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Microbial Responses to Varied Concentrations of Dissolved Organic Carbon in Groundwater

C. K. Knowlton
Pacific Lutheran University, Tacoma, WA

An investigation of groundwater from several different aquifers was completed to evaluate the potential relationship between lithology and dissolved organic carbon (DOC) concentration. The wells tested in this study are from throughout Dutchess County, New York, making use of a range of different aquifer types. Slight differences in the DOC concentrations were found between the various well water sources, but nothing statistically significant. However, some evidence supports that dissolved organic carbon concentration varied between bedrock and non-bedrock aquifer sources with values on the range of 0.1–0.33 mg/L for bedrock sources and 0.23–0.55 mg/L for nonbedrock sources. This investigation also included an evaluation of the effect of DOC concentrations on microbial populations. Microbial responses varied during respiration and bacterial production trials, but yielded very different results. The bacterial production showed slight changes, but did not demonstrate any significant relationship to DOC concentration. However, the respiration rates varied significantly between samples, but no direct correlation to dissolved organic carbon concentrations has yet been found. The analysis of the types of carbon utilized by microbes may hold the key to understanding the respiration results and the potential link between lithological characteristics and the DOC concentration.

AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California