摘要：Environmental controls of sediment denitrification were examined at four agricultural, channelized streams in Eastcentral Illinois between June 2003 and February 2005. Differences in sediment properties, water temperature, and nitrate-N (NO 3 -N) supply varied temporally and spatially among the four streams. Sediment denitrification rates ranged from 0 to 0.3 μg N g dry mass (DM) -1 h -1 at stream sites characterized by low benthic organic matter content and coarse-textured sediments, 0 to 1.5 μg N (g DM) -1 h -1 at stream sites characterized by moderate benthic organic matter content and fine-textured sediments, and 0.2 to 3.3 μg N (g DM) -1 h -1 in emergent grass beds characterized by high benthic organic matter content and fine-textured sediments. Seasonally, sediment denitrification rates were greatest in the summer and least in the winter, with water temperature explaining 42 to 65% of the variation in sediment denitrification rate in three of the four streams. Benthic organic matter concentration explained 21 to 67% of the variation of sediment denitrification in all streams. Denitrification assays conducted on sediments amended with increasing concentrations of NO 3 -N indicated that sediment denitrification was limited by N availability in fine-textured sediments but not in coarse-textured sediments when stream NO 3 -N concentrations were <1 mg L -1 , which was typical in late summer.
