Perry, Eugene C., 1933-
M.S. (Master of Science)
Department of Geology
Water quality--Illinois--Measurement; Water--Pollution--Illinois--Measurement; Sulphates
The isotopic composition of SO₄ was studied to identify the major sources of SO₄ in northern Illinois streams. Attempts to use SO₄ isotopic composition as an environmental tracer rely on the fact that once formed, SO₄ does not appreciably exchange sulfur or oxygen with sulfide minerals or water at near surface conditions. Accumulated data on the isotopic composition and concentration of various sulfur sources, sulfate sources and the end products of sulfate-forming reactions were used to estimate the relative importance of each to the SO₄ load of northern Illinois streams. The present study was intended to be a survey of regional conditions. Sixteen streams were sampled at 20 sampling locations. Stream sampling locations were selected so that several SO₄ terrains were covered, including farmland, urban areas, a former coal surface mining area and an area of sulfide ore mineralization in shallow bedrock. Two rivers were sampled monthly, the Kishwaukee River at DeKalb and the Des Plaines River at River Grove; other streams were sampled 1 to 4 times. As a result 61 pairs of data on the isotopic composition of sulfate have been determined. Results of the study have indicated that the low flow and overall average SO₄ isotopic composition of rural stations can be explained mostly as a function of sulfide mineral weathering in glacial sediments or bedrock. There were, however, several sampling stations in the Chicago metropolitan region with ¹⁸O[sub SO]₄ compositions greater than +5 per mil which does not fit a hypothesis of sulfide mineral oxidation. Other possibilities for the major SO₄ source in that region are 1) a greater component of SO₄ aerosol deposition, 2) point source discharges of SO₄ including municipal sewage treatment plant effluent, 3) S or SO₄ from all possible sources made isotopically indistinguishable through a complex cycling by microorganisms in the shallow ground-water flow regime or in the surface waters. Data collected on SO₄ isotopic composition versus discharge at the monthly sampling stations has led to equations applicable for estimating the percent atmospheric SO₄ for a given discharge. One such model estimates that the atmosphere contributes approximately 20-40% of the SO₄ load during high flow events.
Cipriano, Gary, "Sulfur and oxygen isotope study of sulfate in selected streams of Northern Illinois" (1984). Graduate Research Theses & Dissertations. 5137.
viii, 98 pages
Northern Illinois University
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