Tracer Additions for Spiraling Curve Characterization (TASCC): Quantifying stream nutrient uptake kinetics from ambient to saturation

Abstract

Stream nutrient tracer additions and nutrient spiraling metrics are frequently used to quantify lotic ecosystem behavior. Of particular concern is the influence nutrient concentration exerts on nutrient retention and export. However, characterizing spiraling response curves across a range of concentrations has remained challenging, in part due to the large effort required to develop these curves using traditional (e.g., plateau or steadystate) approaches. Here we outline and demonstrate a new approach to quantify nutrient uptake kinetics from ambient to saturation using Tracer Additions for Spiraling Curve Characterization (TASCC). This approach provides a rapid and relatively easy technique for quantifying ambient-spiraling parameters, nutrient uptake kinetics and kinetic model parameterization, and assessment of stream proximity to saturation. We compare the results from TASCC to traditional breakthrough curve integrated and plateau approaches. We highlight the advantages of the TASCC approach for characterizing continuous spiraling response curves from ambient to saturation with a single tracer addition experiment, and its applicability to larger rivers where achieving plateau conditions (i.e., steady-state) is impractical. Environmental Protection Agency. It has not been formally reviewed by the EPA. The views expressed in this document are solely those of Timothy P. Covino, and the EPA does not endorse any products or commercial services mentioned in this publication. We would like to thank Michelle Baker, Robert Payn, Maury Valett, and Steve Thomas for critcal discussions regarding this work, Galena Ackerman and John Mallard for laboratory analysis, and Tricia Jenkins for help collecting experimental field data. We thank the Big Sky community for allowing access to sampling sites.

Inferring nitrogen removal in large rivers from high‐resolution longitudinal profiling

“…We conclude that while this method may enable important refinements in the spatial ecology and biogeochemistry of rivers, it may not ultimately yield unequivocal inference of kinetics due to small longitudinal concentration gradients that arise within most rivers, and due to the confounding effects of temporally varying removal. Other methods may be better suited, though we note comparing multiple injections (Payn et al 2005) performed at different times of day or even single pulse injections (Covino et al 2010) in long-residence-time systems may also require adjustment for time-varying removal.…”

“…In this ''efficiency-loss model,'' removal is a power function of concentration. Other recent work using plateau (Earl et al 2006) and pulse additions (Covino et al 2010) to assess reaction kinetics has suggested Michaelis-Menten (MM) kinetics where removal becomes completely saturated at high concentration. Empirically resolving controls on removal kinetics in time and space, with network position and in a way that is pathway specific (i.e., assimilation vs. denitrification), is an important priority, with implications for understanding river responses to nutrient enrichment (Mulholland et al 2008).…”

“…Unlabeled nutrient enrichment additions, despite not discriminating removal pathways, are more feasible at higher flows and longer residence times (Tank et al 2008), but may enhance removal rates (Mulholland et al 2002), requiring repeated dosing to varying plateau concentrations to backextrapolate removal at ambient conditions (Payn et al 2005). Pulse injection methods (Covino et al 2010) to estimate both ambient concentration removal rates and removal kinetics with increased concentration obviate constraints of repeated plateau additions, but retain substantial logistical constraints in large rivers, and in river networks.…”

“…Both applications fit a single trend line to the entire profile and did examine the spatial variability. Furthermore, the nature of the fitted trend line implicitly assumed first-order kinetics, an assumption subsequently challenged by multiple studies (Earl et al 2006;O'Brien et al 2007;Covino et al 2010). In this work, we adopt a Lagrangian reference frame to assess river N removal in a manner that is passive and inexpensive (i.e., performed at ambient conditions without isotope or nutrient additions), repeatable, and scalable across river sizes.…”

Land use impact on overland flow: micro-scale field experimental analysis

“…/jwld-2016 by MOŢOC et al [1975], IONIŢĂ et al [2006], MIRCEA et al [2010;, MAETENS et al [2012]; hydrological: PETRESCU [1974], STANCIU [2002], YU et al [1997], BENAVIDES-SOLORIO, MACDONALD [ , JOEL et al [2002; forestry by ABAGIU et al [1973], HARTANTO et al [2003]; biological factors [WAIN-WRIGHT et al 2000]; ecologic by GBUREK and SHAR-PLEY [1998], DEBANO [2000], COVINO et al [2010], ATUCHA et al [2013].…”