Hydrologic and Geochemical Cycling within Karst Versus Non-Karst Basins within the Interior Low Plateau Province of South-Central Kentucky

摘要

This thesis summarizes my research in which I investigated differences and characteristics in hydrologic, nutrient and geochemical cycling between karst versus nonkarst basins within the Interior Low Plateau Province. Field data including stream discharge, evapotranspiration, and dissolved major ion concentrations were collected for a period of one year for two basins within Mammoth Cave National Park. Twelve percent carbonate rocks underlie one basin, while the other consists of 48 percent carbonate rocks. The carbonate rock exposures within both basins exhibit karstification. The hydrologic and geochemical differences between these basins were compared to determine to what extent that cycles are modified or altered within karst terrains. The characteristics of these cycles within both basins were also compared. I found that there were noticeable hydro geochemical effects from the presence of karst within a basin. These effects were either the result of the presence of carbonate rocks within the basin or due to the presence of morphological karst features within the carbonate rocks. The presence of karst serves as a buffer by moderating temperature extremes, lessens the effect of acid precipitation, moderates discharges during storm surges, moderates/lessens a basinu27s evaporative losses, and affects available moisture and nutrients to surface biological processes. These hydrologic effects in turn, also continue to affect the basinu27s geochemistry in noticeable ways. Findings included that it only takes a small percentage of carbonate rocks within a basin to produce an output stream with a calcium/bicarbonate geochemical signature. In these situations, the quantity of karst is perhaps not as important as spatial distribution. Therefore, the quantity of karst within a basin may be more critical to accurately assess when conducting geochemical modeling. Many global geochemical models do not factor in karst affects (Holmen, 1992). Considering the extent of carbonate rocks globally and their potential ability to affect hydrogeochemical cycles, future model modifications may need to factor in karst affects in order to more accurately represent actual real-world field conditions.