Arsenic and fluoride in the upper madison river system: Firehole and gibbon rivers and their tributaries, yellowstone national park, wyoming, and southeast montana
Chemical analyses of 21 water samples from the Firehole and Gibbon Rivers, which combine to form the Madison River, gave arsenic and fluoride values above the Environmental Protection Agency Interim Primary Drinking Water maximum contaminant levels (0.05 mg/l arsenic and 2.0 mg/l fluoride). On 18 October, 1975, during a period of moderate flow (16,600 l/s), the Madison River at West Yellowstone contained 0.23 mg/l arsenic and 6.2 mg/l fluoride. Below Hebgen Lake the Madison River during periods of high flow (56,000 liter/s at West Yellowstone and 708,000 liter/s below Hebgen Lake) would contain 0.05 mg/l arsenic at both stations and 1.5 and 4.0 mg/l fluoride at West Yellowstone and below Hebgen Lake, respectively. The strong correlations of arsenic and fluoride with other chemical constituents of the river water at the sampling sites demonstrate the conservative nature of each element after it reaches the Madison River system. Calculations indicate that water from three sampling sites is above saturation with respect to fluorite.