Differences in hydraulic conductivity and NO[sub 3]-N concentrations between weathered and unweathered zones in late Wisconsin till

Conference · Mon Mar 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:7282803

Vondra, G L; Simpkins, W W ^[1]

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1. Iowa State Univ., Ames, IA (United States). Dept. of Geological and Atmospheric Sciences

Transport of agricultural chemicals in late Wisconsin till of the Des Moines Lobe is a prime focus of the Management System Evaluation Area investigations in central Iowa. Recent hydrogeological and water quality investigations at the Ames Till Hydrology site (ATHS) and in the Walnut Creek Drainage Basin (WCDB) have shown significantly higher NO[sub 3]-N concentrations and saturated hydraulic conductivity (K[sub sat]) at the water table in the weathered, upper 4 m of sediment (WZ)(K[sub sat] = 7 [times] 10[sup [minus]6] ms[sup [minus]1]; NO[sub 3]-N = 0 to 30 mg L[sup [minus]1]) than in the unweathered zone beneath it (UWZ) (K[sub sat] = 6 [times] 10[sup [minus]8] ms[sup [minus]1]; NO[sub 3]N-N < 1.0 mg L[sup [minus]1]). The traditional interpretation for this difference is that weathering in the upper zone has increased porosity through oxidation, dissolution, and the formation of fractures and macropores. As a result, NO[sub 3]-N and other agricultural chemicals that enter the WZ are transported downward rapidly to the water table at about 2 m and then are transported laterally. The purpose of this study was to determine whether the process of weathering alone explains the difference in the K[sub sat] and NO[sub 3]-N between the WZ and UWZ.

• OSTI ID: 7282803
• Report Number(s): CONF-9303210-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:3; Conference: 27. annual Geological Society of America (GSA) North-Central Section meeting, Rolla, MO (United States), 29-30 Mar 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
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MORAINES
WATER POLLUTION
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540220* - Environment
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540250 - Environment
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