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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2004-5049


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. Schumacher and Garrett C. Struckhoff, U.S. Geological Survey, and Joel G. Burken, University of Missouri-Rolla, Department of Environmental Engineering, in cooperation with the U.S. Environmental Protection Agency

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 mg-h/kg (micrograms in headspace per kilogram of wet core) and TCE concentrations as large as 249 mg-h/kg. Soils at the Front Street site contained PCE concentrations as large as 6,200,000 mg/kg (micrograms per kilogram) and ground-water samples contained PCE concentrations as large as 11,000 mg/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 mg/kg or larger or overlying ground water containing PCE concentrations from 5 to 11,000 mg/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 mg/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. Comparison 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.

TABLE OF CONTENTS

Abstract

Introduction

Background

Purpose and Scope

Description of the Study Area

Sample Collection and Analysis

Assessment of Subsurface Contamination at the Front Street Site

Initial Site Assessment Using Tree Cores

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

Comparison of the Tree-Core Sampling to Traditional Soil Sampling Methods

Comparison of the Tree-Core Sampling to Ground-Water Sampling

Assessment of Subsurface Contamination at the Former Dry Cleaning Facility

Initial Site Assessment Using Tree Cores

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

Practical Considerations in Using Tree-Core Sampling for Site Assessment

Diffusion Losses and Uptake, Partioning, and Differences Between Species

Directional Variability in Tree Trunks

Sensitivity of Tree-Core Sampling to Detect Subsurface Contamination

Summary and Conclusions

References

FIGURES

  1. Map showing 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
  2. Map showing results of initial tree-core sampling conducted in downtown New Haven, Missouri, during 1999
  3. Map shwoing 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
  4. Map showing r elation between average tetrachloroethene (PCE) concentrations in tree-core samples and PCE concentrations in soil at the Front Street site (1999–2003)
  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
  6. Map showing relation between average tetrachloroethene (PCE) concentrations in tree-core samples and PCE concentrations in ground-water samples at the Front Street site (1999–2003)
  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
  8. Graph showing relation between tetrachloroethene (PCE) concentrations in tree-core samples and height above the land surface
  9. Graph showing relation between tetrachloroethene (PCE) concentration in soil gas and depth below the land surface along the north side of the Front Street building
  10. Graph showing directional variability in tetrachloroethene (PCE) concentrations in core samples from an eastern red cedar tree (TW02)
  11. Graph showing directional variability in tetrachloroethene (PCE) concentrations in core samples collected from tree TW28 on June 30, 2003

TABLES

  1. Concentrations of tetrachloroethene (PCE) and other volatile organic compounds in tree-core samples collected from downtown New Haven, Missouri, during 1999
  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
  3. Variation in tetrachloroethene (PCE) concentrations in the trunk of tree TW02 with direction and height above the land surface

 

Conversion Factors and Datum
MultiplyByTo obtain
 Length 
   
inch (in.)2.54centimeter (cm)
inch (in.) 25.4millimeter (mm)
foot (ft)0.3048meter (m)
mile (mi)1.609kilometer (km)
   
  Area 
   
acre4,047 square meter (m2)
acre0.4047hectare (ha)
square foot (ft2)929.0square centimeter (cm2)
square foot (ft2)0.09290square meter (m2)
square mile (mi2)259.0hectare (ha)
square mile (mi2)2.590square kilometer (km2)
   
 Volume 
   
gallon(gal)3.785 liter (L)
cubic inch (in316.39cubic centimeter (cm3)
   
 Flow Rate 
   
cubic foot per second (ft3/s)0.02832cubic meter per second (m3/s)
gallon per minute (gal/min)0.00223cubic foot per second (ft3/s)
   
Mass
   
pound, avoirdupois (lb)0.4536kilogram (kg)
   

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

 


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For more information about USGS activities in Missouri contact:

Director

U.S. Geological Survey

Missouri Water Science Center

1400 Independence Road

Rolla, Missouri 65401

Telephone: (573) 308-3667

Fax: (573) 308-3645


or access the USGS Missouri Water Science Center home page at:  http://mo.water.usgs.gov/.




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