Date of Award

12-1995

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. Alan E. Kehew

Second Advisor

Dr. Duane Hampton

Third Advisor

Dr. Michael Barcelona

Access Setting

Masters Thesis-Open Access

Abstract

The purpose of this thesis was to observe and attempt to explain the variations of carbon dioxide in the vadose zone of a nature area in southwestern Michigan. Well nests, consisting of discrete soil gas sampling points and temperature probes set at depths ranging from 3 to 53 feet, were constructed in a sandy, glacial outwash plain. Soil samples were collected for analysis of organic carbon content during installation. Soil gas samples were collected periodically from June, 1992 to March, 1993 and analyzed for CO2 and O2 concentrations. Occasionally, samples were collected and analyzed for isotopic C13 ratios.

Results from the sampling appeared to show strong downward diffusion gradients for CO2 during the summer months and weaker, upward gradients during the winter. Isotopic analyses indicated two different, seasonal sources for the carbon dioxide. Simulations of the data using a modified application of MODFLOW showed a high sensitivity of the CO2 gradient to changes in the production rates and the permeability of root zone.

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