Open-File Report 2007-1028

Prepared in cooperation with the Department of Energy Savannah River National Laboratory

Dichloroethene and Vinyl Chloride Degradation Potential in Wetland Sediments at Twin Lakes and Pen Branch, Savannah River National Laboratory, South Carolina

By Paul M. Bradley

This report is available online in pdf format (355 kb): OFR 2007-1028 (Opens the PDF file in a new window. )

ABSTRACT

A series of 14C-radiotracer-based microcosm experiments was conducted to assess the mechanisms and products of degradation of dichloroethene (DCE) and vinyl chloride (VC) in wetland sediments at the Department of Energy (DOE) Savannah River National Laboratory. This project investigated the potential for biotic and abiotic DCE and VC degradation in wetland sediments from the Twin Lakes area of the C-BRP investigative unit and from the portion of Pen Branch located directly down gradient from the CMP investigative unit.

Substantial degradation of [1,2-14C] DCE and [1,2-14C] VC to 14CO2 was observed in all viable sediment microcosms prepared under oxic conditions. These results indicate that microbial mineralization processes, involving direct oxidation or cometabolic oxidation, are the primary mechanisms of DCE and VC biodegradation in Twin Lake and Pen Branch sediments under oxic conditions.

Substantial degradation of [1,2-14C] DCE and [1,2-14C] VC was observed in all viable sediment microcosms incubated under anoxic conditions. Production of 14CO2 was observed in all sediment microcosms under anoxic conditions. In general, the accumulation of mineralization products (14CO2 and 14CH4) was comparable to the accumulation of those reduced daughter products (14C-VC, 14C-ethene or 14C-ethane) traditionally identified with chloroethene reductive dechlorination. These results indicate that microbial mineralization processes can be an important component of DCE and VC degradation in Twin Lake and Pen Branch sediments under anoxic conditions. These results demonstrate that an evaluation of the efficiency of in situ DCE and VC biodegradation in Twin Lakes and Pen Branch that is based solely on the observed accumulation of reduced daughter products may underestimate substantially the total extent of contaminant biodegradation and, thus, the contribution of biodegradation to overall contaminant attenuation.

No evidence of abiotic degradation of [1,2-14C] DCE or [1,2-14C] VC was observed in heat-sterilized control treatments in this study under oxic or anoxic conditions. Efforts to enrich and isolate microorganisms involved in the mineralization of [1,2-14C] cis-DCE and/or [1,2-14C] VC were unsuccessful.


CONTENTS

Abstract

Introduction

Purpose and Scope

Methods

Degradation under Oxic and Anoxic Conditions

References Cited

Appendix


REPORT AVAILABILITY

This report is available online in pdf format (355 kb): Open-File Report 2007-1028 (Opens the PDF file in a new window. )
To view the PDF document, you need the Adobe Acrobat® Reader installed on your computer. (A free copy of the Acrobat® Reader may be downloaded from Adobe Systems Incorporated.)

To order maps, publications, and other miscellaneous products on paper and compact disc media from the USGS:

USGS Information Delivery
Box 25286
Denver, CO 80225
Telephone: 1-888-ASK-USGS

Accessibility FOIA Privacy Policies and Notices

Take Pride in America home page. FirstGov button U.S. Department of the Interior | U.S. Geological Survey
Persistent URL: https://pubs.water.usgs.gov/ofr2007-1028
Page Contact Information: Publishing Services
Page Last Modified: Wednesday, 07-Dec-2016 20:10:03 EST