MULTI-ELEMENT ANALYSIS OF STREAMS, ADIRONDACK HIGH PEAKS REGION, NEW YORK

The High Peaks Region in the Adirondack Mountains of northern New York includes 46 peaks that attain elevations of over 4000'. Stream water geochemistry in the area is of concern because of acidification and, more recently, mercury deposition. The area is also underlain by the Marcy Massif, a large, Mesoproterozoic anorthosite, composed of large megacrysts of andesine-labradorite plagioclase, that has limited capacity to buffer acidity. Soils are thin to non-existent and have undergone extensive leaching of mobile cations. On October 3-4th, 2008, in conjunction with St. Lawrence University's Outing Club and Peak Weekend, seventeen streams in the High Peaks were sampled by volunteers for multi-element analysis and acid neutralizing capacity. Results show that the streams have limited capacity to neutralize acidity with ANC values ranging between 9 and 95 ueq/L. The total dissolved solids (TDS) concentration of the water is fairly low (6.22 – 16.06 ppm). Seventeen elements were detected in all samples and their average concentrations were Al (261ppm), Ba (3.26), Mg (304 ppm), Na (769 ppm), Rb (0.19 ppm), S (1333 ppm), Si (3712 ppm), Sr (12.1 ppm), Zn (4.14 ppm), and Sc, Y, and the REE at trace levels. Strong positive correlations (R2) exist between Al and Fe (.80) and Zn (.95) and negative correlations with Ca (-.82), Mg (-.76), Si (-.86), Sm (-.97), and Sr (-.87). Ca was strongly correlated with Mg (.91), Na (.74), Si (.84), Sm (.99), and Sr (.88) and negatively correlated with Zn (-.74). Waters with the highest ANC and TDS were derived from John's Brook and Putnam Brook, south of Keene Valley, which drain areas of anorthosite with abundant xenoliths of metasedimentary rock, including marble. The lowest ANC values were recorded in areas of the massif where few or no xenoliths are known. There is not a correlation between water geochemistry and elevation, suggesting variations in bedrock exert a first-order control on stream water chemistry. With the exception of sulfur, all of the major (Al, Ca, Mg, Na, and Si) and minor cations (Ba, K, Sr) in High Peaks stream water can readily be explained by chemical weathering of massif anorthosite and derived detritus. It is our intent to continue this annual sampling in the foreseeable future and add additional analytes to evaluate any long-term trends.