Biodegradation of TCE in fractured shale and saprolite

A series of investigations were conducted to examine biodegradation of trichloroethylene (TCE) contamination in fractured shale and in saprolite (formed from weathered sedimentary rocks). A plume of groundwater contaminated with trichloroethylene (TCE) was detected at the Oak Ridge Reservation (ORR) in eastern Tennessee adjacent to shallow waste trenches in fractured shale. Monitoring wells at the site indicated a downgradient decline in concentration of TCE and the appearance of its daughter products (cw-dichloroethylene (cDCE) and vinyl chloride (VC)), which suggests the likelihood that anaerobic biodegradation of TCE was occurring. This hypothesis is further supported by the existence of redox conditions, including iron reduction, sulfate reduction, and possibly methanogenesis, which are favorable for anaerobic biodegradation. Microbial community analysis using conventional enrichment methods and molecular methods also support this hypothesis by showing the presence of bacteria previously implicated in the anaerobic biodegradation of chlorinated solvents. This is believed to be the first study to show strong evidence of biodegradation of TCE in shale bedrock. Additional investigations were performed using large undisturbed columns of fractured saprolite from an uncontaminated site about 1 km from the waste trenches. The experiment involved continuous pumping of groundwater containing dissolved phase TCE through one column containing the natural microbial communities (the biotic column), and through a second column in which the microorganisms had been inhibited. In effluent from the biotic column evidence of anaerobic biodegradation TCE appeared within a few months. This included decreasing concentration of TCE in the effluent, appearance of daughter products (cDCE and VC), development of iron and sulfate reducing conditions, and appearance of iron and sulfate reducing bacteria. In the inhibited column there were no indicators of TCE degradation. It appears that TCE biodegradation processes in the shale and saprolite are very similar, and that they can occur spontaneously and rapidly without amendments to enhance biodegradation. Current Air Force Center for Environmental Excellence (AFCEE) protocols for determination of natural attenuation, which are based on monitoring of geochemical parameters, are appropriate for assessing the potential for TCE attenuation in the shale and shale saprolite found at the Oak Ridge Reservation

Assessing Fecal Contamination in Groundwater from the Tulum Region, Quintana Roo, Mexico

The Yucatan Peninsula’s groundwater is experiencing increases in degradation due to swelling population and tourism; yet little is known about sources and transport of contaminants in drinking water supplies. The karst allows for rapid transport of microbial and chemical contaminants to the subsurface, resulting in significantly increased potential for pollution of groundwater. The objective of this research is to determine the occurrence, source, and extent of fecal con- tamination in the Tulum region of the Peninsula. A multi-analytical approach was undertaken in impacted and unim- pacted groundwater locations; measurements included physicochemical parameters, total coliform and E. coli, Bacter- oides (human vs total) and caffeine. The results indicate a variation in geochemistry from impacted to protected sites. The total coliform and E. coli show fecal contamination is wide spread. However, the presence of human Bacteriodes and caffeine in the water in the Tulum well field indicates that the recent human activities next to the well field are im- pacting the drinking water supply. This project is an assessment of the area’s current water quality conditions and the probable impact that the aforementioned growth would have on the area’s water supply. By applying multiple source parameter measurements, including molecular microbiology and chemical indicators it was confirmed the extent of fe- cal contamination of human origin covered the entire sampling region.Funding for this research was provided by Northern Illinois University’s Center for Latino and Latin American Studies, the Geology and Environmental Geosciences de- partment, and Library. This work was also funded by the United States Department of Agriculture, Agricultural Re- search Service, Water Management Conservation and Re- search Program. This article is made openly accessible in part by an award from the Northern Illinois University Libraries’ Open Access Publishing Fund

Influence of Microbial Biofilms on the Preservation of Primary Soft Tissue in Fossil and Extant Archosaurs

Background: Mineralized and permineralized bone is the most common form of fossilization in the vertebrate record. Preservation of gross soft tissues is extremely rare, but recent studies have suggested that primary soft tissues and biomolecules are more commonly preserved within preserved bones than had been presumed. Some of these claims have been challenged, with presentation of evidence suggesting that some of the structures are microbial artifacts, not primary soft tissues. The identification of biomolecules in fossil vertebrate extracts from a specimen of Brachylophosaurus canadensis has shown the interpretation of preserved organic remains as microbial biofilm to be highly unlikely. These discussions also propose a variety of potential mechanisms that would permit the preservation of soft-tissues in vertebrate fossils over geologic time. Methodology/Principal Findings: This study experimentally examines the role of microbial biofilms in soft-tissue preservation in vertebrate fossils by quantitatively establishing the growth and morphology of biofilms on extant archosaur bone. These results are microscopically and morphologically compared with soft-tissue extracts from vertebrate fossils from the Hell Creek Formation of southeastern Montana (Latest Maastrichtian) in order to investigate the potential role of microbial biofilms on the preservation of fossil bone and bound organic matter in a variety of taphonomic settings. Base

Comparative Transport of Bacteriophage and Microspheres in an Aquifer Under Forced-Gradient Conditions

The transport of viruses in groundwater was studied by using two bacteriophages (PRD-1 and M-1) and carboxylated latex microspheres (100 nm) under forced gradient conditions. This study was also designed to determine the effects of a change in pH of the aquifer on the transport of viruses and microspheres, and if the microspheres reflected the transport of viruses. The microspheres, bacteriophage, and chloride tracers were injected for a period of 12 hours into a fine- to medium-sand aquifer, 9 to 10 m in depth underlayed by a clay silt bed. Samples were collected 1, 2.5, 4, and 6 m distant from the injection well. After 10 days the pH of the groundwater was increased from 7.5 to 8.5 and samples collected for an additional 7 days. The results of this study indicated that a small increase in the pH of an aquifer can cause detachment of viruses and microspheres from the soil. In addition, the transport behavior of the bacteriophage was found to be different from the carboxylated microspheres.hydrology collectio

Groundwater microbial diversity and antibiotic resistance linked to human population density in Yucatan Peninsula, Mexico

Microbial community composition in selected karst groundwater sites in the Yucatan Peninsula, Mexico, was assessed to determine the environmental variables influencing groundwater microbial diversity. The karst aquifer system is a groundwater-dependent ecosystem and is the world’s second largest underwater karst cave system. The area’s geology allows precipitation to infiltrate into the groundwater system and prevents accumulation of surface water; as such, groundwater is the only source of fresh water on the peninsula. The sampling locations consisted of three karst sinkholes that extend through the freshwater zone into the saline water, and an abandoned drinking water well of an ocean-side resort, during the dry and rainy seasons. The analysis showed that highly diverse microbial communities are present in the Yucatan groundwater, sustained by permanently warm temperatures and high nutrient input from human activity. Proximity to densely populated areas, such as tourist resorts, is the most important factor influencing both the diversity and presence of fecal bacteria and the antibiotic resistance profile.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Ground-Penetrating Radar, Resistivity and Spontaneous Potential Investigations of a Contaminated Aquifer near Cancún, Mexico

pg(s) 231-23

Role of Sediment Size and Biostratinomy on the Development of Biofilms in Recent Avian Vertebrate Remains

Microscopic soft tissues have been identified in fossil vertebrate remains collected from various lithologies. However, the diagenetic mechanisms to preserve such tissues have remained elusive. While previous studies have described infiltration of biofilms in Haversian and Volkmann's canals, biostratinomic alteration (e.g., trampling), and iron derived from hemoglobin as playing roles in the preservation processes, the influence of sediment texture has not previously been investigated. This study uses a Kolmogorov Smirnov Goodness-of-Fit test to explore the influence of biostratinomic variability and burial media against the infiltration of biofilms in bone samples. Controlled columns of sediment with bone samples were used to simulate burial and subsequent groundwater flow. Sediments used in this study include clay-, silt-, and sand-sized particles modeled after various fluvial facies commonly associated with fossil vertebrates. Extant limb bone samples obtained from Gallus gallus domesticus (Domestic Chicken) buried in clay-rich sediment exhibit heavy biofilm infiltration, while bones buried in sands and silts exhibit moderate levels. Crushed bones exhibit significantly lower biofilm infiltration than whole bone samples. Strong interactions between biostratinomic alteration and sediment size are also identified with respect to biofilm development. Sediments modeling crevasse splay deposits exhibit considerable variability; whole-bone crevasse splay samples exhibit higher frequencies of high-level biofilm infiltration, and crushed-bone samples in modeled crevasse splay deposits display relatively high frequencies of low-level biofilm infiltration. These results suggest that sediment size, depositional setting, and biostratinomic condition play key roles in biofilm infiltration in vertebrate remains, and may influence soft tissue preservation in fossil vertebrates