The occurrence of fluoride in groundwaters can be influenced by many factors. In Korea, the fluoride-rich groundwaters are normally associated with rock types, especially granite and gneiss. In Gimcheon, high-fluoride groundwaters (up to a maximum of 2.15 mg/L) were observed with bimodal distribution of concentrations. The groundwater in this area showed relatively high concentrations of anthropogenic chemicals such as nitrate, chloride, and sulfate. Statistical analysis showed that fluoride is positively correlated with pH, alkalinity, sodium, and lithium, indicating that the interaction with granite is the main cause enriching its concentration. In Gimcheon, d 18 O data of groundwater showed a negative correlation with nitrate and can be used as an indicator of groundwater age. The four samples of fluoride-rich groundwater were plotted in the light dD and d 18 O region, showing that they were the result of long water-rock reaction. However, other groundwater with a low-fluoride concentration was evenly distributed throughout all dD and d 18 O ranges and did not show a statistically significant correlation with nitrate, indicating possible mixing with another source of fluoride. Considering the influence from the surface on the geochemical characteristics of groundwater in this area, anthropogenic sources including phosphate fertilizer containing fluoride and pesticides may also have partly contributed to the concentrations of fluoride in the low-fluoride groundwater. The scattered distribution of fluoride-rich groundwater and the significant correlation with lithium suggest that pegmatite is the main rock type increasing fluoride concentration in this area.Keywords High-fluoride groundwater Á Water-rock interaction Á Fertilizer Á dD and d 18 O Á Pegmatite

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A numerical simulation of flow around rectangular 2-D prisms of different cross-sectional aspect ratios, ranging from 0.3 to 7.0, is conducted at a Reynolds number of 105. The large eddy simulation (LES) scheme is utilized to solve the 3-D Navier-Stokes equations using a finite volume method on a non-uniform grid, with the Smagorinsky closure model representing the subgrid scale viscosity. This study identifies the influence of aspect ratio on flow features of the velocity/pressure field, i.e., instantaneous vorticity/pressure contours, mean flow streamlines, mean/RMS pressure distribution around the prism, base pressure, mean/RMS drag/lift coefficients, spectral description of drag/lift time history, the associated wavelet based scalograms, wavelet instantaneous frequency spectra and the Strouhal number. Results exhibit salient features in the flow field and associated pressure/aerodynamic forces due to changes in the after body length, demonstrating good agreement with observations from wind tunnel experiments. Findings include identification of the critical depth/breadth ratio and fluctuations in the drag/lift forces, containing features that vary with aspect ratio. A time-frequency analysis is introduced to identify the transient nature of these fluctuations. Wavelet based signal processing schemes combined with instantaneous vorticity/pressure contours are utilized to further highlight temporal variations in the frequency contents of these fluctuations and their influence on the force coefficients.