Tracking Sources of Unsaturated Zone and Groundwater Nitrate Contamination Using Nitrogen and Oxygen Stable Isotopes at the Hanford Site, Washington

Singleton, Michael; Woods, Katharine N.; Conrad, Mark E.; DePaolo, Donald J.; Dresel, P. Evan

doi:10.1021/es0481070

Cited by 47 publications

(46 citation statements)

References 26 publications

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“…In deep groundwater, Murgulet and Tick (2013) found that δ 18 O-NO 3 − and δ 15 N-NO 3 − values in the coastal aquifer of the Alabama, USA, indicated that the mixing ratios of sewage and fertilizer were consistent with the study area's land use. Singleton et al (2005) found that industrial sources contributed to the major nitrate plumes in groundwater below that those observed in the northeastern USA, where the former's area is 100 times smaller than the latter's. The data highlighted above show that seasonal and spatial changes are the primary factors influencing δ 15 N-NO 3 − and δ 18 O-NO 3 − values.…”

Section: Introductionmentioning

confidence: 86%

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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Section: Introductionmentioning

confidence: 86%

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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“…Samples were analyzed following a version of the denitrifier method (Sigman et al 2001;Singleton et al 2005). Isotopic analysis was conducted at Lawrence Livermore National Laboratory on an IsoPrime continuous-flow mass spectrometer.…”

Section: Nutrient Concentration and Nitrate Isotope Ratiosmentioning

confidence: 99%

Submarine Groundwater Discharge-Derived Nutrient Loads to San Francisco Bay: Implications to Future Ecosystem Changes

Null

Dimova

Knee

et al. 2012

Estuaries and Coasts

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Submarine groundwater discharge (SGD) was quantified at select sites in San Francisco Bay (SFB) from radium ( 223 Ra and 224 Ra) and radon ( 222 Rn) activities measured in groundwater and surface water using simple mass balance box models. Based on these models, discharge rates in South and Central Bays were 0.3-7. − to NH 4 + available to phytoplankton with implications to bay productivity, phytoplankton species distribution, and nutrient uptake rates. This assessment of nutrient delivery via groundwater discharge in SFB may provide vital information for future bay ecological wellbeing and sensitivity to future environmental stressors.

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“…Both low-level waste and natural nitrate flushed from the vadose zone appear to be significant sources of groundwater contamination (Singleton et al 2005). Groundwater samples generally fell in a range between synthetic nitrate and natural nitrate found in uncontaminated vadose zone core.…”

Section: Chlorine-36mentioning

confidence: 99%

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Cantrell¹,

Zachara²,

Dresel³

et al. 2007

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Companion reports that review other subject matter areas relevant to contaminant transport within the vadose zone beneath the SST WMAs, the IDF, and groundwater have been recently published. The specific subject areas include the geology of the SST WMAs iv contaminants released to the vadose zone exhibit a wide range of mobility behaviors. Many tank waste contaminants have been strongly retarded by adsorption and precipitation reactions (e.g., cesium, plutonium, americium, and europium), while others have remained mobile (e.g., technetium, nitrate, and selenium). Still others show variable, waste-specific behaviors (e.g., cesium [where sodium concentrations are very high], strontium, chromium, and uranium) that are closely tied to evolving composition of pore water in the sediments, and for chromium, a change in oxidation state. The temperature of in-ground tank waste has moderated by heat exchange with the subsurface sediment, and high concentrations of base (OH -) have been neutralized through reactions with sediment minerals and secondary mineral precipitation. Major geochemical features that may potentially affect the mobility of key contaminants of interest in the vadose zone include oxidation state, aqueous speciation, solubility, and adsorption reactions.Processes suspected of facilitating the far-field migration of immobile radionuclides, such as formation of stable aqueous complex formation and mobile colloids, were found to be potentially operative, but unlikely to occur in the field. An exception is the enhanced migration of cobalt-60 facilitated by the formation of highly stable aqueous-cyanide complexes. Certain fission-product oxyanions (e. • Adsorption is suppressed by large concentrations of tank waste anions (e.g., NO 3 -, OH -, and CO 3 2-)• Surface charge of clay-size minerals is negative and will therefore tend to repel anions• Unlike chromium, their less-soluble, less-mobile reduced forms are unstable in oxidizing environments.Laboratory studies conducted through PNNL's Vadose Zone Characterization Project and basic-science geochemical studies are expected to continue in partnership to provide information to further refine the conceptual model used for risk assessment modeling. Results of these studies can be used to help ascertain uncertainties associated with the refinement of the conceptual models for contaminant migration in the vadose zone beneath the single-shell tanks. Results can also provide improved parameterization, such as distribution coefficients (K d ), and mathematical constructs used by modelers to predict contaminant mobility under these conditions, and to decrease the degree of conservatism incorporated in these models.For various reasons, risk assessment models typically use various approximations to represent the conceptual model developed for the site. Adsorption is frequently approximated using empirical distribution coefficients (K d s). Although the use of empirical distribution coefficients can potentially lead to erroneous results under certain conditions where the...

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Tracking Sources of Unsaturated Zone and Groundwater Nitrate Contamination Using Nitrogen and Oxygen Stable Isotopes at the Hanford Site, Washington

Cited by 47 publications

References 26 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

Submarine Groundwater Discharge-Derived Nutrient Loads to San Francisco Bay: Implications to Future Ecosystem Changes

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

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