Environmental Controls On Nitrogen And Sulfur Cycles In Surficial Aquatic Sediments

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Chuanhui Gu Ph.D., Assistant Professor (Creator)
Appalachian State University (ASU )
Web Site: https://library.appstate.edu/

Abstract: Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical cycling in aquatic and terrestrial ecosystems. The N and S cycles interact with one another through competition for labile forms of organic carbon between nitrate-reducing and sulfate-reducing bacteria. Furthermore, the N and S cycles could interact through nitrate (NO-3) reduction coupled to S oxidation, consuming NO-3, and producing sulfate (SO2-4). The research questions of this study were: (1) what are the environmental factors explaining variability in N and S biogeochemical reaction rates in a wide range of surficial aquatic sediments when NO-3 and SO2-4 are present separately or simultaneously, (2) how the N and S cycles could interact through S oxidation coupled to NO-3 reduction, and (3) what is the extent of sulfate reduction inhibition by nitrate, and vice versa. The N and S biogeochemical reaction rates were measured on intact surface sediment slices using flow-through reactors. The two terminal electron acceptors NO-3 and SO2-4 were added either separately or simultaneously and NO-3 and SO2-4 reduction rates as well as NO-3 reduction linked to S oxidation were determined. We used redundancy analysis, to assess how environmental variables were related to these rates. Our analysis showed that overlying water pH and salinity were two dominant environmental factors that explain 58% of the variance in the N and S biogeochemical reaction rates when NO-3 and SO2-4 were both present. When NO-3 and SO2-4 were added separately, however, sediment N content in addition to pH and salinity accounted for 62% of total variance of the biogeochemical reaction rates. The SO2-4 addition had little effect on NO-3 reduction; neither did the NO-3 addition inhibit SO2-4 reduction. The presence of NO-3 led to SO2-4 production most likely due to the oxidation of sulfur. Our observations suggest that metal-bound S, instead of free sulfide produced by SO2-4 reduction, was responsible for the S oxidation.

Additional Information

Gu, C., Laverman, A.M., and Pallud, C. (2012). "Environmental Controls On Nitrogen And Sulfur Cycles In Surficial Aquatic Sediments," Frontiers In Terrestrial Microbiology. Version of record available from Frontiers Media SA. [DOI: 10.3389/ fmicb.2012.00045], [ISSN: 1664-302X]
Language: English
Date: 2012
nitrogen cycles, sulfur cycles, surficial aquatic sediments, biogeochemical cycling

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