1.5-in. diameter) mulberry tree
growing along the same old fence row as tree JS106, and tree
JS340 was a 14-in.-diameter ash tree growing about 4 ft east
of tree JS112. Based on the small size of tree JS324, the high
-------
Appendixl. Case Studies 35
38° 36'30" —
38° 36' —
BW-0
Former
corporate
guest house
AREA1
Inset shown
in figure 3.2
1,000
2,000 FEET
EXPLANATION
STREAM REACH CONTAINING MORE THAN 5.0
MICROGRAMS PER LITER PCE
SANITARY SEWER LINE
PCE CONCENTRATION IN TREE-CORE
SAMPLE - Concentrations in micrograms
in headspace per kilogram of wet core (|ig-h/kg).
Circle indicates 2001 sample,
square indicates 2003 sample
• Less than 0.5
• 0.5 to 14.9
O 15.0 to 49.9
O 50.0 to 99.9
• 100 to 120
MONITORING WELL CLUSTER
AND NUMBER - Color indicates
maximum PCE concentration
detected in micrograms
per liter (|ig/L).
BW-°7A Less than 0.2
A 0.2 to 4.9
A 5.0 to 49
A 50.0 to 999
A 1,000 to 9,200
PUBLIC SUPPLY WELL
Figure 3.1. Location of tree-core samples and monitoring wells andtetrachloroethene (PCE) concentrations in Operable Unit 4,
Riverfront Superfund Site, Franklin County, Missouri, as of 2003 (modified from U.S. Environmental Protection Agency, 2003a).
-------
36 User's Guide to the Collection and Analysis of Tree Coresto Assess the Distribution of Subsurface Volatile Organic Compounds
BW-13about A T
130 feet A'
ESTIMATED EXTENT OF
HIGHLY CONTAMINATED
SOILS AND PERMANGANATE
INJECTION AREA
/JS324
,t
o
D
• D
ML204
GROUND-
WATER FLOW
JS106
BW11A-S A
BW-11 A-D**
BW-11 A
JS112 n
}jS340
BW14 about
400 feet
50
100 FEET
EXPLANATION
MONITORING WELL CLUSTER AND NUMBER -
Color indicates maximum PCE concentration
detected in micrograms per liter (ng/L).
A
A
A
A
A
Less than 0.2
0.2 to 4.9
5.0 to 49
50.0 to 999
1,000 to 9,200
D
D
PCE CONCENTRATION IN TREE-CORE
SAMPLE — Concentrations in micrograms in
headspace per kilogram of wet core (jig-h/kg).
• Less than 0.5
O 0.5 to 14.9
O 15.0 to 49.9
O 50.0 to 99.9
• 100 to 120
MAXIMUM PCE CONCENTRATION IN SOIL BORING
SAMPLE AND BORING NUMBER - Concentrations in
micrograms per kilogram (jig/kg).
• Less than 0.5
0.5 to 240
241 to 483
484 to 4,999
5,000 to 499,999
Greater than 500,000
Figure 3.2. Locations of soil borings and tree-core samples in area 1 and tetrachloroethene
(PCE) concentrations (modified from U.S. Environmental Protection Agency, 2003a).
PCE concentration in this tree was interpreted to indicate that
the tree was growing in PCE-contaminated soil or shallow
ground water. The PCE concentration of 74.9 |ig-h/kg in tree
JS340 was comparable to the concentration previously
detected in the 2001 core sample from adjacent tree JS112 of
99.1 |ig-h/kg, confirming results of the 2001 reconnaissance.
Using data from the 2001 and
2003 tree-core samples that
contained PCE concentrations
higher than 15 |ig-h/kg, a prob-
able PCE source area (referred
to as area 1) of about 1 acre was
delineated (fig. 3.1). The average
PCE concentration detected in
tree-core samples from area 1 was
75 ng-h/kg.
Based on delineation of
area 1 by the tree-core sampling
and the high PCE concentrations
detected in well cluster BW-10,
a nest of three monitoring wells
(BW-11 cluster) was installed
during 2004 adjacent to tree
JS112 (fig. 3.2). Perched water
containing several hundred
micrograms per liter of PCE was
encountered less than 15 ft deep
during drilling at this location,
confirming the presence of shal-
low PCE contamination initially
detected by tree-core sampling.
Data from the completed
BW-11 cluster indicated PCE
concentrations of 210 to 350 (ig/L
in perched water within the
overburden (11.5 to 15.5 ft deep),
PCE concentrations of 190 to
440 (ig/L in the shallow bedrock
(18 to 30 ft deep), and lower PCE
concentrations (33 to 36 (ig/L)
deeper in the bedrock (94 to
130 ft deep). The measured PCE
concentrations of 210 to 240 (ig/L
in perched water in well cluster
BW-11 compared favorably to
concentrations of about 400 (ig/L
predicted using the OU1 tree
core and ground-water relation.
The deeper monitoring interval
at cluster BW-11 is of similar
altitude to the deep interval at
cluster BW-10 that contained much
higher PCE concentrations
(320 to 2,300 (ig/L). A comparison
of water-level measurements in the two clusters indicated that
ground-water flow is northward from BW-11 toward BW-10.
The substantially lower PCE concentrations in the deeper
bedrock at cluster BW-11 as compared to those in cluster
BW-10 and the presence of PCE in perched water within the
overburden indicated that cluster BW-11 was slightly south
and upgradient of a PCE source area.
-------
Appendixl. Case Studies 31
Soil and of Tree-Core
Results
During 2004 and 2005, a total of 41 soil borings were
done within area 1 (20 borings), at the former corporate
guest house (11 borings), and along the sanitary sewer
main (10 borings). These borings were installed to provide
definitive evidence of the extent and magnitude of subsurface
contamination within area 1, to confirm the absence of PCE
contamination at the former corporate guest house, and to
determine if widespread PCE contamination was present in
soils near the sanitary sewer main. A total of 236 soil samples
were collected and analyzed by a portable gas chromatograph
(GC) for volatile organic compounds (VOCs) (234 samples)
or fixed laboratory (23 samples). Continuous soil cores
were obtained at each boring location and were typically
subsampled every 2 ft of depth for portable GC analysis.
None of the soil borings at the former corporate guest
house contained detectable concentrations of PCE or other
target VOCs, confirming the tree-core data, which indicated an
absence of shallow subsurface contamination at this facility.
Four of 10 soil boring locations along the sanitary sewer line
contained low (less than 240 micrograms per kilogram
(Hg/kg) concentrations of PCE. All concentrations detected in
soils were less than one-half the U.S. Environmental Protec-
tion Agency (USEPA) Region 9 residential soil preliminary
remediation goal (PRO) of 484 jig/kg. PCE detections in
boreholes along the sewer line generally were found at depths
greater than 12 ft.
Substantial PCE concentrations were detected in area 1
soil borings. PCE was detected in 18 of the 20 borings with
a maximum concentration of 1,200,000 (ig/kg in a laboratory
soil sample collected from 13.5 ft deep in boring ML204 near
the center of area 1 (fig. 3.2). Several thin (0.5-in.-thick) bands
of black oily substance suspected to be PCE-rich DNAPL
(dense non-aqueous phase liquid) were present at depths
between 10 and 12 ft in this boring. On the basis of the soil
boring data, the footprint of the PCE-contaminated soils inside
area 1 was estimated to be less than about 5,000 square feet
(ft2) (Rob Blake, Black and Veatch Special Projects Corpora-
tion, oral commun., 2006). Generally, PCE concentrations
in area 1 soil borings increased with increasing depth, with
the largest extent of contamination in the 12- to 16-ft-deep
interval. Contamination extended through the soil into the top
of the weathered bedrock estimated at 11 to 18 ft below the
surface. Using the soil boring data, the USEPA estimated the
total volume of contaminated soil/residuum in area 1 is about
2,500 cubic yards (yd3) containing an estimated 760 kilograms
(kg) of PCE or about 125 gallons of pure PCE product.
To provide additional evidence that area 1 was the likely
source of the bedrock PCE plume in the northern part of the
city, in 2005, the USEPA installed two additional shallow (less
than 145 ft deep) monitoring well clusters near area 1. One
well cluster was installed upgradient (BW-14) and a second
well cluster (BW-13) was installed about 600 ft downgradient
from area 1 and about one-half the distance between area 1
and existing well cluster BW-10 (fig. 3.1). PCE concentrations
in upgradient well cluster BW-14 were less than 2 |,ig/L,
whereas PCE concentrations in the BW-13 cluster were
9,000 iig/L. Currently (2007), the USEPA is completing a
removal action to address the contaminated soils in area 1
using in situ chemical oxidation (permanganate oxidation) and
continuing with completion of the OU4 Remedial Investiga-
tion/Feasibility Study.
lines. J.I-.., andEmmett, L.E., 1994, Geohydrology of the
Ozark Plateaus aquifer system it) parts of Missouri, Arkan-
sas, Oklahoma, and Kansas: U.S. Geological Survey Profes-
sional Paper 1414-D, 127 p.
Schumacher, J.G., Struckhoff, G.C., and Burken, J.G., 2004,
Assessment of subsurface chlorinated solvent contamina-
tion using ttee cores at the Front Street site and a former
diy cleaning facility at the Riverfront Superfund site, New
Haven, Missouri, 1999-2003: U.S. Geological Survey Sci-
entific Investigations Report 2004-5049, 35 p.
U.S. Department of Commerce, 2002, Climatological Data,
accessed March 2002 at http://lwf.ncdc.noaa.gov/oa/ncdc.
html.
U.S. Environmental Protection Agency, 2001, Expanded
site investigation/remedial investigation results for the
Riverfront Superfund site, New Haven, Missouri: U.S.
Environmental Protection Agency Region 7, Contract
DW1495212801-2, 56 p.
U.S. Environmental Protection Agency, 2003a, Focused
remedial investigation of operable units OU1 and OU3,
Riverfront Superfund site, Franklin County, Missouri:
U.S. Environmental Protection Agency Region 7, Contract
DW1495217301-2, 128 p. plus appendixes.
U.S. Environmental Protection Agency, 2003b, Record of
decision, Operable Unit 1, Front Street site, Franklin
County, Missouri: U.S. Environmental Protection Agency
Region 7, MOD981720246, 107 p. including appendixes.
U.S. Environmental Protection Agency, 2003c, Record of
decision, Operable Unit 3, Old city dump site, Franklin
County, Missouri: U.S. Environmental Protection Agency
Region 7, MOD981720246, 53 p. including appendixes.
U.S. Environmental Protection Agency, 2006, Record of deci-
sion, Operable Unit 5, Old hat factory, Franklin County,
Missouri: U.S. Environmental Protection Agency Region 7,
MOD981720246, 53 p. including appendixes.
-------
38 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
4: and BIEX in
By James E. Landmeyer,1 Don A. Vroblesky,1 and Paul M. Bradley1
Reprinted with permission from Battelle Press (Landmeyer, I.E., Vroblesky, D.A., and Bradley, P.M., 2000, MTBE in trees
transpiring gasoline-contaminated ground water, Second International Conference on Remediation of Chlorinated and Recalci-
trant Compounds, May 22-25, 2000, Monterey, California: Columbus, Ohio, Battelle Press).
Abstract
The fuel oxygenate compound methyl fcrf-butyl ether
(MTBE) and the conventional gasoline compounds benzene.
toluene, elhylbenzene, and the isomers of xylene and trimeth-
ylbcnzcne were detected and identified using purge-and-trap
gas chromatography/mass spectrometry methods in core
material of mature live oak trees (Quercus virginiana) located
above a gasoline-contaminated shallow aquifer. Conversely,
these gasoline compounds were not detected in core material
of oaks located outside of the gasoline plume. This detection
of gasoline compounds in trees at a contaminated field
site is important, particularly for the more soluble and less
biodegradable compounds MTBE and benzene, because it-
provides unequivocal field evidence that trees can act as sinks
to remove contaminants from ground-water systems.
Introduction
Results of laboratory-scale studies have suggested that
herbaceous and woody plants have the potential to take up
a variety of dissolved petroleum-derived compounds during
transpiration. For example, it has been recognized for some
time that pesticide uptake can occur in a wide variety of
non-woody plants, including bailey (Schone and Wood, 1972;
Donaldson et al, 1973; Briggs et al, 1982), bean (Lichtner,
1983), corn (Darmstadt et al., 1983; Leroux and Gredt, 1977;
Upadhyaya and Nooden, 1980), peanuts (Hawxby et al.,
1972), and soybeans (Moody et al., 1970; McEarlane et al.,
1987; McCrady et al., 1987). For woody plants, Burken and
Schnoor (1997) demonstrated the uptake and metabolism of
the widely used herbicide atrazine by poplar trees (Popultts
deltoides). Additionally, a preliminary report (Newman et
al., 1999) indicated that poplar (Populus spp.) and eucalyptus
(Eucalyptus spp.) could take up the fuel oxygenate compound
methyl tert-butyl ether (MTBE) under laboratory conditions.
More recently, Burken and Schnoor (1998) reported the
uptake, translocation, and volatilization of the common
ground-water contaminants benzene, toluene, ethylbenzene,
and xylene (BTEX) by poplar cuttings in short-term hydro-
ponic experiments in the lab. Their results confirm that the
'U.S. Geological Survey, Columbia, South Carolina.
relative ease of compound uptake is related to the logarithm
of the oclanol-water partition coefficient (log KaJ, as slated
initially by Briggs et al. (1982). Essentially, compounds
having a log Kow between 0.5 and 3.0 are preferentially taken
up by roots. Because the log Kow of the ground-water con-
taminants MTBE, benzene, toluene, elhylbenzene, o-xylene,
m-xylene, andp-xylene arc within this range (1.20, 2.13, 2.65,
3.13, 2.95, 3.20, and 3.18, respectively), their uptake during
laboratory transpiration studies is not surprising.
However, the uptake of these gasoline compounds by
mature trees has not been documented under field conditions.
For example, in the study cited above (Burken and Schnoor,
1998) that indicated uptake of MTBE by poplar (Populus
spp.) and eucalyptus (Eucalyptus spp.) cuttings under
laboratory conditions, no MTBE uptake was measured in
mature trees at an MTBE-conlaminated site. This current
study was undertaken, therefore, to determine if the soluble
fuel compounds MTBE, benzene, toluene, elhylbenzene. and
o-, m-, andp-xylcnes shown to be taken up under laboratory
conditions are present in mature live oaks growing above
gasoline-contaminated ground water.
Study Site. The study site is a gasoline station (fig. 4.1)
near Beaufort, South Carolina (SC). Fuel-oxygenated gasoline
from a leaking underground storage tank was detected in the
shallow, water-table aquifer in late 1991 (Landmeyer et al.,
1996). The water-table aquifer is comprised of well-soiled
sand. The water-table aquifer is underlain by a regional clay-
rich confining unit at around 45 feet (ft) (13.7 m). There is less
than 0.01 % natural sedimentary organic matter in the sandy
aquifer. The depth to water is about 13 ft (3.9 m) near the
release area and from 9 to 2 ft (2.7 to 0.6 m) near a drainage
ditch approximately 700 ft (215 m) downgradient (fig. 4.1)
of the release area. Recharge to the water-table aquifer is by
rainwater infiltration, with precipitation approaching 60 inches
per year (in/yr) (132 cm/yr).
The study site is characterized by a dense stand of mature
(>40 years old) live oak trees (Quercus virginiana) (fig. 4.1).
Live oaks derive their common name from their ability to
maintain leaves throughout winter, even though they arc
deciduous. As a result, live oaks transpire water continually
throughout the year and, therefore, are an excellent genus
to study transpiration-related processes. The trees at the site
have well-developed and extensive networks of horizontal and
vertical roots, as evidenced by conspicuous root material at
-------
Appendixl. Case Studies 39
LJ
C
10,110(1 1.0110 2(1
50 100 150 200 FEET
Tree 7
EXPLANATION
EQUAL MTBE CONCENTRATION (ng/L)
EQUAL BENZENE CONCENTRATION (ng/L)
MONITORING WELL
MULTILEVEL SAMPLER
TREE LOCATION AND NUMBER
Figure 4.1. Study site near Beaufort, South Carolina, indicating location and
reference number of tree samples, monitoring wells mentioned in text, and
isoconcentration contours of methyl fert-butyl ether (MTBE) and benzene in ground
water (collected January 1998).
land surface some distance from tree trunks and the presence
of observable root material at the water table in boreholes
completed near trees.
Methods
Ground-Water Geochemistry. The distribution of
gasoline compounds as well as geochemical parameters that
indicate the redox zonations at the site have been documented
over seven sampling events between 1993 and 1998 (Land-
meyer et al., 1996; Landmeyer et al., 1998). However, only
the gasoline compound distribution will be discussed here.
Conventional polyvinyl chloride (PVC)
monitoring wells (2-inch [4.4 cm] diameter,
screened across or below the water table
with 12.5 ft [3.8 m] screens) and multi-level
sampling wells (1-inch [2.2 cm] diameter,
with variably spaced screened intervals)
were analyzed for MTBE and BTEX at
each sampling event. Before sampling, each
well was purged until stable measurements
of water temperature (in degrees Celsius)
and pH (in standard units) were obtained.
MTBE and BTEX samples were collected in
40-mL glass vials using a peristaltic pump
at a low flow rate, preserved with 3 drops of
concentrated hydrochloric acid, and capped
using Teflon-lined septa. BTEX compounds
were quantified using purge-and-trap gas
chromatography with flame-ionization
detection. MTBE was quantified using
direct-aqueous injection gas chromatography
with mass spectrometry (GC/MS) detection
by the Oregon Graduate Institute (Church et
al., 1997).
Tree-Core Sample Collection and
Analysis. Cores of tree tissue were obtained
from trees located in uncontaminated areas
upgradient of the ground-water source
area and plume, and from trees growing
in the area delineated by dissolved-phase
ground-water contamination (fig. 4.1) using
an increment borer in mid-June 1999. Tree
coring methods have been used previously
to determine the presence of chlorinated
solvents (Vroblesky et al., 1999) and metals
(Forget and Zayed, 1995) in tree rings.
Cores were collected at a height of 1 ft
(0.3 m) above ground on the northeast side
of each tree. Replicate cores about 2 inches
apart were taken at each tree sampled. The
average core collected was about 2.0 inches
by 1/4 inch (volume of 0.09 in3) (4 cm by
0.5 cm; volume of 0.72 cm3), and consisted
of the most recent growth rings, which
contain the water-conducting xylem in ring-
porous trees such as oaks. Each core was
immediately placed into a 40-mL glass vial and capped with
a Teflon stopper. At the time of sampling, the air temperature
was about 85 degrees Fahrenheit (°F), skies were sunny, winds
were from the west at 5 miles per hour (mph) and low relative
humidity (<60%). Because the site is an active gas station, air
samples for gasoline compound detection were also collected
in 40-mL glass vials, after waving an open vial for a few
seconds near the contaminated area downgradient of the fuel
release.
In the laboratory, the volatile organic compounds in the
tree core were separated and identified using a purge-and-trap
-------
40 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
GC/MS method similar to U.S. EPA method 8260. Prior to
purging of each sample, 5 mL of pesticide-grade methanol
was added to each 40-mL vial containing core material,
and brought to a final volume of 25 mL using organic-free
reagent water. Each vial was then purged with helium, the
volatile compounds trapped in a tube containing sorbent
material, and manually injected onto a 30 in, 0.25 mm inside
diameter capillary column coated with Rtx 502.2 (RESTEK)
at a 1.4 pn film thickness. Identification of target gasoline
compounds was confirmed by comparing sample mass spectra
to the mass spectra of reference material from the National
Institute of Standards and Technology under identical run
conditions. Three internal standards (fluorobenzene, 2-bromo-
1-chloropropane, and 1,4-dichlorobutane) and three surrogate
standards (1,4-difluorobenzene, d8-toluene, 4-bromofluo-
robenzene) were used. Surrogate recoveries ranged between
93 and 100%. Target compound concentrations are reported
as concentrations in micrograms per liter in the headspace of
vials containing core material.
Results and Discussion
MTBE and BTEX Detection in Tree Cores. MTBE,
benzene, toluene, ethylbenzene, and the xylene isomers
were not detected in the headspace samples of core material
collected from oaks growing hydrologically upgradient of the
release area (table 4.1, Trees 1 and 2; fig. 4.1). Trees 1 and
2 are located about 146 ft (46 m) and 136 ft (45 in) north of
well 5, respectively (fig. 4.1). Well 5 is located about 75 ft
(35 m) upgradient of the release area, screened across the
water table, and MTBE and BTEX concentrations there have
remained below detection limits since monitoring activities
began at the site in 1993 (Landmeyer et al, 1998).
Table 4.1. Concentrations (in micrograms per liter) of the gasoline compounds MTBE,
benzene, toluene, ethylbenzene, and the isomers of xylene and trimethylbenzene (TMB) in
the headspace of vials containing tree cores collected at a field site near Beaufort, South
Carolina, June 1999,
[Non deteclion is represented by nd. nol analyzed by naj
Compound
MTBE
Benzene
Toluene
Ethylbenzene
m,p -Xylene
o-Xylene
1.3,5-TMB
1,2,4-TMB
Uppa client of
Former Source
Area
Tree 1
nd
nd
nd
nd
nd
nd
nd
nd
Tree 2
nd
nd
nd
nd
nd
nd
nd
nd
Former Source
Area
TreeS
nd
nd
5.4
nd
nd
nd
nd
6
Tree 4
nd
nd
nd
nd
5
6.3
nd
19.6
Dissolwed-Phase
Plume
Tree 5
9.4
7.2
26.2
nd
10.1
5.6
7.8
5.3
Tree 6
54
4.8
10
8.5
10.8
7.4
6.1
5.4
Vertical Flow
Area
Well?
5,800
508
674
149
580
na
na
Tree?
nd
nd
nd
nd
nd
nd
nd
nd
However, MTBE, benzene, toluene, ethylbenzene, and
the xylene isomers were detected in the headspace of core
samples taken from trees growing above the former source
area (table 4.1, Trees 3 and 4; fig. 4.1) and the delineated
plume of ground-water contamination (table 4.1, Trees 5
and 6; fig. 4.1). Headspace samples of core material from
Tree 3 had detections for toluene at 5.4 (ig/L, and Tree 4
had no toluene but m-, p-xylene (5 |,ig/L total), and oxylene
(6.3 (ig/L) were detected. These detections in Trees 3 and 4 are
related to the residual contamination in the former source area
due to incomplete removal of contaminated sediments in 1993
(Landmeyer et al., 1998). This incomplete removal of source-
area material has also caused a "wake" of dissolved-phase
contamination to continue to be observed between the source
area and downgradient wells in the direction of ground-water
flow, even 6 years after source removal activities (fig. 4.1).
Headspace samples of core material from live oaks
sampled in the area delineated by gasoline compounds down-
gradient of the former source area contained chromatographic
peaks confirmed by MS to be MTBE, benzene, toluene,
ethylbenzene, and the xylene and trimethylbenzene (TMB)
isomers (table 4.1, Trees 5 and 6; fig. 4.1). For example,
headspace samples of core material from Tree 6, located about
11 ft (4 m) east of well 8 (fig. 4.1), had 54.0 [ig/L MTBE,
4.8 |ig/L benzene, 10.1 |ig/L toluene, 8.5 [ig/L ethylbenzene,
10.8 |ig/L m- and/7-xylene, 7.4 |ig/L o-xylene, 6.1 (ig/L
1,3,5-TMB, and 5.4 (.ig/L 1,2,4-TMB. The concentration of
MTBE in Tree 6 was the highest detected in all trees cored.
Tree 5 adjacent to Tree 6 had the highest detection of toluene
(26.2 (ig/L). In August 1998, samples of ground water from
well 8, which is screened across the water table in the area
where root penetration has been observed, had 5,800 [ig/L
MTBE, 508 (ig/L benzene, 674 fig/L toluene, 149 (ig/L
ethylbenzene, and 580 [ig/L total xylenes. This detection of
MTBE and benzene in transpiration-
stream water of a mature tree at a
contaminated field site is the first
known field-scale confirmation of
laboratory-scale experimental data.
Headspace samples of air collected
from this area did not contain peak
responses representative of MTBE,
benzene, toluene, ethylbenzene, or
the isomers of xylene or TMB (data
not shown).
No compound detections for
MTBE and BTEX were seen in
headspace samples of core material
from Tree 7 (table 4.1), even though
this tree is located downgradient
of the release area. This lack of
compound detection can be explained
by the location of Tree 7 being (1)
at the edge of the delineated plume
boundary (fig. 4.1), which probably
results in the majority of transpiration
-------
Appendixl. Case Studies 41
water being derived from uncontaminated ground water, and
(2) in an area where dissolved-phase contamination originally
near the water-table surface is pushed deeper into the aquifer
by vertical recharge of percolating rainwater (Landmeyer et
al, 1998). This vertical displacement of the dissolved-phase
plume deeper into the aquifer away from root interaction is
why no trees were cored downgradient of Tree 7.
As stated above, the trimethylbenzene isomers
1,3,5-TMB and 1,2,4-TMB were also identified in the cored
material in Trees 3, 4, 5, and 6 located above the original
source area and delineated dissolved-phase plume (table 4.1).
The TMB isomers are common components of gasoline, and
because their solubility and sorption characteristics are similar
to benzene and toluene, these relatively nonbiodegradable
isomers are routinely used as conservative tracers to estimate
biodegradation rates of aromatic hydrocarbons from field data
(Weidemeier et al., 1997). The detection of the TMB isomers
in transpiration stream water follows from a log Kow of 3.78 for
1,2,4-TMB. The fact that trees can remove TMB isomers from
contaminated ground water needs to be considered if TMB
isomers are to be used as conservative tracers in ground-water
studies of contaminant transport.
The chlorinated compounds chloroform and methyl
chloride were detected in tree cores collected in uncontami-
nated and contaminated areas. Chloroform concentrations in
the headspace of vials containing tree cores ranged from 18.7
to 89.1 (ig/L, and methyl chloride concentrations ranged from
20.1 to 63.3 [ig/L (data not shown). Chloroform and methyl
chloride have log Kow's that would suggest uptake by trees
(1.90 and 0.90, respectively). Their detection in tree cores
suggests that the most likely source is chlorinated irrigation
water. A nationwide survey of 1,501 shallow ground-water
samples conducted by the U.S. Geological Survey indicated
that chloroform was the most commonly detected volatile
organic compound in shallow wells (Squillace et al., 1996).
The detection of the common ground-water contaminants
MTBE, BTEX, and the TMB isomers in mature trees that
grow above a shallow aquifer characterized by a fuel spill is
important because it extends laboratory-scale observations to
real field sites. These results suggest the possible use of trees
to remove soluble gasoline-related compounds such as MTBE
and benzene from contaminated ground-water systems. The
transpiration process of trees requires large volumes of water
(up to 53 gal/day for 5-year old trees [Newman et al., 1997J)
to balance transpiration losses. Although trees most commonly
use recent rainfall to meet short-term water demands, ground
water can provide water during times of low precipitation
to meet longer-term needs. Because tree-root systems often
contact the water-table surface, the potential exists for sources
of contaminants containing non-aqueous phase liquids, such as
petroleum hydrocarbon compounds and chlorinated solvents
dissolved in ground water to come into contact with tree roots,
particularly in discharge zones where ground-water flowlines
converge to bring even the denser chlorinated compounds to
the surface. Results from our study suggest that trees exhibit
the potential to uptake synthetic organic compounds dissolved
in ground water, particularly those gasoline-related compounds
that are accidentally released into the environment. It is not yet
clear whether uptake of soluble ground-water contaminants
by trees may serve to remove substantial amounts of hydro-
carbons from contaminated ground-water systems. However,
these results show that contaminant uptake occurs in measur-
able quantities, and suggest that mis phenomenon may have
important environmental applications.
References
Briggs, G.G., R.H. Bromilow, and A.A. Evans. 1982. Pesticide
Science. 13, 495-504.
Burken, J.G., and J.L. Schnoor. 1997. Environmental Science
& Technology. 31,1399-1406.
Burken, J.G., and J.L. Schnoor. 1998. "Predictive relationships
for uptake of organic contaminants by hybrid poplar ttees."
Environmental Science & Technology. 32, 3379-3385.
Church, C.D., L.M. Isabelle, J.F. Pankow, D.L. Rose, and P.O.
Tratnyek. 1997. "Method for determination of methyl tert-
butyl ether and its degradation products in water." Environ-
mental Science & Technology. 31, 3723-3726.
Darmstadt, G.L., N.E. Balke, and L.E. Schrader. 1983. Pesti-
cide Biochem. Physiology. 19, 172-183.
Donaldson, T.W., D.E. Bayer, and O.A. Leonard. 1973. Plant
Physiology. 52, 638-645.
Forget, E., and J. Zayed. 1995. "Tree-ring analysis for moni-
toring pollution by metals," in Lewis, T.E., eds., Tree, rings
as indicators of ecosystem health: CRC Press, 157-176.
Hawxby, K., E. Easier, and P.W. Santelmann. 1972. Weed Sci-
ence. 20, 285-289.
Landmeyer, .I.E., F.H. Chapelle, and P.M. Bradley. 1996.
"Assessment of intrinsic bioremediation of gasoline con-
tamination in the shallow aquifer, Laurel Bay Exchange,
Marine Corps Air Station, Beaufort, South Carolina." U.S.
Geological Survey Water-Resources Investigations Report
96-4026, 50 p.
Landmeyer, I.E., F.H. Chapelle, P.M. Bradley, J.F. Pankow,
C.D. Church, and P.O. Tratnyek. 1998. "Fate of MTBE
relative to benzene in a gasoline-contaminated aquifer
(1993-1998)" Ground Water Mon. & Kerned, 18, 93-102.
Landmeyer, J.E., D.A. Vroblesky, and P.M. Bradley. 2000.
MTBE and BTEX in trees above gasoline-contaminated
ground water, in Wickramanayake, G.B., and others, eds.,
Case studies in the remediation of chlorinated and recal-
citrant compounds, Proceedings of the 2nd International
Conference on Remediation of Clorinated and Recalcitrant
Compounds, Monterey, California, May 22-25, 2000,
v. C2-7, p. 17-24.
-------
42 User's Guide to the Collection and Analysis of Tree Coresto the Distribution of Subsurface Volatile Organic Compounds
Leroux, P., and M. Gredt. 1977. Neth. Journal Plant Pathol.
83, 51-61.
Lid-liner, F.T. 1983. Plant, Physiology, 71, 307-312.
McCrady, J.K., C. McFarlane, and F.T. Lindstrom. 1987. J.
Experimental Botany. 38, 1875-1890.
McFarlane, J.C., T. Pfleeger, and J. Fletcher. 1987. J. Environ.
Quality. 16, 372-376.
Moody, K., C.A. Kust, andD.P. Buchholtz. 1970. Weed Sci-
ence. 18, 642-647.
Newman, L., S. Strand, J. Duffy, N. Cnoe, G. Ekuan, M.
Ruszaj, B. Siiurtleff, J. Wilmoth, P. Heilman, and M.
Gordon. 1997. Environmental Science & Technology. 31,
1062-1067.
Newman, L.A., M.P. Gordon, P. Heilman, D.L. Cannon, E.
Lory, K. Miller, J. Osgood, and S.E. Strand. 1999. "Phy-
toremediation of MTBE at a California naval site." Soil &
Groundwater Cleanup. 42-45.
Scfaone, M.G.T., and A.V. Wood. 1972. Weed Research. 12,
337-347.
Squillace, P.J., J.S. Zogorski, W.G. Wilber, and C.V. Price.
1996. Environ. Sci. "& Tech. 30, 1721-1730.
Upadhyaya, M.K., and L.D. Nooden. 1980. Plant Physiology.
66, 1048-1052.
Vroblesky, D.A., C.T. Nietch, and J.T. Morris. 1999. "Chlo-
rinated ethenes from groundwater in tree trunks." Environ.
Science & Technol. 33, 510-515.
Wcidcmcicr, T.H., M.A. Swanson, J.T. Wilson, D.H. Kamp-
bell, R.N. Miller, and I.E. Ilansen. 1997. Intrinsic Bioreme-
diation: Battelle Press, 3(1), 31-51.
-------
Appendix 2
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 1 of 17
AIR SAMPLE ANALYSIS
FOR
VOLATILE ORGANIC COMPOUNDS
By Scott Clifford, U.S. Environmental Protection Agency
The Office of Environmental Measurement and Evaluation
EPA Region New England
11 Technology Dr.
North Chelmsford, MA 01863
This reprint contains minor formatting modifications by the U.S. Environmental Protection
Agency from document EIA-FLDGRAB4.WPD
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 2 of 17
Table of Contents
Section
Subject
Page
1. Scope and Application 3
2. Summary of Method 4
3. Definitions 4
4. Health and Safety Warnings 5
5. Cautions 6
6. Interference 6
7. Personnel Qualifications 6
8. Equipment and Supplies 7
9. Instrument Preparation 8
10. Sample Analysis 10
11. Identification and Quantitation 12
12. Data and Records Management 12
13. Quality Control 13
14. References 14
Tables:
1. Quality Control Table 15
Figures:
1. Chromatogram - PID 16
2. Chromatogram - BCD 17
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 3 of 17
1.0 Scope and Application:
1.1 The procedure contained herein is applicable to all EPA Region I chemists performing
screening for volatile organic compounds for air grab samples.
1.2 Reporting Levels:
Reporting levels can vary depending upon instrument performance and settings, as well as
data quality objectives. Typical achievable reporting levels using a photoionization detector
(PID) and an electron capture detector (BCD) are given below.
Reporting limit in
Analyte parts per billion by
volume (ppb/v)
1,1-Dichloroethene: 10
trans-1,2- Dichloroethene: 10
c/5-l,2-Dichloroethene: 15
Benzene: 10
Trichloroethene: 10
Toluene: 40
Tetrachloroethene: 2
Ethylbenzene: 50
Chlorobenzene: 50
w/p-xylenes: 50
o-xylene: 80
1,1,1- Trichloroethane: 6
1.3 This method may be used when the quality assurance objectives are either QA1 or QA2
as defined in Interim Final Guidance for the Quality Assurance/Quality Control Guidance
for Removal Activities, April 1990. Briefly, QA1 is a screening objective to afford a
quick preliminary assessment of site contamination. QA2 is a verification objective used
to verify analytical (field or lab) results. A minimum of 10% of samples screened must
be analyzed by a full protocol method for qualitative and quantitative confirmation.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 4 of 17
2.0 Summary of Method:
2.1 Field screening using the portable gas chromatograph is used for tentative identification
and quantitation of volatile organic compounds in air samples. This screening technique
can provide quick and reliable results to assist in important on-site decision making.
2.2 An aliquot of the air sample is injected into a calibrated gas chromatography (GC)
equipped with a photoionization detector (PID) and electron capture detector (BCD).
The compounds are separated on a megabore capillary or packed column. Retention
times are used for compound identification and peak heights are used for quantitation of
the identified compounds.
2.3 This method can be used to provide analytical data in a timely manner for guidance of
ongoing work in the field.
2.4 Based on the project=s data quality objectives (DQOs), the operator can modify some
conditions. For example, the injection volumes can be changed depending on the levels
found at the site.
3.0 Definitions:
3.1 FIELD DUPLICATES (FD1 and FD2): Two separate samples collected at the same time
and place under identical circumstances and treated exactly the same throughout field and
laboratory procedures. Analyses of FD1 and FD2 give a measure of the precision
associated with sample collection, preservation, and storage, as well as with laboratory
procedures.
3.2 Headspace: Air above water standard in sample vial.
3.3 Laboratory Duplicate (LD1 and LD2): Two injections from the same sample. The
analyses of LD1 and LD2 give a measure of the precision associated with the laboratory
procedure.
3.4 LABORATORY REAGENT BLANK (LRB) - An aliquot of reagent water or other
blank matrix that is treated exactly as a sample including exposure to all glassware,
equipment, solvents, reagents, internal standards, and surrogates that are used with other
samples. The LRB is used to determine if method analytes or other interferences are
present in the laboratory environment, the reagents, or the apparatus.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 5 of 17
3.5 STOCK STANDARD SOLUTION - A concentrated solution containing one or more
method analytes prepared in the laboratory using assayed reference materials or
purchased from a reputable commercial source.
3.6 WORKING STANDARD SOLUTION - A solution of several analytes prepared in the
laboratory from stock standard solutions and diluted as needed to prepare calibration
solutions and other needed analyte solutions.
3.7 SECONDARY STANDARD - A standard from another vender or a different lot number
that is used to check the primary standard used for quantitation.
4.0 Health and Safety Warnings:
4.1 The toxicity or carcinogenicity of each reagent used in this method has not been precisely
determined; however, each chemical should be treated as a potential health hazard.
Exposure to these reagents should be reduced to the lowest possible level. The
laboratory is responsible for maintaining a current awareness file of OSHA regulations
regarding the safe handling of the chemicals specified in this method. A reference file of
data handling sheets should be made available to all personnel involved in these analyses.
Use these reagents in a fume hood whenever possible and if eye or skin contact occurs
flush with large volumes of water.
4.2 Always wear safety glasses or a shield for eye protection, protective clothing, and
observe proper mixing when working with these reagents.
4.3 Some method analytes have been tentatively classified as known or suspected human or
mammalian carcinogens. Pure standard materials and stock standard solutions of these
compounds should be handled with suitable protection to skin, eyes, etc.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 6 of 17
5.0 Cautions:
5.1 The stock standard and secondary stock standard are replaced every three months.
5.2 The working and secondary standards are good for 7 days provided these standards are
stored on ice with no headspace.
6.0 Interferences:
6.1 Method interferences may be caused by contaminants in solvents, reagents, glassware
and other sample processing hardware that lead to discrete artifacts and/or elevated
baselines in the chromatograms. All of these materials must routinely be demonstrated to
be free from interferences under the conditions of the analysis by running laboratory
method blanks.
6.2 Matrix interferences may be caused by contaminants that coelute with the target
compounds. The extent of matrix interferences will vary considerably from source to
source. A different column or detector may eliminate this interference.
6.3 Contamination by carry-over can occur whenever high level and low level samples are
sequentially analyzed. To reduce carry-over, a VOC free water blank should be analyzed
following an unusually concentrated sample to assure that the syringe is clean.
7.0 Personnel Qualifications:
7.1 The analyst should have at least a four year degree in a physical science.
7.2 The analyst should be trained at least one week and have a working knowledge of this
method and quality control before initiating the procedure.
7.3 All personnel shall be responsible for complying with all quality assurance/quality
control requirements that pertain to their organizational/technical function.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 7 of 17
80 Equipment and Supplies:
8.1 Photovac 10A10 portable gas chromatography equipped with a PID and a 4 ft, 1/8 in, SE-
30 packed column.
8.2 Shimadzu 14A portable gas chromatography equipped with a PID, BCD, and a 30 m,
0.53 mm megabore DBFS 624 capillary column, or equivalent.
8.3 Syringes: Hamilton, steel barrel, 250 uL to 500 uL.
8.4 Vial: 40 mL VOA vials with Teflon lined septum caps.
8.5 Air Standard:
8.5.1 Standard Preparation and Use: Standard should be prepared in water at a 10 ug/L
concentration, and labeled. Standards should be made up fresh weekly from a
methanol stock solution (Supelco or equivalent vender), and stored with no head
space on ice until ready for use. Standard preparation should be recorded in the
Field Standard Log notebook. After preparation, the standard is placed into a 40
mL VOA vial, filling the vial to the top leaving no head space. The standard is
then put into a cooler on an ice bath for storage until it is ready to use. When the
standard is ready to use in connection with air sampling and analysis, 10 mL of
liquid from the 10 ug/L standard VOA vial are withdrawn to give a head space
above the liquid standard. The standard is then placed into an ice bath. It is
important to realize that the concentration of the volatile organic compounds in
the head space was calibrated at approximately 0 - 1°C. Therefore, it is
mandatory that the working standard be stored in a cooler in an ice bath, septa
side down.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 8 of 17
.5.2 The head space above a 10 ug/L aqueous standard at approximately 0 - 1°C (Standard
must be in an ice bath) is used for an air standard. Through in-house
experimentation, we have determined the vapor concentration* of various volatile
organic compounds in the head space of a 10 ug/L aqueous standard at
approximately 0 - 1°C to be as follows:
1,1 - Di chl oroethene: 5 5 4 ppb/v
trans 1,2-Dichloroethene: 202 ppb/v
cis 1,2- Dichloroethene: 90 ppb/v
Benzene: 151 ppb/v
Trichloroethene: 142 ppb/v
Toluene: 159 ppb/v
Tetrachl oroethene: 201 ppb/v
Ethylbenzene: 145 ppb/v
Chlorobenzene: 70 ppb/v
m/p-xylenes: 136 ppb/v
o-xylene: 112 ppb/v
1,1,1 - Tri chl oroethane: 3 3 0 ppb/v
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 9 of 17
9.0 Instrument Preparation:
The Photovac 10A10 GC and the Shimadzu GC 14A should always have carrier gas
flowing through their columns. The Photovac uses zero air and the Shimadzu uses zero
nitrogen as carrier gas.
9.1 The following steps are taken before analysis of samples on the Photovac:
o Check detector. Insure that the detector source is on by observing the "source off"
lamp (red) on the face of the instrument. When the source is on, the "source off
lamp should not be illuminated. Another method of checking the detector is to
remove the detector housing with an alien wrench. With the detector on, you will
observe a purple glow inside the Teflon detector chamber.
o Check carrier gas flow. The gas flow is checked using a flow meter hooked up to the
detector out vent port. Flow can be adjusted to the desired rate by using the vernier
knobs on the left side of the instrument face or by adjusting the delivery pressure on
the carrier gas cylinder regulator. A desirable flow is from 200 - 600 cc/min,
depending upon application.
o Check injection port septum. It is a good idea to put in a new septum before
analyzing a large number of samples.
o Check to be sure that signal cable is connected from Photovac output to strip chart
recorder input.
o Set strip chart recorder input to 100 MV full scale and chart speed to 60 cm/hr. for
Photovac 10A10. (Recorder input for Photovac 10S50 should be set to 1 V full scale).
o Adjust needle on Photovac output meter using the offset dial so when instruments
attenuation is changed, the needle does not deflect. Setting the output somewhere
between 4-10 Mv DC will usually achieve this.
o Set recorder zero to 5% of chart full scale and establish an acceptable base line.
9.2 The following steps are taken before analysis of samples on the Shimadzu GC 14A using
isothermal conditions.
o Check injection port septum. It is a good idea to put in a new septum before
analyzing a large number of samples. The system must be cool before changing
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 10 of 17
the septum.
o Check PID detector Temperature. It should be set to 150°C from the external PID
power source. It can take up to 3 hrs. to warm up the detector from cold. Insure
that the detector lamp is on by quickly observing the lamp (purple) on the left side
of the instrument.
o Turn on the instrument and the instrument heaters on the face of the instrument.
On the control keyboard, hit the START button and set the default temperature
conditions.
o Injector 125°C
o BCD detector 190°C
o Oven 60°C
• After a 30 -60 minute warm-up, monitor actual temperatures using
the control keyboard.
o Check zero nitrogen carrier gas flow. The gas flow is checked using a flow meter
hooked up to the detector out vent port. Flow can be adjusted to the desired rate
by using the vernier knobs on the gas control unit on top of the instrument. A
desirable flow is from 20 - 60 cc/min, depending upon application.
o Check to be sure that signal cables are connected from PID and BCD outputs to
strip chart recorder inputs.
o Set strip chart recorder input to 5 MV full scale for the PID and 50 MV full scale
for the BCD, and chart speeds to 60 cm/hr.
o Set recorder zero to 5% of chart full scale and establish acceptable base lines.
10.0 Sample Analysis:
Air analysis generally consists of taking a 200 uL volume grab sample of air
using a 250 uL steel barrel syringe with a 2 inch, 25 gauge needle, and injecting it
into the GC injection port.
At the sample collection location, flush the syringe barrel three times using the
plunger. After flushing, pull the plunger up to the 200 uL point on the barrel and
place a spare GC septa on the tip of the needle to seal in the sample. Get the
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 11 of 17
sample to the GC as soon as possible for analysis. Put the syringe needle into the
GC injection port, and push the needle through the septum until the barrel comes
up against the injection port and immediately push the plunger with a quick
action. Turn on the strip chart recorder and note on the chart:
1. start of run
2. sample number
3. sample volume
4. attenuation or gain
5. any other relevant comments
The order in which analyses of a group of samples is performed is as follows:
1. Standard - Inject a 200 uL sample of your 10 ug/L standard, at 0 -
1 °C head space into the GC. Keep standard peaks at
approximately 50% scale or more, if possible, by adjusting the
attenuation or gain.
2. Repeat 10 ug/L standard to check for reproducibility. Standard
chromatograms should have compound peak heights within + 15%
of each other and identical retention times.
3. Inject the secondary standard for confirmation. The acceptance
criteria is + 20% of the true value.
4. Blank - Inject a 200 ul sample of clean air into the gas
chromatograph with the attenuation set at the same level or lower
than what your samples will be run on. Blank clean air is taken
from the head space above VOA free water in a 40 ml VOA vial.
5. Samples - Inject 200 ul sample volumes into the GC at the same
attenuation or lower, than the standard was run. If contaminant
levels on the chromatograms are off-scale on the recorder, adjust
the attenuation or gain to decrease instrument response. If the
chromatographic peaks are still off-scale rerun the samples using a
smaller injection volume.
6. Repeat 10 ug/L standard every 10 samples and at the end of the
sample batch to check the calibration and reproducibility.
Standard chromatograms should have compound peak heights
within + 20% of each other and identical retention times.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 12 of 17
11.0 Identification and Quantitation:
Identifications of compounds present in a sample are made by matching retention times
of peaks in the sample chromatogram to the retention times of standard peaks. After a
compound is identified, quantitation is done by a peak height comparison.
Example: If the 10 ug/L aqueous standard head space had a benzene peak height of
32 units from a 200 uL injection with instrument attenuation at 2, an
identified benzene peak 12 units high from an 200 uL sample injection
with instrument attenuation at 2 would represent a sample concentration of
57 ppb benzene.
32 units = 12 units
151ppb/v* Xppb/v
X = 57 ppb/v Benzene
* See Air Standard Section 8.5.2
120 Data and Records Management:
12.1 All work performed for the analyses of samples should be entered into the field screening
logbook. The analyses data should be presented to the project manager on site. This is
followed up by an Internal Correspondence Report that is reviewed by the Advanced
Analytical Chemistry Expert from the Chemistry Section of the EIA Laboratory.
Chromatograms generated should be saved and filed in the project folder. The samples
analyzed should also be logged into the laboratory information management system.
12.2 Chromatograms:
12.2.1 Site name, analyst name, and date at the start of the chromatogram strip chart.
12.2.2 Every chromatogram/every sample/standard
Sample number or standard
Sample volume injected
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 13 of 17
Instrument gain or attenuation setting
13 0 Quality Control:
13.1 A blank and a one point standard is used for instrument=s calibration. Initially run 10
ug/L standard to determine retention times and response factors of instrument. Repeat a
second 10 ug/L standard to check the reproducibility. Acceptance criteria: within +
15% difference from the first standard.
13.2 Blanks are analyzed at the initial calibration and periodically to be sure of no carry over
from previous injections. Technical judgment is used to determine frequency.
Acceptance criteria: No target compound peaks greater than one-half the reporting
level.
13.3 A second source standard containing some compounds of interest is analyzed daily to
verify calibration standard. Acceptance criteria: within + 20% agreement of true
value.
13.4 A standard is run at least every 10 samples and at the end of the sample batch to update
the instrument=s calibration due to changes from temperature fluctuations with respect to
retention times and response factors. Acceptance criteria: + 20%D agreement with the
previous calibration.
13.5 Analyze upwind samples to determine background concentrations during outdoor
ambient air sample events and report results.
13.6 Run field and laboratory duplicates when possible (i.e., soil gas analysis and passive
vapor sample analysis) The acceptance criterion is agreement within + 20% RPD
between the two values.
13.7 When possible (i.e., soil gas, ambient air), GC/MS confirmation of 10% of the field
samples analyzed should be performed. This is done, dependent upon the project data
quality objective. Summa canisters are used for collecting confirmation samples for
GC/MS confirmation.
14.0 References:
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 14 of 17
14.1 Interim Final Guidance for the Quality Assurance/Quality Control Guidance for Removal
Activities, April 1990.
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 15 of 17
Quality Control Table
QC Item
Initial
Calibration
Blank
Second
Source Std
Continue
Calibration
Upwind
Samples
Field
Duplicate
Lab.
Duplicate
Frequency
Daily, before
samples
Daily, every
batch
Daily, every
batch
Every 10
samples and
at the end
Option, if the
situation
warranted
Option,
depends on
DQOs
Option,
depends on
DQOs
Acceptance
Criteria
< 15%D from the
first std1
< 1/2 RL1
< 20%D, from
the true value l
< 20%D, from
the previous std 1
None.
Report results l
<20%RPD1
< 20% RPD1
Corrective
Action
Inject another std, check system
Repeat blank injection, prepare a new
blank, check system, increase RLs
depending on the DQOs
Inject another std, repeat initial
calibration, check system
Inject another std, repeat initial
calibration, check system
Repeat injection, run another duplicate
Repeat injection, run another duplicate
1_
= Acceptance criteria defined based on technical judgment
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 16 of 17
Figure 1
Volatile Organic Screening Method
Target Compound Chromatogram (PID)
1. 1,1 -Di chl oroethene
2. t-l,2-Dichl oroethene
3. c-l,2-Dichl oroethene
4. Benzene
5. Trichloroethene
6. Toluene
7. Tetrachloroethene
8. Chlorobenzene
9. Ethyl Benzene
10. m/p-Xylenes
11. o-Xylene
-a
3
"a.
10
aj
Q_
JO
tu
cc
Relative ElutionTime
Instrument: Shimadzu gas chromatography 14A
Detector: Photoionization Detector (PID)
Column: DBFS 624, 30 m, 0.53 micron
Temperature: 60°C
Carrier Gas: Zero grade nitrogen
Flow rate: 30-60 cc/min
Chart speed: 1 cm/min
-------
EIA-FLDGRAB4.WPD
VOCs in Air Samples
02/12/02
Page 17 of 17
Figure 2
Volatile Organic Screening Method
Target Compound Chromatogram (BCD)
1. 1,1 -Dichloroethene
2. Trichloroethene
3. Tetrachloroethene
Relative ElutionTime
Instrument: Shimadzu gas chromatography 14A
Detector: Electron Capture Detector (BCD)
Column: DBFS 624, 30 m, 0.53 micron
Temperature: 60°C
Carrier Gas: Zero grade nitrogen
Flow rate: 30-60 cc/min
Chart speed: 1 cm/min
-------
-------
Prepared by:
USGS Enterprise Publishing Network
Raleigh Publishing Service Center
3916 Sunset Ridge Road
Raleigh, NC 27607
For additional information regarding this publication, contact:
Don A. Vroblesky
USGS South Carolina Water Science Center
720Gracern Road, Suite 129
Columbia, SC 29210
phone: 1-803-750-6100
email: vroblesk@usgs.gov
Or visit the South Carolina Water Science Center website at:
http://sc, water, usgs,go¥
This publication is available online at:
http://pubs.water.usgs.gov/sir2m8-5088
-------
CD
00
00
CD
CD
o
**
CD
O
o_
CD"
a
o'
—
•s
CD
CD
O
O
5
o'
3
a
CO
9)
o
CD
<
O
o
oo
o
CD
00
to
Q3
rt-
o'
CD
-a
o
s
NO
CD
CD
cn
CD
oo
oo
------- |