Cover Photographs: Tree-core sample in a 40-milliliter vial for headspace analysis (left photo). Collecting a 

tree-core sample from an oak tree at the Riverfront Superfund Site, New Haven, Missouri, 2000 (right photo).
Assessment of Subsurface Chlorinated Solvent 

Contamination Using Tree Cores at the Front 

Street Site and a Former Dry Cleaning Facility at 

the Riverfront Superfund Site, New Haven, 

Missouri, 1999–2003

By John G. Schumacher1, Garrett C. Struckhoff1, and Joel G. Burken2

1U.S. Geological Survey

2University of Missouri-Rolla, Department of Environmental Engineering

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

U.S. Environmental Protection Agency,

Region VII

Scientific Investigations Report 2004-5049
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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Telephone: 1-888-ASK-USGS

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Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation:

Schumacher, J.G., Struckhoff, G.C., and Burken, J.G., 2004, Assessment of subsurface chlorinated solvent contamination 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 Scientific Investigations Report 2004-5049, 35 p.
iii

CONTENTS

Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Description of the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Sample Collection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Assessment of Subsurface Contamination at the Front Street Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Initial Site Assessment Using Tree Cores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Comparison of Tree-Core Sampling to Traditional Soil and Ground-Water Sampling at the Front 

Street Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Comparison of Tree-Core Sampling to Traditional Soil Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . 11

Comparison of Tree-Core Sampling to Ground-Water Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Assessment of Subsurface Contamination at the Former Dry Cleaning Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Initial Site Assessment Using Tree Cores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Comparison of Tree-Core Sampling to Traditional Soil Sampling at the Former Dry Cleaning 

Facility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Practical Considerations in Using Tree-Core Sampling for Site Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Diffusion Losses and Uptake, Partitioning, and Differences Between Species . . . . . . . . . . . . . . . . . . . . . . . . 17

Directional Variability in Tree Trunks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Sensitivity of Tree-Core Sampling to Detect Subsurface Contamination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
iv

Figures

1–4. Maps showing: 

1. Location of operable units and potential tetrachloroethene (PCE) source areas in relation to 

contaminated public water-supply wells (W1 and W2) at the Riverfront Superfund Site, 

New Haven, Missouri. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

2. Results of initial tree-core sampling conducted in downtown New Haven, Missouri, 

during 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

3. Ground-water flow in the Missouri River alluvium at the Front Street site during normal 

stage (January 23, 2001) and high stage (June 12, 2001) of the Missouri River. . . . . . . . . . . . . . . . . .6

4. Relation between average tetrachloroethene (PCE) concentrations in tree-core 

samples and PCE concentrations in soil at the Front Street site (1999–2003) . . . . . . . . . . . . . . . . . 12

5. Graphs showing relation between tetrachloroethene (PCE) concentrations in tree-core 

samples to PCE concentrations in soil and ground-water samples from the Front 

Street site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6. Map showing relation between average tetrachloroethene (PCE) concentrations in treecore samples and PCE concentrations in ground-water samples at the Front Street 

site (1999–2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7. Map showing location of tree-core and soil samples at and in the vicinity of the former dry 

cleaning facility near downtown New Haven, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8–11. Graphs showing:

8. Relation between tetrachloroethene (PCE) concentrations in tree-core samples and 

height above the land surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

9. Relation between tetrachloroethene (PCE) concentration in soil gas and depth below 

the land surface along the north side of the Front Street building . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

10. Directional variability in tetrachloroethene (PCE) concentrations in core samples 

from an eastern red cedar tree (TW02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

11. Directional variability in tetrachloroethene (PCE) concentrations in core samples 

collected from tree TW28 on June 30, 2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Tables

1. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core 

samples collected from downtown New Haven, Missouri, during 1999. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core 

samples collected from the Front Street site and former dry cleaning facility, 2000–2003. . . . . . . . . . . 29

3. Variation in tetrachloroethene (PCE) concentrations in the trunk of tree TW02 with direction 

and height above the land surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
v

Conversion Factors and Datum

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 x °C) + 32

Vertical coordinate information is referenced to the “National Geodetic Vertical Datum of 1929 

(NGVD 29).”

Altitude, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in soil are given in micrograms per kilogram (μg/kg) and 

concentrations of chemical constituents in tree-core samples are given as micrograms in headspace per kilogram of wet core (μg-h/kg).

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

square foot (ft2

) 929.0 square centimeter (cm2)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2)

Volume

gallon (gal) 3.785 liter (L)

cubic inch (in3

) 16.39 cubic centimeter (cm3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.00223 cubic foot per second (ft3/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)
Assessment of Subsurface Chlorinated Solvent 

Contamination Using Tree Cores at the Front Street Site 

and a Former Dry Cleaning Facility at the Riverfront 

Superfund Site, New Haven, Missouri, 1999–2003

By John G. Schumacher1, Garrett C. Struckhoff1, and Joel G. Burken2

Abstract

Tree-core sampling has been a reliable and inexpensive 

tool to quickly assess the presence of shallow (less than about 

30 feet deep) tetrachloroethene (PCE) and trichloroethene 

(TCE) contamination in soils and ground water at the Riverfront 

Superfund Site. This report presents the results of tree-core 

sampling that was successfully used to determine the presence 

and extent of chlorinated solvent contamination at two sites, the 

Front Street site (operable unit OU1) and the former dry cleaning facility, that are part of the overall Riverfront Superfund 

Site. Traditional soil and ground-water sampling at these two 

sites later confirmed the results from the tree-core sampling. 

Results obtained from the tree-core sampling were used to 

design and focus subsequent soil and ground-water investigations, resulting in substantial savings in time and site assessment costs.

The Front Street site is a small (less than 1-acre) site 

located on the Missouri River alluvium in downtown New 

Haven, Missouri, about 500 feet from the south bank of the Missouri River. Tree-core sampling detected the presence of subsurface PCE contamination at the Front Street site and beneath 

residential property downgradient from the site. Core samples 

from trees at the site contained PCE concentrations as large as 

3,850 μg-h/kg (micrograms in headspace per kilogram of wet 

core) and TCE concentrations as large as 249 μg-h/kg. Soils at 

the Front Street site contained PCE concentrations as large as 

6,200,000 μg/kg (micrograms per kilogram) and ground-water 

samples contained PCE concentrations as large as 11,000 μg/L 

(micrograms per liter). The former dry cleaning facility is 

located at the base of the upland that forms the south bank of the 

Missouri River alluvial valley. Tree-core sampling did not indicate the presence of PCE or TCE contamination at the former 

dry cleaning facility, a finding that was later confirmed by the 

analyses of soil samples collected from the site.

The lateral extent of PCE contamination in trees was in 

close agreement with the extent of subsurface PCE contamination determined using traditional soil and ground-water sampling methods. Trees growing in soils containing PCE concentrations of 60 to 5,700 μg/kg or larger or overlying ground water 

containing PCE concentrations from 5 to 11,000 μg/L generally 

contained detectable concentrations of PCE. The depth to contaminated ground water was about 20 to 25 feet below the land 

surface. Significant quantitative relations [probability (p) values of less than 0.05 and correlation coefficient (r2

) values of 

0.88 to 0.90] were found between PCE concentrations in trees 

and subsurface soils between 4 and 16 feet deep. The relation 

between PCE concentrations in trees and underlying ground 

water was less apparent (r2 value of 0.17) and the poor relation 

is thought to be the result of equilibrium with PCE concentrations in soil and vapor in the unsaturated zone. Based on PCE 

concentrations detected in trees at the Front Street site and trees 

growing along contaminated tributaries in other operable units, 

and from field hydroponic experiments using hybrid poplar cuttings, analysis of tree-core samples appears to be able to detect 

subsurface PCE contamination in soils at levels of several hundred micrograms per liter or less and PCE concentrations in the 

range of 8 to 30 μg/L in ground water in direct contact with the 

roots.

Loss of PCE from tree trunks by diffusion resulted in an 

exponential decrease in PCE concentrations with increasing 

height above the land surface in most trees. The rate of loss also 

appeared to be a function of the size and growth characteristics 

of the tree as some trees exhibited a linear loss with increasing 

height. Diffusional loss of PCE in small (0.5-inch diameter) 

trees was observed to occur at a rate more than 10 times larger 

than in trees 6.5 inches in diameter. Concentrations of PCE also 

exhibited directional variability around the tree trunks and concentration differences as large as five-fold were observed 

around the trunks of several trees. The directional differences 

were attributable to spatial differences in PCE concentrations in 

soils around the trees and to natural “twisting” of the tree trunks. 

The directional differences also may be caused by diffusion of 

PCE vapors in the unsaturated zone into the tree roots. Compar1U.S. Geological Survey

2

University of Missouri-Rolla, Department of Environmental Engineering
2 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

ison of PCE concentrations in core and sap samples confirms 

laboratory sorption studies and indicates that the vast majority 

(greater than 95 percent) of the PCE and TCE reside in the wood 

phase and not the transpiration stream.

Introduction

The assessment of shallow, subsurface contamination by 

volatile organic compounds (VOCs) generally has involved the 

collection of soil, soil-gas, or ground-water samples from boreholes. While advances in drilling, sample collection, and on-site 

analysis have greatly improved site characterization, the collection of these samples must still be done by invasive methods 

using equipment that typically requires vehicle access across 

the site. Unfortunately, cultural features or overgrowth of vegetation limits access to many abandoned or potential waste-disposal sites. In addition, contaminants in ground water may 

migrate beneath adjacent parcels of land where access for sampling can be limited by local landowners. Recent research has 

shown that VOCs are present in core samples from trees 

exposed to contaminated ground water (Burken and Schnoor, 

1998; Compton and others, 1998; Vroblesky and others, 1999). 

Vroblesky and others (1999) demonstrated that trees growing 

above contaminated shallow ground water at the Savannah 

River site in South Carolina contained concentrations of trichloroethene (TCE) and cis-1,2-dichloroethene (cis-DCE) that generally reflected concentrations in a chlorinated solvent plume 

previously identified by analyses of water samples from monitoring wells and piezometers. In laboratory studies, concentrations of TCE in the transpiration stream of hybrid poplar trees 

were shown to correlate with TCE concentrations in simulated 

ground water (Ma and Burken, 2002, 2003).

The available literature suggests that tree-core sampling 

may be an effective tool for the assessment of subsurface VOC 

contamination. Tree-core samples have been successfully used 

to map subsurface contamination by chlorinated solvents and 

guide the placement of monitoring wells at the Riverfront 

Superfund Site (U.S. Environmental Protection Agency, 2001). 

Tree-core sampling, in conjunction with traditional soil and 

ground-water sampling, was used to map the extent and magnitude of subsurface VOC contamination at several operable units 

at the Riverfront Superfund Site and to identify several additional areas for future investigation (U.S. Environmental Protection Agency, 2003). Application of tree-core sampling at the 

Riverfront Superfund Site is unique, in that unlike previous 

field studies (Vroblesky and others, 1999; Cox, 2002), no subsurface data previously existed at the Riverfront Superfund Site 

and tree-core sampling was the primary tool used in the initial 

site assessment. 

Background

The Riverfront Superfund Site is located in Franklin 

County, Missouri, about 40 mi (miles) west of St. Louis, Missouri, in the town of New Haven, Missouri (fig. 1). During routine public water-supply well testing in 1986, the Missouri 

Department of Natural Resources (MDNR) detected the VOC 

tetrachloroethene (PCE) in two public water-supply wells (W1 

and W2) drilled to more than 800 ft (feet) deep in the northern 

part of New Haven. Following the discovery of the PCE contamination above the U.S. Environmental Protection Agency 

(USEPA) maximum contaminant level (MCL) of 5 μg/L 

(micrograms per liter) for PCE, two new public water-supply 

wells (W3 and W4) were installed in the southern part of the 

city, and several investigations of potential sources of the contamination were made by the MDNR and the USEPA during the 

late 1980’s and early 1990’s.

The initial investigations of PCE contamination of the 

public water-supply wells indicated several facilities that were 

potential sources of the PCE. These facilities included:

• an abandoned manufacturing building in downtown 

New Haven on Front Street (Front Street site);

• a former dry cleaning facility at the intersection of Wall 

and Miller Streets;

• a metal fabrication plant (metal plant) in south New 

Haven on Industrial Drive (Kellwood site);

• a metal finishing plant unit on the east side of the city 

on East Industrial Drive;

• a fabric plant in the east part of the city on Orchard 

Street;

• the old city dump on the east side of the city limits; and

• an old (abandoned) hat factory on Wall Street south of 

public water-supply well W1.

The abandoned manufacturing building in downtown New 

Haven and former dry cleaning facility were identified as two 

of the most likely sources of the contamination because they are 

within 600 ft of the contaminated city wells (fig. 1). In 1998, the 

USEPA asked the U.S. Geological Survey (USGS) for technical 

assistance in understanding the geohydrology of the New 

Haven area and to provide information on the possible directions of ground-water flow and PCE migration from potential 

sources previously identified. The USGS technical assistance 

was performed as an Expanded Site Investigation/Remedial 

Investigation (ESI/RI) that was completed in 2000 (U.S. Environmental Protection Agency, 2001). The ESI/RI included an 

initial assessment of several sites using tree cores. In December 

2000, as a result of the additional data collected during the ESI/

RI, the site officially was placed on the National Priorities List 

(NPL) or “Superfund”. The Riverfront Superfund Site currently 

(2003) has five operable units that include several abandoned 

and existing manufacturing facilities where PCE was or may 

have been used and disposed within the city (fig. 1). Core samples collected from hundreds of trees have been used in the 

characterization of subsurface VOC contamination at the various Remedial Investigation (RI) operable units and along sanitary sewer lines throughout the city. The RI and Feasibility 

Study (FS) for one of the operable units, the Front Street site,
Introduction 3

New Haven

Boeuf

Creek

Missouri River

210 tributary

500 tributary

Orchard Street

Miller

Street

East Drive Industr ai l

Wall Street

Industrial

Drive

C

100

OU4

OU3

OU2

OU5

OU1

Orchard

Street

area

&

&

&

&

&

W4

Pepsi

W3 Well

W2

W1

91o13'30" 91o

12'30"

38o

36'

38o

35'

Base from U.S. Geological Survey digital data, 1:100,000, 1927

Universal Transverse Mercator projection,

Zone 15

& W3 PUBLIC WATER-SUPPLY OR INDUSTRIAL WELL

AND IDENTIFIER

FIELD HYDROPONIC STUDY SITE

OPERABLE UNIT AND NUMBER

INTERMITTENT STREAM

OU5

EXPLANATION

0 2,000 4,000 FEET

0 500 1,000 METERS

Figure 1. Location of operable units and potential tetrachloroethene (PCE) source areas in relation to

contaminated public water-supply wells (W1 and W2) at the Riverfront Superfund Site, New Haven, Missouri.

Fabric

plant

Former dry

cleaning

facility

Old

hat

factory

Metal

finishing

plant

Old city

dump

Kellwood Site

(metal plant)

Front Street

site

St.

Louis

New

Haven

Springfield

Plateau

MISSOURI

Salem

Plateau
4 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

were completed in 2003 (U.S. Environmental Protection 

Agency, 2003; Black and Veatch Special Projects Corporation, 

2003). A Record of Decision (ROD) for the Front Street site was 

prepared by the USEPA in September 2003. 

Purpose and Scope

The report describes the assessment of subsurface chlorinated solvent contamination using tree cores at two sites in 

downtown New Haven, Missouri (Front Street site and the 

former dry cleaning facility) that were investigated as part of the 

Riverfront Superfund Site. During an initial assessment in 

1999, core samples were collected from 32 trees in the downtown area. Results from these samples were used to scope and 

design the subsurface characterization of soils and a groundwater monitoring network at what would become RI operable 

unit OU1 (Front Street site). The former dry cleaning facility is 

within several hundred feet of OU1 and was investigated as part 

of the OU1 investigation. During the RI, which began in 2000, 

hundreds of soil and dozens of ground-water samples were collected to characterize the extent and magnitude of contamination at these two sites. Additional tree-core samples also were 

collected during the RI to better understand the relations 

between chlorinated solvent concentration in trees and the subsurface. As of May 2003, more than 70 trees have been sampled 

in the vicinity of the Front Street site and the former dry cleaning facility. Data from tree-core sampling were compared to 

more traditional site characterization data, such as data from 

soil borings and monitoring wells, to demonstrate that the initial 

assessment using tree cores was a reliable indicator of the presence or absence of subsurface VOC contamination at these two 

sites. Relations between concentrations of VOCs in tree cores, 

soil, and ground water are presented along with data suggesting 

that concentrations of VOCs in the tree-core samples are dependent upon the VOC concentrations in the subsurface, depth to 

ground water, collection height, tree size and species, and directional location around the tree trunk. Practical considerations 

and possible limitations on the use of tree coring in site assessment based on experiences at the Riverfront Superfund Site also 

are presented.

Description of the Study Area

The Front Street site is on the northwest corner of the intersection of Front Street and Cottonwood Street in downtown 

New Haven (fig. 2). The site consists of a vacant 15,000 ft2

(square foot), one-story building (Front Street building) situated 

on a 1.5-acre lot east of Cottonwood Street, and a 0.1-acre 

vacant lot on the west side of Cottonwood Street (fig. 2). The 

building lot is level with less than 1.5 ft of relief. Front Street 

provides access to a boat ramp on the Missouri River about 500 

ft northeast of the site and to the city wastewater lagoon east of 

the site. The Front Street site is behind a flood protection levee 

designed and built by the U.S. Army Corps of Engineers 

(USACE) that surrounds downtown New Haven (fig. 2).

Several industries have operated at the site since the 

1950’s and the Front Street building was built in at least five 

phases. The initial part of the building was built in the late 

1940’s and operated as a local “machine shop”. In the early 

1950’s, a major manufacturer of tents and outdoor products 

moved several production facilities into New Haven. From the 

early 1950’s through 1972, the machine shop was contracted to 

manufacture and finish aluminum tent poles and stakes and several additions were made to the building to accommodate the 

increased business. The process included cleaning the poles 

with PCE. After 1972, several other industries operated for 

short periods at the facility, including a hospital bed manufacturer, a truck spring plant, a golf cart supplier, and an automobile repair shop.

The Front Street site is located on the Missouri River flood 

plain about 400 ft from the south bank of the river, and is underlain by between 20 and 35 ft of alluvial sediments. The surface 

of the alluvium is gently sloping and ranges from an altitude of 

about 501 ft near the railroad tracks south of the building to 

about 490 ft at the boat ramp northeast of the site (fig. 2). The 

edge of the alluvium is immediately south of the railroad tracks, 

and its thickness increases toward the Missouri River where it 

is more than 50 ft thick. The stratigraphy of the alluvium at OU1 

is relatively homogeneous, consisting mostly of silt and siltyloam from 0 to about 20 ft deep, grading into fine- and coarsegrained sands deeper than 20 to 25 ft (U.S. Environmental Protection Agency, 2003). Ground water in the alluvium beneath 

the site averages about 20 to 25 ft below the land surface. During periods of flooding, water levels rise to within 10 ft below 

the land surface, and may be shallower during prolonged periods of flooding such as occurred during 1993 and 1995. At normal river stages, ground-water flow in the alluvium beneath the 

site is northeast toward the Missouri River. However, during 

periods of high river stages, a trough develops in the alluvial 

water table just northeast of the site and parallel to the river (fig. 

3). 

The former dry cleaning facility is located near the intersection of Wall Street and Miller Street near the base of the 

upland slope composing the south boundary of the Missouri 

River valley (fig. 2). The site is in a residential area and is about 

300 ft from the contaminated city well W2. From the late 1950’s 

through the early 1970’s, dry cleaning was done in the basement 

of what is now a residence situated on a small (less than 0.2 

acre) lot on the south side of Wall Street (U.S. Environmental 

Protection Agency, 2003). The lot slopes steeply from Wall 

Street to the south property line, which borders the back yard of 

an adjacent residence. Access to the site is restricted because of 

the high density of homes and steep slopes. The site is underlain 

by a mixture of loess and colluvium. City utility workers indicate that bedrock beneath Wall Street north of the former dry 

cleaning facility is less than 7 ft deep. A small intermittent 

creek, which drains about 0.1 mi2

 (square mile) of residential 

area to the south, is about 100 ft south of the former dry cleaning 

facility. The creek flows beneath Miller Street north of city well 

W2 and enters a concrete storm drain near the railroad tracks. 
Introduction 5

38o36'55"

38o

36'45"

91o12'50" 91o

12'40"

EXPLANATION

TREE-CORE SAMPLE AND IDENTIFIER

AVERAGE TETRACHLOROETHENE (PCE) CONCENTRATION IN

TREE-CORE SAMPLE—Concentration in micrograms in headspace

per kilogram of wet core

Not sampled during 1999

Not detected

0.1 to 4.9

INTERMITTENT STREAM

PUBLIC WATER-SUPPLY WELL AND IDENTIFIER

5.0 to 49.9

50 to 162

TR02

250 500 FEET

100 METERS

0

0 50

Base from U.S. Geological Survey digital orthophoto quarter-quadrangle, 1:12,000, 1986

Universal Transverse Mercator projection

Zone 15

W2 &

Figure 2. Results of initial tree-core sampling conducted in downtown New Haven, Missouri, during 1999.

Front Street

Cottonwood Street

Front Street

Flood protection levee

Wall Street

Missouri River

Boat

ramp

City park

Former

automobile

dealer

Former dry

cleaning

facility

Downtown

buisness

district

Front

Street

building

Front

Street site

property

line

Wastewater

lagoon

Farm supply

W2

Residence

City

utilities

shed

Railroad tracks

Main Street

Miller Street

&

&W1

TG03

TG04 TG02

TG01

Vacant

lot

TW04 TW07 TW05

TW06

TW08 TB01

TW09

TR02

TW02

TW03

TA02

TA01

TB02
6 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

l

l l

l

l

l

l l

l lll l l l l l l l l lll

lll

l

l

l

l

l

l l l l l lll l l l l l l l

Wastewater lagoon

Missouri River

TW-G

TW-F

TW-D

TW-E

TW-C

TW-B

TW-A

City

utilities

shed

Front Street

building

472

474

478

476

477

475

473

Flood protection levee

Wastewater lagoon

Missouri River

490.5

490.5

490.7

490.9

TW-G

TW-F

TW-D

TW-E

TW-C

TW-B

TW-A

490.3

City

utilities

shed

Front Street

building

Flood protection levee

Figure 3. Ground-water flow in the Missouri River alluvium at the Front Street site during

normal stage (January 23, 2001) and high stage (June 12, 2001) of the Missouri River.

EXPLANATION

Base from U.S. Geological Survey digital data, 1:100,000,1927

Universal Transverse Mercator projection,

Zone 15

Modified from the U.S. Environmental

Protection Agency (2003)

June 12, 2001

January 23, 2001

0

0 25

100

50 METERS

200 FEET

POTENTIOMETRIC CONTOUR—Shows altitude at

which water level would have stood in tightly cased

wells. Contour interval is variable, in feet. Vertical

datum is NGVD 29

FRONT STREET SITE PROPERTY LINE

ROAD OR CONCRETE SLAB

RAILROAD TRACK

472

l l

MONITORING WELL AND NUMBER

MAXIMUM TETRACHLOROETHENE (PCE)

CONCENTRATION IN GROUND-WATER

SAMPLE—Concentration in micrograms per liter

Not detected

0.1 to 4.9

5.0 to 499

500 to 670

TW-A &

38o36'48"

38o

36'53"

91o

12'45" 91o12'40"

38o

36'48"

38o

36'53"

&

&

&

&

&

&

&

&

&

&

&

&

&

&
Introduction 7

Sample Collection and Analysis

Core samples generally were collected from trees with 

diameters of 3 in. (inches) or larger. If multiple species were 

present at a single location, preference was given to species that 

are known to grow rapidly and have deep root systems, such as 

mulberry, poplar, and cottonwood. A 0.169- by 6-in. long increment borer was used to collect the core samples. During the initial assessment in 1999, composite samples from trees were prepared by collecting two cores from opposite sides of each tree 

about 3 ft above the land surface. Only one core was collected 

from trees smaller than about 6-in. diameter. Cores from each 

tree were placed in a single pre-weighed 40-mL (milliliter) standard VOC vial fitted with a Teflon-lined septum cap. Cores 

were collected as quickly as possible to minimize volatilization 

loss. Typically, cores from a single tree were collected within 

one minute and the vial was capped immediately after the collection of each core. At least one core sample was collected 

from the side facing the suspected contaminated area. For 

example, trees on the north side of the Front Street building 

were initially cored on the south side, then on the north side 

depending on the diameter of the tree. Trees along the railroad 

tracks initially were cored on the south side, then on the north 

side depending on their diameter. Cores collected from trees at 

the former dry cleaning facility were collected from opposite 

sides of each tree, but at no specified side because the suspected 

area of dumping, if any occurred, was not known at that time. 

Because of concerns about PCE volatilization from the vial 

when adding the second core, after 1999, only single cores were 

collected from each tree.

After collection, vials were returned to the USGS laboratory in Rolla, Missouri, and allowed to equilibrate overnight at 

room temperature to allow PCE and other VOCs to diffuse from 

the cores into the headspace in the vial. A 250-μL (microliter) 

sample of the headspace in the vials was collected using a glass 

syringe. The samples were analyzed using a Photovac 10S Plus 

gas chromatograph (GC) equipped with a photoionization 

detector. Chromatographic separation was performed isothermally at 40 oC (degrees Celsius) for 500 seconds with a CPSIL5 capillary column with an air flow rate of 10.5 mL/min (milliliters per minute). Standards were prepared daily by placing 5 

μL of a methanol-based standard solution containing certified 

quantities of PCE, TCE, cis-DCE, benzene, and toluene into a 

40 mL septum-capped vial containing 20 mL of organic-free 

distilled water. The stock standard solution was obtained from 

Supelco in sealed glass ampules and stored at -20 oC until use. 

Samples containing concentrations of individual VOCs larger 

than 50 μg/L were rerun and diluted by injecting a smaller quantity of sample collected from the headspace of the vial.

Concentrations of PCE and other VOCs in tree cores initially were expressed as micrograms of VOC per kilogram of 

wet core (U.S. Environmental Protection Agency, 2001, 2003). 

This was done assuming that the partitioning of PCE and other 

VOCs between the headspace and core was similar to that 

between air and water. Recent research has provided partitioning coefficients between air/wood and wood/water for TCE and 

PCE (Ma and Burken, 2002, 2003; Struckhoff, 2003) and concentrations expressed in this report have been adjusted and 

reported as mass (micrograms) of VOC in the headspace per 

kilogram of wet core (μg-h/kg). This unit of measure was chosen because it is a compromise between the inherent inaccuracy 

of reporting only headspace concentration and the more accurate approach of reporting wood and transpiration stream concentrations using partitioning coefficients between water, 

wood, and air. A limitation of using partitioning coefficients to 

determine the fractions of VOCs in wood, water, and air is that 

it is necessary to determine partitioning coefficients for every 

compound in every type of plant material being sampled. 

Recently published values of partitioning coefficients of PCE 

into poplar trees indicate that about 95 percent of the PCE is 

sorbed into the wood while only about 5 percent is present in the 

water phase (Struckhoff, 2003). Because the majority of PCE in 

the core resides in the wood phase, the headspace concentrations in this report were normalized to the total core mass, rather 

than to the core water mass. By normalizing to total core mass, 

all that is required is to multiply the headspace concentration by 

the headspace volume and divide by the total core mass.

There are some limitations associated with expressing concentrations as micrograms in headspace per mass of core. First, 

the headspace in the vial (empty vial less volume of core) containing the core must be known. The volume of core often is calculated using an assumed density of the tree core. In this report, 

the core density was assumed to be 1.0 g/cm3

 (gram per cubic 

centimeter). Actual densities of trees cored in the New Haven 

area probably are in the range of 0.5 to 0.9 g/cm3

 reported for 

cedar, maple, and oak (CRC Press Inc., 1989). Because of the 

generally small volume of core to total vial volume, the error in 

reported VOC concentration introduced by assuming the core 

density of 1.0 is less than 5 percent. Second, in cases where 

composite samples of multiple cores are placed in the same vial, 

there can be significant loss of the contaminant in the few seconds while the vial lid is open. This can be understood by considering that Henry’s Law indicates that about 40 percent of 

PCE goes into the headspace and the observation that when a 

core is placed into a vial and capped, condensation usually can 

be seen almost immediately on the inside of the glass. The rapid 

formation of condensation indicates a rapid loss of water, and 

probably VOCs, from the core, and demonstrates that the vials 

must be capped as quickly as possible. Another limitation in 

headspace analysis is variability between different sampling 

procedures such as the use of different sized vials. If two cores 

of the same size are placed into different sized vials, measured 

VOC concentrations will be different when reported as micrograms in headspace per kilogram of wet core. Therefore, the 

size of cores in proportion to the vial size should remain approximately the same during field sampling efforts or results will not 

be directly comparable.
8 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

Assessment of Subsurface Contamination at 

the Front Street Site

Through interviews with local residents and former 

employees of the relevant facilities, the USEPA determined that 

PCE was used and probably disposed at the Front Street site 

during the 1950’s and 1960’s. However, specific information 

regarding the quantities of PCE used and manner and location 

of disposal at the site was not known. Because the site is near a 

USACE-sponsored flood protection levee, stringent limitations 

exist on the installation of subsurface borings and monitoring 

wells to protect the stability of the levee foundation. In addition 

to limitations on subsurface boring and drilling, the property 

north and northeast of the Front Street building is residential 

and under private ownership. Because of the restrictions on subsurface boring and the occasional reluctance of some residential 

property owners to grant access for drill rigs, the site was a good 

candidate for an initial reconnaissance using tree-coring methods.

Initial Site Assessment Using Tree Cores

The initial tree-core sampling at the Front Street site was 

conducted during July and August 1999. Trees were selected 

based on their proximity to the Front Street building. Several 

trees were cored again during October 1999 to serve as positive 

controls for the initial assessment of the former dry cleaning 

facility. PCE was detected in 13 of the 26 trees cored in the 

downtown area (fig. 2). Concentrations of PCE detected ranged 

from a trace concentration of 0.32 μg-h/kg (microgram in headspace per kilogram of wet core) in a hackberry tree (TW09) 

west of the site to 162 μg-h/kg in a mulberry tree (TW08) on the 

north side of the building (table 1). Except for the trace PCE 

concentrations (less than 1.0 μg-h/kg) in trees TW09 and TA02, 

all PCE detections were in trees along the north side of the 

building or on residential property north of the site.

TCE was detected in only five trees and at concentrations 

less than 5.0 μg-h/kg (table 1). The largest TCE concentration 

detected was 3.14 μg-h/kg in tree TW08. Concentrations of 

TCE generally were positively correlated with PCE concentrations. Four background trees (TG01, TG02, TG03, and TG04) 

were sampled in the western part of the downtown area to serve 

as negative controls (fig. 2). None of the background trees contained PCE or TCE, but three of the four did contain detectable 

concentrations of toluene (1.32 to 4.44 μg-h/kg) or benzene 

(7.47 μg-h/kg). Toluene also was detected in samples from trees 

TW01 and TW02 (0.39 and 1.33 μg-h/kg). There was an automobile dealership, a bulk fuel depot, and several former gasoline service stations in downtown New Haven, and several old 

underground fuel tanks were identified during the RI (U.S. 

Environmental Protection Agency, 2003). Leaks or spills at 

these facilities may be a source of the small concentrations of 

benzene and toluene detected in some trees. Several trees also 

contained small concentrations of what appeared to be cisDCE; however, core samples from negative control trees in a 

remote national forest contained small (few micrograms in 

headspace per kilogram of wet core) concentrations of a compound with a similar retention time to cis-DCE; therefore, concentrations of cis-DCE less than 10 μg-h/kg are considered 

unreliable.

Considerable variability (52 to 55 percent difference) was 

present in replicate core samples collected from trees TW02 and 

TW08 with the replicate sample being smaller. This variability 

is probably caused by differences in sampling technique as the 

replicate cores were placed in vials that contained 5 mL of 

organic-free water and were stored in an inverted position 

before analysis. The water was added to reduce the potential for 

diffusive loss of VOCs through the septa of the vials. Rather 

than preventing VOC loss, the addition of water appeared to 

enhance VOC loss because the replicate samples contained up 

to 55 percent less PCE than the original sample. The smaller 

concentrations in the replicate samples probably result from 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. The addition of water to 

replicate vials was not done after August 1999.

Based on the results of the initial tree-core sampling, the 

USEPA determined that PCE contamination was present at the 

Front Street site and that additional investigation of the site was 

warranted. The absence of significant PCE concentrations in 

trees south and west of the Front Street building was interpreted 

to mean that potential spills along the railroad tracks or at the 

old automobile dealership (west of the site) probably were not 

the source of PCE contamination. Based on the presumed direction of ground-water flow in the alluvium beneath the site 

(north-northeast toward the Missouri River) and the large concentrations of PCE in trees along the north side of the building, 

a conceptual model of PCE contamination at the site was developed (U.S. Environmental Protection Agency, 2003). This conceptual model was that PCE was disposed at or in the immediate 

vicinity of the Front Street building and that a plume of PCE 

contaminated ground water was moving beneath the private 

property north of the site and discharging into the Missouri 

River.

Comparison of Tree-Core Sampling to Traditional Soil 

and Ground-Water Sampling at the Front Street Site

During the RI of the Front Street site, an additional 39 trees 

near the site were sampled (U.S. Environmental Protection 

Agency, 2003). These trees were sampled as part of a larger 

effort to characterize the extent and magnitude of subsurface 

contamination at the site, which included the collection of subsurface soil samples from more than 140 locations, and groundwater samples from 7 monitoring wells and 21 temporary drive 

point locations in the alluvial aquifer near the site (U.S. Environmental Protection Agency, 2003). During the RI, tree-core 

samples generally were collected contemporaneously with soil 

and ground-water samples. However, in the case of a private
Table 1. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from downtown New Havenduring 1999[All concentrations in micrograms per liter in headspace per kilogram of wet core; Rep, replicate; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; t-DCE, tr

--, no data; <, less than; in., trunk diameter in inches; J, estimated concentration below the method reporting limit]

Tree

identifier Date Time Rep PCE TCE cis-DCE t-DCE Benzene Toluene Descr

Trees sampled near the Front Street building or downtown area

TA01 08/11/99 -- -- 1.38 <0.8 <10 <0.8 <0.8 <0.8 10 in. Hard mapleTA02 08/11/99 -- -- .58 J <.8 <10 <.8 <.8 <.8 10 in. Birch, 3 trunk

TB01 08/11/99 -- -- 35.7 .77 J <10 <.8 <.8 <.8 11 in. Walnut

TB02 07/13/99 1236 -- .93 <.8 <10 <.8 <.8 <.8 20 in. Silver maple

08/11/99 -- -- .99 <.8 <10 <.8 <.8 <.8 20 in. Silver maple

TG01 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 1.32 34 in. Chinese elm

TG02 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 2.66 34 in. Chinese elm

TG03 08/11/99 -- -- <.8 <.8 <10 <.8 7.47 4.44 36 in. Chinese elmTG04 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 34 in. Silver maple

TM01 08/20/99 -- -- <.8 <.8 .64 <.8 <.8 <.8 30 in. BoxelderTM02 08/20/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 38 in. Silver maple

TM03 08/20/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 12 in. Hard maple

TR01 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 7 in. HackberryTR02 08/11/99 -- -- .57 J <.8 <10 <.8 <.8 <.8 6 in. Chinese elmTR03 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 4 in. Hackberry, 3 tr

TR04 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 4 in. Hackberry

TW01 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 .39 J 11 in. Mulberry

TW02 08/11/99 -- -- 37.1 <.8 <10 <.8 <.8 1.33 10 in. Eastern red ce

10/22/99 1719 -- 53.2 <.8 .21 J <.8 <.8 2.38 10 in. Eastern red ce10/22/99 1719 R 24.1 <.8 .56 J <.8 <.8 <.8 10 in. Eastern red ce

TW03 08/11/99 -- -- 9.93 <.8 2.05 J <.8 1.45 <.8 6 in. Chinese elm

10/22/99 1719 -- 9.94 <.8 1.41 J <.8 <.8 <.8 6 in. Chinese elm

TW04 08/11/99 -- -- 47.6 .10 <10 <.8 .04 J <.8 3 in. Mulberry, 2 tru

TW05 08/11/99 -- -- 34.5 <.8 <10 <.8 <.8 <.8 4 in. Mulberry

TW06 08/11/99 -- -- 75.9 1.85 <10 <.8 .48 J <.8 3 in. Mulberry

TW07 08/11/99 -- -- 41.1 1.37 <10 <.8 <.8 <.8 10 in. Cottonwood

TW08 07/13/99 1226 -- 84.0 .42 J <10 <.8 <.8 <.8 8 in. Mulberry

07/13/99 1226 R 55.4 .17 J <10 <.8 <.8 <.8 8 in. Mulberry08/11/99 -- -- 162 3.14 2.58 J <.8 .37 J <.8 8 in. Mulberry

TW09 08/11/99 -- -- .32 J <.8 <10 <.8 .05 J <.8 20 in. Hackberry

TW10 08/11/99 -- -- <.8 <.8 <10 <.8 .12 J <.8 3 in. Chinese elm
Trees sampled near the former dry cleaning facility DF-1 10/20/99 1125 -- <0.8 <0.8 0.48 J <0.8 <0.8 <0.8 36 in. Chinese elm, 

DF-1 10/21/99 1125 R <.8 <.8 .41 J <.8 <.8 <.8 36 in. Chinese elm, DF-1 10/20/99 1140 -- <.8 <.8 7.61 J <.8 <.8 <.8 36 in. Chinese elm, DF-2 10/20/99 1130 -- <.8 <.8 1.07 J <.8 <.8 <.8 30 in. Silver maple, DF-2 10/21/99 1130 -- <.8 <.8 .95 J <.8 <.8 <.8 30 in. Silver maple, DF-3 10/20/99 1135 -- <.8 <.8 <10 <.8 <.8 <.8 30 in. Silver maple, 

DF-3 10/20/99 1135 -- <.8 <.8 <10 <.8 <.8 <.8 30 in. Silver maple, 

HS-1a 09/09/99 1615 -- <.8 <.8 <10 <.8 <.8 <.8 34 in. Chinese elm, 

HS-2a 09/09/99 1615 -- <.8 <.8 <10 <.8 <.8 <.8 10 in. Mulberry, 2 tr

HS-3a 09/09/99 1625 -- <.8 <.8 <10 <.8 <.8 <.8 20 in. Hackberry, so

HS-4a 09/09/99 1630 -- <.8 <.8 <10 <.8 <.8 <.8 20 in. Chinese elm, 

HS-5a 09/09/99 1635 -- <.8 <.8 <10 <.8 <.8 <.8 22 in. Redbud, south 

T201 07/13/99 1216 -- <.8 <.8 <10 <.8 <.8 <.8 34 in. Silver maple, 

T201 07/13/99 1216 R <.8 <.8 <10 <.8 <.8 <.8 34 in. Silver maple, T202 08/11/99 -- -- <.8 <.8 <10 <.8 <.8 <.8 12 in. Chinese elm, 

Count 32 16 4 1<1025 Minimum detected concentration 0.93 0.10 0.64 <10 1.45 1.32 Maximum detected concentration 161.92 3.14 0.64 <10 7.47 4.44 Average detected concentration 42.10 1.61 0.64 <10 4.46 2.43 Table 1. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from downtown New Haven

during 1999—Continued [All concentrations in micrograms per liter in headspace per kilogram of wet core; Rep, replicate; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; t-DCE, tr

--, no data; <, less than; in., trunk diameter in inches; J, estimated concentration below the method reporting limit] Tree identifier Date Time Rep PCE TCE cis-DCE t-DCE Benzene Toluene Descr
Assessment of Subsurface Contamination at the Front Street Site 11

residence between the site and the Missouri River, permission 

was given for the collection of tree-core samples in 2001, but 

permission for soil and ground-water sampling was not 

obtained until 2003. Results of tree-core sample analysis from 

this parcel were used to select locations for the collection of soil 

and ground-water samples.

Results of the tree-core sampling during the ESI/RI and RI 

indicate subsurface PCE contamination on the south and north 

sides of the Front Street building, and in an area extending from 

the building to the Missouri River (fig. 4). The area of contamination was estimated to be about 600 ft long and 200 to 300 ft 

wide. The largest PCE concentrations (370 to 3,850 μg-h/kg) 

detected within this area were in tree TW11 (a 6-in. diameter 

Chinese elm) adjacent to the south side of the building. Large 

PCE concentrations also were detected along the north side of 

the building in trees TW02 (35.4 to 1,017 μg-h/kg), TW06 (27.2 

to 1,410 μg-h/kg), and TW28 (146 to 1,090 μg-h/kg). The core 

sample from tree JS77, located on the private parcel between 

the Front Street building and the Missouri River, also contained 

a large PCE concentration (717 μg-h/kg).

Comparison of Tree-Core Sampling to Traditional Soil 

Sampling Methods

Results of the soil investigation indicated substantial PCE 

contamination at the site with PCE detected at 128 of the 144 

soil locations sampled (U.S. Environmental Protection Agency, 

2003). The soil samples were collected from a combination of 

soil borings made during the RI and from borings and excavations made during a 2000 USEPA emergency removal action to 

replace a contaminated municipal water-supply line and associated soils beneath Front Street (fig. 4). Soil samples from boreholes generally were collected every 2 ft in depth and most 

boreholes extended to the base of the alluvium (about 28 to 32 

ft deep beneath the site). The largest PCE concentrations [as 

large as 6,200,000 μg/kg (micrograms per kilogram)] were 

detected beneath the southeastern part of the Front Street building and along Front Street (fig. 4). In general, PCE concentrations and the lateral extent of PCE contaminated soils increased 

with increasing depth and reached a maximum at the 14- to 16-

ft depth interval.

Concentrations of PCE in trees appear to be a good indicator of PCE concentrations in subsurface soils. In general, PCE 

was detected in trees growing in areas where soil samples from 

less than 16 ft deep contained PCE concentrations greater than 

60 μg/kg, whereas trees growing outside of these areas generally contained little or no detectable PCE (fig. 4). A quantitative 

relation between PCE concentrations in tree-core samples and 

soil samples also was observed. Regression analyses indicate a 

statistically significant (probability values, p, less than 0.05) 

positive correlation between PCE concentrations in tree-core 

samples and soil samples collected from 4, 6, 8, 10, 12, and 16 

ft below the surface (fig. 5). Concentrations were converted to 

logarithms (base 10) because PCE concentrations in soil 

spanned more than 7 orders of magnitude, and PCE concentrations in tree cores spanned more than 4 orders of magnitude. 

Results of the regression analyses for each depth were similar 

with correlation coefficient (r2) values ranging from 0.88 to 

0.90. The best fit (r2 of 0.90) was a linear equation obtained 

between PCE concentrations in trees and soils at 12 ft deep:

 log[PCE in tree (μg-h/kg)] = 

0.598*log[PCE in soil (μg/kg) at 12 ft deep]

The regression constants were not significantly different 

from zero (p values much larger than 0.05). The similar r2

 values for the various depths probably are related to the correlation 

between PCE concentrations at various depths. In most locations where trees were cored, soil samples collected from 

between 4 to 16 ft deep had PCE concentrations of similar magnitudes.

Soil samples generally were collected for the purpose of 

mapping the extent of subsurface PCE contamination, and not 

for the expressed purpose of defining the relation between PCE 

concentrations in the tree and adjacent soil. Therefore, soil borings were not always located near each tree sampled and PCE 

concentrations in soil beneath each tree were estimated as a 

weighted average of PCE concentrations from the nearest three 

soil sample locations (in some cases several tens of feet from 

the sampled tree). However, soil borings were made adjacent to 

trees containing the largest PCE concentrations (TW02, TW06, 

TW08, TW11, and TW28).

The strong relation between PCE in trees and soil samples 

at the site may be related to PCE being sorbed to soils during 

periods of high ground-water levels and the probable shallow 

tree root depth compared to the average depth to ground water. 

During periods of high Missouri River stage, contaminated 

ground water that normally is 20 to 25 ft beneath the land surface rises to within 10 ft or less of the land surface, and PCE is 

sorbed to soils in what normally is the unsaturated zone. This 

mechanism explains the detection of PCE in soils above the 

water table outside of areas along Front Street where it was disposed (fig. 4) such as on the residential property between the 

site and the Missouri River (U.S. Environmental Protection 

Agency, 2003). For example, PCE concentrations in soil samples from the residential property gradually increased from 

below detection at the surface to a maximum of 180 μg/kg at 

depths of about 16 ft (probable top of the capillary fringe under 

normal river stages), then increase steadily to as large as 2,780 

μg/kg at depths below 25 ft (U.S. Environmental Protection 

Agency, 2003). Trees at the Front Street site are not flood-tolerant species and their root systems likely will not develop in 

the permanently saturated, oxygen limited (iron to sulfate 

reducing conditions) soils that exist beneath about 20 ft deep. 

Runoff from the site is restricted because of the flood protection 

levee, and the soils are silty-loams that have high infiltration 

rates leading to sufficient soil moisture contents (20 to 25 percent by weight) for tree growth throughout the year at depths 

below about 6 ft (U.S. Environmental Protection Agency, 

2003). Because of the sufficient supply of soil moisture, root 

systems in trees at the Front Street site probably develop at
12 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

llll l lllll l l l l l l l

l l l ll

lll l l l l l ll l l

Missouri River Missouri River

Wastewaterlagoon

Wastewaterlagoon

JS6

TCR0

JS6

TCR04

TA02

TA01

TB02

TW09

TB01

JS62

JS79

JS80

JS77

TW08

TW28 TW07TW06

TW05

TW04

TW02

JS64

TW03 TW17

JS78

JS66

JS65

JS113

JS67

TW16

TW14

TW01

TW22

TW18

TW19

TW12

TR02

TW11

TA02

TA01

TB02

TB01

TW09

TW08 JS80

JS62

JS79 JS77

TW07

TW06

TW05

TW04

TW28

TW03

TW17

TW16

JS78

JS64

JS67

JS65

JS113

JS66

TW14

TW22

TW18

TW19

TW12

TW01

TW02

TR02

TW11

Figure 4. Relation between average tetrachloroethene (PCE) concentrations in tree-core samples and PCE concentrations in soil at the Front Street site (1999–2003).

EXPLANATION

57,000 to 570,000570,000 to 10,000,000

00 20 METERS

100 FEET

Modified from U.S. Environmental Protection Agency (2003)

SUBSURFACE CONTAMINATION IDENTIFIED

BY TREE-CORE SAMPLESProbable contaminationMaximum contamination

CONTAMINATED WATER LINEFRONT STREET SITE PROPERTY LINEROAD OR CONCRETE SLABRAILROAD TRACK l l

PCE CONCENTRATION IN SOIL—Concentration in micrograms

per kilogram. Data from 14 to 15 feet deep. Individual soilsamples too numerous to plot

60 to 5,7005,700 to 19,00019,000 to 57,000

TREE-CORE SAMPLE AND IDENTIFIERAVERAGE PCE CONCENTRATION IN TREE-CORE

SAMPLE—Concentration in micrograms in headspaceper kilogram of wet core

Less than 0.10.1 to 9.910 to 99.9

100 to 9991,000 to 1,500

TR02

38o36'48"

38o36'53"

91o12'45" 91o12'40" 91o12'45" 91o12'40"

Front Street

Base from U.S. Geological Survey digital data, 1:100,000, 1927Universal Transverse Mercator projection,Zone 15

Front Street

Flood protection levee

lood pro F

ec t ion levee t

PCE IN TREE-CORE

SAMPLES

PCE IN SOIL

(NOTE: Soil samples

not plotted)

Cottonwood Street

Cottonwood Street
Assessment of Subsurface Contamination at the Front Street Site 13

depths less than about 10 to 12 ft. The suspected shallow root 

depths as compared to the average depth to ground water (20 to 

25 ft deep) is an important factor contributing to the strong relation between PCE in trees and soil at the site.

The strong relation between PCE concentrations in trees 

and soil at this site has important implications for the use of tree 

cores in mapping subsurface contamination by chlorinated solvents. Although Vroblesky and others (1999) first demonstrated 

that trees growing above a known plume of shallow (less than 5 

ft deep) contaminated ground water can uptake chlorinated solvents, results from the Front Street site indicate that where 

depths to contaminated ground water are deeper (20 to 25 ft), 

VOC concentrations in the soil or unsaturated zone may have 

more affect on the VOC concentrations detected in trees.

Comparison of Tree-Core Sampling to Ground-Water 

Sampling

Ground-water samples collected from a network of 7 monitoring wells and 21 temporary direct-push well screen locations during 1999–2003 indicate that a plume of PCE contaminated ground water extends from Front Street south of the Front 

Street building northeast to the Missouri River (fig. 6). The 

plume is about 600 ft long and less than 300 ft wide. The areal 

extent of the PCE plume defined by ground-water sample analyses is of similar size and shape to the subsurface plume estimated using the tree-core data (fig. 4). The core of the groundwater plume, which contains PCE concentrations between 500 

and 11,000 μg/L, is less than 100 ft wide (fig. 6). The largest 

PCE concentrations were detected in ground-water samples 

from beneath the east part of the Front Street building at temporary well screen locations G67 (11,000 μg/L), G50 (6,600 μg/

L), and G51 (6,100 μg/L). Large PCE concentrations also were 

detected about 500 ft downgradient (northeast) from the building near the boat ramp in samples from monitoring well TW-G 

(less than 1 to 670 μg/L) and temporary well screen locations 

GP22 (less than 130 to 1,100 μg/L) and GP28 (5.9 to 340 μg/L). 

PCE was not detected upgradient (south) from the site in monitoring well TW-A or west of the site in monitoring well TW-F.

A qualitative relation also exists between the detection of 

PCE in tree cores and the presence of PCE in ground water at 

the Front Street site. Trees overlying the ground-water PCE 

plume generally contained detectable concentrations of PCE, 

whereas trees outside the area of PCE contaminated ground 

water generally did not contain detectable concentrations of 

PCE (fig. 6). However, in contrast to the strong quantitative 

relation between PCE concentrations in tree cores and soil, the 

relation between PCE concentrations in trees and underlying 

ground water was less apparent (fig. 5). Regression analyses 

indicated a poor relation (r2 of 0.17) between PCE concentrations in tree cores and PCE concentrations in the underlying 

ground water. The regression constant was significantly different from zero (p value of 0.012) and was included in the regresLOG PCE IN GROUND-WATER SAMPLE,

IN MICROGRAMS PER KILOGRAM

Figure 5. Relation between tetrachloroethene (PCE) concentrations in tree-core samples to PCE concentrations in

soil and ground-water samples from the Front Street site.

PCE IN TREE-CORE SAMPLES, IN MICROGRAMS

IN HEADSPACE PER KILOGRAM OF WET CORE

LOG PCE IN SOIL SAMPLE AT 12 FEET DEEP,

IN MICROGRAMS PER KILOGRAM

NOTE: Error bars represent one standard deviation from the

mean PCE concentration detected in each tree sampled

log(PCE_tree) = 0.804 + 0.414log(PCE_gw)

r 2 = 0.17

p value = 0.001

10-1 100 101 102 103 104 105

log(PCE_tree) = 0.598log(PCE_soil12)

r 2 = 0.90

p value = 0.000

10-1

10-1

10-2

10-2

100

100

101

101

102

102

103

103

104

104 105 106
14 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

l l l ll l l l

l l l l l l l l l

llll l l llll l l l l l l l

Missouri River Missouri River

Wastewaterlagoon

Wastewaterlagoon

JS6

TCR

JS62 JS64

JS67

JS65

JS113

JS66 JS79

TA02

TA01

TB02

TB01 JS80

JS77

TW03

TW17

TW16

TW14

JS78

TW02

TW07

TW06

TW04

TW05

TW08

TW28

TW09

TW11

TR02

TW22

TW18

TW19 TW12 TW01

G67

G51

GP28

GP22

G50

TW-A

TW-B

TW-C

TW-D

TW-E

TW-F

TW-G

EXPLANATION

Modified from U.S. Environmental Protection Agency (2003)

Figure 6. Relation between average tetrachloroethene (PCE) concentrations in tree-core samples and PCE concentrations in ground-water samples at the Front Streetsite (1999–2003).

GROUND-WATER SAMPLE AND IDENTIFIER—Triangle

indicates temporary direct-push well screen; pentagonindicates monitoring well

MAXIMUM PCE CONCENTRATION IN GROUND-WATER

SAMPLE—Concentration in micrograms per liter

Less than 0.10.1 to 5.05.0 to 49.9

GROUND WATER CONTAINING PCE

Less than 5 micrograms per literGreater than 500 micrograms per literFRONT STREET SITE PROPERTY LINE

ROAD OR CONCRETE SLABRAILROAD TRACK l l

TREE-CORE SAMPLE AND IDENTIFIERAVERAGE PCE CONCENTRATION IN TREE-CORE

SAMPLE—Concentration in micrograms in headspaceper kilogram of wet core

Less than 0.10.1 to 9.910 to 99.9

100 to 9991,000 to 1,500

TR02 TW-C

50 to 499500 to 4,9995,000 to 11,000

Base from U.S. Geological Survey digital data, 1:100,000, 1927Universal Transverse Mercator projection,Zone 15 0

0 20 METERS

100 FEET

38o36'48"

38o36'53"

91o12'45" 91o12'40" 91o12'45" 91o12'40"

Front Street

Front Street

Flood protection levee

Flood p otection levee r

PCE IN TREE-CORE

SAMPLES

PCE IN GROUND-WATER

SAMPLES

Cottonwood Str ee t

Cottonwood Street
Assessment of Subsurface Contamination at the Former Dry Cleaning Facility 15

sion. This poor relation is in contrast to previous work that has 

shown direct relations between concentrations of TCE in trees 

and ground water or bulk solution concentrations in laboratory 

studies (Neitch and others, 1999; Vroblesky and others, 1999; 

Orchard and others, 2000; Ma and Burken, 2003).

The poor relation between PCE concentrations in trees and 

underlying ground water at the Front Street site probably occurs 

because the tree roots are not in contact with the ground water, 

and PCE sorbed to soils in the unsaturated zone is not in direct 

proportion to PCE concentrations in the underlying ground 

water. Because it is unlikely that roots of trees at the Front 

Street site are in direct contact with the water table, water (and 

its associated PCE) taken into the transpiration stream by roots 

is most likely from the capillary fringe or shallow unsaturated 

zone, and may be at or near equilibrium with PCE concentrations in soils. If PCE at the water table was being directly incorporated into the tree roots, diffusive exchange with PCE in soil, 

soil moisture, and vapors in the unsaturated zone would likely 

modify PCE concentrations in the transpiration stream moving 

up through the roots. Struckhoff (2003) has shown that diffusive 

exchange between roots and PCE vapor in the unsaturated zone 

can be as important or more important than PCE concentrations 

in the ground water. While Vroblesky and others (1999) demonstrated that concentrations of TCE and cis-DCE in trees at the 

Savannah River site reflected the distribution of TCE and cisDCE in the underlying shallow ground water, the depth to the 

contaminated ground water was less than about 5 ft. In contrast, 

Cox (2002) did not detect TCE in trees growing above a plume 

of TCE contaminated ground water at McChord Air Force Base 

(AFB) in Washington. Although TCE concentrations at the 

McChord AFB site and Savannah River site were of similar 

magnitude (tens to a few hundreds of micrograms per liter), the 

depth to ground water at the McChord AFB site (about 30 ft) 

was more than six times the depth to ground water at the Savannah River site. Cox (2002) postulated that the absence of TCE 

in trees at the McChord AFB site might be because ground 

water at the site was below the depth that tree roots growing at 

the site could reach in addition to cumulative losses within the 

plants. The poor quantitative relation between PCE in trees and 

ground water at the Front Street site is consistent with observations by Cox (2002) and indicates that the depth to the contaminated ground water is an important factor controlling VOC 

concentrations in trees.

Assessment of Subsurface Contamination at 

the Former Dry Cleaning Facility

The former dry cleaning facility near the intersection of 

Wall Street and Miller Street is about 500 ft southwest of the 

Front Street site (fig. 7). Because of its proximity to contaminated public water-supply wells W1 and W2 (fig. 1), the former 

dry cleaning facility was considered a possible source of the 

PCE contamination detected in wells W1 and W2 (Singleton, 

1987). However, no sampling was done at the former dry cleaning facility during the initial investigations conducted during 

the late 1980’s and early 1990’s (Singleton, 1987; Jacobs Engineering Group, Inc., 1994). Dry cleaning operations took place 

in the southeast corner of the basement of a small (about 35 by 

50 ft) two-story building, which currently (2003) is a private 

residence. Interviews of local residents conducted by the 

USEPA during the RI of the Front Street site determined that 

waste dry cleaning fluids were dumped on the land surface in a 

small (about 20 by 40 ft) area along a short (7 ft high) but steep 

(45 degree) slope behind the former dry cleaning facility. However, the interviews could not establish the types of dry cleaning 

fluids used, only that the fluids used were apparently flammable; therefore, probably not TCE or PCE (Shelley Brodie, U.S. 

Environmental Protection Agency, written commun., March 

2003). Because of the uncertainly regarding the type of dry 

cleaning fluids used, the absence of environmental samples 

from the site, and proximity to the contaminated city wells, the 

USEPA conducted reconnaissance sampling of the former dry 

cleaning facility as part of their investigation of the Front Street 

site. The site was selected for an initial tree-core reconnaissance 

because access to the area where waste dry cleaning fluid was 

reportedly dumped is limited by steep slopes and closely spaced 

homes.

Initial Site Assessment Using Tree Cores

Because of difficulty contacting various property owners 

at and in the vicinity of the former dry cleaning facility, the preliminary assessment of the site using tree-core sampling was 

conducted over a 4-month period from July through October 

1999. Core samples were collected from a total of 11 trees at the 

site and vicinity (fig. 7). Core samples were collected immediately down slope of the building where dry cleaning took place 

(trees DF-1, DF-2, and HS-3), within and near the area where 

dumping reportedly occurred (trees HS-1, HS-2, and HS-4) and 

along a short gravel drive (HS-5) near the dump area. Trees 

were sampled along the side most likely to face the dumping 

area. The surface of the dumping area was covered with rocks, 

gravel, and scrub brush and had obviously been disturbed. Core 

samples also were collected from two trees (T201 and T202) 

along an intermittent creek south of the dumping area. None of 

the core samples contained detectable concentrations of PCE or 

other chlorinated solvents. However, several unknown VOCs 

suspected to be hydrocarbons with GC retention times between 

vinyl chloride and cis-DCE were present in core samples from 

trees HS-1 and HS-5. 

Comparison of Tree-Core Sampling to Traditional Soil 

Sampling at the Former Dry Cleaning Facility

Five additional trees (DF101 through DF105) were cored 

in January 2002 to verify the results of the preliminary reconnaissance of the site. These trees were located within and 

slightly west and down slope of the reported dumping area (fig. 
16 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

7). Sample DF105 was a composite of two trees growing along 

the south property line in the back yard of an adjacent private 

residence. None of the trees cored in January 2002 contained 

detectable concentrations of PCE, but trees DF101, DF102, and 

DF105 contained trace concentrations (0.25 to 1.6 μg-h/kg) of 

toluene (table 2, at the back of this report), and sample DF104 

contained a trace concentration (0.73 μg-h/kg) of TCE. Because 

of the trace concentration of TCE detected in sample DF104, 

four soil borings (HSS01 to HSS04) were done in February 

2002. The soil borings were done using a hand auger and drilled 

to 3 ft deep. Soil samples were collected at 1 ft intervals and 

analyzed for VOCs by headspace using the portable GC and by 

the USGS contract laboratory in Arvada, Colorado, using 

USEPA method 8260. Soils in borings HSS01, HSS02, and 

Approximate area

where dry cleaning

waste was dumped Former dry cleaning

facility

&

TREE-CORE SAMPLE AND NUMBER— &

Tetrachloroethene (PCE) not detected

SOIL SAMPLE AND NUMBER—Maximum PCE

concentration in soil sample, in microgram per

kilogram

Not detected

0.1 to 0.2

HSS01

HSS04

T201 TW-A

0 100 200 FEET

0 25 50 METERS

Figure 7. Location of tree-core and soil samples at and in the vicinity of the former dry cleaning facility near

downtown New Haven, Missouri.

MONITORING WELL IN THE ALLUVIUM AND IDENTIFIER

CONTAMINATED PUBLIC WATER-SUPPLY WELL AND IDENTIFIER

INTERMITTENT STREAM

EXPLANATION

W2

Base from U.S. Geological Survey digital orthophoto quarter-quadrangle, 1:12,000, 1986

Universal Transverse Mercator projection

Zone 15

HSS04

HSS02

HSS03

HSS01

Miller

Street

Railroad Tracks

Farm supply and

feed mill

Front Street site

(100 feet)

Wall Street

W2 &

TW-A &

DF-3

DF-2

DF-1

DF103

DF104

DF102

DF101

HS-5

HS-2 HS-1

HS-3 HS-4

T201

DF105

T202

38o36'48"

38o

36'45"

91o12'50" 91o

12'47"
Practical Considerations in Using Tree-Core Sampling for Site Assessment 17

HSS03 were stained gray and appeared to contain lint or some 

other powdery material. The presence of stained soils is consistent with information provided by USEPA interviews, which 

indicated that the waste material from the dry cleaning facility 

was a gray color. The portable GC detected toluene (0.45 to 

21.44 μg-h/kg) in samples from boreholes HSS01, HSS02, and 

HSS03 and a possible trace concentration of PCE (0.16 μg-h/

kg) in the 1 ft deep sample from borehole HSS04. Laboratory 

samples did not contain detectable concentrations of PCE or 

other VOCs.

The results of soil sampling confirmed the tree-core data, 

indicating the absence of PCE contamination at the former dry 

cleaning facility. The presence of toluene in several trees and 

soil samples and gray stained soils suggests that tree-core and 

soil samples were collected in the area where the dry cleaning 

waste was disposed. The absence of PCE in tree cores at this site 

served as a negative control for tree-core sampling at other 

operable units at the Riverfront Superfund Site.

Practical Considerations in Using Tree-Core 

Sampling for Site Assessment

Data presented here and ongoing studies at the Riverfront 

Superfund Site have demonstrated that tree cores can be an 

effective tool for assessing the presence of subsurface PCE contamination. Data in this report are consistent with other investigations that indicated concentrations of TCE and cis-DCE in 

trees mimic concentrations of these compounds in underlying 

shallow (less than 10 ft deep) ground water (Vroblesky and others, 1999; Ma and Burken, 2003). However, Cox (2002) did not 

detect TCE in trees where the depth to the TCE contaminated 

ground water was about 30 ft. Research into the mechanisms of 

VOC incorporation and fate in trees is in its infancy and little is 

known about the interaction between the many environmental 

variables that affect tree growth and the distribution of VOCs in 

the subsurface. Some of these variables include the depth and 

concentrations of VOCs in the ground water, VOC concentration and distribution in soil and soil vapors, diffusion in the subsurface and diffusive losses from the tree trunk, variability 

between tree species, variability with tree size, age and root 

structure, concentration variability around the tree trunk, transpiration rate, and seasonal differences in ground-water concentrations, precipitation, and transpiration rate, among others. The 

following discussion presents some practical considerations 

and possible limitations on the use of tree coring for site assessment based on experiences at the Riverfront Superfund Site.

Diffusion Losses and Uptake, Partitioning, and 

Differences Between Species

Research has shown that VOC diffusion out of tree trunks 

is a significant loss mechanism to the atmosphere (Ma and 

Burken, 2002, 2003). More recently, it has been shown that diffusion between tree roots and vapor in the unsaturated zone can 

lead to significant losses, or uptake of PCE in trees (Struckhoff, 

2003). Diffusive loss leads to a profile of decreasing VOC concentrations in tree trunks with increasing height above land surface. Data presented in Vroblesky and others (1999) and from 

trees growing above a TCE plume at the Aberdeen Proving 

Ground (Ma and Burken, 2003) indicate that the decrease in 

VOC concentrations with increasing height is not linear. A similar non-linear decrease in PCE concentrations with increasing 

height was observed in trees TW02, TW08, and TW28 at the 

Front Street site (fig. 8). The observed decreases with increasing height in these trees can be closely approximated with an 

exponential function (r2

 = 0.96 to 0.99). However, a linear 

decrease in PCE concentrations with increasing height was 

observed in tree TW11 (r2 = 0.98). From the standard diffusion 

equation, the mass of PCE lost by diffusion from the trunk to the 

atmosphere should be proportional to the concentration gradient, surface area, and time (approximated by height), and 

inversely proportional to the path length (approximated by the 

tree radius). The non-linear decrease in PCE concentrations 

with increasing height in trees TW02, TW08, and TW28 is 

probably caused by diffusion loss being driven by a changing 

concentration gradient. For example, as PCE is lost from the 

transpiration stream between 1 and 2 ft in height, there is a 

smaller gradient of PCE (difference between PCE concentration 

inside and outside the tree) driving diffusion between 2 and 3 ft, 

and the proportion of PCE lost to PCE remaining, decreases 

each foot and asymptotically approaches zero.

The diameter of the tree trunk also affects the rate of diffusional loss from the tree. 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, decrease the concentration gradient (diffusive driving force), and result in a non-linear concentration loss with increasing height. For example, 

Struckhoff (2003) showed that a 0.5-in. diameter poplar cutting 

planted into contaminated soil or water has a 24 percent concentration loss in 5 in. of height, whereas tree TW11 (a 6.5-in. 

diameter Chinese elm) has the same percent loss in 5 ft of 

height—about a ten-fold difference. This difference is similar to 

the calculated volume-to-area ratios of trees (2 divided by the 

radius) with diameters of 0.5 and 6.5 in. of about 7. The linear 

loss in PCE concentrations with increasing height in tree TW11 

also may be a function of the growth pattern of the tree. Trees 

TW02, TW08, and TW28 have relatively straight trunks, 

whereas the trunk of tree TW11 (Chinese elm) forked about 

every 4 to 5 ft. Compared to the other trees, tree TW11 is 

unusual in that its incremental volume and surface area 

decreased as a linear function with height, and interestingly, so 

did its PCE concentrations.

In addition to diffusion loss of VOCs from the tree trunks, 

there is some indirect evidence that PCE in soil vapors can diffuse into tree roots at the Riverfront Superfund Site. This mechanism of PCE incorporation into trees at the site was postulated 

by Schumacher (2001). Concentrations of PCE in soil gas were 

measured monthly from July 2002 through April 2003 in samples collected along the north side of the Front Street building. 
18 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

Soil-gas samplers were installed in clusters at depths of 3.5, 9.0, 

12.0, and 14.5 ft deep adjacent to trees TW02, TW06, and 

TW08. A logarithmic increase (r2 of 0.92) in PCE concentration 

in soil gas with increasing depth was observed with the maximum detected PCE concentrations ranging from 1.1 ppmV 

(parts per million volume) at 3.5 ft deep to 104 ppmV at 14.5 ft 

deep (fig. 9). The dramatic increase in PCE concentration with 

increasing depth indicates that the diffusion of PCE into roots 

from vapors in the unsaturated zone may be significant. The 

average measured PCE concentration (about 50 ppmV) in soilgas samplers below 10 ft deep was smaller than the theoretical 

average concentration of 260 ppmV calculated using PCE concentrations, moisture contents, and organic carbon contents 

measured in soil samples from the site. During purging, the soilgas samplers lost vacuum within one to two seconds, indicating 

porous subsurface conditions. The smaller than expected measured PCE concentrations in soil gas may be related to vapor 

loss to the atmosphere.

An experiment was done to determine if PCE vapors in the 

unsaturated zone could be a source of PCE in trees. Two small 

(0.5-in. diameter by 16-in. long) poplar cuttings were planted 

above contaminated soils adjacent to the south side of the Front 

Street building, and two were placed above contaminated soils 

at another operable unit (OU2) (fig. 1). The poplar cuttings were 

planted in potting soil inside bags constructed from an agricultural mesh that excluded roots. The bags were planted above, 

but not within contaminated soils and watered weekly with tap 

water. After 2 months, the cuttings and soil inside the mesh bags 

were sampled. Two of the cuttings that survived contained measurable concentrations of PCE (80.1 μg-h/kg in the cutting from 

the Front Street site and 242 μg-h/kg in the cutting from OU2). 

No PCE was detected in soil samples from within the bags. A 

0 5 10 15 20

100

200

300

400

500

TW08

y = -147.25Ln(x) + 483.66

r 2 = 0.96

0 4 8 12 16

200

300

400

500

600

TW02 (average)

y = -109.83Ln(x) + 577.21

r 2 = 0.99

0 5 10 15 20

300

400

500

600

700

800

900

0 5 10 15

300

400

500

600

700

800

TW11

PCE CONCENTRATION, IN MICROGRAMS IN HEADSPACE PER KILOGRAM OF WET CORE

HEIGHT ABOVE LAND SURFACE, IN FEET

y = -28.851x + 768.1

r 2 = 0.98

Figure 8. Relation between tetrachloroethene (PCE) concentrations in tree-core samples and height

above the land surface.

TW28 (average)

y = -449.3Ln(x) + 1,579.2

r 2 = 0.97
Practical Considerations in Using Tree-Core Sampling for Site Assessment 19

soil-gas sampler placed within the mesh bag of a poplar cutting 

on the south side of the Front Street building contained PCE at 

about 0.2 ppmV (about 0.001 μg/L air). The detection of PCE 

in this soil-gas sampler and the poplar cuttings in the mesh bags 

strongly suggests that PCE in soil vapor accumulates in tree 

roots at this site.

During the 1999 initial assessment, it was thought that a 

significant fraction of VOCs in tree-core samples was within 

the water fraction of the core, and that partitioning from the core 

into the vial headspace was similar to that from water to air. As 

a result, VOC concentrations in tree-core samples were originally reported in units of micrograms per liter of core water 

(Schumacher, 2001). Other researchers such as Vroblesky and 

others (1999) have normalized VOC concentrations in core 

samples to core water content. While water content is important, recent studies by Ma and Burken (2002, 2003) and Struckhoff (2003) have shown that the predominant mass of VOCs in 

tree trunks resides in the wood tissue. Struckhoff (2003) calculated a PCE water-wood (Klw) partitioning coefficient of 0.049 

L/g (liter per gram) indicating that PCE is about 20 times more 

concentrated in the wood phase than the water phase. Core samples from trees at the Riverfront Superfund Site averaged about 

50 percent by weight water indicating that more than 95 percent 

of the PCE in the trees resides in the wood and not the transpiration stream. Field data collected from tree TW28 at the Front 

Street site substantiate the Klw value derived by Struckhoff 

(2003). Concentrations of PCE in sap samples collected from 

tree TW28 at 7.0 and 19 ft above the land surface were 36.8 and 

13.6 μg/L, respectively (table 2). These concentrations are comparable to concentrations of 12.9 and 10.1 μg/L calculated using 

PCE concentrations determined in core samples at these heights 

and the Klw (0.049 L/g) value determined by Struckhoff (2003).

Although concentrations of PCE may vary depending on 

the tree species sampled, data from the Front Street site were not 

conclusive. In general, there were few locations where multiple 

species of trees existed in proximity to one another. For example, the average PCE concentrations in core samples collected 

from tree TW28 on June 30, 2003, at heights of 3, 7, and 16 ft 

(587, 412, and 268 μg-h/kg) were about twice as large as the 

average PCE concentrations in core samples collected from tree 

TW08 at the same heights (334, 176, and 106 μg-h/kg). Tree 

TW28 is an 8-in. diameter Chinese elm and tree TW08 is an 8-

in. diameter mulberry that are growing less than 3 ft apart along 

the north side of the Front Street building. Concentrations of 

PCE in tree TW28 exhibited considerable directional variability 

that may be related to diffusion of vapors from beneath the 

building slab. The average PCE concentration on the north side 

of tree TW28 (277 μg-h/kg) was similar to the average PCE 

concentration on the south side of tree TW8 (253 μg-h/kg). The 

PCE concentration of 717 μg-h/kg in tree JS77 (an 18-in. diameter buckeye) was substantially larger than the PCE concentration of 90.3 μg-h/kg measured in a nearby sweet gum (tree 

JS80). Vroblesky and others (1999) noted differences in VOC 

concentrations between tree species at the Savannah River site 

with bald cypress, tupelo, and loblolly pine containing larger 

TCE concentrations than nearby oak and sweet gum. The limited data from the Front Street site suggest that, although there 

may be a difference in the uptake of PCE between different tree 

species (for example, elm and buckeye may uptake PCE to a 

greater extent than mulberry or sweet gum), this difference may 

be overshadowed by directional variability around the tree 

trunk.

Directional Variability in Tree Trunks

Concentrations of PCE exhibited directional variability 

around tree trunks, which makes the location of the core sample 

an important factor to consider when using tree coring as a site 

assessment tool. For example, PCE concentrations in core samples collected from tree TW02 at 1.5 and 7 ft above the land surface on July 9, 2003, varied by a factor of about 3 to 5 around 

the circumference of the tree (table 3). This variability is the 

result of spatial differences in PCE concentrations in soils 

around the tree and natural “twisting” of the tree trunk with 

growth. The smallest PCE concentrations (about 20 to 35 percent of the maximum concentration detected) at each height 

were on the southwest side of the tree (fig. 10). This part of the 

tree was growing above a concrete storm drain cover buried 

about 1.5 ft below the soil surface. The small PCE concentrations on this side of the tree were expected because the soils 

above this slab had no detectable PCE concentrations and presumably roots growing above the slab are in contact with uncontaminated soils and infiltration. The fact that any PCE was 

detected on this side of the tree may indicate diffusion from 

areas of larger PCE concentrations in the trunk or diffusion of 

PCE vapors through the unsaturated zone into the area above the 

concrete slab. From the exterior of the tree, it is apparent that the

y = 2.67Ln(x) + 2.62

r2 = 0.92

0

0 20 40 60 80 100 120

2

4

6

8

10

12

14

16

PCE CONCENTRATION IN SOIL GAS,

IN PARTS PER MILLION VOLUME

DEPTH, IN FEET BELOW LAND SURFACE

Figure 9. Relation between tetrachloroethene (PCE)

concentration in soil gas and depth below the land

surface along the north side of the Front Street

building.
20 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

trunk of this eastern red cedar twists in a clockwise direction.

The PCE concentrations reflect this twisting of the trunk as the 

maximum concentration shifted from east at 1.5 ft in height to 

the southeast at 7 ft in height (fig. 10). The largest concentration 

detected at the 7 ft height (921 μg-h/kg) actually was about 20 

percent larger than the maximum concentration detected at the 

1.5 ft height (755 μg-h/kg). Diffusion from the trunk should 

cause concentrations to decrease with increasing height above 

the land surface, and the larger concentration in the 7 ft sample 

suggests that the density of sampling points around the tree was 

not sufficient to completely resolve the directional variability 

around the trunk. 

Directional variability also was observed in tree TW28. 

This tree is growing adjacent to the Front Street building, and it 

was impossible to core all sides of the tree at various heights 

above land surface. Core samples collected from the south side 

of the tree had almost four times the PCE concentrations of 

those collected from the north side of the tree (fig. 11). The 

large PCE concentrations on the south side of this tree compared to the north are unexpected because PCE concentrations 

in soil and ground-water samples in proximity to this tree are 

similar. Because this tree is growing adjacent to the building, it 

is possible that roots on the south side must reach deeper to 

obtain sufficient soil moisture, or that the building slab acts like 

a cap trapping PCE vapors in localized areas. Soil samples collected adjacent to tree TW28 indicates a dramatic increase in 

PCE concentrations from less than 500 μg/kg at less than 10 ft 

deep to more than 7,000 μg/kg at depths below 14 ft (U.S. Environmental Protection Agency, 2003). Large concentrations of 

PCE vapors in the unsaturated zone were observed during the 

excavation of a contaminated water line beneath Front Street on 

the south side of the building, and it is possible that these vapors 

may be migrating through the gravel backfill beneath the building slab in the vicinity of tree TW28.

The directional variability in very small diameter trees 

may not be evident because of their small root footprint, the 

large ratio of core sample to trunk volume, and the fact that a 

single core may easily penetrate nearly the entire diameter of 

the tree. Ma and Burken (2003) showed that TCE concentrations decreased towards the exterior of a hybrid poplar tree 

growing at the Aberdeen Proving Ground site. While providing 

additional evidence for diffusion, the decrease toward the exterior of the tree indicates that core samples collected from larger 

trees may underestimate VOC concentrations in the trunk 

Table 3. Variation in tetrachloroethene (PCE) concentrations in the trunk of tree TW02 with direction 

and height above the land surface

[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene]

Tree identifier

Height above 

the land surface 

(feet) Date PCE

Azimuth 

(degrees from 

true north)

OU1-TW02 1 06/30/03 1,010 75

OU1-TW02 1 06/30/03 339 255

OU1-TW02 1 06/30/03 360 5

OU1-TW02 1.5 07/09/03 368 30

OU1-TW02 1.5 07/09/03 755 75

OU1-TW02 1.5 07/09/03 329 120

OU1-TW02 1.5 07/09/03 415 165

OU1-TW02 1.5 07/09/03 252 210

OU1-TW02 1.5 07/09/03 480 280

OU1-TW02 1.5 07/09/03 286 345

OU1-TW02 3 06/30/03 685 75

OU1-TW02 3 06/30/03 228 255

OU1-TW02 3 06/30/03 506 5

OU1-TW02 6 07/09/03 404 55

OU1-TW02 6 07/09/03 921 120

OU1-TW02 6 07/09/03 423 165

OU1-TW02 6 07/09/03 179 210

OU1-TW02 6 07/09/03 219 255

OU1-TW02 6 07/09/03 404 300

OU1-TW02 6 07/09/03 437 10

OU1-TW02 7 06/30/03 386 75

OU1-TW02 7 06/30/03 151 255

OU1-TW02 7 06/30/03 543 5

OU1-TW02 15 06/30/03 303 75

OU1-TW02 15 06/30/03 249 255
Practical Considerations in Using Tree-Core Sampling for Site Assessment 21

Concete drainage ditch

Storm

sewer drop

box

Concrete slab

Front Street Building

Concrete slab

Property fence

Fence post

0 20 40 60 80 100 0 20 40 60 80 100

1.5 FEET ABOVE THE LAND SURFACE 7.0 FEET ABOVE THE LAND SURFACE

PERCENTAGE OF THE MAXIMUM PCE CONCENTRATION DETECTED AT EACH

HEIGHT. DIRECTION IN DEGREES FROM NORTH

Figure 10. Directional variability in tetrachloroethene (PCE) concentrations in core samples

from an eastern red cedar tree (TW02).

Not to Scale

0O

330O

300O

270O

240O

210O

180O

150O

120O

90O

60O

30O

TW02

0O

330O

300O

270O

240O

210O

180O

150O

120O

90O

60O

30O

N

Soil and soil-gas

sample location

Soil boring done during the

remedial investigation

(U.S. Environmental Protection

Agency, 2003)

TW02
22 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

because they are sampling a disproportionately larger volume of 

wood that contains smaller VOC concentrations.

Sensitivity of Tree-Core Sampling to Detect 

Subsurface Contamination

An important consideration in using tree-core analysis to 

assess subsurface VOC contamination is the overall sensitivity 

of the technique to detect contamination. A wide variety of factors undoubtedly affect the ratio of VOCs such as PCE in a tree 

to concentrations in the underlying soil, soil vapors, and ground 

water. Laboratory hydroponic studies (Ma and Burken, 2002, 

2003) have shown that TCE concentrations in the transpiration 

stream of hybrid poplar trees are about 0.2 to 0.75 times the concentration observed in simulated ground water. However, these 

studies were performed at simulated ground-water TCE concentrations of 50,000 μg/L. Of interest for the Riverfront Superfund Site was an estimate of the potential lower threshold of 

ground-water concentrations that could possibly be detected in 

trees; that is, the sensitivity of the method to detect subsurface 

contamination. 

A field hydroponic experiment was conducted to provide 

an estimate of the maximum sensitivity of tree-core samples to 

detect PCE contamination in ground water in contact with the 

tree roots. In the experiment, six hybrid poplar cuttings (approximately 0.5-in. diameter by 12-in. long) were planted directly 

into each of two PCE contaminated streams, the 500 tributary 

and the 210 tributary (fig. 1). The cuttings were planted at lowflow conditions on July 30, 2003, and removed 8 days later. The 

500 tributary is southwest of operable unit OU2, and is affected 

by PCE contamination from that facility (U.S. Environmental 

Protection Agency, 2003). The 210 tributary is affected by an 

unknown PCE source in operable unit OU4. Stream discharge 

and PCE concentrations were measured at days 1 and 8. On day 

8, the cuttings were removed and samples from them were analyzed by headspace GC as previously described. During the 

experiment, the average PCE concentration in water samples 

collected from the 500 tributary was 83 μg/L and its discharge 

was estimated at 18 gal/min (gallons per minute). The 210 tributary water samples contained an average PCE concentration of 

22 μg/L and had an estimated discharge of about 0.03 gal/min.

Samples from poplar cuttings placed in the 500 tributary 

contained an average PCE concentration of 135 μg-h/kg in the 

stem sampled just above the water, yielding a calculated transpiration stream concentration of 14 μg/L. Samples from cuttings placed in the 210 tributary contained an average PCE concentration of 31 μg-h/kg in the stem sampled just above the 

water surface, and a calculated transpiration stream concentration of 4.6 μg/L. The above concentrations were calculated 

using the measured headspace concentrations of PCE, wet and 

dry mass of core samples, and water-wood (Klw) and air-plant 

or air-core (Kaw) partitioning coefficients for PCE in hybrid 

poplar trees reported by Struckhoff (2003). The relations 

between PCE concentrations in the vapor (headspace), wood 

(dry core), and liquid phase (water in the core) are: 

where:

Cdw = the PCE concentration in the dry wood (dried core 

sample), in milligrams per gram;

Cl = the PCE concentration in the aqueous phase in the 

core sample (such as transpiration stream), in milligrams per 

liter;

Ct = the PCE concentration in the plant (wet core sample), in micrograms per gram; and 

Ca = the PCE concentration in the air or headspace, in 

micrograms per liter.

These results lead to a PCE transpiration stream concentration factor (TSCF) of about 0.2. The calculated TSCF is the 

ratio of the PCE concentration in the transpiration stream to the 

PCE concentration in the water entering the roots (average PCE 

concentration in the tributaries). Because these trees were sampled directly above the water in which they were growing, there 

was very little chance for PCE to diffuse from the tree stem into 

the atmosphere. These results represent the anticipated upper 

limit of PCE transport in a poplar tree compared to the ground 

water in contact with the roots under field conditions. The overall findings of this report and related research (Struckhoff, 

2003) introduce a new mechanism, vapor phase exchange, in 

VOC uptake and translocation. The degree of vapor phase 

exchange in the subsurface can then alter the observed TSCF at 

different sites.

Klw 0.049

Cdw

Cl

---------, Kaw 0.0081 Ct

Ca

= = = = -----

0

200

400

600

800

1,000

1,200

1,400

3 5 7.5 12.5 16.5

Figure 11. Directional variability in tetrachloroethene

(PCE) concentrations in core samples collected from

tree TW28 on June 30, 2003.

HEIGHT ABOVE LAND SURFACE, IN FEET

PCE CONCENTRATION, IN MICROGRAMS IN HEADSPACE

PER KILOGRAM OF WET CORE

North side of tree

South side of tree

TW28
Summary and Conclusions 23

A comparison of the ratios of PCE concentration in the 

poplar cuttings and streams in the field hydroponic tests (about 

1.4 to 1.6) indicates that at a headspace method detection limit 

(MDL) of about 0.8 μg-h/kg, a PCE concentration of 0.5 μg/L 

theoretically could be detected in ground water using tree-core 

analysis. This is a “best-case scenario”, however, and this sensitivity cannot be achieved in the natural settings because the 

field hydroponic experiment did not take into account losses 

within the roots and trunk.

A better indication of the practical sensitivity of the treecore method is the ratio of PCE concentrations in core samples 

collected from trees growing adjacent to the 500 and 210 tributaries to those in the water. Core samples collected from willow 

trees adjacent to the 500 tributary at the conclusion of the field 

hydroponic experiment in 2003 contained an average PCE concentration of 10 μg-h/kg; using the average PCE concentration 

in tributary 500 (83 μg/L), a tree core/water ratio of about 0.1 is 

obtained. Core samples collected during April 2001 from several hackberry, elm, and oak trees growing along the 210 tributary contained estimated PCE concentrations of 0.23 to 0.52 μgh/kg (average of 0.4 μg-h/kg) (U.S. Environmental Protection 

Agency, 2003). The average PCE concentration along the reach 

of the 210 tributary during April 2001 when the tree-core samples were collected was 12 μg/L (U.S. Environmental Protection Agency, 2003), giving a tree core/water ratio of about 0.03. 

A comparison of these ratios to the headspace MDL of about 0.8 

μg-h/kg indicates that detectable PCE concentrations should be 

present in trees in contact with ground water containing PCE 

concentrations in the range of 8 to about 30 μg/L. Even under 

the best conditions, it seems unlikely that analysis of tree cores 

at this site could reliably detect ground-water contamination at 

the current MCL of 5 μg/L or smaller. 

The sensitivity of tree cores to detected PCE contamination in soils is difficult to estimate because PCE concentrations 

in soils at OU1 typically are large (tens of thousands of micrograms per kilogram or more) and because of the potential for a 

mixture of contaminated soil, soil vapor, and ground water at 

most locations at OU1. Detectable concentrations of PCE have 

been found in core samples from trees at the Front Street site 

that are growing in soil contaminated with as little as a few tens 

to hundreds of micrograms per kilogram. In addition, PCE was 

detected in hybrid poplar cuttings planted in soils at operable 

unit OU2 that contained PCE concentrations less than 1,000 μg/

kg. The data indicate that PCE should be present in core samples from trees growing in soils containing PCE concentrations 

of several hundred micrograms per kilogram or less.

Summary and Conclusions

Tree-core sampling has been a reliable and inexpensive 

tool to quickly assess the presence of shallow (less than about 

30 feet deep) tetrachloroethene (PCE) and trichloroethene 

(TCE) contamination in soils and ground water at the Riverfront 

Superfund Site. Tree-core sampling was used during the initial 

assessment of two sites, the Front Street site (operable unit 

OU1), and the former dry cleaning facility, that are part of the 

overall Riverfront Superfund Site. Results of tree-core sampling were later compared to, and confirmed by, traditional soil 

and ground-water sampling at these two sites. Tree-core sampling detected the presence of subsurface PCE contamination at 

the Front Street site and beneath private property downgradient 

from the site. Tree-core sampling did not indicate PCE contamination at the former dry cleaning facility, a finding that was 

confirmed by later soil sampling.

The Front Street site is on the Missouri River alluvium and 

has large PCE concentrations in soil [as large as 6,200,000 μg/

kg (micrograms per kilogram)] and ground water [as large as 

11,000 μg/L (micrograms per liter)]. The lateral extent of PCE 

contamination in trees at this site was in close agreement with 

the extent of subsurface PCE contamination determined using 

traditional soil and ground-water sampling. Trees growing in 

soils containing PCE concentrations of 60 to 5,700 μg/kg or 

larger, or overlying ground water containing PCE concentrations in the tens to as large as 11,000 μg/L, generally contained 

detectable concentrations of PCE. Depth to contaminated 

ground water is about 20 to 25 feet below the land surface.

A variety of conventions have been used to express volatile organic compound (VOC) concentrations in tree-core samples. The convention chosen for this report was to express concentrations as mass in the vial headspace per mass of wet core. 

This convention requires that only the volume of the core placed 

in the vials be known. The core volume was estimated from the 

mass of core placed in the vial assuming that the core density 

was 1.0 g/cm3

 (gram per cubic centimeter). This assumption 

introduces a small (less than 5 percent) error in the calculated 

headspace concentrations at wood densities ranging from 0.6 to 

1.0 g/cm3

 that are typical for trees growing at the site. Another 

popular convention is to express VOC concentrations as concentration in the headspace per mass of water in the core. This 

convention may introduce error because the partitioning coefficients generally are not known for each compound of interest 

and each tree species sampled.

Significant quantitative relations [probability (p) values of 

less than 0.05 and correlation coefficient (r2

) values of 0.88 to 

0.90] were found between PCE concentrations in trees and subsurface soils between 4 and 16 feet deep. The best fit (r2 of 0.90) 

was obtained between PCE in trees and soils at 12 feet below 

the surface according to the relation log(PCE in tree, in micrograms in headspace per kilogram of wet core) = 0.598*log(PCE 

in soil, in micrograms per kilogram). The relation between PCE 

concentrations in trees and underlying PCE contaminated 

ground water was less apparent (r2

 value of 0.17). The quantitative relation between PCE concentrations in trees and soils at 

this site is thought to represent the distribution of PCE in soils 

and soil vapors caused by direct disposal of PCE to the surface 

in some parts of the site and by the sorption of PCE to soils in 

downgraident areas caused by seasonal rises in underlying contaminated ground water. The seasonal rises are driven by 

changes in stage of the Missouri River. 
24 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003

While it was beyond the scope of this field-oriented study 

to investigate the various mechanisms that affect the incorporation and loss of PCE in trees, several observations consistent 

with published studies were noted. An exponential decrease in 

PCE concentrations in tree-core samples with increasing height 

above the land surface was observed in most trees. This loss was 

consistent with diffusion of VOCs from tree trunks postulated 

by other researchers at the Savannah River site in the late 

1990’s and recently confirmed in laboratory studies at the University of Missouri-Rolla. The rate of loss also appeared to be a 

function of the size and growth characteristics of the tree. Loss 

of PCE in small (0.5-inch) diameter trees was observed to occur 

at a rate more than ten times faster than in trees 6.5 inches in 

diameter. In addition to loss of PCE by diffusion, there is indirect evidence from the site that PCE vapors in the unsaturated 

zone can diffuse into tree roots. PCE was observed in poplar 

tree cuttings planted in uncontaminated potting soil above PCE 

contaminated soils at the site. Soil-gas measurements confirmed the presence of PCE vapor adjacent to the roots of the 

poplar cuttings and PCE concentrations in soil gas were 

observed to increase logarithmically with increased depth at the 

site.

Concentrations of PCE also exhibited directional variability around the tree trunks. Three- to five-fold concentration differences were observed around the trunks of several trees growing along the north side of the Front Street building. In one tree, 

the directional differences were attributable to spatial differences in PCE concentrations in soils around the tree. In the other 

instance, the differences may be caused by diffusion of PCE 

vapors in the unsaturated zone into the tree roots. Directional 

differences in PCE concentrations around the tree trunks also 

were related to natural “twisting” of tree trunks. PCE concentrations may be dependent upon the tree species, with Chinese elm 

and buckeye tending to have larger concentrations than adjacent 

or nearby mulberry or sweet gum. The concentration differences between species at this site may be overshadowed by 

directional variability around the tree trunks.

The sensitivity of tree-core sampling to detect subsurface 

contamination was estimated using measured PCE concentrations in trees growing along contaminated tributaries at the Riverfront Superfund Site and from field hydroponic experiments. 

Data collected from trees growing along PCE-contaminated 

streams and hybrid poplar cuttings planted in these streams 

indicate that tree-core sampling can be used to detect PCE concentrations as small as about 8 to 30 μg/L in shallow ground 

water at this site. This range assumes that the tree roots are in 

direct contact with the contaminated ground water, and that the 

depth to ground water is less than a few feet deep. The sensitivity of tree cores to detected PCE contamination in soils is difficult to estimate because PCE concentrations in soils at the Front 

Street site typically are large (tens of thousands of micrograms 

per kilogram or more), and because a mixture of contaminated 

soil, soil vapor, and ground water is present at most locations at 

the Front Street site. The data indicate that PCE should be 

present in core samples from trees growing in soils containing 

PCE concentrations of several hundred micrograms per kilogram or less.

References

Black and Veatch Special Projects Corporation, 2003, Feasibility study report, Riverfront Superfund Site, New Haven, Missouri—Volume 1, Operable Unit 1 Front Street site and 

Volume 2, Operable Unit 3, old city dump February 28, 

2003: U.S. Environmental Protection Agency, contract 68-

W5-0004, work assignment 063-RICO-07PY.

Burken, J.G., and Schnoor, J.L., 1998, Predictive relationship 

for uptake of organic contaminants by hybrid poplar trees: 

Environmental Science and Technology, v. 32, no. 21, p. 

3,379–3,385.

Compton, H.R., Haroski, D.M., Hirsh, S.R., and Wrobel, J.G., 

1998, Pilot-scale use of trees to address VOC contamination, 

in Wickramanayake, G.B., and Hinchee, R.E., eds., Phytoremediation of recalcitrant organic compounds: Monterey, 

Calif., Battle Press, p. 245–249.

Cox, S.E., 2002, Preliminary assessment of using tree-tissue 

analysis and passive-diffusion samplers to evaluate trichloroethene contamination of ground water at Site SS-34N, 

McChord Air Force Base, Washington, 2001: U.S. Geological Survey Water-Resources Investigations Report 02–4274, 

13 p.

CRC Press Inc., 1989, Density of various solids in Weast, R.C., 

Astle, M.J., and Beyer, W.B., eds., Handbook of chemistry 

and physics: Boca Raton, Fla., 69th Edition.

Jacobs Engineering Group, Inc., 1994, Expanded site inspection 

report for New Haven public water supply site, New Haven, 

Missouri: U.S. Environmental Protection Agency Region 7, 

contract No. 68-W8-0122, 11 p.

Ma, Xingmao, 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. 

4,663–4,668.

Ma, Xingmao, and Burken, J.G., 2003, TCE diffusion to the 

atmosphere in phytoremediation applications: Environmental Science and Technology, v. 37, no. 11, p. 2,534–2,539.

Nietch, C.T., Morris, J.T., and Vroblesky, D.A., 1999, Biophysical mechanisms of trichloroethene uptake and loss in baldcypress growing in shallow contaminated groundwater: 

Environmental Science and Technology, v. 33, no. 17, p. 

2,899–2,904.

Orchard, B.J., Doucette, W.J., Chard, J.K., and Bugbee, B., 

2000, Uptake of trichloroethene by hybrid poplar trees grown 

hydroponically in flow-through plant growth chambers: 

Environmental Toxicology and Chemistry, v. 19, no. 4, p. 

895–903.

Schumacher, J.G., 2001, Detection of ground-water contamination through analysis of tree-ring tissue: Charleston, South 

Carolina, presented at the Annual Meeting of the U.S. Geo-
References 25

logical Survey Department of Defense Environmental Conservation (DODEC) Program, May 1–4, 2001.

Singleton, K.C., 1987, Hazardous waste unit hazardous waste 

site preliminary assessment report—New Haven Public 

Water Supply: Missouri Department of Natural Resources, 

St. Louis Regional Office, 6 p.

Struckhoff, G.C., 2003, Uptake of PCE vapor by 

plants—Impacts for phytoremediation: Rolla, University of 

Missouri, Department of Environmental Engineering, unpublished M.S. thesis, 57 p. 

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, 2003, 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 pages plus appendixes.

Vroblesky, D.A., Nietch, C.T., and Morris, J.T., 1999, Chlorinated ethenes from groundwater in tree trunks: Environmental Science and Technology, v. 33, no. 3, p. 510–515.
TABLE
Table 29

Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 2000–2003[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated 

concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream]

Tree identifier

Height 

above land 

surface 

(feet) Date PCE TCE cis-DCE Benzene Toluene Comments

Trees sampled at the Front Street site

OU1-JS113 3 09/05/01 0.88 <0.8 <10 <0.8 <0.8 20 in. AppleOU1-JS62 3 04/18/01 1.12 <.8 <10 <.8 <.8 10 in. Ornamental cherryOU1-JS62 3 04/18/01 .58 J <.8 <10 <.8 <.8 10 in. Ornamental cherryOU1-JS63 3 04/18/01 .59 J <.8 <10 <.8 <.8 20 in. BoxelderOU1-JS63 3 04/18/01 .25 J <.8 <10 <.8 <.8 20 in. BoxelderOU1-JS64 3 04/18/01 32.8 .18 <10 <.8 <.8 13 in. PecanOU1-JS64 3 04/18/01 26.5 .10 <10 <.8 <.8 13 in. PecanOU1-JS64 0 09/05/01 <.8 <.8 <10 <.8 .24 J 11 in. Apple, NW side of treeOU1-JS64 0 09/05/01 <.8 <.8 <10 <.8 .17 J 11 in. Apple, NW side of treeOU1-JS64 0 09/05/01 <.8 <.8 <10 <.8 .18 J Apple core, SO side of treeOU1-JS64 3 09/05/01 117.25 J <.8 .04 J <.8 <.8 13 in. PecanOU1-JS65 3 04/18/01 4.43 .56 2.00 J <.8 <.8 10 in. Mulberry, 3 trunksOU1-JS66 3 04/18/01 .72 J .07 .19 J <.8 <.8 11 in. AppleOU1-JS66 3 04/18/01 .85 .12 .24 J <.8 <.8 11 in. AppleOU1-JS66 0 09/05/01 <.8 <.8 <10 <.8 <.8 Apple fruit sample OU1-JS66 0 09/05/01 <.8 <.8 <10 <.8 <.8 Apple fruit sample OU1-JS66 0 09/05/01 .1 J <.8 <10 <.8 <.8 Apple fruit sample OU1-JS66 3 09/05/01 .96 <.8 <10 <.8 <.8 10 in. AppleOU1-JS67 3 04/18/01 14.5 .03 .1 J <.8 <.8 13 in. PecanOU1-JS67 3 04/18/01 7.47 .03 .1 J <.8 <.8 13 in. PecanOU1-JS68 3 04/18/01 <.8 <.8 <10 <.8 <.8 17 in. Silver mapleOU1-JS70 3 04/19/01 <.8 <.8 <10 <.8 <.8 8 in. AshOU1-JS77 3 04/21/01 717 6.48 <10 <.8 <.8 18 in. Buckeye

OU1-JS78 3 04/21/01 16.4 .09 <10 <.8 <.8 10 in. MulberryOU1-JS79 3 04/21/01 6.54 <.8 <10 <.8 <.8 9 in. WalnutOU1-JS80 3 04/21/01 90.3 .59 <10 <.8 <.8 34 in. Sweet gumOU1-TA02 3 04/19/01 .41 J <.8 <10 <.8 <.8 10 in. BirchOU1-TCR01 3 11/27/00 <.8 <.8 <10 <.8 <.8 8 in. Sycamore, next to well TW-GOU1-TCR02 3 11/27/00 <.8 <.8 <10 <.8 <.8 14 in. Boxelder, west TW-G (xylene and ethyl benzene detected)OU1-TCR03 3 11/27/00 <.8 <.8 <10 <.8 <.8 10 in. Boxelder, 2 trunks
30 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003 Trees sampled at the Front Street site—Continued OU1-TCR04 3 11/27/00 0.98 <0.8 1.24 <0.8 <0.8 8 in. Sycamore OU1-TCR05 3 11/27/00 <.8 <.8 <10 <.8 <.8 14 in. Sycamore OU1-TCR06 3 11/27/00 <.8 <.8 <10 <.8 <.8 8 in. Boxelder OU1-TCR07 3 11/27/00 <.8 <.8 <10 <.8 <.8 13 in. Rock elm OU1-TCR08 3 11/27/00 <.8 <.8 <10 <.8 <.8 6 in. Sycamore, 2 trunks OU1-TW01 3 04/11/01 <.8 <.8 <10 <.8 <.8 11 in. Twin mulberry OU1-TW01 3 04/11/01 .33 J .72 J 6.0 J <.8 <.8 11 in. Twin mulberry OU1-TW02 3 06/29/00 197 <.8 <10 <.8 25.1 10 in. Eastern red cedar OU1-TW02 3 02/06/01 35.4 .15 J .2 J .05 J 3.39 10 in. Eastern red cedar OU1-TW02 3 04/11/01 254 .72 J 5.8 J <.8 9.19 10 in. Eastern red cedar OU1-TW02 3 04/11/01 302 3.41 14.7 <.8 57.6 10 in. Eastern red cedar OU1-TW02 3 04/11/01 141 <.8 1.3 J <.8 28.9 10 in. Eastern red cedar OU1-TW02 3 06/27/01 130 .47 J .2 J 2.19 7.58 10 in. Eastern red cedar OU1-TW02 3 09/05/01 272 8.23 <10 <.8 17.8 10 in. Eastern red cedar OU1-TW02 3 11/27/01 270 22.2 1.4 J <.8 50.1 10 in. Eastern red cedar OU1-TW02 3 02/12/02 148 <.8 5.5 J <.8 7.51 10 in. Eastern red cedar OU1-TW02 3 07/01/02 1,020 <.8 <10 <.8 <.8 10 in. Eastern red cedar OU1-TW02 3 07/01/02 831 <.8 <10 <.8 <.8 10 in. Eastern red cedar OU1-TW02 3 07/01/02 601 <.8 <10 <.8 <.8 10 in. Eastern red cedar OU1-TW02 3 06/30/03 316 <.8 <10 <.8 64.8 10 in. Eastern red cedar OU1-TW03 3 02/06/01 14.5 .27 .2 J .22 J <.8 6 in. Chinese elm OU1-TW03 3 04/11/01 15.6 .30 <10 <.8 <.8 6 in. Chinese elm OU1-TW03 3 04/11/01 1.79 .26 <10 <.8 <.8 6 in. Chinese elm OU1-TW03 3 04/11/01 1.84 <.8 1.2 J <.8 <.8 6 in. Chinese elm OU1-TW03 3 02/12/02 11.6 .89 6.5 J <.8 <.8 6 in. Chinese elm OU1-TW04 3 04/11/01 32.6 <.8 2.35 <.8 <.8 3 in. Mulberry, 2 trunks OU1-TW04 3 04/11/01 30.3 <.8 10.0 <.8 <.8 3 in. Mulberry, 2 trunks OU1-TW04 3 04/11/01 1.51 <.8 3.0 J <.8 <.8 3 in. Mulberry, 2 trunks OU1-TW06 3 06/29/00 105 1.89 <10 <.8 <.8 3 in. Mulberry OU1-TW06 3 02/06/01 27.2 .15 5.6 J .12 J <.8 3 in. Mulberry Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 2000–2003—Continued [All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream] Tree identifier Height above land surface (feet) Date PCE TCE cis-DCE Benzene Toluene Comments
Table 31

Trees sampled at the Front Street site—Continued

OU1-TW06 3 06/27/01 82.1 10.2 0.9 J 0.04 J <0.8 3 in. MulberryOU1-TW06 3 09/05/01 255 3.23 <10 <.8 <.8 3 in. MulberryOU1-TW06 3 11/27/01 166 41.5 <10 <.8 <.8 3 in. MulberryOU1-TW06 3 02/12/02 240 3.78 <10 <.8 <.8 3 in. MulberryOU1-TW06 3 06/28/02 1,411 <.8 <10 <.8 <.8 3 in. MulberryOU1-TW06 3 06/28/02 696 <.8 <10 <.8 <.8 3 in. MulberryOU1-TW06 3 06/28/02 490 <.8 <10 <.8 <.8 10 in. CottonwoodOU1-TW07 3 04/11/01 10.9 <.8 <10 <.8 <.8 10 in. CottonwoodOU1-TW07 3 04/11/01 6.70 <.8 1.3 J <.8 <.8 10 in. CottonwoodOU1-TW07 3 04/11/01 .5 J <.8 5.7 J <.8 <.8 10 in. CottonwoodOU1-TW07 3 11/27/01 33.0 <.8 235 <.8 <.8 10 in. CottonwoodOU1-TW08 3 06/29/00 151 2.07 <10 <.8 <.8 8 in. MulberryOU1-TW08 3 11/27/01 293 30.8 <10 <.8 <.8 8 in. MulberryOU1-TW08 3 02/12/02 158 2.96 <10 <.8 <.8 8 in. MulberryOU1-TW08 3 02/12/02 113 2.28 <10 <.8 <.8 8 in. MulberryOU1-TW08 3 07/29/02 522 <.8 <10 <.8 <.8 8 in. MulberryOU1-TW08 1 06/30/03 736 .77 <10 <.8 <.8 8 in. Mulberry, NE sideOU1-TW08 1 06/30/03 194 .20 <10 <.8 <.8 8 in. Mulberry, NW sideOU1-TW08 1 06/30/03 544 .57 <10 <.8 <.8 8 in. Mulberry, SO sideOU1-TW08 3 06/30/03 614 .64 <10 <.8 <.8 8 in. Mulberry, NE sideOU1-TW08 3 06/30/03 215 .22 <10 <.8 <.8 8 in. Mulberry, NW sideOU1-TW08 3 06/30/03 173 .18 <10 <.8 <.8 8 in. Mulberry, SO sideOU1-TW08 7 06/30/03 224 .23 <10 <.8 <.8 8 in. Mulberry, NW sideOU1-TW08 7 06/30/03 68.2 .07 <10 <.8 <.8 8 in. Mulberry, SO sideOU1-TW08 16 06/30/03 98.3 .10 <10 <.8 <.8 8 in. Mulberry, NO sideOU1-TW08 16 06/30/03 114 .12 <10 <.8 <.8 8 in. Mulberry, SO sideOU1-TW11 3 06/29/00 1,900 131 9.3 J <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 06/29/00 3,850 249 17.3 <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 06/29/00 1,910 131 9.4 J <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 11/27/00 1,914 144 239 <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 04/18/01 1,090 62.3 59.7 <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 04/18/01 1,010 89.3 101 <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 06/27/01 1,930 171 212 <.8 <.8 6 in. Chinese elm, SO sideOU1-TW11 3 09/05/01 457 13.82 <10 <.8 29.9 6 in. Chinese elm, SO sideOU1-TW11 1.5 02/12/02 521 99.8 .9 J <.8 .89 6 in. Chinese elm, SO side

Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 

2000–2003—Continued

[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated 

concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream]

Tree identifier

Height 

above land 

surface 

(feet) Date PCE TCE cis-DCE Benzene Toluene Comments
32 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003 Trees sampled at the Front Street site—Continued OU1-TW11 3.5 06/28/02 2,460 <0.8 <10 <0.8 <0.8 6 in. Chinese elm, SO side OU1-TW11 6.5 06/28/02 1,920 <.8 <10 <.8 <.8 6 in. Chinese elm, SO side OU1-TW11 3 06/28/02 3,310 <.8 <10 <.8 <.8 6 in. Chinese elm, SO side OU1-TW11 .7 07/09/03 768 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW11 3.5 07/09/03 704 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW11 5.8 07/09/03 587 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW11 7.9 07/09/03 552 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW11 10.3 07/09/03 467 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW11 13.5 07/09/03 370 -- -- -- -- 6 in. Chinese elm, SO side OU1-TW12 3 06/29/00 29.6 <.8 <10 <.8 <.8 2 in. Chinese elm OU1-TW13 3 04/11/01 <.8 <.8 1.05 <.8 <.8 6 in. Mulberry, 4 trunks OU1-TW13 3 04/11/01 <.8 <.8 <10 <.8 <.8 6 in. Mulberry, 4 trunks OU1-TW13 3 07/29/02 <.8 <.8 <10 <.8 <.8 6 in. Mulberry, 4 trunks OU1-TW14 3 04/11/01 <.8 <.8 <10 <.8 <.8 6 in. Mulberry OU1-TW14 3 04/11/01 2.23 <.8 23.0 <.8 <.8 6 in. Mulberry OU1-TW14 3 07/29/02 <.8 <.8 <10 <.8 <.8 6 in. Mulberry OU1-TW15 3 04/11/01 <.8 <.8 <10 <.8 <.8 4 in. Mulberry OU1-TW15 3 04/11/01 <.8 <.8 13.5 <.8 <.8 4 in. Mulberry OU1-TW15 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Mulberry OU1-TW16 3 04/11/01 1.62 <.8 5.12 <.8 <.8 4 in. Catalpa OU1-TW16 3 04/11/01 1.61 <.8 1.96 <.8 <.8 4 in. Catalpa OU1-TW16 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Catalpa OU1-TW17 3 04/11/01 1.51 <.8 <10 <.8 <.8 3 in. Chinese elm OU1-TW17 3 04/11/01 2.76 <.8 <10 <.8 <.8 3 in. Chinese elm OU1-TW18 3 07/29/02 134 <.8 <10 <.8 <.8 4 in. Chinese elm, 2 trunks OU1-TW19 3 07/29/02 495 <.8 <10 <.8 <.8 3 in. Chinese elm OU1-TW20 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Ash OU1-TW21 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Chinese elm OU1-TW22 3 07/29/02 29.3 <.8 <10 <.8 <.8 3 in. Chinese elm, 5 trunks OU1-TW23 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Silver maple OU1-TW24 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Silver maple OU1-TW25 3 07/29/02 <.8 <.8 <10 <.8 <.8 5 in. Chinese elm

OU1-TW26 3 07/29/02 <.8 <.8 <10 <.8 <.8 3 in. WalnutOU1-TW27 3 07/29/02 <.8 <.8 <10 <.8 <.8 4 in. Mulberry, 2 trunksOU1-TW28 3 07/29/02 1,090 <.8 <10 <.8 <.8 8 in. Chinese elm

Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 

2000–2003—Continued

[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated 

concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream]

Tree identifier

Height 

above land 

surface 

(feet) Date PCE TCE cis-DCE Benzene Toluene Comments
Table 33

Trees sampled at the Front Street site—Continued

OU1-TW28 1 06/30/03 307 0.32 <10 <0.8 <0.8 8 in. Chinese elmOU1-TW28 3 06/30/03 267 .28 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 3 06/30/03 907 .94 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 7 06/30/03 506 20.5 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 7 06/30/03 318 .33 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 12 06/30/03 405 19.4 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 12 06/30/03 318 .33 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 16 06/30/03 319 .21 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 16 06/30/03 216 .22 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 19 06/30/03 307 .32 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 19 06/30/03 306 .32 <10 <.8 <.8 8 in. Chinese elmOU1-TW28 sap 7 06/30/03 36.8 <.8 -- -- -- Sap from 8 in. Chinese elmOU1-TW28 sap 19 06/30/03 13.6 <.8 -- -- -- Sap from 8 in. Chinese elmOU1-TW28 1 07/30/03 312 -- -- -- -- 8 in. Chinese elmOU1-TW28 3 07/30/03 401 -- -- -- -- 8 in. Chinese elmOU1-TW28 3 07/30/03 551 -- -- -- -- 8 in. Chinese elmOU1-TW28 5 07/30/03 504 -- -- -- -- 8 in. Chinese elmOU1-TW28 5 07/30/03 1,290 -- -- -- -- 8 in. Chinese elmOU1-TW28 7.5 07/30/03 359 -- -- -- -- 8 in. Chinese elmOU1-TW28 7.5 07/30/03 869 -- -- -- -- 8 in. Chinese elmOU1-TW28 12.5 07/30/03 186 -- -- -- -- 8 in. Chinese elmOU1-TW28 12.5 07/30/03 689 -- -- -- -- 8 in. Chinese elmOU1-TW28 16.5 07/30/03 146 -- -- -- -- 8 in. Chinese elmOU1-TW28 16.5 07/30/03 545 -- -- -- -- 8 in. Chinese elm

Trees sampled near the former dry cleaning facility

OU1-DF101 3 01/31/02 <0.8 <0.8 <10 <0.8 0.37 10 in. BoxelderOU1-DF102 3 01/31/02 <.8 <.8 <10 <.8 .25 20 in. Chinese elmOU1-DF103 3 01/31/02 <.8 <.8 <10 <.8 <.8 8 in. Chinese elmOU1-DF104 3 01/31/02 <.8 .73 <10 <.8 <.8 8 in. Chinese elmOU1-DF105 3 01/31/02 <.8 <.8 <10 <.8 1.6 Composite, 16 in. Chinese elm, 6 in. Redbud

Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 

2000–2003—Continued

[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated 

concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream]

Tree identifier

Height 

above land 

surface 

(feet) Date PCE TCE cis-DCE Benzene Toluene Comments
34 Assessment of Subsurface Chlorinated Solvent Contamination Using Tree Cores at New Haven, Missouri, 1999–2003 Poplar tree cuttings planted adjacent to Front Street building OU1-SAP-GS01 0.20833 10/22/02 80.1 <0.8 <10 <0.8 <0.8 Potting soil bag, Poplar sapling, SO side OU1-SAP-GS01 1 10/22/02 <.8 <.8 <10 <.8 <.8 Potting soil bag, Poplar sapling, leaves OU1-SAP-GS01 -.2 10/22/02 98.1 <.8 <10 <.8 <.8 Potting soil bag, Poplar sapling OU1-SAP-GS02 .20833 10/22/02 <.8 <.8 <10 <.8 <.8 Poplar sapling, SO side OU1-SAP-GS02 1 10/22/02 <.8 <.8 <10 <.8 <.8 Poplar sapling, leaves OU1-SAP-GS02 -.2 10/22/02 51.9 <.8 <10 <.8 <.8 Poplar sapling, shoot below ground OU1-SAP-GS126 -.5 07/09/03 8.04 <.8 <10 <.8 <.8 Poplar sapling, shoot below ground OU1-SAP-GS126 0 07/09/03 .07 <.8 <10 <.8 <.8 Poplar sapling, SO side OU1-SAP-GS126 .5 07/09/03 <.8 <.8 <10 <.8 <.8 Poplar sapling, leaves OU1-SAP-GS127 -.5 07/09/03 22.1 <.8 <10 <.8 <.8 Poplar sampling, adjacent to TW08 OU1-SAP-GS127 0 07/09/03 9.25 <.8 <10 <.8 <.8 Poplar sampling, adjacent to TW08 OU1-SAP-GS127 .5 07/09/03 <.8 <.8 <10 <.8 <.8 Poplar sampling, adjacent to TW08 Poplar tree cuttings planted in tributaries 500TB and 210TB OUX-500tb-GS1 0 07/16/03 0 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS1 .729 07/16/03 0 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS2 0 07/16/03 95.3 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS2 .729 07/16/03 6.8 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS3 0 07/16/03 136 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS3 0.729 07/16/03 16.3 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS4 0 07/16/03 176 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS4 .729 07/16/03 26.2 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS5 0 07/16/03 129 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS5 .729 07/16/03 14.7 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS6 0 07/16/03 137 -- -- -- -- Poplar cutting in 500TB OUX-500tb-GS6 .729 07/16/03 9.6 -- -- -- -- Poplar cutting in 500TB OU4-210tb-GS7 .729 07/16/03 26.2 -- -- -- -- Poplar cutting in 210TB OU4-210tb-GS7 0 07/16/03 19.5 -- -- -- -- Poplar cutting in 210TB OU4-210tb-GS7 -.44 07/16/03 8.2 -- -- -- -- Poplar cutting in 210TB OU4-210tb-GS8 .729 07/16/03 35.8 -- -- -- -- Poplar cutting in 210TB OU4-210tb-GS8 0 07/16/03 8.7 -- -- -- -- Poplar cutting in 210TB OU4-210tb-GS8 -.44 07/16/03 3.5 -- -- -- -- Poplar cutting in 210TB Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 2000–2003—Continued [All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream] Tree identifier Height above land surface (feet) Date PCE TCE cis-DCE Benzene Toluene Comments
Table 35

PCE concentrations in tributaries 500TB and 210TB

OUX-500TB-2 0 06/30/03 90 -- -- -- -- Water from 500TB-2

OUX-500TB-2 0 07/16/03 76.4 -- -- -- -- Water from 500TB-2

OUX-500TB-2 0 07/16/03 84.1 -- -- -- -- Water from 500TB-2

OUX-500TB-2 0 07/16/03 64.1 -- -- -- -- Water from 500TB-2

OU4-210TB-C6 0 06/30/03 21.7 -- -- -- -- Water from 210TB-C6

OU4-210TB-C6 0 07/16/03 27.0 -- -- -- -- Water from 210TB-C6

OU4-210TB-C6 0 07/16/03 23.8 -- -- -- -- Water from 210TB-C6

OU4-210TB-C6 0 07/16/03 15.8 -- -- -- -- Water from 210TB-C6

Trees sampled along the bank of tributary 500TB

OU2-GCS01 3 06/30/03 10.9 4.61 2.8 J <0.8 <0.8 11 in. Willow at 500TB-2 on LBOU2-GCS02 3 06/30/03 4.31 <.8 <10 <.8 <.8 5 in. Willow, RB 60ft DS 500TB-2OUX-GCS01 3 06/30/03 <.8 -- -- -- -- 11 in. Willow at 500TB-2 on LB

OUX-GCS02 3 06/30/03 <.8 -- -- -- -- 5 in. Willow, RB 60ft DS 500TB-2

OUX-GCS01 3 07/09/03 .97 -- -- -- -- 11 in. Willow at 500TB-2 on LB

OUX-GCS01 3 07/09/03 13.5 3.41 9.1 J <0.8 2.15 11 in. Willow at 500TB-2 on LBOUX-GCS03 3 07/09/03 <.8 -- -- -- -- Sycamore

OUX-GCS03 3 07/09/03 <.8 <.8 5.6 J <.8 <.8 SycamoreOUX-GCS04 3 07/09/03 <.8 -- -- -- -- Sycamore

OUX-GCS04 3 07/09/03 11.0 2.84 8.9 J <.8 <.8 Sycamore

Soil samples from the former dry cleaning facility (concentrations in micrograms per kilogram)

OU1-HSS01 2.00 02/08/02 <0.8 <0.8 27.3 <0.8 21.4 Soil sampleOU1-HSS02 1.00 02/08/02 <.8 <.8 <.8 <.8 20.2 Soil sampleOU1-HSS02 2.00 02/08/02 <.8 <.8 <.8 <.8 5.67 Soil sampleOU1-HSS03 1.00 02/08/02 <.8 <.8 <.8 <.8 .5 Soil sampleOU1-HSS03 2.00 02/08/02 <.8 <.8 <.8 <.8 .45 J Soil sampleOU1-HSS04 1.00 02/08/02 .16 J <.8 <.8 <.8 <.8 Soil sampleOU1-HSS03 3.00 02/08/02 <.8 <.8 <.8 <.8 1.5 Soil sample

Table 2. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from the Front Street site and former dry cleaning facility, 

2000–2003—Continued

[All concentrations in micrograms in headspace per kilogram of wet core; PCE, tetrachloroethene; TCE, trichloroethene; cis-DCE, cis-1,2-dichloroethene; <, less than; in., trunk diameter in inches; J, estimated 

concentration below the method reporting limit; NW, northwest; SO, south; NE, northeast; NO, north; SW, southwest; --, no data; LB, left bank; RB, right bank; ft, feet; DS, downstream]

Tree identifier

Height 

above land 

surface 

(feet) Date PCE TCE cis-DCE Benzene Toluene Comments