Chemical Anatomy of the Firehole River, Yellowstone National Park: Results for As, Li, F, Hg, SiO2, and Cl from the September 2007 Synoptic Sampling

During September 15-17, 2007 low-flow conditions, synoptic water samples and discharges were obtained to quantify thermal solute loading to the Firehole River and to determine if solute loading is attenuated through mineral precipitation or sorption reactions. Of the major tributaries, the combined Iron Spring-Little Firehole River inflow contributes the most, 27% of the total flow at the lower gauge; the Firehole River, above any thermal inputs, contributes 18%; Nez Perce contributes 14%; Sentinel and Fairy Creeks 6%; White, Tangled, Mallard, and Rabbit Creeks 5%; and other tributaries 1%. The remaining 29% (or 65 cfs) is from both thermal and non-thermal surface and subsurface inflows but the majority is from thermal sources. Allen and Day (1935) directly measured all thermal inputs and reported a total of 55 cfs of thermal inflow to the Firehole River. Hence, no substantial long-term change in thermal inflow has occurred for at least 73 years. Preliminary data indicate that no perceptible attenuation of trace elements is observed except for Hg and SiO2. Major and trace solutes from thermal sources move directly into the rivers, are transported downstream, and out of the Park. For chloride, 40,000 kg/d are discharged by the Firehole River, for fluoride, 6,000 kg/d, for Li, 400 kg/d, for As, 235 kg/d, for Hg, 2 g/d, and for SiO2, 65,000 kg/d. Short-term variations in thermal inputs can be observed from continuous monitoring of electrical conductivity at both gauges on the Firehole River. Cycles of major geyser activity are observed with Lone Star Geyser appearing in the upper gauge monitoring results and other geysers in the lower gauge results. The conductivity results indicate that travel times and continuous monitoring of geysers can be obtained year-round with simple and inexpensive equipment.