Evaluating Changes In Strontium Chemistry Of Stream Waters In Response To Environmental Stress
نویسنده
چکیده
The first measurements of Sr isotopic composition and concentration of archived stream water samples from the Hubbard Brook Experimental Forest in central New Hampshire were collected to evaluate long term trends. The presented data are for two watersheds, one of which was timber harvested in late 1983, and the other is a control watershed. Excess anion deposition, deforestation, and drought are three environmental stresses whose effects are examined in terms of the data set. The relevance of using Sr as a chemical proxy for Ca in environmental studies and the suitability of using Sr isotopic compositions in linear mixing models to characterize and identify the sources of Sr in a complex environment are evaluated using the new Sr isotopic data. Results indicate the need for caution when using Sr as a proxy for Ca in order to create nutrient budgets. The Sr isotopic data are best described in terms of a two-stage mixing model 1) between rain water and the forest canopy and 2) between the resultant mixture (throughfall) and the soil weathering end-member. The similarity in composition between throughfall and stream water makes estimates of the amount of atmospherically derived Sr in the stream waters suspect. Variations in the data presented here are interpreted based on the physical conditions of the system and on the natural and anthropogenic stresses that have been applied to the system over the 27 year history of the archived waters at Hubbard Brook. Thesis Supervisor: Dr. Samuel A. Bowring Y _
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