Paper No. 82
Presentation Time: 9:00 AM-6:00 PM
POSSIBLE MICROBIAL INFLUENCE ON DISSOLUTION OF PYRITE IN DEMOPOLIS CHALK NE, MISSISSIPPI
The objective of this research was to determine if the formation of pyrite concretions in Demopolis Chalk, Oktibbeha County, Mississippi, is related to microbial activity. At the site, oxidized pyritic samples were weathered out on the surface of the outcrop. Pyritic concretions were present throughout the site; these concretions ranged from iridescent orange and purple to metallic gold in color and were, on average, 1.27 cm in diameter. Samples were collected from the site and catalogued. An average spacing of 15 ft between each pyrite concretion was found using a GPS with an accuracy of 8 ft. Except for one outlying sample, the concretions were evenly distributed throughout the study area. The samples were cut, polished and prepared for X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), confocal laser scanning microscopy, and petrographic microscopy. Results from XRD revealed that some pyrite samples were sulfur deficient and one sample contained gypsum. Petrographic microscopy confirmed the presence of pyrite and gypsum crystals. Using the petrographic microscope, photos were taken of crystalline structures and evidence of microbes. The results of confocal laser scanning microscopy determined that the samples did contain traces of organic matter. The SEM revealed signs of dissolution that may explain why the samples examined by XRD were sulfur deficient. SEM images also showed traces of biofilm and organic matter that could be related to microbial activity. This study is applicable for a wide range of issues such as bioremediation, industry, agriculture, and healthcare.