Dataset: GP17-OCE Beryllium-7 in seawater and aerosols

Name: Aerosol and seawater beryllium-7 concentrations from the US GEOTRACES GP17-OCE cruise on R/V Roger Revelle (RR2214) in the South Pacific and Southern Oceans from December 2022 to January 2023
Published: 2024-05-14
Keywords: beryllium-7, aerosols, oceans

Cite This Dataset

DOI:10.26008/1912/bco-dmo.927107.1

Spatial Extent: N:-18.499 E:-75.751 S:-67.007 W:-152.002

South Pacific and Southern Oceans

Temporal Extent: 2022-12-03 - 2023-01-19

Project:

GEOTRACES GP-17 OCE: Measurement of 7Be as a Tracer of Upper Ocean Processes (GP17-OCE Be-7)

US GEOTRACES GP17 Section: South Pacific and Southern Ocean (GP17-OCE) (GP17-OCE)

Program:

U.S. GEOTRACES (U.S. GEOTRACES)

Principal Investigator:

Mark Stephens (Florida International University, FIU)

BCO-DMO Data Manager:

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

Version:

Version Date:

2024-05-14

Restricted:

Validated:

Yes

Current State:

Final no updates expected

Aerosol and seawater beryllium-7 concentrations from the US GEOTRACES GP17-OCE cruise on R/V Roger Revelle (RR2214) in the South Pacific and Southern Oceans from December 2022 to January 2023

Abstract:

Beryllium-7, a radioactive isotope with a half-life of 53.3 days, is formed in the atmosphere, attaches to aerosol particles, and is deposited on the earth’s surface through wet and dry processes. In this project, we measured Be-7 concentrations in aerosol particles and in seawater samples (depths < 200 meters) collected on the GEOTRACES GP17-OCE cruise aboard R/V Roger Revelle. The cruise originated in Papeete, Tahiti, French Polynesia on 1 December 2022 and concluded on 25 January 2023 in Punta Arenas, Chile. Sixteen aerosol samples and seawater from twelve stations in the South Pacific and Southern Oceans were collected. The dataset will be used to study the deposition of trace elements and isotopes (TEIs) and upper ocean mixing processes. Aerosol deposition is an important source of TE micronutrients to open ocean areas that are far removed from riverine sources. But, while the collection aerosol of samples for TEI analysis is straightforward, estimating the deposition flux also requires an appropriate deposition velocity (i.e. deposition flux is the product of the aerosol concentration and deposition velocity). Because Be-7 is supplied to the open ocean exclusively through aerosol deposition and it is removed through radioactive decay, the water column inventory and aerosol concentration of Be-7 can be used to derive the deposition velocity applicable to aerosol TEIs. The penetration of dissolved Be-7 below the ocean mixed layer is limited by the isotope's half-life and the rate of vertical diffusive mixing. Through modeling, the shape of the Be-7 profile below the mixed layer provides an estimate for the vertical diffusivity coefficient (Kz), which can be used to calculate fluxes of chemical species (e.g. oxygen) and physical properties (e.g. heat).

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Archival Copy

Version Date	Archive	Persistent Identifier (PID)	Date PID Issued
2024-05-14	Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)	10.26008/1912/bco-dmo.927107.1	2024-05-24

Methods & Sampling

Seawater sampling: The procedures used on the GEOTRACES GP17-OCE cruise were identical to those described for the GEOTRACES GP15 and GP16 cruises by Kadko et al. (2017, 2020). Briefly, a 1 horsepower (hp) centrifugal pump on deck pulled seawater from selected depths via a 1.5-inch PVC hose. 400 to 700 liters (L) of seawater were delivered to large plastic tanks in this manner. Beryllium-7 (Be-7) was then extracted by pumping the seawater through 200 grams of iron impregnated acrylic fibers at a rate of ~10 liters per minute (Lai et al., 1988; Krishnaswami et al., 1972; Lee et al., 1991). A portable CTD (model: YSI EXO1) was attached to the end of the hose so that temperature, depth, and salinity could be recorded.

Aerosol sampling: Aerosol samples were collected according to protocols set forth in the GEOTRACES cookbook using a Tisch TE-5170V-BL high-volume aerosol sampler modified to collect 12 replicate samples on 47-millimeter (mm) diameter Whatman-41 (W-41) filters (Wallace et al, 1977; Baker et al., 2006). In order to minimize filter blanks, the W-41 filters were pre-cleaned inside a HEPA-filtered laminar flow hood using three cycles of leaching with 0.5M HCl (Optima) and then rinsing with ultra-high purity water (UHP water) according to trace element protocols (Morton et al., 2013; similar to Baker et al., 2006). Sector control, which was accomplished via a Campbell Scientific data logger, was set such that the sampler would only operate during winds of >0.5 meters per second (m/s) and from ± 60° of the ship's bow to avoid sampling air influenced by the ship's exhaust. Three replicate filters from each deployment, placed in PetriSlides, were sent to FIU for Be-7 analysis.

Analytical procedures: Samples were counted for Be-7 onshore using low background germanium gamma detectors at Florida International University (FIU). FIU's facilities include four HPGe detectors: three Ortec Coaxial GEM series detectors and one Canberra Broad Energy gamma detector. For aerosols, the three replicate 47 mm filters were stacked in a Petri dish for counting. For seawater, the fibers were dried and then ashed. The powder remaining after ashing was pressed into a 5.8-centimeter (cm) diameter pellet, and the pellet thickness was measured. The iron hydroxide pellet was placed in a Petri dish for gamma counting. Be-7 has a readily identifiable gamma peak at 478 kiloelectron volts (keV), and the spectra were evaluated using Maestro (Ortec) or Genie 2000 (Canberra) software.

The detectors were calibrated for each geometry by adding a commercially prepared mixed isotope solution of known gamma activities (Eckert & Ziegler Mixed Nuclide Solution 7500) to three W-41 filters (for aerosol samples) and pellets of various thicknesses (for seawater) to derive a calibration curve using peaks associated with following isotopes: Sn-113 @ 392 keV, Sr-85 @ 514 keV, Cs-137 @ 662 keV. The counting efficiencies of the four detectors ranges from 0.05686 to 0.11415 for Be-7 on aerosol filters. And for the seawater pellets from this cruise, the counting efficiencies ranged from 0.03480 to 0.08590.

Data Processing Description

Data Processing:
Be-7 has a readily identifiable gamma peak at 478 keV, and the spectra were evaluated using Maestro (Ortec) or Genie 2000 (Canberra) software.

Reported Be-7 activities were corrected to the time of sampling. The calculation is as follows:

[Be-7, dpm m-3] = {cpm • ct • λ • exp(λ•d) } / {CE • PE • FE • V • [1-exp(-λ•ct)]}, where:

cpm = background corrected counts per minute for the region of interest (ROI);
ct = count time (days);
λ = the Be-7 radioactive decay constant (0.013 day-1);
CE = counting efficiency;
PE = photon emission probability (0.104 for Be-7);
FE – fiber extraction efficiency (92 ±3%);
V= volume (m-3);
d = time from sample collection to start of count (days)

The error (in counts) associated with each measurement is the statistical counting error (σ) and the uncertainty in the blank, √(σ2 + σb2), multiplied by {ct • λ • exp(λ•d) } / {CE • PE • FE • V • [1-exp(-λ•ct)]}. The uncertainty of the extraction efficiency (3%) and the detector efficiency (2%) was in all cases smaller than the statistical counting error.

Quality Flags:
Quality flags were applied following the GEOTRACES policy (https://www.geotraces.org/geotraces-quality-flag-policy/), which recommends the SeaDataNet Scheme:
0 = no quality control;
1 = good value;
2 = probably good value;
3 = probably bad value;
4 = bad value;
5 = changed value;
6 = value below detection; (see attached Supplemental File for detection limits for Be-7 samples)
7 = value in excess;
8 = interpolated value;
9 = missing value;
A = value phenomenon uncertain.

Intercalibration and detection limits are provided in the attached Supplemental File "RR2214_Intercal_and_Detection_Limits_Be7.pdf".

BCO-DMO Processing

- Imported original file "RR2214_dataTemplate (1).xlsx" into the BCO-DMO system.
- Renamed fields to comply with BCO-DMO naming conventions.
- Created ISO 8601 date-time fields.
- Converted date columns to YYYY-MM-DD.
- Removed empty columns (Gear_ID, Rosette_Position).
- Saved the final file as "927107_v1_gp17-oce_beryllium-7.csv".

Data Files

File
927107_v1_gp17-oce_beryllium-7.csv (Comma Separated Values (.csv), 10.44 KB) MD5:e728479c3b6ddd2149a64add5005d03a Primary data file for dataset ID 927107, version 1

Supplemental Files

File
Be-7 Intercalibration and detection limits filename: RR2214_Intercal_and_Detection_Limits_Be7.pdf (Portable Document Format (.pdf), 149.80 KB) MD5:e79028e616c9d7072c62a891c327ad4b Supplemental file for dataset ID 927107, version 1. Intercalibration results and detection limits for Be-7 samples.

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-2147723

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
RR2214	GP17 GP17-OCE 33RR20221201	2022-12-01	R/V Roger Revelle	Benjamin Twining (Chief Scientist) Gregory A. Cutter (Co-Chief Scientist) Jessica N. Fitzsimmons (Co-Chief Scientist)	data info

Instruments

Aerosol Sampler

Supplied Name: Tisch TE-5170V-BL high volume aerosol sampler

Supplied Description:

Instrument Type

Generic Name: Aerosol Sampler

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/13/

Generic Description:

A device that collects a sample of aerosol (dry particles or liquid droplets) from the atmosphere.

Data Logger

Supplied Name: Campbell Scientific data logger

Supplied Description:

Instrument Type

Generic Name: Data Logger

Generic Description:

Electronic devices that record data over time or in relation to location either with a built-in instrument or sensor or via external instruments and sensors.

Germanium detector

Supplied Name: low background germanium gamma detectors

Supplied Description:

FIU's facilities include four HPGe detectors: three Ortec Coaxial GEM series detectors and one Canberra Broad Energy gamma detector. The detectors were calibrated for the each geometry by adding a commercially prepared mixed isotope solution of known gamma activities (Eckert & Ziegler Mixed Nuclide Solution 7500) to three W-41 filters (for aerosol samples) and pellets of various thicknesses (for seawater) to derive a calibration curve using peaks associated with following isotopes: Sn-113 @ 392 keV, Sr-85 @ 514 keV, Cs-137 @ 662 keV. The counting efficiencies of the four detectors ranges from 0.05686 to 0.11415 for Be-7 on aerosol filters. And for the seawater pellets from this cruise, the counting efficiencies ranged from 0.03480 to 0.08590.

Instrument Type

Generic Name: Germanium detector

Generic Description:

Germanium detectors are semiconductor diodes having a p-i-n structure in which the intrinsic (i) region is sensitive to ionizing radiation, particularly x rays and gamma rays. Under reverse bias, an electric field extends across the intrinsic or depleted region. When photons interact with the material within the depleted volume of a detector, charge carriers (holes and electrons) are produced and are swept by the electric field to the p and n electrodes. This charge, which is in proportion to the energy deposited in the detector by the incoming photon, is converted into a voltage pulse by an integral charge sensitive preamplifier. Germanium detectors are mostly used for gamma spectroscopy in nuclear physics, as well as x-ray spectroscopy.

Pump

Supplied Name: centrifugal pump

Supplied Description:

A 1 hp centrifugal pump on deck pulled seawater from selected depths via a 1.5-inch pvc hose.

Instrument Type

Generic Name: Pump

Generic Description:

A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift, displacement, and gravity pumps

YSI EXO multiparameter water quality sondes

Supplied Name: portable CTD (model: YSI EXO1)

Supplied Description:

Instrument Type

Generic Name: YSI EXO multiparameter water quality sondes

Acronym: YSI EXO

Generic Description:

Comprehensive multi-parameter, water-quality monitoring sondes designed for long-term monitoring, profiling and spot sampling. The EXO sondes are split into several categories: EXO1 Sonde, EXO2 Sonde, EXO3 Sonde. Each category has a slightly different design purpose with the the EXO2 and EXO3 containing more sensor ports than the EXO1. Data are collected using up to four user-replaceable sensors and an integral pressure transducer. Users communicate with the sonde via a field cable to an EXO Handheld, via Bluetooth wireless connection to a PC, or a USB connection to a PC. Typical parameter specifications for relevant sensors include dissolved oxygen with ranges of 0-50 mg/l, with a resolution of +/- 0.1 mg/l, an accuracy of 1 percent of reading for values between 0-20 mg/l and an accuracy of +/- 5 percent of reading for values 20-50 mg/l. Temp ranges are from-5 to +50 degC, with an accuracy of +/- 0.001 degC. Conductivity has a range of 0-200 mS/cm, with an accuracy of +/-0.5 percent of reading + 0.001 mS/cm and a resolution of 0.0001 - 0.01 mS/cm.

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
Station_ID	Station ID number (blank values = no station number for aerosol sampler deployments)	unitless	station
Event_ID	Event ID	unitless	event
Start_Date_UTC	Sample collection start date Format: %Y-%m-%d	unitless	date_start
Start_Time_UTC	Sample collection start time (UTC) Format: %H:%M:%S	unitless	time_start
Start_ISO_DateTime_UTC	Sample collection start date and time (UTC) in ISO 8601 format Format: %Y-%m-%dT%H:%M:%SZ	unitless	ISO_DateTime_UTC
End_Date_UTC	Sample collection end date (for aerosol sampler deployments) Format: %Y-%m-%d	unitless	date_end
End_Time_UTC	Sample collection end time (for aerosol sampler deployments) (UTC) Format: %H:%M:%S	unitless	time_end
End_ISO_DateTime_UTC	Sample collection send date and time (UTC) in ISO 8601 format (for aerosol sampler deployments) Format: %Y-%m-%dT%H:%M:%SZ	unitless	ISO_DateTime_UTC
Start_Latitude	Latitude at start of sample collection	decimal degrees	lat
Start_Longitude	Longitude at start of sample collection	decimal degrees	lon
End_Latitude	Latitude at end of sample collection (for aerosol sampler deployments)	decimal degrees	lat
End_Longitude	Longitude at end of sample collection (for aerosol sampler deployments)	decimal degrees	lon
Sample_ID	GEOTRACES sample ID number	unitless	sample
Sample_Depth	Depth of seawater sample	meters (m)	depth
Be_7_D_CONC_PUMP_zo1nvd	Seawater beryllium-7 activity concentration	microBecquerel per kilogram (uBq/kg)	trace_metal_conc
SD1_Be_7_D_CONC_PUMP_zo1nvd	One standard deviation for Be_7_D_CONC_PUMP_zo1nvd	microBecquerel per kilogram (uBq/kg)	trace_metal_conc
Flag_Be_7_D_CONC_PUMP_zo1nvd	Quality flag for Be_7_D_CONC_PUMP_zo1nvd. SeaDatNet flag scheme.	unitless	q_flag
Be_7_A_T_CONC_HIVOL_b7gzuk	Aerosol beryllium-7 activity concentration	milliBecquerel per cubic meter (mBq/m^3)	metal_conc_air
SD1_Be_7_A_T_CONC_HIVOL_b7gzuk	One standard deviation for Be_7_A_T_CONC_HIVOL_b7gzuk	milliBecquerel per cubic meter (mBq/m^3)	metal_conc_air
Flag_Be_7_A_T_CONC_HIVOL_b7gzuk	Quality flag for Be_7_A_T_CONC_HIVOL_b7gzuk. SeaDataNet flag scheme.	unitless	q_flag