Assessment of indigenous reductive dechlorinating potential at a TCE-contaminated site using microcosms, polymerase chain reaction analysis, and sitedata

A combination of microcosm studies, polymerase chain reaction (PCR) analysi s, and site data was used to assess the indigenous reductive dechlorinating potential in a trichloroethene (TCE)-contaminated aquifer at Ca pe Canaver al Air Station, Florida. Sediment and groundwater were obtained from two di stinct locations approximately 10 m apart, Microcosm studies were performed to assess dechlorinating activity under a variety of nutrient and electron donor amendment conditions. Most live microcosms constructed using materia l from the first location, near well 9 (W09), were negative for dechlorinat ion. All live microcosms constructed using material from the second locatio n (W06) exhibited dechlorination of TCE to vinyl chloride (VC) and ethene ( ETH). DNA encoding 16S ribosomal RNA (rDNA) with a sequence nearly identica l with that from Dehalococcoides ethenogenes strain 195 was detected in the active microcosms and in the sediment from W06 with polymerase chain react ion (PCR) using primers targeted to unique regions of Dehalococcoides 16S r DNA. Dehalococcoides was not detected in the autoclaved microcosms from W06 , nor in sediment and most microcosms from W09. The results of the microcos m studies and PCR analysis were supported by field data, which indicated si gnificant accumulation of cis-1,2-dichloroethene (cisDCE) and VC at W06, bu t not at W09, The different microcosm results obtained far the two location s and the spatial variation of positive PCR results indicates heterogeneous distribution of dechlorinating activity and a specific dechlorinating orga nism, Dehalococcoides, at the site. As both Dehalococcoides and dechlorinat ion activity were similarly, heterogeneously distributed, this suggests tha t molecular-probing (which could and should be extended in the future to in clude virtually all known dechlorinators and/or dehalogenases) can provide a relatively quick and facile method far investigating spatial distribution s of dechlorinators on-site.