KNOB BROOK, ADIRONDACK STATE PARK, NY: A STUDY IN THE INTERACTION OF A SLAG PILE AND ITS ENVIRONMENT BASED ON SEDIMENT LOAD, WATER CHEMISTRY, AND SOIL PH

Knob Brook is an approximately 2.3 mile-long stream that flows north from Knob Pond to Dudley Pond in the hamlet of Ironville, Crown Point, New York. Ironville is located in the eastern region of the Adirondack State Park, near the southern tip of Lake Champlain. The hamlet is the former site of a flourishing nineteenth century smelting operation that processed magnetite ore, producing iron slag as a byproduct. Knob Brook runs through the eastern portion of the iron slag pile. Stream sediment, water chemistry (total hardness, total alkalinity, TDS, and pH), and nearby soil pH samples were collected at discrete intervals along the brook, beginning upstream from the slag pile and continuing through and below the pile. Map data was also collected to clarify the extent of the slag pile and to adjust the initial assessment of 4,000 ft³.

Detailed sediment analysis of 14 sites indicates that the presence of the slag pile has clearly impacted the sediment load in Knob Brook. Slag is only found in the sediment downstream and adjacent to the pile. Slag pieces are commonly angular to subangular, while the natural sediments range from subangular to rounded. Magnetite ore is also prevalent in sediment samples downstream and adjacent to the pile, but absent in sediments upstream of the site, despite upstream sediments being closer to the ore source. Select pieces of slag from the brook were analyzed with the SEM and some show evidence of dissolution. SiO₂ and CaO account for almost 80 wt. % of the slag's bulk composition and trace amounts of Ba, Ti, Ni, and Cr are present.

At each of the sediment sites, basic water chemistry values were obtained. Upstream, total hardness is 100 ppm and changes to 0 ppm at the slag pile. Total alkalinity begins at 40 ppm and decreases by half at the slag pile. TDS values are consistently 20 ppm until the stream reaches the slag pile, where values become variable. Along the stream path, pH varies between 6.4 and 7.8, but this range is not a function of proximity to the slag pile. Soil pH values are more tightly linked to proximity to the pile. Upstream of the pile, the average soil pH is 6, while around the pile and downstream the pH trends consistently towards 8.