Date of Award

Fall 2006

Project Type


Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

William H McDowell


The effect of NO3- deposition on NH4 +, DON, and DOC retention as well as abiotic NO3 - retention via the hypothesized "ferrous wheel" mechanism was examined in oxic and anoxic tropical and oxic temperate soils using sorption isotherm experiments. Adsorption of NH4+, DON, and DOC by mineral soils was examined in forest floor extracts with DOC levels of 0-50 mg/L. Experimental treatments included no added NO3-, 4mg/L of added NO3-, or 4 mg/L of NO3 - and 2 mg/L of Fe3+. Ferric iron was added since it would likely increase DOC retention in the context of podzolization, and it might also influence N retention. Retention of NH4 + and DOC did not change upon NO3- addition in any of the soils. Although there are some experimental conditions that could be changed, the results indicate that the ferrous wheel hypothesis does not explain the NO3- retention by mineral soils that has been observed in the field. (Abstract shortened by UMI.).