Nitrate vulnerability projections from Bayesian inference of multiple groundwater age tracers [electronic resource]

Nitrate Vulnerability; Age Tracers; Bayesian Inference; Uncertainty Analysis; Lumped Parameter Models; Residence Time Distribution.

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Bibliographic Details
Online Access: Online Access (via OSTI)
Corporate Author: Lawrence Berkeley National Laboratory (Researcher)
Format: Government Document Electronic eBook
Language:English
Published: Washington, D.C. : Oak Ridge, Tenn. : United States. Department of Energy. ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy, 2016.
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MARC

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245 0 0 |a Nitrate vulnerability projections from Bayesian inference of multiple groundwater age tracers  |h [electronic resource] 
260 |a Washington, D.C. :  |b United States. Department of Energy. ;  |a Oak Ridge, Tenn. :  |b distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,  |c 2016. 
300 |a p. 167-181 :  |b digital, PDF file. 
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500 |a 04/20/2016. 
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500 |a Journal of Hydrology 543 PA ISSN 0022-1694 AM. 
500 |a Jamal Alikhani; Amanda L. Deinhart; Ate Visser; Richard K. Bibby; Roland Purtschert; Jean E. Moran; Arash Massoudieh; Bradley K. Esser. 
520 3 |a Nitrate is a major source of contamination of groundwater in the United States and around the world. We tested the applicability of multiple groundwater age tracers (<sup>3</sup>H, <sup>3</sup>He, <sup>4</sup>He, <sup>14</sup>C, <sup>13</sup>C, and <sup>85</sup>Kr) in projecting future trends of nitrate concentration in 9 long-screened, public drinking water wells in Turlock, California, where nitrate concentrations are increasing toward the regulatory limit. Very low <sup>85</sup>Kr concentrations and apparent <sup>3</sup>H/<sup>3</sup>He ages point to a relatively old modern fraction (40-50 years), diluted with pre-modern groundwater, corroborated by the onset and slope of increasing nitrate concentrations. An inverse Gaussian-Dirac model was chosen to represent the age distribution of the sampled groundwater at each well. Model parameters were estimated using a Bayesian inference, resulting in the posterior probability distribution - including the associated uncertainty - of the parameters and projected nitrate concentrations. Three scenarios were considered, including combined historic nitrate and age tracer data, the sole use of nitrate and the sole use of age tracer data. Each scenario was evaluated based on the ability of the model to reproduce the data and the level of reliability of the nitrate projections. The tracer-only scenario closely reproduced tracer concentrations, but not observed trends in the nitrate concentration. Both cases that included nitrate data resulted in good agreement with historical nitrate trends. Use of combined tracers and nitrate data resulted in a narrower range of projections of future nitrate levels. However, use of combined tracer and nitrate resulted in a larger discrepancy between modeled and measured tracers for some of the tracers. In conclusion, despite nitrate trend slopes between 0.56 and 1.73 mg/L/year in 7 of the 9 wells, the probability that concentrations will increase to levels above the MCL by 2040 are over 95% for only two of the wells, and below 15% in the other wells, due to a leveling off of reconstructed historical nitrate loadings to groundwater since about 1990. 
520 0 |a Nitrate Vulnerability; Age Tracers; Bayesian Inference; Uncertainty Analysis; Lumped Parameter Models; Residence Time Distribution. 
536 |b AC52-07NA27344. 
650 7 |a Environmental Sciences.  |2 edbsc. 
650 7 |a Geosciences.  |2 edbsc. 
710 2 |a Lawrence Berkeley National Laboratory.  |4 res. 
710 1 |a United States.  |b Department of Energy.  |4 spn. 
710 2 |a Geological Survey (U.S.).  |4 spn. 
710 1 |a United States.  |b Department of Energy.  |b Office of Scientific and Technical Information.  |4 dst. 
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