Stimulating in situ denitrification in an aerobic, highly permeable municipal drinking water aquifer

Critchley, K.; Rudolph, David L.; Devlin, J.F.; Schillig, P. C.

doi:10.1016/j.jconhyd.2014.10.008

Cited by 35 publications

(52 citation statements)

References 41 publications

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“…Denitrification causes both δ 15 N and δ 18 O values of the residual NO 3 − to increase. Sigman et al (2005) and Granger et al (2008)) found that δ 15 N and δ 18 O values of residual NO 3 − increased at a ratio of 2 during denitrification.However, some other surface and groundwater studies found that denitrification caused δ 18 O and δ 15 N to increase at a ratio of more than 1:1(Minet et al 2012; Dale et al 2014a, b) and some closed to 2(Burns et al 2009;Baily et al 2011;Critchley et al 2014;Wexler et al 2014) in agricultural watersheds. However, these lower ratios were not found in urban watersheds(Kaushal et al 2011), presumable because denitrification was limited by less organic carbon(Barnes and Raymond 2010;Wong et al 2015).…”

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confidence: 96%

“…The reported ratio of δ 15 N-NO 3 − and δ 18 O-NO 3 − values (1.13 to 2.1)(Vidal- Gavilan et al 2013;Wexler et al 2014) as being indicative of denitrification is widely used in groundwater system and groundwater surface-water interactions. The relationship between enriched δ 15 N and δ 18 O values of the residual NO 3 − is used byCritchley et al (2014) to provide evidence of in situ denitrification after a cross-injection experiment in glacial sand gravel aquifer Izbicki et al (2015). pointed out that storage of nitrate in thick unsaturated zones and dilution with lownitrate groundwater rather than denitrification are the primary attenuation mechanisms for nitrate from septic discharges in an arid area in California, based on the weak relationship between δ 15 N-NO 3 − and δ 18 O-NO 3 − values, even though denitrifying bacteria are abundant.…”

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confidence: 99%

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A stable isotope approach and its application for identifying nitrate source and transformation process in water

Kang

Sun

2015

Environ Sci Pollut Res

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Nitrate contamination of water is a worldwide environmental problem. Recent studies have demonstrated that the nitrogen (N) and oxygen (O) isotopes of nitrate (NO3(-)) can be used to trace nitrogen dynamics including identifying nitrate sources and nitrogen transformation processes. This paper analyzes the current state of identifying nitrate sources and nitrogen transformation processes using N and O isotopes of nitrate. With regard to nitrate sources, δ(15)N-NO3(-) and δ(18)O-NO3(-) values typically vary between sources, allowing the sources to be isotopically fingerprinted. δ(15)N-NO3(-) is often effective at tracing NO(-)3 sources from areas with different land use. δ(18)O-NO3(-) is more useful to identify NO3(-) from atmospheric sources. Isotopic data can be combined with statistical mixing models to quantify the relative contributions of NO3(-) from multiple delineated sources. With regard to N transformation processes, N and O isotopes of nitrate can be used to decipher the degree of nitrogen transformation by such processes as nitrification, assimilation, and denitrification. In some cases, however, isotopic fractionation may alter the isotopic fingerprint associated with the delineated NO3(-) source(s). This problem may be addressed by combining the N and O isotopic data with other types of, including the concentration of selected conservative elements, e.g., chloride (Cl(-)), boron isotope (δ(11)B), and sulfur isotope (δ(35)S) data. Future studies should focus on improving stable isotope mixing models and furthering our understanding of isotopic fractionation by conducting laboratory and field experiments in different environments.

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confidence: 96%

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confidence: 99%

A stable isotope approach and its application for identifying nitrate source and transformation process in water

Kang

Sun

2015

Environ Sci Pollut Res

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“…503) “high‐resolution characterization of the aquifer heterogeneity at the subdecimeter scale would be needed to fully capture three‐dimensional transport details,” a conclusion with relevance to PVP investigations. Critchley et al () modeled the aquifer at the Woodstock site as a six‐layer system, including the high‐velocity zone identified by the PVPs. They calculated a velocity in the 1‐m thick highly permeable unit of 18 m/d, compared with 0.5 m/d in surrounding less permeable zones.…”

Section: Resultsmentioning

confidence: 99%

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Schillig

Devlin²,

Rudolph

2015

Groundwater

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Small-scale point velocity probe (PVP)-derived velocities were compared to conventional large-scale velocity estimates from Darcy calculations and tracer tests, and the possibility of upscaling PVP data to match the other velocity estimates was evaluated. Hydraulic conductivity was estimated from grain-size data derived from cores, and single-well response testing or slug tests of onsite wells. Horizontal hydraulic gradients were calculated using 3-point estimators from all of the wells within an extensive monitoring network, as well as by representing the water table as a single best fit plane through the entire network. Velocities determined from PVP testing were generally consistent in magnitude with those from depth specific data collected from multilevel monitoring locations in the tracer test, and similar in horizontal flow direction to the average hydraulic gradient. However, scaling up velocity estimates based on PVP measurements for comparison with site-wide Darcy-based velocities revealed issues that challenge the use of Darcy calculations as a generally applicable standard for comparison. The Darcy calculations were shown to underestimate the groundwater velocities determined both by the PVPs and large-scale tracer testing, in a depth-specific sense and as a site-wide average. Some of this discrepancy is attributable to the selective placement of the PVPs in the aquifer. Nevertheless, this result has important implications for the design of in situ treatment systems. It is concluded that Darcy estimations of velocity should be supplemented with independent assessments for these kinds of applications.

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“…Denitrification appears to proceed within metres of the NO3 -source, suggesting relatively short residence times and redox conditions at the water table may be conducive to denitrification reactions (Critchley et al, 2014;Clague et al, 2015). The combination of the approach outlined here with measurement of groundwater age indicators would allow for better constraints on groundwater flow velocities and determination of denitrification rates (Böhlke and Denver, 1995;Katz et al, 2004;McMahon et al, 35 2004;Clague et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…These results indicate that infiltration to groundwater systems in glacial sediments where NO3 -can be naturally attenuated is likely to be preferable to off-farm export via runoff or drainage networks. 35 Hydrol. Earth Syst.…”

Section: Conclusion 25mentioning

confidence: 99%

Sources and fate of nitrate in groundwater at agricultural operations overlying glacial sediments

Bourke¹,

Iwanyshyn²,

Köhn³

et al. 2018

Preprint

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for using a Monte Carlo approach. When denitrification could be quantified, we reconstructed the initial NO3-N concentration and NO3-N/Cl -ratio at the point of entry to the groundwater system. The addition of NO3 -to the local groundwater system from temporary manure piles and pens equalled or exceeded NO3 -additions due to leaching from earthen manure storages at these sites. Nitrate attenuation at both sites is attributed to a spatially 20 variable combination of mixing and denitrification, but is dominated by denitrification. On-site denitrification reduced agriculturally derived NO3 -concentrations by at least half and, in some wells, completely. These results indicate that infiltration to groundwater systems in glacial sediments where NO3 -can be naturally attenuated is likely preferable to off-farm export via runoff or drainage networks. The application of isotopes of nitrate to constrain a mixing model based on concentrations of Cl -and NO3 -, which can be routinely monitored in 25 groundwater, provides a relatively simple method to assess the sources and fate of agriculturally derived NO3 -in these settings.

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Stimulating in situ denitrification in an aerobic, highly permeable municipal drinking water aquifer

Cited by 35 publications

References 41 publications

A stable isotope approach and its application for identifying nitrate source and transformation process in water

A stable isotope approach and its application for identifying nitrate source and transformation process in water

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Sources and fate of nitrate in groundwater at agricultural operations overlying glacial sediments

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