Dilution of Nonpoint‐Source Nitrate in Groundwater

Altman, Susan J.; Parizek, Richard R.

doi:10.2134/jeq1995.00472425002400040023x

Cited by 108 publications

(81 citation statements)

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“…For unretentive buffers, much of the benefit of having a buffer comes from removing some of the source area that supplies materials rather than from retention within the buffer. Source elimination works to reduce landscape discharge even where buffer retention might fail, as when flow bypasses the riparian zone (Denver 1991, Jordan et al 1993, Altman and Parizek 1995. Where material reductions are due to source elimination rather than buffer retention, adding other land uses that neither release nor retain materials would have the same effect on material discharge as adding buffer ecosystem.…”

Section: Source Reduction and Buffer Retentionmentioning

confidence: 99%

“…Many important complexities of riparian buffers were not considered in our models, including: differences between surface and subsurface retention (Peterjohn and Correll 1984); effects of cover type (Correll 1997); retention mechanisms (Altier et al 1994, Gold and Kellogg 1997; saturation of retention over time ; variations with slope, soil type, and surface characteristics (Phillips 1989, Xiang 1996; and channelized or deep subsurface flow (Staver et al 1988, Dillaha et al 1989, Denver 1991, Jordan et al 1993, Altman and Parizek 1995, Bohlke and Denver 1995, Lowrance et al 1997. Instead, we used a simple, first-order model of retention and focused on the effects of landscape structure and the interactions among landscape elements.…”

Section: Landscape Theorymentioning

confidence: 99%

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Heuristic Models for Material Discharge from Landscapes with Riparian Buffers

Weller¹,

Jordan²,

Correll³

1998

Ecological Applications

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Abstract. For landscapes with riparian buffers, we develop and analyze models predicting landscape discharge based on material release by an uphill source area, the spatial distribution of riparian buffer along a stream, and retention within the buffer. We model the buffer as a grid of cells, and each cell transmits a fixed fraction of the materials it receives. We consider the effects of variation in buffer width and buffer continuity, quantify the relative contributions of source elimination and buffer retention to total discharge reduction, and develop statistical relationships to simplify and generalize the models. Width variability reduces total buffer retention, increases the width needed to meet a management goal, and changes the importance of buffer retention relative to source elimination. Variablewidth buffers are less efficient than uniform-width buffers because transport through areas of below-average buffer width (particularly gaps) dominates landscape discharge, especially for narrow buffers of highly retentive cells. Uniform-width models overestimate retention, so width variability should be considered when testing for buffer effects or designing buffers for water quality management. Adding riparian buffer to a landscape can decrease material discharge by increasing buffer retention and by eliminating source areas. Source elimination is more important in unretentive or wide buffers, while buffer retention dominates in narrow, retentive buffers. We summarize model results with simpler statistical relationships. For unretentive buffers, average width is the best predictor of landscape discharge, while the frequency of gaps was best for narrow, retentive buffers. Together, both predictors explain Ͼ90% of the variance in average landscape transmission for any value of buffer retentiveness. We relate our results to ecological theory, landscape-scale buffer effects, buffer management, and water quality models. We recommend more empirical studies of buffer width variability and its effects on material discharge. Landscape models should represent width variability and the nonlinear interactions between buffers and source areas.

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Section: Source Reduction and Buffer Retentionmentioning

confidence: 99%

Section: Landscape Theorymentioning

confidence: 99%

Heuristic Models for Material Discharge from Landscapes with Riparian Buffers

Weller¹,

Jordan²,

Correll³

1998

Ecological Applications

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“…Additionally, process understanding can be attained by e.g., determination of Cl/NO 3 ratios differences in natural abundance of 15 N (denoted as d 15 N) of NO 3 -N in groundwater. An increase in the Cl/NO 3 ratio indicates that nitrate removal processes occur, e.g., denitrification (Altman and Parizek 1995;Mengis et al 1999). Crop uptake also results in increasing Cl/NO 3 ratios because relative NO 3 uptake rates exceed Cl uptake rates (Marschner 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Since measuring actual loads of nutrients towards open water systems is complicated, we followed the approach commonly used, namely measuring nitrate concentrations in shallow groundwater (Dhondt et al 2002;Altman and Parizek 1995;Lowrance et al 2000;Sabater et al 2003;Borin and Bigon 2002;Haycock and Burt 1993;Haycock and Pinay 1993;Kuusemets et al 2001;Novak et al 2002;Mengis et al 1999). We also considered changes in Cl/NO 3 ratios and in d 15 N in groundwater as indicators for nitrate removal.…”

Section: Introductionmentioning

confidence: 99%

Reduced nitrate concentrations in shallow ground water under a non-fertilised grass buffer strip

Beek

Heinen

Clevering

2007

Nutr Cycl Agroecosyst

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In this paper the suitability of a buffer strip to reduce nitrate concentrations in the upper groundwater was tested for a sandy arable soil in The Netherlands during two consecutive leaching seasons. The bufferstrip was a 3.5 m wide unfertilised grass strip adjacent to a ditch on an arable field. In total 24 groundwater wells were installed in 4 transects perpendicular to the ditch to determine Cl, NO 3 and d 15 N concentrations. Piezometers were installed to assess the groundwater flow, which was in the direction of the ditch with small downward leakage across a peat layer at about 3 m depth. Nitrogen was dominantly present as nitrate (NO 3 ). The NO 3 -N concentrations under the bufferstrip were significantly lower than under the adjacent arable field. The lower concentrations were due to dilution, uptake by grass and denitrification. Nitrate was actively removed in the bufferstrip, since the Cl/NO 3 ratios were higher in the bufferstrip than in the remainder of the field. Furthermore, d 15 N data indicated that denitrification occurred in the groundwater and increased with decreasing distance to the ditch. NO 3 -N loads to the ditch were estimated at 8.5 kg ha -1 yr -1 , which is relatively low for this area. We can, however, not determine whether these relatively low NO 3 -N loads were causally related to the reduced NO 3 -N concentrations in the bufferstrip. Nevertheless, the results of the present study are promising and justify additional research on the efficiency of bufferstrips to reduce NO 3 concentrations in shallow groundwater, and subsequently reduce NO 3 loading of surface water, under Dutch conditions.

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“…Models were fitted using the MIXED procedure (SAS, 2003). To separate the effect of groundwater NO 3 -N denitrification from dilution, groundwater NO 3 -N retention is studied by evaluating concurrently groundwater NO 3 -N and Cl -concentration (Altman and Parizek, 1995). To investigate the effect of dilution on the study area Cl -was also inputted into the model.…”

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confidence: 99%

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

Fenton

Richards

Kirwan

et al. 2009

Journal of Environmental Management

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a b s t r a c tGroundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate-N (NO 3 -N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO 3 -N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (K sat ) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO 3 -N L À1 showed, when assessed individually in a step wise procedure, K sat was significantly related to groundwater NO 3 -N concentration. Distance of the point dirty water pollution source becomes significant when included with K sat in the model. The model relationships show areas with higher K sat values have less time for denitrification to occur, whereas lower K sat values allow denitrification to occur. Areas with higher permeability transport greater NO 3 -N fluxes to ground and surface waters. When the distribution of Cl À was examined by the model, K sat and ground elevation had the most explanatory power but K sat was not significant pointing to dilution having an effect. Areas with low NO 3 concentration and unaffected Cl À concentration points to denitrification, low NO 3 concentration and low Cl À chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO 3 -N was significantly (P < 0.05) related to groundwater N 2 /Ar ratio, redox potential (Eh), dissolved O 2 and N 2 and was close to being significant with N 2 O (P ¼ 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.

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Dilution of Nonpoint‐Source Nitrate in Groundwater

Cited by 108 publications

References 0 publications

Heuristic Models for Material Discharge from Landscapes with Riparian Buffers

Heuristic Models for Material Discharge from Landscapes with Riparian Buffers

Reduced nitrate concentrations in shallow ground water under a non-fertilised grass buffer strip

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

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