Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

C-13 and H-2 in methane, and methane concentration in ground, lake, river, and coastal ocean water of Alaska

Sampling and Analytical Methodology:
Discrete groundwater, lake, and river water samples were collected from Toolik Lake in September 2013 and July 2014. Groundwater samples were collected in all locations from freshly dug pits or temporary PVC well points of variable depth depending on the depth of the water table. All water samples were collected by submersible pump. Sample collection followed previously established methods into glass wheaton bottles, as did measurement of methane concentration. Dissolved CH₄ concentrations in water samples were measured using a headspace equilibration technique. Water samples were collected by direct filling of 125 mL or 160 mL glass serum bottles. The serum bottles were sealed without headspace using blue butyl stoppers, and saturated HgCl₂ solution (0.3 mL) was added immediately after sample collection to halt biological activity. Before analysis, 10 % of total water sample volume was removed; replaced by the same volume of helium gas as the headspace. Sample vials were shaken vigorously for 3 minutes and placed on a shaker for 30 min at room temperature (25 ºC).

CH₄ concentrations for all samples were measured on an SRI 310 Gas Chromatograph (GC) equipped with a flame ionization detector and an Alltech Haysep S 100/120 column (6’ x 1/8” x 0.085”). 0.25 mL of gas was removed from the headspace with a syringe for analysis, and the same volume of Milli-Q water was injected to replace the volume of the gas removed. Helium was used as the carrier gas at a flow rate of 15 mL min^-1, and the column and detector temperatures were maintained at 50 °C and 150 °C, respectively. Peak integration was performed using Peak Simple NT software. Gas mixtures used for GC calibration and standard curves were made using successive dilutions of 1000 ppm CH₄. Total [CH₄] in the water samples was calculated by adding the measured headspace [CH₄] and the amount of CH₄ remaining in the water sample after headspace equilibration, calculated from the solubility equation of (Yamamoto et al. 1976). The average combined standard error of sampling and analysis was 3.6 % (n= 27). After methane concentration analysis, the remaining headspace gas samples were split into two 10-mL exetainers for δ¹³C-CH₄ and δD-CH₄ analysis. δD-CH₄ was analyzed at the UC Davis Stable Isotope Facility on a ThermoScientific PreCon concentration system interfaced to a ThermoScientific Delta V Plus isotope ratio mass spectrometer (ThermoScientific, Bremen, DE). δ¹³C-CH₄ was analyzed at the Lawrence Livermore National Laboratory using the standard TraceGas preconcentration system interfaced with an IsoPrime isotope ratio mass spectrometer (IsoPrime Ltd, UK) as described by Fisher et al. (2006). The mass requirements for δ¹³C-CH₄ and for δD-CH₄ analyses was 10 nmoles and 2 nmoles respectively.

BCO-DMO Processing Notes
- Generated from original file "AK discrete methane concetration and isotopes.xlsx"  contributed by Alanna Lecher
- Parameter names edited to conform to BCO-DMO naming convention found at Choosing Parameter Name
- Longitude values converted to negative for West Longitude
- "nd" (no data) inserted into blank cells
- "NA" replaced with "nd" (no data)
- Date reformatted to YYYYMMDD

Extracted from the NSF award abstract:
The major objective of this proof of concept study is to evaluate the contribution of Subterranean Groundwater Discharge (SGD) in the Arctic to the global methane budget. Methane is a potent greenhouse gas and large natural reservoirs exist in Arctic soils and permafrost. The working hypothesis is that methane released from thawing permafrost in the Arctic is transported via groundwater flow (above and below the permafrost layer) and enters the atmosphere via coastal waters and lakes. This source of methane may be realized as an important source of natural methane to the atmosphere and may provide a positive feedback to global warming.

The objectives of the study are:

1) To estimate the magnitude of subterranean groundwater discharge and associated methane flux into lakes and coastal waters in Alaska at three representative sites.

2) To evaluate methane evasion rates from the water column to the atmosphere.

3) To determine if the contribution of methane input from subterranean groundwater discharge to the global methane budget is significant, and if so

4) To use the preliminary data to design a more through research plan that will enable precise estimates of fluxes and provide a basis for global extrapolation of results such that the contribution of this source to current and future climate changes and the global methane budget will be possible.

The project will support a graduate student full time for two years. Undergraduate students in the ACCESS program and the California Alliance for Minority Participation in Science, Engineering and Mathematics program at UCSC will also participate in the proposed work. The PIs will work with COSEE Alaska to ntegrate this work in their outreach and education activities including teacher workshops, symposia, and work with local communities in Alaska.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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Ms. Alanna Lecher , Dr. Natasha Dimova , Ms. Katy Sparrow , Dr. Fenix Garcia-Tigreros , Mr. Joseph Murray , Dr. Slawek Tulaczyk , Dr. John Kessler. "Groundwater Discharge a Conduit for Methane Emissions in the Arctic," Nature Geoscience, 2015.