November 30, Jean Moran (CSU East Bay), Brad Esser, Michael Singleton (Lawrence Livermore National Laboratory)

Transcription

1 November 30, 2012 Jean Moran (CSU East Bay), Brad Esser, Michael Singleton (Lawrence Livermore National Laboratory)

2 Presentation Outline Overview of State Water Resources Control Board GAMA program Analytical tools for tracking recharge sources and residence times Applications in the Sacramento Valley River recharge near Sacramento and Chico Basin-wide recharge and residence times Nitrate sources in Chico

3 Groundwater Ambient Monitoring and Assessment Program Projects staffed by State Water Resources Control Board, USGS, LLNL, CSU East Bay to assess CA groundwater quality Well owners volunteer wells to be sampled Over 4,000 wells sampled to date Groundwater tested for standard water quality constituents and hundreds of trace-level and isotopic analytes

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5 GAMA Special Studies Program Municipal well Is high nitrate from orchards or farm supply? Small dairy farm Transport & fate of dairy-derived nitrate to underlying aquifer Managed Aquifer Recharge Operation Is high arsenic caused by recent recharge operation? Groundwater basin Sources of nitrate and impact of nutrient management plans

6 GAMA Special Studies Program uses innovative approaches Groundwater Age Dating Delineate groundwater recharge, flow & contaminant transport Proxy for aquifer susceptibility Tool for assessment of management practices Isotope & Dissolved Gas Geochemistry Water source (stable isotopes of water) Water tagging (introduced gas tracers) Contaminant source (isotopic composition) Contaminant degradation (e.g. denitrification) Industrial VOCs & Emerging Contaminants Proxy for aquifer susceptibility Contaminant source tracers Emerging contaminant transport & degradation in subsurface

7 What is Tritium? p p n n p n Protium Deuterium Tritium These atoms are isotopes of hydrogen. They all have one proton and one electron, but different numbers of neutrons.

8 Tritium decays to 3 He p p n n p n 3 H 3 He Tritium ( 3 H) is an unstable nucleus and ejects an energetic electron to become an atom of helium-3 ( 3 He )

9 Tritium atoms Helium-3 atoms For every tritium decay, an atom of 3 He is produced Time (years) 0

10 The 3 He from 3 H decay starts Groundwater age = the time since recharge to accumulate once the water has The 3 He from become 3 H decay groundwater starts to accumulate once the water has become groundwater 0 years 12 years 24 years Age (years) = 18 x ln( He / 3 H )

11 Tritium has natural and anthropogenic sources Cosmic rays Tritium DL < 1 pci/l Rainfall today = ~10 pci/l Tritium MCL = 20,000 pci/l HTO Atmospheric weapons testing Tritium in groundwater is affected by age (source activity) of young water and by mixing with old tritium-dead water. The tritium/he-3 method age dates the young water component Groundwater recharge

12 Collecting a dissolved gas sample

13 We analyze ten samples at a time. The analysis system is automated and runs overnight

14 We remove gases like oxygen and nitrogen by exposing them to hot titanium metal

15 Helium isotopes are separated in a magnetic sector analyzer The detection level for 3 He is 1 zeptomole (600 atoms)

16 Results from H- 3 He age measurements in Orange Co. CA Groundwater age in years

17 Temperature and Pressure determine the solubility of gases in water 2.0E-04 Solubility (mole/mole, 1 atm) 1.5E E E E+00 Xenon Krypton Argon Neon Helium Temperature (C)

18 Most results are from Longscreened Production Wells Advantages You get a good, clean sample (both dissolved gases and low level VOCs) Characteristics are usually known It s the water people are using and drinking Disadvantages Vertical information is smeared Signal is diluted Flow field is altered It s the water people are drinking

19 Groundwater age tracers act as proxies for groundwater susceptibility Vadose zone Contaminated Recharge Young vulnerable water Saturated zone Older pristine water Groundwater age by Tritium/Helium ( 3 H/ 3 He) To determine mean age, or residence time Stable isotopic composition of water To distinguish sources of water

20 Stable isotopes of the water molecule

21 The map shows the value of 18 O/ 16 O relative to seawater in parts per thousand

22 Stable isotope ranges for Northern CA

23 Nested monitor

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25 The river recharge phenomenon occurs all along the Central Valley

26 Once end-members are identified, the fraction of river water produced at each well can be calculated

27 Recharge temperatures indicate predominantly wintertime infiltration of American River water

28 Number of Samples Northern Sacramento Valley and Volcanic Provinces Tritium-dead, recharged before 1950 Modern precip, recent recharge Tritium Conc. (pci/l)

29 Depth (ft bgs) Wells screened exclusively below 300 do not produce modern water 0 Tritium Conc. (pci/l) Tritium vs Depth Tritium vs top perf

30 Tritium concentrations exhibit a wide range

31 Groundwater ages reflect water use patterns

32 Cross Sections nested monitor wells Nested monitor

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34 Cross Sections nested monitor wells Nested monitor

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36 Nitrate contamination is a water quality issue of state-wide relevance Sources of nitrate are often co-located and non-point source.

37 Nitrate-contaminated groundwater: Distinguishing sources Shallow groundwater is contaminated by nitrate Deeper groundwater is the primary source of drinking water What is the source & age of the contamination? High-density septic systems? Legacy or current agricultural practices? 3 H/ 3 He time-scale

38 Overlapping fields on dual isotope plot make source identification ambiguous

39 Trace organics can be used to distinguish between septic & agricultural sources of nitrate Trace Organics Agricultural Septic Agricultural Herbicides (1) Herbicide degradates (2) Septic DEET (1) Caffeine (2) Surfactants (1) Carbamazepine (4)

40 Tritium/helium-3 age dating can be used to distinguish between recent and past sources of nitrate Trace Organics Agricultural Septic Nitrate contamination in Chico High-density septic system discharge is a source of nitrate within the city limits Fertilizer from agricultural operations is a source of nitrate on the periphery of the city Nitrate contamination is ongoing and associated with current practices

41 Denitrification may decrease the amount of nitrate transport to drinking water wells under the right conditions NO 3 - NO 3 - N 2 MICROBIALLY controlled denitrification Does denitrification provide a sink for some nitrate?

42 Denitrification Age and excess N 2 help in understanding nitrate fate and transport Septic impacted Dairies Provides an understanding of where the denitrification is taking place: In these dairy wells the nitrate must travel deep enough into the system before reaching the denitrification zone below the water table In the septic impacted wells (Chico) the denitrification happens quickly because it is occurring near the leach lines

43 Surface water acts to dilute nitrate concentrations Low nitrate in water from higher elevations

44 Conclusions River water is an important source of recharge for a large portion of the study area A large volume of old (pre-modern) groundwater is produced at drinking water wells Paleowater is present in deep aquifers on the western side of the valley The shallow aquifer in Chico is affected by nitrate from septic discharge; current efforts to build sewer systems are worthwhile

45 Technical Reports Carle, S. F., Moran, J. E., and Esser, B. K., California GAMA Special Study: Groundwater Age Simulation and Deconvolution Methods for Interpretation of 3H-3He Data. Lawrence Livermore National Laboratory LLNL-TR Esser, B. K., Hudson, G. B., Moran, J. E., Beller, H., Carlsen, T., Dooher, B., Paula Krauter, Mcnab, W., Madrid, V., Rice, D., Verce, M., and Rosenberg, N., Nitrate Contamination in California Groundwater: An Integrated Approach to Basin Assessment and Resource Protection. Lawrence Livermore National Laboratory LLNL-TR Esser, B. K., Beller, H. R., Carle, S. F., Hudson, G. B., Kane, S. R., Leif, R. N., LeTain, T. E., McNab, W. M., and Moran, J. E., California GAMA Program: Impact of dairy operations on groundwater quality. Lawrence Livermore National Laboratory. Esser, B. K., Owens, J. E., Vu, A. K., and Leif, R., California GAMA Special Study: Analysis of Carbamazepine, Oxcarbazepine and Metabolites as Wastewater Tracers in Water Resource Studies. Lawrence Livermore National Laboratory LLNL-TR Draft. McNab Jr, W. W., Singleton, M. J., Moran, J. E., and Esser, B. K., California GAMA Special Study: Ion exchange and trace element surface complexation reactions associated with applied recharge of low-tds water in the San Joaquin Valley, California. Lawrence Livermore National Laboratory LLNL-TR Moran, J., Ruiz, R., Ford, T., Singleton, M., Esser, B. K., Soto, G. T., Velsko, C., and Hillegonds, D., California GAMA Program: Development of a Field Deployable Dissolved Gas Extraction Apparatus. Lawrence Livermore National Laboratory, LLNL-TR Moran, J. E., California GAMA Program: Fate and transport of wastewater indicators: Results from ambient groundwater and from groundwater directly influenced by wastewater. Lawrence Livermore National Laboratory, UCRL-TR Moran, J. E., Beller, H., Eaton, G. F., Ekwurzel, B. E., Esser, B. K., Hu, Q., Hudson, G. B., Leif, R., McNab, W., and Moody-Bartel, C., California GAMA program: Sources and transport of nitrate in groundwater in the Livermore Valley Basin, California. Lawrence Livermore National Laboratory, UCRL-TR Moran, J. E., Carle, S. F., and Esser, B. K., California GAMA Special Study: Interpretation of Isotopic Data in the Sonoma Valley, California. Lawrence Livermore National Laboratory LLNL-TR Moran, J. E., Hudson, G. B., Eaton, G. F., and Leif, R., California GAMA Program: Groundwater Ambient Monitoring and Assessment Results for the Sacramento Valley and Volcanic Provinces of Northern California. Lawrence Livermore National Laboratory, UCRL-TR Moran, J. E., McNab, W. W., Esser, B. E., and Hudson, G. B., California GAMA program: Sources and transport of nitrate in shallow groundwater in the Llagas Basin of Santa Clara County, California. Lawrence Livermore National Laboratory, UCRL-TR Moran, J. E., Singleton, M. J., McNab, W. M., Leif, R., and Esser, B. K., California GAMA Program: Tracking Water Quality Changes During Groundwater Banking at Two Sites in San Joaquin County. Lawrence Livermore National Laboratory. Singleton, M. J., Moran, J. E., Esser, B. K., Roberts, S. K., and Hillegonds, D. J., California GAMA Special Study: An isotopic and dissolved gas investigation of nitrate source and transport to a public supply well in California s Central Valley. Lawrence Livermore National Laboratory LLNL- TR Singleton, M. J., Roberts, S. K., and Esser, B. K., California GAMA Domestic Wells Data Report: Water and Nitrate Isotopic Data for the San Diego County. Lawrence Livermore National Laboratory LLNL-TR Singleton, M. J., Roberts, S. K., Moran, J. E., and Esser, B. K., California GAMA Domestic Wells: Nitrate and Water Isotopic Data for Tulare County. Lawrence Livermore National Laboratory LLNL-TR

46 Publications Carle, S. F., Esser, B. K., and Moran, J. E., High-resolution simulation of basin scale nitrate transport considering aquifer system heterogeneity. Geosphere Carle, S. F., Tompson, A. F. B., McNab, W. W., Esser, B. K., Hudson, G. B., Moran, J. E., Beller, H. R., and Kane, S. R., Simulation of nitrate biogeochemistry and reactive transport in a California groundwater basin. In: Miller, C. T. (Ed.),Computational Methods in Water Resources International Conference XIV (Chapel Hill, June 13-17, 2004), Chapel Hill, North Carolina USA. Cey, B. D., Hudson, G. B., Moran, J. E., and Scanlon, B. R., Impact of artificial recharge on dissolved noble gases in groundwater in California. Environmental Science & Technology 42, Cey, B. D., Hudson, G. B., Moran, J. E., and Scanlon, B. R., Evaluation of Noble Gas Recharge Temperatures in a Shallow Unconfined Aquifer. Ground Water 47, Esser, B. K., Singleton, M., and Moran, J., Identifying groundwater nitrate sources and sinks. Southwest Hydrology (Nitrates in Groundwater Special Issue) 8, 32. McNab Jr, W. W., Singleton, M. J., Moran, J. E., and Esser, B. K., Ion exchange and trace element surface complexation reactions associated with applied recharge of low-tds water in the San Joaquin Valley, California. Applied Geochemistry 24, McNab, W. W., Singleton, M. J., Moran, J. E., and Esser, B. K., Assessing the impact of animal waste lagoon seepage on the geochemistry of an underlying shallow aquifer. Environmental Science & Technology 41, Moore, K., Ekwurzel, B. E., Esser, B. K., Hudson, G. B., and Moran, J. E., Sources of groundwater nitrate revealed using residence time and isotope methods. Applied Geochemistry 21, Singleton, M. J., Esser, B. K., Moran, J. E., Hudson, G. B., McNab, W. W., and Harter, T., Saturated zone denitrification: Potential for natural attenuation of nitrate contamination in shallow groundwater under dairy operations. Environmental Science & Technology 41,