| Abstract: | Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater-stream water mixing within sediment cores, which provided a well-defined one-dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic-anaerobic interface. Ammonium (NH4+) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO3-) equaling ???25% of the NH4+ loss was produced in the upper sediments. The NH4+ and NO3- profiles in the uppermost sediments resulted from coupled nitrification-denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42-209 and 53-160 mg N m-2 day-1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River. |
| Genre: | Article |
| ProdID: | 70025723 |
| Citation Author: | Sheibley, R. W.; Duff, J. H.; Jackman, A. P.; Triska, F. J. |
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| Citation End Page: | 1140 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Limnology and Oceanography |
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| Citation Number Of Pages: | 12 |
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| Citation Search Results Text: | Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores; 2003; Article; Journal; Limnology and Oceanography; Sheibley, R. W.; Duff, J. H.; Jackman, A. P.; Triska, F. J. |
| Citation Start Page: | 1129 |
| Citation Volume: | 48 |
| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores; 2003; Article; Journal; Limnology and Oceanography; Sheibley, R. W.; Duff, J. H.; Jackman, A. P.; Triska, F. J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 2003 00:00 -0600 |
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