Opdyke Matthew R, David Mark B, Rhoads Bruce L
University of Illinois, Department of Natural Resources and Environmental Sciences, 1102 S. Goodwin Ave., Urbana, IL 61801, USA.
J Environ Qual. 2006 Oct 27;35(6):2103-12. doi: 10.2134/jeq2006.0072. Print 2006 Nov-Dec.
Within fluvial systems, the spatial variability of geomorphological characteristics of stream channels and associated streambed properties can affect many biogeochemical processes. In agricultural streams of the midwestern USA, it is not known how geomorphological variability affects sediment denitrification rates, a potentially important loss mechanism for N. Sediment denitrification was measured at channelized and meandering headwater reaches in east-central Illinois, a region dominated by intensive agriculture and high NO(3)-N stream export, between June 2003 and February 2005 using the chloramphenicol-amended acetylene inhibition procedure. Sediment denitrification rates were greatest in separation zones, ranging from 0.6 to 76.4 mg N m(-2) h(-1), compared with riffles, point bars, pools, and a run ranging from 0 to 36.5 mg N m(-2) h(-1). Differences in benthic organic matter (r = 0.70) and the percentage of fine-grained sediments (r = 0.93) in the streambeds controlled much of the spatial variations in sediment denitrification among the geomorphological features. Although two meandering study reaches removed 390 and 99% more NO(3)-N by sediment denitrification than adjacent channelized reaches, NO(3)-N loss rates from all reaches were between 0.1 and 15.7% d(-1), except in late summer. Regardless of geomorphological characteristics, streams in east-central Illinois were not able to process the high NO(3)-N loads, making sediment denitrification in this region a limited sink for N.
在河流系统中，河道地貌特征及相关河床特性的空间变异性会影响许多生物地球化学过程。在美国中西部的农业溪流中，地貌变异性如何影响沉积物反硝化速率尚不清楚，而沉积物反硝化是氮素一种潜在的重要损失机制。2003年6月至2005年2月期间，在伊利诺伊州中东部的渠化和蜿蜒源头河段测量了沉积物反硝化速率，该地区以集约农业和高硝酸盐氮溪流输出为主，采用氯霉素修正的乙炔抑制法进行测量。分离区的沉积物反硝化速率最高，范围为0.6至76.4毫克氮·平方米⁻²·小时⁻¹，而浅滩、点坝、深潭和一段急流的反硝化速率范围为0至36.5毫克氮·平方米⁻²·小时⁻¹。河床中底栖有机物（r = 0.70）和细粒沉积物百分比（r = 0.93）的差异控制了地貌特征间沉积物反硝化的大部分空间变化。尽管两条蜿蜒研究河段通过沉积物反硝化去除的硝酸盐氮比相邻的渠化河段多390%和99%，但除夏末外，所有河段的硝酸盐氮损失率在0.1%至15.7%天⁻¹之间。无论地貌特征如何，伊利诺伊州中东部的溪流都无法处理高硝酸盐氮负荷，使得该地区的沉积物反硝化成为氮素的一个有限汇。
