Microbial Community Dynamics of PCB Dechlorination in SedimentsEPA Grant Number: R825449
Title: Microbial Community Dynamics of PCB Dechlorination in Sediments
Investigators: Rhee, G-Yull , Braun-Howland, Ellen , Sokol, Roger C.
Current Investigators: Rhee, G-Yull
Institution: Wadsworth Center: New York State Department of Health
Current Institution: The State University of New York at Albany
EPA Project Officer: Chung, Serena
Project Period: January 1, 1997 through December 31, 1999 (Extended to December 31, 2000)
Project Amount: $508,964
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Investigations of PCB dechlorination so far have had little success in isolating and culturing responsible microorganisms or microbial consortia. The lack of information on these organisms in both culture as well as in the natural setting has been a major impediment to progress on stimulating and sustaining microbial activities for remediation. This information gap has also limited our ability to determine whether or not natural remediation is an acceptable option for a given site and, if not, how we can artificially enhance remediation either in situ or ex situ. The present study will investigate dechlorinating sediment microbial communities using the methods of chemical and molecular ecology [i.e., phospholipid fatty acids (PLFA) and group-specific 16S-rRNA hybridization probes], which have been successfully employed to investigate various natural microbial communities, in parallel with the traditional technique of the most probable number (MPN).
Specifically, this work will determine: 1) the dynamics and structure of the dechlorinating microbial community in defined functional and phylogenic groups (including the dechlorinating population, methanogens, sulfidogens, and spore formers) during the course of dechlorination. A typical time course shows a sigmoidal curve, consisting of an initial lag followed by a relatively rapid dechlorination and then a stationary plateau with no further change. Special emphasis will thus be placed on understanding community dynamics during the transitions from the lag to the dechlorination phase and from the dechlorination to the stationary phase; 2) the kinetics of dechlorination based on population-normalized rates. Since PCB dechlorination is very slow taking place over months and the population size of dechlorinating organisms and community composition may also vary with PCB concentration, it is necessary to determine the rate normalized with the size of the dechlorinating population to understand true kinetics; and 3) based on the kinetic data, information on sediment microorganisms, and the congener patterns of PCBs, a method will be developed to determine the current stage of dechlorination in situ. We will then select 15 sites in the St. Lawrence River including several with co-contaminants [PAHs and non-aqueous phase liquids NAPL] and analyze them for the size of dechlorinating populations, sediment community structure, PCB concentrations and congener patterns. Using the above method, the potential for further dechlorination at each site will be determined. The present work will employ laboratory sediment microcosms as well as analyses of natural sediments, focusing on the PCB contaminated sites in the St. Lawrence River which we have been investigating for the last 5 years. The results of this study are crucial to best sustain and accelerate the microbial activities and be able to monitor remediation. They are also indispensable for making remediation strategies.