Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds<sup>1</sup>

Watson, Tara K.; Kellogg, D. Q.; Addy, Kelly; Gold, Arthur J.; Stolt, Mark H.; Donohue, Sean W.; Groffman, Peter M.

doi:10.1111/j.1752-1688.2010.00418.x

Cited by 16 publications

(9 citation statements)

References 36 publications

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“…Our results clearly show that urban wetlands have the potential to function as denitrifi cation sinks for NO 3 − . Denitrifi cation rates (<0.1 to 193.2 μg N kg −1 d −1 ) at our sites are similar to those reported for both urban and nonurban sites (Addy et al, 2002Kellogg et al, 2005;Whitmire and Hamilton, 2005;Watson et al, 2010;Kaushal et al, 2008b). Th e rates here were similar to previous denitrifi cation measurements in restored and unrestored stream banks at Minebank Run (<1 to 262 μg N kg −1 d −1 ) (Kaushal et al, 2008b) that were determined to be signifi cant relative to stream water NO 3 − loads.…”

Section: In Situ Denitrifi Cation Rates Among Wetlandssupporting

confidence: 88%

Denitrification in Alluvial Wetlands in an Urban Landscape

et al. 2011

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Riparian wetlands have been shown to be eff ective "sinks" for nitrate N (NO 3 − ), minimizing the downstream export of N to streams and coastal water bodies. However, the vast majority of riparian denitrifi cation research has been in agricultural and forested watersheds, with relatively little work on riparian wetland function in urban watersheds. We investigated the variation and magnitude of denitrifi cation in three constructed and two relict oxbow urban wetlands, and in two forested reference wetlands in the Baltimore metropolitan area. Denitrifi cation rates in wetland sediments were measured with a 15 N-enriched NO 3 − "push-pull" groundwater tracer method during the summer and winter of 2008. Mean denitrifi cation rates did not diff er among the wetland types and ranged from 147 ± 29 μg N kg soil −1 d −1 in constructed stormwater wetlands to 100 ± 11 μg N kg soil −1 d −1 in relict oxbows to 106 ± 32 μg N kg soil −1 d −1 in forested reference wetlands. High denitrifi cation rates were observed in both summer and winter, suggesting that these wetlands are sinks for NO 3 − year round. Comparison of denitrifi cation rates with NO 3 − standing stocks in the wetland water column and stream NO 3 − loads indicated that mass removal of NO 3 − in urban wetland sediments by denitrifi cation could be substantial. Our results suggest that urban wetlands have the potential to reduce NO 3 − in urban landscapes and should be considered as a means to manage N in urban watersheds.

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Section: In Situ Denitrifi Cation Rates Among Wetlandssupporting

confidence: 88%

Denitrification in Alluvial Wetlands in an Urban Landscape

et al. 2011

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“…Furthermore, over the course of an inundation event, soil redox conditions become more suitable for denitrification [ Ensign et al , 2008], potentially increasing rates as microbes synthesize new denitrifying enzymes in response to changing environmental conditions [ Brock , 1961]. However, some previous studies have shown no relationship between floodplain denitrification rates and NO 3 − availability [ Watson et al , 2010; Orr et al , 2007], and Roley et al [2012] found that the addition of stream water usually had no effect on denitrification rates in floodplain soils. Therefore, further experimentation is necessary to understand how floodplain soil denitrification responds to inundation in agriculturally influenced streams.…”

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confidence: 99%

Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream

2012

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[1] Stream ecotones, specifically the lateral floodplain and subsurface hyporheic zone, can be important sites for nitrogen (N) removal via denitrification, but their role in streams with constructed floodplains has not been examined. We studied denitrification in the hyporheic zone and floodplains of an agriculturally influenced headwater stream in Indiana, USA, that had floodplains added as part of a "two-stage ditch" restoration project. To examine the potential for N removal in the hyporheic zone, we seasonally measured denitrification rates and nitrate concentrations by depth into the stream sediments. We found that nitrate concentration and denitrification rates declined with depth into the hyporheic zone, but denitrification was still measureable to a depth of at least 20 cm. We also measured denitrification rates on the restored floodplains over the course of a flood (pre, during, and post-inundation), and also compared denitrification rates between vegetated and non-vegetated areas of the floodplain. We found that floodplain denitrification rates increased over the course of a floodplain inundation event, and that the presence of surface water increased denitrification rates when vegetation was present. Stream ecotones in midwestern, agriculturally influenced streams have substantial potential for N removal via denitrification, particularly when they are hydrologically connected with high-nitrate surface water.

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“…The push‐pull method assesses reaction rates of microbial activity by injecting a reactive solute plus tracer into groundwater and later extracting groundwater from the same location while measuring the reduction or accumulation of the various reactants and products (Trudell et al, 1986; Istok et al, 1997). The 15 N‐NO 3 push‐pull method has been used to quantify denitrification in a variety of riparian settings, including fens (Well et al, 2001), freshwater and brackish riparian zones (Addy et al, 2002), pasture and grassland hydromorphic soils (Well et al, 2003), forested riparian sites (Kellogg et al, 2005; Watson et al, 2010), the riparian zone–stream interface of restored urban streams (Kaushal et al, 2008), seepage wetlands (Zaman et al, 2008), and urban wetlands (Harrison et al, 2011).…”

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Shallow Groundwater Denitrification in Riparian Zones of a Headwater Agricultural Landscape

et al. 2014

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Riparian zones adjacent to cropped lands are effective at reducing nitrate (NO) loads to receiving water bodies primarily through plant assimilation and denitrification. Denitrification represents a permanent removal pathway and a greenhouse gas source, converting NO to inert N gas or nitrous oxide (NO), and has been the subject of many studies in agricultural landscapes. Despite the prevailing notion that riparian zones can be areas of enhanced denitrification, there is a lack of in situ denitrification measurements from these areas that buffer streams and rivers from NO originating in upland cropped soils, especially over time scales that capture seasonal dynamics. We measured in situ groundwater denitrification rates in two riparian zones of an intensive dairy farm located in the headwaters of the Susquehanna River. Denitrification rates determined monthly over a 1-yr period with the N-NO push-pull method ranged from 0 to 4177 μg N kg soil d (mean, 830 ± 193 μg N kg soil d). Denitrification showed a distinct seasonal pattern, with highest rates observed in the spring and summer, concomitant with warmer temperatures and decreasing dissolved oxygen. We estimate an annual N loss of 470 ± 116 kg yr ha of riparian zone via denitrification in the shallow saturated zone, with the potential for >20% of this amount occurring as NO. Total denitrification from shallow groundwater in the riparian zone was equivalent to 32% of manure N spread on the adjacent upland field, confirming the importance of riparian zones in agricultural landscapes at controlling N loads entering downstream waters.

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Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds¹

Cited by 16 publications

References 36 publications

Denitrification in Alluvial Wetlands in an Urban Landscape

Denitrification in Alluvial Wetlands in an Urban Landscape

Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream

Shallow Groundwater Denitrification in Riparian Zones of a Headwater Agricultural Landscape

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Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds1

Cited by 16 publications

References 36 publications

Denitrification in Alluvial Wetlands in an Urban Landscape

Denitrification in Alluvial Wetlands in an Urban Landscape

Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream

Shallow Groundwater Denitrification in Riparian Zones of a Headwater Agricultural Landscape

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Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds¹