Mixing-induced groundwater denitrification beneath a manured field in southern Alberta, Canada

McCallum, J.E.; Ryan, M. Cathryn; Mayer, Bernhard; Rodvang, S. J.

doi:10.1016/j.apgeochem.2008.03.018

Cited by 30 publications

(18 citation statements)

References 45 publications

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“…Sci. Discuss., https://doi.org /10.5194/hess-2018- Nitrate isotope values in groundwater at the two CFOs studied are generally consistent with previous studies reporting denitrification of manure-derived NO3 -at dairy farms (Wassenaar, 1995;Wassenaar et al, 2006;Singleton et al, 2007;McCallum et al, 2008;Baily et al, 2011 (Mengis et al, 2001;Wassenaar et al, 2006;Xue et al, 2009). To the best of our knowledge, however, no inorganic fertilizers have been applied at these study sites.…”

Section: Discussionsupporting

confidence: 77%

“…These values are consistent with literature values for manure-sourced NO3 -, which report δ 15 NNO3 ranging from 5 35 to 25‰ and δ 18 ONO3 ranging from -5 to 5‰ (Wassenaar, 1995;Wassenaar et al, 2006;Singleton et al, 2007;McCallum et al, 2008;Baily et al, 2011 deviation of 0.05. At CFO4, the coefficient of proportionality was also described by a normal distribution with a mean of 0.42 and standard deviation of 0.035 (see Fig.…”

Section: Values and Evolution Of Stable Isotopes Of Nitratesupporting

confidence: 81%

“…Decreasing NO3-N/Cl -(or NO3 -/Cl -) ratios have been used to define denitrification based on the assumption that NO3 -is reactive while Cl -is non-reactive (conservative), such that denitrification results in a decrease in the NO3-N/Cl -ratio (Kimble et al, 1972;Weil et al, 1990;Liu et al, 2006;McCallum et al, 2008). However, NO3-N/Cl -ratios can also change in response to mixing of groundwater with different NO3-N/Cl -ratios or when groundwater sampling traverses 20 hydraulically disconnected formations (Bourke et al, 2015b).…”

Section: Groundwater Containing Significant Agriculturally Derived No3mentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 77%

Section: Values and Evolution Of Stable Isotopes Of Nitratesupporting

confidence: 81%

Section: Groundwater Containing Significant Agriculturally Derived No3mentioning

confidence: 99%

See 1 more Smart Citation

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

Bourke¹,

Iwanyshyn²,

Köhn³

et al. 2018

Preprint

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“…One feature of karst aquifers that may facilitate denitrification is large difference in hydraulic conductivity, and thus water age and chemistry, between karstic aquifer matrices and conduits. McCallum et al (2008) showed that mixing of groundwaters of different ages, NO − 3 concentrations, and redox potentials can promote aquifer denitrification, and such oxic-anoxic interfaces are widely recognized as locations of significant biogeochemical reactivity in surface waters (Dahm et al, 1998) and groundwaters (McMahon, 2001). Similar phenomena might be occurring throughout the considerable surface area of the conduit-matrix interface in karstic systems, and its occurrence and distribution might vary sufficiently to generate the observed differences in denitrification among UFA springs.…”

Section: Magnitude and Mechanisms Of Nitrate Reductionmentioning

confidence: 99%

Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer

et al. 2012

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Abstract. Aquifer denitrification is among the most poorly constrained fluxes in global and regional nitrogen budgets. The few direct measurements of denitrification in groundwaters provide limited information about its spatial and temporal variability, particularly at the scale of whole aquifers. Uncertainty in estimates of denitrification may also lead to underestimates of its effect on isotopic signatures of inorganic N, and thereby confound the inference of N source from these data. In this study, our objectives are to quantify the magnitude and variability of denitrification in the Upper Floridan Aquifer (UFA) and evaluate its effect on N isotopic signatures at the regional scale. Using dual noble gas tracers (Ne, Ar) to generate physical predictions of N 2 gas concentrations for 112 observations from 61 UFA springs, we show that excess (i.e. denitrification-derived) N 2 is highly variable in space and inversely correlated with dissolved oxygen (O 2 ). Negative relationships between O 2 and δ 15 N NO3 across a larger dataset of 113 springs, well-constrained isotopic fractionation coefficients, and strong 15 N: 18 O covariation further support inferences of denitrification in this uniquely organic-matter-poor system. Despite relatively low average rates, denitrification accounted for 32 % of estimated aquifer N inputs across all sampled UFA springs. Back-calculations of source δ 15 N NO3 based on denitrification progression suggest that isotopically-enriched nitrate (NO − 3 ) in many springs of the UFA reflects groundwater denitrification rather than urban-or animal-derived inputs.

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“…Furthermore, they suggested that ground water discharge can adversely affect the surface water quality. Ground water monitoring results on a farm with Lethbridge Northern Irrigation district showed evidence of local denitrification as a result of mixing between percolating water and deeper ground water (McCallum et al, 2008). According to scenario 1 the maximum RCHRG_DP constituted an average of 61% of the total seepage outside the root zone.…”

Section: Calibration Validationmentioning

confidence: 99%

Two-Way Calibration-Validation of SWAT Model for a Small Prairie Watershed with Short Observed Record

Rahbeh

Chanasyk

Miller

2011

Canadian Water Resources Journal / Revue canadienne des ressour

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The Soil Water Assessment Tool (SWAT) model was calibrated for a small watershed with extensive irrigation, low runoff, and a short (2004)(2005)(2006)(2007) period of record in the semi-arid region of the Canadian prairies. The watershed is located on a segment of a river. The net flow between the upstream (inlet) and downstream (outlet) locations of the reach comprises only a fraction of the streamflow at the outlet. This type of watershed is rarely investigated and generally different from the ''pear shaped'' single outlet watersheds presented in SWAT literature. The objectives of this study were to determine if SWAT could be calibrated and validated on this unique watershed using one-and two-way calibration-validation methods, and to determine the effect of a variable climatic record on calibrated and validated parameters. To study the effect of a variable climatic record on the calibrated parameters for this watershed a two-way calibration verification scheme that involved two scenarios was used. Scenario 1 involved calibration using 2004 (average precipitation) and 2005 (above average precipitation) and validation on 2006 and 2007 (both below average precipitation). For scenario 2, the calibration and validation periods were reversed. A third scenario utilized the period of 2004Á2006 for calibration and reserved the 2007 data for validation. The objective criteria used to evaluate model performance included decomposition of the Root Mean Square Error (RMSE) into systematic and unsystematic error, the Nash-Sutcliffe efficiency coefficient (EF) and the coefficient of determination (R 2 ) as model best fit objective functions. The calibration results were satisfactory for scenarios 1 and 3. The calibration of scenario 2 and the validation results for all three scenarios were unsatisfactory. The objective criteria calculated separately for each year in the calibration records showed the calibration results were satisfactory for 2005 only, which is the only wet year in the observed record with above average precipitation. Thus, calibrated parameters were mainly influenced by the 2005 wet season. Therefore, SWAT model calibration on a mixed record of wet and dry conditions will reflect the hydrological processes dominant during wet conditions rather than those observed during dry ones.

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Mixing-induced groundwater denitrification beneath a manured field in southern Alberta, Canada

Cited by 30 publications

References 45 publications

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

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

Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer

Two-Way Calibration-Validation of SWAT Model for a Small Prairie Watershed with Short Observed Record

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