Author

Lo Vetere

Date of Award

8-1996

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. Alan E. Kehew

Second Advisor

Dr. William Sauck

Third Advisor

Dr. W. Thomas Straw

Access Setting

Masters Thesis-Open Access

Abstract

Ground-water sampling in a shallow unconfined aquifer within a predominantly agricultural area in southwestern Michigan indicated spatial and temporal variability in the distribution of nitrate. The unconfined aquifer, which is about 40 feet thick, consists of glacially-deposited sand and gravel with interbedded clay lenses and is separated from a lower semi-confined aquifer by a 3-to 26-feet-thick till layer.

The site of the study was a 47-acre agricultural field, characterized by corn and alfalfa hay production, to which hog manure and commercial fertilizers were frequently applied. The shallow water table and relatively permeable glacial sands in the vadose zone combined to allow rapid infiltration of nitrate - derived from the fertilizer and manure - to the ground water.

Ground-water sampling at the site consisted of monthly monitoring (September 95-April 96) for nitrates and quarterly monitoring (June 95-April 96) for major ions at seven newly installed wells and one existing well. Nitrate-N concentrations reflected significant variability, ranging from non-detect to 48 mg/1, with maximum concentrations occurring in the fall after the corn was harvested.

The results demonstrate that stratigraphy, crop type and management, depth to water table and rates and amounts of fertilizer application all combine to influence the spatial and temporal distribution of nitrate in ground water.

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