Groundwater nitrification and denitrification are not always strictly aerobic and anaerobic processes, respectively: an assessment of dual-nitrate isotopic and chemical evidence in a stratified alluvial aquifer

Utom, Ahamefula U.; Werban, Ulrike; Leven, Carsten; Müller, Christin; Knöller, Kay; Vogt, Carsten; Dietrich, Peter

doi:10.1007/s10533-020-00637-y

Cited by 29 publications

(4 citation statements)

References 63 publications

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“…Other groundwater samples were all negative, with none showing a positive result for the NirS gene (data not shown). The functional role of denitrifiers’ community both in groundwater and landfill leachate environments are complex and very different, as reported in previous studies (Cao et al, 2019 ; Cerminara et al, 2020 ; Heffernan et al, 2012 ; Utom et al, 2020 ). In our study, we can confirm that leachate hosts a denitrifying population that is compatible with a reducing environment in which nitrate can be used as an alternative electron acceptor by denitrifiers.…”

Section: Resultsmentioning

confidence: 82%

Microbial, chemical, and isotopic monitoring integrated approach to assess potential leachate contamination of groundwater in a karstic aquifer (Apulia, Italy)

Beneduce,

Piergiacomo,

Limoni

et al. 2024

Environ Monit Assess

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Landfill sites are subjected to long-term risks of accidental spill of leachate through the soil and consequential contamination of the groundwater. Wide areas surrounding the landfill can seriously be threatened with possible consequences to human health and the environment. Given the potential impact of different coexisting anthropic pollution sources (i.e., agriculture and cattle farming) on the same site, the perturbation of the groundwater quality may be due to multiple factors. Therefore, it is a challenging issue to correctly establish the pollution source of an aquifer where the landfill is not isolated from other anthropic land uses, especially in the case of a karstic coastal aquifer. The present study is aimed at setting in place an integrated environmental monitoring system that included microbiological, chemical, and isotope methods to evaluate potential groundwater pollution in a landfill district in the south of Italy located in Murgia karstic aquifer. Conventional (microbial plate count and physical–chemical analyses) and advanced methods (PCR-ARISA, isotope analysis of δ18O, δ2H, 3H, δ 13C, δ 15N-NO3−, and δ 18O-NO3−) were included in the study. Through data integration, it was possible to reconstruct a scenario in which agriculture and other human activities along with seawater intrusion in the karst aquifer were the main drivers of groundwater pollution at the monitored site. The microbiological, chemical, and isotope results confirmed the absence of leachate effects on groundwater quality, showing the decisive role of fertilizers as potential nitrate sources. The next goal will be to extend long-term integrated monitoring to other landfill districts, with different geological and hydrogeological characteristics and including different sources of pollution, to support the ecological restoration of landfills.

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Section: Resultsmentioning

confidence: 82%

Microbial, chemical, and isotopic monitoring integrated approach to assess potential leachate contamination of groundwater in a karstic aquifer (Apulia, Italy)

Beneduce,

Piergiacomo,

Limoni

et al. 2024

Environ Monit Assess

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“…The prevalence of NO 3 − in this area was surprising considering the anoxic condition observed of the aquifer (Table 1). While NO 3 − concentration in anoxic aquifers has also been observed elsewhere (e.g., Utom et al, 2020), more samples in Dauphin Beach have to be acquired to accurately determine the biogeochemical processes occurring in this area. To the best of our knowledge, no other data or studies related to subsurface nutrient concentration exist in Dauphin Island.…”

Section: Dauphin Beachmentioning

confidence: 78%

Storm-Driven Fresh Submarine Groundwater Discharge and Nutrient Fluxes From a Barrier Island

et al. 2021

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Quantifying and characterizing groundwater flow and discharge from barrier islands to coastal waters is crucial for assessing freshwater resources and contaminant transport to the ocean. In this study, we examined the groundwater hydrological response, discharge, and associated nutrient fluxes in Dauphin Island, a barrier island located in the northeastern Gulf of Mexico. We employed radon (222Rn) and radium (Ra) isotopes as tracers to evaluate the temporal and spatial variability of fresh and recirculated submarine groundwater discharge (SGD) in the nearshore waters. The results from a 40-day continuous 222Rn time series conducted during a rainy season suggest that the coastal area surrounding Dauphin Island was river-dominated in the days after storm events. Groundwater response was detected about 1 week after the precipitation and peak river discharge. During the period when SGD was a factor in the nutrient budget of the coastal area, the total SGD rates were as high as 1.36 m day–1, or almost three times higher than detected fluxes during the river-dominated period. We found from a three-endmember Ra mixing model that most of the SGD from the barrier island was composed of fresh groundwater. SGD was driven by marine and terrestrial forces, and focused on the southeastern part of the island. We observed spatial variability of nutrients in the subterranean estuary across this part of the island. Reduced nitrogen (i.e., NH4+ and dissolved organic nitrogen) fluxes dominated the eastern shore with average rates of 4.88 and 5.20 mmol m–2 day–1, respectively. In contrast, NO3– was prevalent along the south-central shore, which has significant tourism developments. The contrasting nutrient dynamics resulted in N- and P-limited coastal water in the different parts of the island. This study emphasizes the importance of understanding groundwater flow and dynamics in barrier islands, particularly those urbanized, prone to storm events, or located near large estuaries.

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“…The dual stable isotopes of water (δH 2 O: δ 18 O–H 2 O and δ 2 H–H 2 O) and nitrate (δNO 3 − : δ 15 N–NO 3 and δ 18 O–NO 3 ) have both been used as tools for identifying sources, inferring processes, and determining the contributions of various inputs (Böhlke & Denver, 1995; Sulzman, 2007; Weitzman, Brooks, et al., 2021). Specifically, δH 2 O values can reveal the origins, residence times, and flowpaths of different water sources (e.g., Brooks et al., 2012; McGuire & McDonnell, 2007; Sprenger et al., 2019; Sprenger, Erhardt, et al., 2016; Sprenger, Seeger, et al., 2016), while δNO 3 − values can differentiate between source inputs of nitrate and reveal dominant N transformation processes (e.g., Kendall et al., 2007; Mayer et al., 2002; Qin et al., 2019; Suchy et al., 2018; Utom et al., 2020; Xue et al., 2009).…”

Section: Introductionmentioning

confidence: 99%

Vadose zone flushing of fertilizer tracked by isotopes of water and nitrate

Weitzman,

Brooks,

Compton

et al. 2024

Vadose Zone Journal

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A substantial fraction of nitrogen (N) fertilizer applied in agricultural systems is not incorporated into crops and moves below the rooting zone as nitrate (NO3−). Understanding mechanisms for soil N retention below the rooting zone and leaching to groundwater is essential for our ability to track the fate of added N. We used dual stable isotopes of nitrate (δ15N–NO3− and δ18O–NO3−) and water (δ18O–H2O and δ2H–H2O) to understand the mechanisms driving nitrate leaching at three depths (0.8, 1.5, and 3.0 m) of an irrigated corn field sampled every 2 weeks from 2016 to 2020 in the southern Willamette Valley, Oregon, USA. Distinct periods of high nitrate concentrations with lower δ15N–NO3− values indicated that a portion of that nitrate was from recent fertilizer applications. We used a mixing model to quantify nitrate fluxes associated with recently added fertilizer N versus older, legacy soil N during these “fertilizer signal periods.” Nitrate leached below 3.0 m in these periods made up a larger proportion of the total N leached at that depth (∼52%) versus the two shallower depths (∼13%–16%), indicating preferential movement of recently applied fertilizer N through the deep soil into groundwater. Further, N associated with recent fertilizer additions leached more easily when compared to remobilized legacy N. A high volume of fall and winter precipitation may push residual fertilizer N to depth, potentially posing a larger threat to groundwater than legacy N. Optimizing fertilizer N additions could minimize fertilizer losses and reduce nitrate leaching to groundwater.

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Groundwater nitrification and denitrification are not always strictly aerobic and anaerobic processes, respectively: an assessment of dual-nitrate isotopic and chemical evidence in a stratified alluvial aquifer

Cited by 29 publications

References 63 publications

Microbial, chemical, and isotopic monitoring integrated approach to assess potential leachate contamination of groundwater in a karstic aquifer (Apulia, Italy)

Microbial, chemical, and isotopic monitoring integrated approach to assess potential leachate contamination of groundwater in a karstic aquifer (Apulia, Italy)

Storm-Driven Fresh Submarine Groundwater Discharge and Nutrient Fluxes From a Barrier Island

Vadose zone flushing of fertilizer tracked by isotopes of water and nitrate

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