HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Moore, P. A. Articles by Graetz, D. A. Search for Related Content PubMed Articles by Moore, P. A., Jr. Articles by Graetz, D. A. Agricola Articles by Moore, P. A. Articles by Graetz, D. A.

Nutrient Transformations in Sediments as Influenced by Oxygen Supply

Southeast Res. and Extension Center, Univ. of Arkansas, P.O. Box 3508, Monticello, AR 71655;

K. R. Reddy and D. A. Graetz

Soil Science Dep., 106 Newell Hall, Univ. of Florida, Gainesville, FL 32611.

^* Corresponding author.

ABSTRACT

The oxidation status of sediments greatly affects biogeochemical processes. The objective of this study was to determine the influence of various levels of O₂ on nutrient transformations in lake sediments. Decomposition of sediment organic matter was evaluated under varying levels of O₂. Bulk sediment samples obtained from a hypereutrophic lake in central Florida were incubated in stirred microcosms at 25°C for 100 d at four O₂ levels. The O₂ levels were accomplished by bubbling N₂ containing 0, 0.2, 2.0, and 20.0% O₂ through the stirred suspensions. Redox potential (Eh) measurements indicated that the two highest O₂ levels (i.e., 2.0 and 20.0% O₂) resulted in oxidizing conditions (Eh > 400 mV), whereas the lowest O₂ levels (0 and 0.2% O₂) resulted in reduced conditions (Eh < –300 mV). First-order rate constants calculated based on CO₂ evolution were 0.00010, 0.00027, 0.00062, and 0.00068 d^–1 for the 0, 0.20, 2.0, and 20.0% O₂ levels, respectively. Methane was detected in the sediments incubated under 0 and 0.2% O₂ level, with CO₂/CH₄ ratios of 3.5 and 160, respectively. Accumulation of soluble organic C (SOC) was greater under reduced conditions than oxidized conditions. Ammonium concentrations decreased rapidly in the oxidized treatments, with concurrent increases in NO₃-N concentrations, whereas under reducing conditions NH₄-N concentrations slowly increased. Rates of N mineralization were slightly higher under oxidized conditions. Although the ratio of N mineralized to CO₂ evolved was higher at low O₂ levels, the amount of N mineralized vs. the sum of C metabolites (CO₂ + CH₄ + SOC) was relatively constant under all O₂ levels (6.7:1). Reducing conditions resulted in a depletion of SO^2–₄, whereas under oxidizing conditions SO^2–₄ concentrations increased, probably due to sulfide oxidation. Soluble reactive P concentrations were lower under oxidizing conditions.

Florida Agricultural Experiment Station Journal Series xxxx.

Contribution from the Soil Science Dep., Univ. of Florida.

Received for publication May 6, 1991.

This article has been cited by other articles:

				J. Song, Y. Luo, Q. Zhao, and P. Christie Microcosm Studies on Anaerobic Phosphate Flux and Mineralization of Lake Sediment Organic Carbon J. Environ. Qual., November 1, 2004; 33(6): 2353 - 2356. [Abstract] [Full Text] [PDF]