Factors affecting denitrification in agricultural headwater streams in Northeast Ohio, USA

Abstract

As a result of increased anthropogenic nitrogen (N) loading in surface waters of agricultural watersheds, there is enhanced interest to understand and quantify N removal mechanisms. Denitrification, an important N removal mechanism in aquatic systems, may contribute to reducing N pollution in agricultural headwater streams. However, the key factors controlling this process in lotic systems remain unclear. The objective of our study was to examine the factors regulating rates of denitrification in the sediments of agricultural headwater streams in the midwestern USA. Denitrification rates were variable among streams and treatments (\0.1-28.0 lg N g AFDM -1 h -1 ) and on average, were higher than those reported for similar headwater streams. Carbon quantity and quality, and pH had no effect on denitrification, while temperature and nitrate (NO À 3 ) concentrations had a positive effect on rates of denitrification. Specifically, NO À 3 controlled denitrification followingMichaelis-Menten kinetics. We calculated a value of k m (1.0 mg NO À 3 -N L -1 ) that was comparable to other studies in aquatic sediments but was well below the median in-stream NO À 3 concentrations (5.2-17.4 mg NO À 3 -N L -1 ) observed at the study sites. Despite high rates of denitrification, this removal mechanism is most likely NO À 3 saturated in the agricultural headwater streams we examined, suggesting that these systems are not effective at removing in-stream N.

Multi-scale measurements and modeling of denitrification in streams with varying flow and nitrate concentration in the upper Mississippi River basin, USA

“…5a). Although the saturation equation is used commonly to describe enzymatic limitation on reaction rates in homogeneous systems, and it has been used to describe nutrient uptake rates in streams (Garcia-Ruiz et al 1998b;Payn et al 2005;Opdyke and David 2007;Herrman et al 2008), there is not necessarily a direct link between these different applications, and a mechanistic model for this relation may be complex for systems with benthic gradients and(or) hyporheic flow.…”

“…e Estimated values of k1 denit calculated from v f,denit /depth; depth was calculated from Q using the empirical relation (Leopold and Maddock 1953) Herrman et al 2008). Temperature effects include changes in microbial community structure and biomass, as well as thermal effects on enzymatic processes, resulting in complex functions with effective q10 values ranging from around 1 (no temperature effect) to 2 (doubling the rate for 10°C increase in T) or more (e.g., Herbert and Nedwell 1990), where q10 is defined by: rate T /rate 20 = q10 [(T-20)/10] , with T, 10, and 20 in°C.…”

Effect of dissolved oxygen and nitrogen on emission of N 2 O from rivers in China

“…Previous studies have demonstrated that N 2 O production and emission from diverse rivers respond significantly to increasing anthropogenic N loading (Cole and Caraco, 2001;Garnier et al, 2006). Numerous investigations have reported strong correlations between dissolved N 2 O and NO 3 -concentration in river waters (Herrman et al, 2008;Silvennoinen et al, 2008). Yan et al (2012) concluded that NO 3 -is a valid predictor of river N 2 O production in a large-deep river.…”

Sources of sediment-bound organic matter infiltrating spawning gravels during the incubation and emergence life stages of salmonids

“…In contrast, the bulk nitrogen isotope values passed the mass conservation test for all of the sampling sites (Table 2). It is, nevertheless, important to recognise that nitrogen isotopic fractionation can be induced by a number of processes including nitrification, denitrification, nitrogen fixation and assimilation (Montoya and McCarthy, 1995;Lehmann et al, 2002;Hantush, 2007;Herman et al, 2008). On this basis, the tendency for transformations of bulk isotope fingerprints during fluvial transport warrants further work (Kendall et al, 2001;Fox et al, 2010).…”