Microbially Mediated Reductive Dechlorination of Dichlorobenzene

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. AGENCY USE ONLY (Leave blank)2. REPORT DATE August 1999 REPORT TYPE AND DATES COVEREDFinal May 1997 -August 1999 TITLE AND SUBTITLEMicrobially Mediated Reductive Dechlorination of Dichlorobenzene AUTHOR(S)Quistorff, Anne S. FUNDING NUMBERSC: F08637-97-C-6013 P: 62202F JON: 1900B56A/2103B58A PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)Cornell The microbially mediated reductive dechlorination of 1,2-, 1,3-, and 1,4-dichlorobenzene (DCB) was studied using site material from eight different locations. The soil and groundwater from each site were anaerobically added to multiple serum bottles and mixed. All three DCB isomers were added to each serum bottle to a total nominal concentration of 30 micro-mole per liter for some microcosms and 600 micro-mole per liter for other microcosms. In addition, electron donor in the form of yeast extract (100 mg/L) was added to some microcosms and some microcosms were autoclaved and served as abiotic controls. The microcosms were then incubated, inverted, in the dark at 24 deg C and periodically monitored by headspace injections into a gas Chromatograph system. Reductive dechlorination of the DCB isomers was noted in microcosms from five of the eight locations and ranged from 10% to nearly 100%. Additionally, in all the positive microcosms, dechlorination proceeded independent of whether yeast extract was added. Due to the rapid onset of dechlorination in some of the microcosms, it is likely that DCB dechlorination is occurring on site. Generally, 1,2-DCB was the nost readily degraded DCB isomer. 1,3-DCB was the next most readily degraded isomer, distantly followed by 1,4-DCB. Reductive dechlorination of the DCB isomers was noted in microcosms from five of the eight locations: Louisiana wetland sediment, Kelly AFB, Robins AFB at well BIA4 at both 17-and 25-foot depths and slight dechlorination for the digested sludge. The extent of MCB production from DCB dechlorination was about 10% SUBJECT TERMSfor the digested sludge and ranged from about 50% to 100% for the other microcosms. The most successful microcosms (exhibiting close to 100% transformation in some instances) were the Louisiana wetland sediment and the Robins AFB well BIA4 at 25-foot depth.Additionally, in all the positive microcosms, dechlorination proceeded independent of whether yeast extract was addedprobably because the indigeno...

Reductive Dehalogenation of Dichlorobenzenes and Monochlorobenzene to Benzene in Microcosms

“…These studies have demonstrated that microcosms constructed using Chambers Works sediments can reductively dehalogenate all three DCB isomers to MCB. Similar to other results (20,22,25), 1,2-DCB was used most readily and 1,4-DCB was used the slowest. It is common for adjacent chlorines in chloroaromatics to be more readily dehalogenated than those ortho or para to each other (14,20,29,30).…”

“…A potential advantage of benzene as a product is its high solubility, which may enhance soubilization of a DCB or MCB DNAPL. Moreover, our findings that significant amounts of benzene can be produced from MCB added to other evidence of MCB dehalogenation to benzene (22,25,27) should be taken into account in attempts at modeling the environmental fates of DCBs and MCB.…”

“…In sediment microcosms from the Saale River, Germany, fed DCBs, small amounts of benzene were produced along with MCB, but only during DCB reductive dehalogenation in a seemingly cometabolic process (25). Similar results were obtained with samples from Robins Air Force Base, Georgia (22). More recently, Nijenhuis and colleagues (26,27) used natural carbon isotope fractionation, and 13 biotraps to obtain evidence for MCB dechlorination to benzene in the chlorobenzene-contaminated Bitterfeld site in Germany.…”

“…The greatest difference between these microcosm studies and previous ones is the large amount of benzene produced from DCBs and MCB and the timing of benzene production. Nowak et al (25) and Quistorff (22) detected maximal concentrations of 10-50 µmol/L benzene, which was only a small percentage to the MCB produced, and in both cases benzene production occurred only during DCB dechlorination to MCB, suggesting that it was a side reaction concurrent with DCB dehalogenation. In contrast, in these studies benzene in some samples accumulated to over 5000 µmol/L, and its accumulation did not require concurrent metabolism of DCBs, and indeed seemed to be inhibited during DCB dehalogenation in some instances.…”

A Role for Dehalobacter spp. in the Reductive Dehalogenation of Dichlorobenzenes and Monochlorobenzene

“…Prior to our recent work, dehalogenation of the less chlorinated DCBs and MCB was observed mainly in sediment microcosms. − These studies did not address the organisms responsible for the reductive dehalogenation, and MCB was dehalogenated to benzene in only trace amounts, if at all. In a recent study, we used sediments from a contaminated site in Salem County, New Jersey, and monitored microcosms given DCBs or MCB.…”