Browsing by Subject "soil"

Now showing 1 - 3 of 3
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    Results of Austin's stream sediment tests, 1991-2002
    (City of Austin, 2003) City of Austin
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    The Interactions of Iron with Soil Organic Acids
    (University of Texas at Austin, 1965-12) Oldham, W.K.; Gloyna, E.F.
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    Water Chemistry of Shoal Creek And Waller Creek, Austin, Texas, and Potential Sources of Nitrate
    (U.S Geological Survey, 1996) Ging, Patricia B.; Lee, Roger W.; Silva, Steven R.
    Steep limestone slopes, thin soils, sparse vegetation, and impervious cover within the Shoal Creek and Waller Creek watersheds, Austin, Texas, contribute to rapid runoff that can quickly carry contaminants such as nitrate, into the creeks. Land use within the watershed is predominantly residential (single-family and multifamily dwellings). Impervious cover within both watersheds was about 55 percent during 1994 95. Water samples were collected for chemical analysis at seven sites in the Shoal Creek and Waller Creek watersheds from September 1994 to April 1995. Samples were collected during 4 stormflow events and 3 base-flow periods. Water samples were analyzed for major ions and nutrients as well as for nitrogen and oxygen isotopes in the nitrate anion. Concentrations of dissolved constituents, including nitrate, are smaller in stormflow samples than in base-flow samples. Calculated dissolved solids range from 16 to 187 milligrams per liter for stormflow samples and from 213 to 499 milligrams per liter for base-flow samples. Nitrogen and oxygen isotopes in dissolved nitrate in conjunction with water chemistry were used to indicate sources of nitrate in surface water. A combination of atmospheric nitrate, and soil nitrate and ammonium fertilizer is the most likely source of nitrate in stormflow samples (assuming that there is little or no use of synthetic nitrate fertilizers in the watersheds). Nitrogen and oxygen isotopic data in nitrate for stormflow samples are in or near the isotopic composition ranges for atmospheric nitrate, and soil nitrate and ammonium fertilizer sources. Nitrogen and oxygen isotopic data in nitrate for base-flow samples are in or near the isotopic composition ranges for soil nitrate and ammonium fertilizer, and sewage and animal waste sources of nitrate. Sewage is the most likely source of nitrate in base flow because of the potential for older sewer lines to leak, the proximity of sewer lines to creek beds, and an excess of chloride relative to sodium at some sampling sites (an indicator of the presence of sewage) under base-flow conditions. Nitrate in the creeks at any given time is a mixture that results predominantly from surface sources (atmospheric nitrate, soil nitrate and ammonium fertilizer) during stormflow and predominantly from subsurface sources (sewage) during base flow.