Denitrification in nitrate-contaminated groundwater: Occurrence in steep vertical geochemical gradients

Smith, Richard L.; Howes, Brian L.; Duff, John H.

doi:10.1016/0016-7037(91)90026-2

Cited by 223 publications

(167 citation statements)

References 34 publications

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“…6A-C); calculations for the deep STZ are based on the location at piezometer 6 where freshwater nitrate mixed into the deep STZ (Fig. 6D-F ; where e is enrichment factor; e 5 213.9 for denitrification (Smith et al 1991); e 5 221 for nitrification (Kendall and McDonnell 1998). { Dilution is the decrease in concentration not accounted for by isotopically fractionating loss processes.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen biogeochemistry of submarine groundwater discharge

Kroeger

Charette

2008

Limnology & Oceanography

193

190

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To investigate the role of the seepage zone in transport, chemical speciation, and attenuation of nitrogen loads carried by submarine groundwater discharge, we collected nearshore groundwater samples (n 5 328) and examined the distribution and isotopic signature (d 15 N) of nitrate and ammonium. In addition, we estimated nutrient fluxes from terrestrial and marine groundwater sources. We discuss our results in the context of three aquifer zones: a fresh groundwater zone, a shallow salinity transition zone (STZ), and a deep STZ. Groundwater plumes containing nitrate and ammonium occurred in the freshwater zone, whereas the deep STZ carried almost exclusively ammonium. The distributions of redox-cycled elements were consistent with theoretical thermodynamic stability of chemical species, with sharp interfaces between water masses of distinct oxidation : reduction potential, suggesting that microbial transformations of nitrogen were rapid relative to dispersive mixing. In limited locations in which overlap occurs between distribution of nitrate with that of ammonium and dissolved . Loss of nitrogen was not apparent in the shallow STZ, perhaps because of short water residence time. Despite organic Cpoor conditions, the nearshore aquifer and subterranean estuary are biogeochemically active zones, where attenuation of N loads can occur. Extent of attenuation is controlled by the degree of mixing of biogeochemically dissimilar water masses, highlighting the critical role of hydrogeology in N biogeochemistry. Mixing is related in part to thinning of the freshwater lens before discharge and to dispersion at the fresh : saline groundwater interface, features common to all submarine groundwater discharge zones.

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Section: Resultsmentioning

confidence: 99%

Nitrogen biogeochemistry of submarine groundwater discharge

Kroeger

Charette

2008

Limnology & Oceanography

193

190

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“…Earlier studies indicated that denitrification in sediments underlying and adjacent to the river removed a part of the nitrate from groundwater before its discharge to the river (McMahon and B6hlke, 1996). However, those studies did not identify the factors affecting denitrification, such as nitrate concentration, organic carbon availability, and temperature (Smith and Duff, 1988;Morris et al, 1988;Fujikawa and Hendry, 1991;Smith et al, 1991;Korom, 1992;Starr and Gillham, 1992;Bradley et al, 1992Bradley et al, , 1995Hanson et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments

Pfenning

McMahon

1997

Journal of Hydrology

166

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Follow this and additional works at: http://digitalcommons.unl.edu/usgsstaffpub Part of the Earth Sciences CommonsThis Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of Nebraska -Lincoln. It has been accepted for inclusion in USGS Staff --Published Research by an authorized administrator of DigitalCommons@University of Nebraska -Lincoln.Pfenning, K. S. and McMahon, P. B., "Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments" (1996) Abstract A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N20) production rates in laboratory incubations of riverbed sediments to evaluate the effect of varying nitrate concentrations, organic carbon concentrations and type, and water temperature on potential denitrification rates. Sediment incubations amended with nitrate, at concentrations ranging from 357 to 2142 ~tmol 1 -I (as measured in the field), produced no significant increase (P > 0.05) in N20 production rates, indicating that the denitrification potential in these sediments was not nitrate limited. In contrast, incubations amended with acetate as a source of organic carbon, at concentrations ranging from 0 to 624 ~mol 1-1, produced significant increases (P < 0.05) in N20 production rates with increased organic carbon concentration, indicating that the denitrifieation potential in these sediments was organic carbon limited. Furthermore, N20 production rates also were affected by the type of organic carbon available as an electron donor. Acetate and surface-water-derived fulvic acid supported higher N20 production rates than groundwater-derived fulvic acid or sedimentary organic carbon. Lowering incubation temperatures from 22 to 4°C resulted in about a 77% decrease in the N20 production rates. These results help to explain findings from previous studies indicating that only 15-30% of nitrate in groundwater was denitrified before discharging to the South Platte River and that nitrate concentrations in the river generally were higher in winter than in summer.

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“…Inorganic nitrogen ammonia and nitrate is a significant plume component, with concentra-Ž tions often exceeding 1 mM LeBlanc, 1984;Savoie . and LeBlanc, 1998;Smith et al, 1991 . Dissolved organic carbon in the plume is 2-4 mg l y1 and is Ž composed of mostly refractory compounds Barber .…”

mentioning

confidence: 98%

Evaluation of gel filtration resins for the removal of PCR-inhibitory substances from soils and sediments

Miller

2001

Journal of Microbiological Methods

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Denitrification in nitrate-contaminated groundwater: Occurrence in steep vertical geochemical gradients

Cited by 223 publications

References 34 publications

Nitrogen biogeochemistry of submarine groundwater discharge

Nitrogen biogeochemistry of submarine groundwater discharge

Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments

Evaluation of gel filtration resins for the removal of PCR-inhibitory substances from soils and sediments

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