Impact of the 1988 forest fires on the chemistry of ground water in Yellowstone National Park
Statistical tests (two-way ANOVA at 95 percent confidence interval) show that for most wells, there is no significant difference between pre-fire and post-fire chemistry of the shallow ground waters. Despite the lack of significance changes in water chemistry, there do appear to be differences in the interactions between chemical and physical parameters, as measured under pre-fire and post-fire conditions. For post-fire data from the most severely burned site, the concentrations of ground-water solutes appear to be inversely related to the depth of the water table, whereas this inverse relationship is not seen clearly for the pre-fire and control data. The apparent change in solute behavior seen in the post-fire ground water from the severely burned site may be due to the complete, although temporary, removal of the biotic component from the system, thereby altering the cycling of nutrients in this highly oligotrophic ecosystem. Although concentrations of nitrate in the ground water have not increased appreciably over the pre-fire values, samples of the soil solution from the severely burned site contained high concentrations of nitrate-N (as much as 67 mg/L). An increase in the activity of nitrifying bacteria, due to post-fire conditions, is thought to be responsible for the high concentrations of nitrate in the post-fire soil solution. Geochemical computer modeling indicates that mineral weathering by water of snowmelt composition can describe the transition in solute content from that of snowmelt to that of the ground water. In contrast, just the mixing of different solutions (i.e., a percentage of pure snowmelt plus a percentage of ash leachate) cannot create a solution approximating the chemical composition measured in samples of post-fire ground water. The modeling, however, does not rule out a combination of weathering and mixing (snow + ash) to produce the chemistry observed for the post-fire ground waters.
- Research Organization:
- Colorado Univ., Boulder, CO (United States)
- OSTI ID:
- 6612074
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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