Dataset: AT15-56 Porewater Geochemistry

Name: Porewater geochemistry, including methane, CO2, sulfate, and sulfide from Guaymas Basin hydrothermal sediments collected on R/V Atlantis cruise AT15-56 in Nov-Dec 2009
Published: 2023-02-24
Keywords: Guaymas Basin, porewater methane, porewater DIC, porewater sulfide, porewater sulfate, methane d13C, DIC d13C, porewater, oceans

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Cite This Dataset

Spatial Extent: N:27.007333 E:-111.4091667 S:27.007333 W:-111.4091667

Temporal Extent: 2009-11-23 - 2009-12-04

Project:

Microbial carbon and sulfur cycling in the hydrothermally altered sediments of Guaymas Basin (Guaymas Basin Vents)

Principal Investigator:

Andreas Teske (University of North Carolina at Chapel Hill, UNC-Chapel Hill)

Co-Principal Investigator:

Daniel B. Albert (University of North Carolina at Chapel Hill, UNC-Chapel Hill)

Barbara J. MacGregor (University of North Carolina at Chapel Hill, UNC-Chapel Hill-IMS)

Christopher S. Martens (University of North Carolina at Chapel Hill, UNC-Chapel Hill)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2023-02-24

Restricted:

Validated:

Current State:

Data not available

Porewater geochemistry, including methane, CO2, sulfate, and sulfide from Guaymas Basin hydrothermal sediments collected on R/V Atlantis cruise AT15-56 in Nov-Dec 2009

Abstract:

Porewater geochemistry of Guaymas Basin hydrothermal sediments (Southern Spreading segment, 27°00.44'N and 111°24.55'W, 2000 m water depth) including methane, CO2, sulfate, and sulfide, were measured during R/V Atlantis cruise AT15-56 to Guaymas Basin in 2009. Sampling was conducted on Alvin dives 4562 to 4573. The association of bacterial and archaea communities with hydrothermal seepage and the habitat preferences of various types of microbes were investigated by geochemical and microbiological characterization of hydrothermally active sediments in combination with temperature measurements down to 40 centimeters (cm) sediment depth. This dataset includes sulfide, sulfate, dissolved inorganic carbon (DIC), delta 13C-DIC, methane, delta 13C-methane, and VFAs. Corresponding temperature gradients of hydrothermal sediments for Alvin dives during AT15-56 are available at https://www.bco-dmo.org/dataset/3676

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Methods & Sampling

Geochemical Analyses:
Sulfate concentration measurements were completed shipboard; after centrifuging sediment-filled 15-milliliter (ml) tubes, the overlying porewater was filtered through 0.45-micrometer (um) filters, acidified with 50 microliters (ul) of 50% HCl and bubbled with nitrogen for 4 minutes to remove sulfide. Sulfate concentrations were then measured shipboard using a 2010i Dionex Ion Chromatograph (Sunnyvale, CA, USA) through Ag exchange columns (Dionex) so as to remove Cl (Martens et al., 1999). For sulfide, 1 ml porewater samples were combined with 0.1 molar (M) zinc acetate and concentrations were analyzed spectrophotometrically on the ship (Cline, 1969).

Headspace methane concentrations were determined onboard by standard gas chromatography with a flame ionization detector (FID), specifically using a HACH Carle Series 100 AGC Gas Chromatograph (GC) with an Alltech Molecular Sieve 5A packed column (80/100 mesh, 3.05 meters (m) length, 3.2 millimeter internal diameter (mm ID)) and an 80 degree Celsius (C) isothermal temperature profile. Stable isotopic compositions of the same methane samples were measured post-cruise at the University of North Carolina (UNC) via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) on a Finnigan MAT 252 Isotope Ratio Mass Spectrometer, using an HP 5890 Series II Gas Chromatograph with an HP Plot Q column (30 m length, 0.32 mm ID, 20 um film thickness) and a 30 degree C isothermal temperature profile.

To measure DIC, 2 ml of unamended porewater from each sediment horizon were injected into evacuated serum vials (30 ml) and stored upside down at -20 degrees C. At UNC, the samples were thawed, and DIC was reacted to gaseous CO2 by adding 1 ml of a 30% phosphoric acid solution to each serum vial and shaking vigorously before GC analysis (Kelley et al., 1990). Stable isotopic values and concentrations of DIC were analyzed via coupled GC (Hewlett Packard 5890) and Isotope Ratio Mass Spectrometer (Finnigan MAT 252).

Porewater concentrations of dissolved organic acids were measured via High-Pressure Liquid Chromatography (HPLC) after the cruise, using a Beckman Model 332 gradient liquid chromatograph combined with an ISCO V4 UV/VIS detector and a Shimadzu CR3-A integrator (Albert and Martens, 1997).

Data Processing Description

BCO-DMO Processing Notes:
- combined the following original files/sheets into one dataset:
-- sheet named "Annotated clean data" of file named "guaymas methane 2009.xls"
-- sheet named "Clean Data" of file named "Guaymas DIC 2009.xls"
-- sulfate and sulfide data in file named "Sulfate_sulfide_temperatures 2009.xlsx" (re-organized from separate sheets into one table)
- renamed fields to comply with BCO-DMO naming conventions.

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-0647633

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
AT15-56		2009-11-22	R/V Atlantis	Andreas Teske (Chief Scientist)	data info
AT15-56_Alvin_Dives		2009-11-23	Alvin	Andreas Teske (Chief Scientist)	data info

Instruments

Centrifuge

Supplied Name: centrifuge

Supplied Description:

Instrument Type

Generic Name: Centrifuge

Generic Description:

A machine with a rapidly rotating container that applies centrifugal force to its contents, typically to separate fluids of different densities (e.g., cream from milk) or liquids from solids.

Flame Ionization Detector

Supplied Name: flame ionization detector (FID)

Supplied Description:

Headspace methane concentrations were determined onboard by standard gas chromatography with a flame ionization detector (FID).

Instrument Type

Generic Name: Flame Ionization Detector

Acronym: FID

Generic Description:

A flame ionization detector (FID) is a scientific instrument that measures the concentration of organic species in a gas stream. It is frequently used as a detector in gas chromatography. Standalone FIDs can also be used in applications such as landfill gas monitoring, fugitive emissions monitoring and internal combustion engine emissions measurement in stationary or portable instruments.

Gas Chromatograph

Supplied Name: HACH Carle Series 100 AGC Gas Chromatograph

Supplied Description:

Headspace methane concentrations were determined onboard by standard gas chromatography with a flame ionization detector (FID).

Instrument Type

Generic Name: Gas Chromatograph

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB02/

Generic Description:

Instrument separating gases, volatile substances, or substances dissolved in a volatile solvent by transporting an inert gas through a column packed with a sorbent to a detector for assay. (from SeaDataNet, BODC)

Hewlett Packard 5890 Series II gas chromatograph

Supplied Name: HP 5890 Series II Gas Chromatograph

Supplied Description:

Stable isotopic compositions of the methane samples were measured via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) on a Finnigan MAT 252 Isotope Ratio Mass Spectrometer, using a HP 5890 Series II Gas Chromatograph with a HP Plot Q column (30 m length, 0.32 mm ID, 20 um film thickness) and a 30 degree C isothermal temperature profile.

Stable isotopic values and concentrations of DIC were analyzed via coupled GC (Hewlett Packard 5890) and Isotope Ratio Mass Spectrometer (Finnigan MAT 252).

Instrument Type

Generic Name: Hewlett Packard 5890 Series II gas chromatograph

Acronym: HP 5890 Series II GC

Generic Description:

A gas chromatograph that separates and analyses compounds that do not degrade or decompose in the gas phase. The sample is dissolved in a solvent and vaporised in the instrument. A chemically inert gas, (e.g. helium or nitrogen) carries the vaporised analyte through a stationary phase which is coated inside the capillary column that is maintained at an elevated temperature. The analyte mixture separates on the stationary phase leading to chromatographic separation of the molecules. The HP 5890 Series II is completely customisable depending on the application, with choices of inlets, columns, detectors, sampling systems, flow and pressure control components. Optional detectors include Flame Ionization Detector (FID), Nitrogen-Phosphorus Detector (NPD), Electron Capture Detector (ECD), Thermal Conductivity Detector (TCD), Photoionisation Detector (PID), Flame Photometric Detector (FPD) and mass spectrometer. The instrument was originally manufactured by Hewlett Packard (HP), but part of this business was sold to Agilent Technologies in 1999. This model is no longer in production.

High-Performance Liquid Chromatograph

Supplied Name: Beckman Model 332 gradient liquid chromatograph

Supplied Description:

Instrument Type

Generic Name: High-Performance Liquid Chromatograph

Acronym: HPLC

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB11/

Generic Description:

A High-performance liquid chromatograph (HPLC) is a type of liquid chromatography used to separate compounds that are dissolved in solution. HPLC instruments consist of a reservoir of the mobile phase, a pump, an injector, a separation column, and a detector. Compounds are separated by high pressure pumping of the sample mixture onto a column packed with microspheres coated with the stationary phase. The different components in the mixture pass through the column at different rates due to differences in their partitioning behavior between the mobile liquid phase and the stationary phase.

HOV Alvin

Supplied Name: Alvin dives 4562-4574

Supplied Description:

Instrument Type

Generic Name: HOV Alvin

Generic Description:

Human Occupied Vehicle (HOV) Alvin is part of the National Deep Submergence Facility (NDSF). Alvin enables in-situ data collection and observation by two scientists to depths reaching 6,500 meters, during dives lasting up to ten hours.

Commissioned in 1964 as one of the world’s first deep-ocean submersibles, Alvin has remained state-of-the-art as a result of numerous overhauls and upgrades made over its lifetime. The most recent upgrades, begun in 2011 and completed in 2021, saw the installation of a new, larger personnel sphere with a more ergonomic interior; improved visibility and overlapping fields of view; longer bottoms times; new lighting and high-definition imaging systems; improved sensors, data acquisition and download speed. It also doubled the science basket payload, and improved the command-and-control system allowing greater speed, range and maneuverability.

With seven reversible thrusters, it can hover in the water, maneuver over rugged topography, or rest on the sea floor. It can collect data throughout the water column, produce a variety of maps and perform photographic surveys. Alvin also has two robotic arms that can manipulate instruments, obtain samples, and its basket can be reconfigured daily based on the needs of the upcoming dive.

Alvin's depth rating of 6,500m gives researchers in-person access to 99% of the ocean floor. Alvin is a proven and reliable platform capable of diving for up to 30 days in a row before requiring a single scheduled maintenance day. Recent collaborations with autonomous vehicles such as Sentry have proven extremely beneficial, allowing PIs to visit promising sites to collect samples and data in person within hours of their being discovered, and UNOLs driven technological advances have improved the ability for scientific outreach and collaboration via telepresence

Alvin is named for Allyn Vine, a WHOI engineer and geophysicist who helped pioneer deep submergence research and technology.

(from https://www.whoi.edu/what-we-do/explore/underwater-vehicles/hov-alvin/, accessed 2022-09-09)

Ion Chromatograph

Supplied Name: 2010i Dionex Ion Chromatograph

Supplied Description:

Instrument Type

Generic Name: Ion Chromatograph

Generic Description:

Ion chromatography is a form of liquid chromatography that measures concentrations of ionic species by separating them based on their interaction with a resin. Ionic species separate differently depending on species type and size. Ion chromatographs are able to measure concentrations of major anions, such as fluoride, chloride, nitrate, nitrite, and sulfate, as well as major cations such as lithium, sodium, ammonium, potassium, calcium, and magnesium in the parts-per-billion (ppb) range. (from http://serc.carleton.edu/microbelife/research_methods/biogeochemical/ic.html)

Isotope-ratio Mass Spectrometer

Supplied Name: Finnigan MAT 252 Isotope Ratio Mass Spectrometer

Supplied Description:

Stable isotopic values and concentrations of DIC were analyzed via coupled GC (Hewlett Packard 5890) and Isotope Ratio Mass Spectrometer (Finnigan MAT 252).

Instrument Type

Generic Name: Isotope-ratio Mass Spectrometer

Acronym: IR Mass Spec; IRMS

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB16/

Generic Description:

The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
Date	Date of sample collection/dive Format: %Y-%m-%d	unitless	date
Alvin_Dive_Number	Alvin dive number	unitless	dive_id
Core_Number	Core number	unitless	core_id
Dive_Core	Identifier composed of dive number and core number	unitless	sample
Core_Depth_Range	Depth range within the core	centimeters (cm)	depth_core
Mid_Depth	Mid-depth within the core	centimeters (cm)	depth_core
Peak_Area	Peak area	?	no_bcodmo_term
Calculated_SO4_Concentration	Calculated porewater SO4-2 concentration	millimolar (mM)	SO4
Sulfide	Sulfide porewater concentration	millimolar (mM)	sulfide
CH4_mM	Methane porewater concentration	millimolar (mM)	CH4
d13C_CH4	delta 13C of methane values	per mil?	d13C
DIC_mM	Dissolved inorganic carbon (DIC) porewater concnetration	millimolar (mM)	DIC
d13C_DIC	delta 13C of DIC values	per mil?	d13C
Notes_DIC	Notes on DIC measurements	unitless	comment

Database

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Dataset: AT15-56 Porewater Geochemistry