Nitrogen attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches

Smith, Thor E.; Laursen, Andrew E.; Deacon, Jeffrey R.

doi:10.1007/s10533-008-9186-7

Cited by 19 publications

(18 citation statements)

References 27 publications

(17 reference statements)

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“…A major benefit of modeling metabolism and denitrification together is that, through the use of a Bayesian statistical framework, we are able to first estimate K 600 using the diel patterns of oxygen [ Holtgrieve et al ., ; Hotchkiss and Hall , ; Hall et al ., ]. By first modeling oxygen, we estimated K 600 , avoiding labor‐intensive tracer injections which have been used to estimate K for previous open‐channel N 2 models [ Laursen and Seitzinger , ; McCutchan et al ., ; Smith et al ., ]. However, empirical estimates of K could easily be included in our modeling approach, particularly for ecosystems with higher values of K which would necessitate an empirical, rather than modeling approach.…”

Section: Discussionmentioning

confidence: 99%

Sediment, water column, and open‐channel denitrification in rivers measured using membrane‐inlet mass spectrometry

et al. 2016

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Riverine biogeochemical processes are understudied relative to headwaters, and reach-scale processes in rivers reflect both the water column and sediment. Denitrification in streams is difficult to measure, and is often assumed to occur only in sediment, but the water column is potentially important in rivers. Dissolved nitrogen (N) gas flux (as dinitrogen (N 2 )) and open-channel N 2 exchange methods avoid many of the artificial conditions and expenses of common denitrification methods like acetylene block and 15 N-tracer techniques. We used membrane-inlet mass spectrometry and microcosm incubations to quantify net N 2 and oxygen flux from the sediment and water column of five Midwestern rivers spanning a land use gradient. Sediment and water column denitrification ranged from below detection to 1.8 mg N m À2 h À1 and from below detection to 4.9 mg N m À2 h À1 , respectively. Water column activity was variable across rivers, accounting for 0-85% of combined microcosm denitrification and 39-85% of combined microcosm respiration. Finally, we estimated reach-scale denitrification at one Midwestern river using a diel, open-channel N 2 exchange approach based on reach-scale metabolism methods, providing an integrative estimate of riverine denitrification. Reach-scale denitrification was 8.8 mg N m À2 h À1 (95% credible interval: 7.8-9.7 mg N m À2 h À1 ), higher than combined sediment and water column microcosm estimates from the same river (4.3 mg N m À2 h À1 ) and other estimates of reach-scale denitrification from streams. Our denitrification estimates, which span habitats and spatial scales, suggest that rivers can remove N via denitrification at equivalent or higher rates than headwater streams.

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Section: Discussionmentioning

confidence: 99%

Sediment, water column, and open‐channel denitrification in rivers measured using membrane‐inlet mass spectrometry

et al. 2016

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“…Error in measured N 2 and Ar was assumed to be due to limits of precision and error in equilibrium concentrations due to measurement error of temperature. Error in groundwater inputs was assumed to be 10 % of the measured value (McCutchan et al 2003), and depth and surface area error were set at 2.5 % which lies in between values reported in McCutchan et al (2003) and Smith et al (2008). Variance in groundwater concentrations of N 2 , Ar, N 2 O, and 222 Rn was assumed to be due to spatial variation along the reach; therefore, the standard deviation of the 3-5 piezometers was used (Table 3).…”

Section: Uncertainty Analysismentioning

confidence: 99%

“…The open channel method (Laursen and Seitzinger 2002;McCutchan et al 2003) is one such method used to measure in-stream denitrification at the reach scale (10 1 -10 4 meters) and has been applied in a variety of riverine systems (Harrison et al 2005;Pribyl et al 2005;Smith et al 2008;Yan et al 2004). Laursen and Seitzinger (2002) developed a multistation method that applies a Lagrangian sampling design to estimate denitrification within a conceptual moving parcel of water while accounting for atmospheric exchange.…”

Section: Introductionmentioning

confidence: 99%

Balancing watershed nitrogen budgets: accounting for biogenic gases in streams

et al. 2016

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Denitrification is critical for removal of reactive nitrogen (Nr) from ecosystems. However, measuring realistic, scalable rates and understanding the role of denitrification and other dissimilatory processes in watershed nitrogen (N) budgets remains a significant challenge in biogeochemistry. In this study, we focused on the stream reach and network scale in three Mid-Atlantic coastal plain watersheds. We applied open channel methods to measure biogenic N 2 and N 2 O gas fluxes derived from both in-stream and terrestrial nitrogen processing. A large portion of biogenic N 2 flux through streams (33-100 %, mean = 74 %) was a result of groundwater delivery of biogenic N 2 with the remaining portion due to instream N 2 production. In contrast, N 2 O was largely produced in-stream, with groundwater delivery contributing on average 12 % of the total biogenic N 2 O flux. We scaled these measurements across one stream network and compared them to hydrologic Nr export and net anthropogenic N inputs (NANI) to a 4.8 km 2 watershed. The N budget revealed that, during the study period, the biogenic N 2 flux through streams was comparable to the difference between NANI and hydrologic Nr export (i.e. the ''missing'' N). This study provides a methodological and conceptual framework for incorporating terrestrial and in-stream derived biogenic N gas fluxes into watershed N budgets and supports the hypothesis that denitrification is the primary fate of NANI that is not exported in streamflow.

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“…Residence time decreases with increasing river discharge, reducing the opportunity and duration for different biogeochemical reactions to remove nutrients (Madsen et al, 2001;Smith et al, 2008). Nutrient retention capacity decreases with increasing river discharge as the contact surface between sediment and river water is also reduced (or increasing volume:surface area ratio), decreasing nutrient processing efficiency (Alexander et al, 2000;Pieterse et al, 2003;Chen et al, 2011a).…”

mentioning

confidence: 99%

A modified load apportionment model for identifying point and diffuse source nutrient inputs to rivers from stream monitoring data

Chen

Dahlgren

Lü

2013

Journal of Hydrology

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s u m m a r yDetermining point (PS) and diffuse source (DS) nutrient inputs to rivers is essential for assessing and developing mitigation strategies to reduce excessive nutrient loads that induce eutrophication. However, application of watershed mechanistic models to assess nutrient inputs is limited by large data requirements and intensive model calibration efforts. Simple export coefficient models and statistical models also require extensive primary watershed attribute information and further they cannot address seasonal patterns of nutrient delivery. In practice, monitoring efforts to identify all PSs within a watershed are very difficult due to time and economic limitations. To overcome these issues, based on the fundamental hydrological differences between PS and DS pollution, a modified load apportionment model (LAM) was developed relating the river nutrient load to nutrient inputs from PS, DS and upstream inflow sources while adjusting for in-stream nutrient retention processes. Estimates of PS and DS inputs can be easily achieved through Bayesian calibration of the five model parameters from commonly available stream monitoring data. It considers in-stream nutrient retention processes, temporal changes of PS and DS inputs, and nutrient contributions from upstream inflow waters, as well as the uncertainty associated with load estimations. The efficacy of this modified LAM was demonstrated for total nitrogen (TN) source apportionment using a 6-year record of monthly water quality data for the ChangLe River in eastern China. Aimed at attaining the targeted river TN concentration (2 mg L À1 ), required input load reductions for PS, DS and upstream inflow were estimated. This modified LAM is applicable for both district-based and catchment-based water quality management strategies with limited data requirements, providing a simple, effective and economical tool for apportioning PS and DS nutrient inputs to rivers.

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Nitrogen attenuation in the Connecticut River, northeastern USA; a comparison of mass balance and N2 production modeling approaches

Cited by 19 publications

References 27 publications

Sediment, water column, and open‐channel denitrification in rivers measured using membrane‐inlet mass spectrometry

Sediment, water column, and open‐channel denitrification in rivers measured using membrane‐inlet mass spectrometry

Balancing watershed nitrogen budgets: accounting for biogenic gases in streams

A modified load apportionment model for identifying point and diffuse source nutrient inputs to rivers from stream monitoring data

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