Aerosol and seawater beryllium-7 concentrations from Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1815) on R/V Roger Revelle from October to November 2018 (NCEI Accession 0278594)

This dataset contains chemical and physical data collected on R/V Roger Revelle during cruise RR1815 in the North Pacific Ocean and South Pacific Ocean from 2018-10-25 to 2018-11-22. These data include depth, metal concentration in atmosphere, and trace metal concentration. The instruments used to collect these data include Aerosol Sampler, Gamma Ray Spectrometer, and Pump. These data were collected by David C. Kadko of Florida International University as part of the "GEOTRACES Pacific Meridional Transect: Measurement of Beryllium-7 as a Tracer of Upper Ocean Processes (PMT Be-7)" and "US GEOTRACES Pacific Meridional Transect (U.S. GEOTRACES PMT)" projects and "U.S. GEOTRACES (U.S. GEOTRACES)" program. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) submitted these data to NCEI on 2020-04-21.

The following is the text of the dataset description provided by BCO-DMO:

Be-7 activity

Dataset Description:
Acquisition Description:
Be-7 Aerosol:
Aerosol samples were collected between Sept 20, 2018 and Nov 23, 2018 during the U.S. GEOTRACES PMT cruise, R/V Roger Revelle (RR1814), 18 September 2018 - 24 November 2018, Seattle, Washington - Papeete, Tahiti, French Polynesia (with a port stop in Hilo, Hawaii, 21-25, October 2018). Aerosol samples were obtained with a Tisch TE-5170V-BL high volume aerosol sampler, modified to collect 12 replicate samples on acid-washed (Wallace et al, 1977; Baker et al., 2006) 47mm diameter Whatman-41 (W-41) filters, using procedures of the US GEOTRACES aerosol program (Morton et al., 2013). In order to minimize the filter blanks for our experiment, the W-41 filters were pre-cleaned before deployment using three cycles of leaching with 0.5M HCl (Optima) then rinsing with ultra-high purity water (UHP water) according to trace element protocols in a HEPA-filtered laminar flow hood (Morton et al., 2013; similar to Baker et al., 2006).

For 7Be, three of the 47mm aerosol samples were stacked in a plastic Petri dish and counted by gamma spectroscopy. Be-7 has a readily identifiable gamma peak at 478 keV. The counting system was calibrated for all samples by preparing a commercial standard in geometry identical to the samples.

Be-7 Seawater:
A weighted sampling hose, attached to a submersible pump with a portable ctd was deployed over the aft of the ship to collect seawater for Be-7 analysis. The seawater was collected in plastic 700 liter holding tanks and then passed through iron-oxide impregnated acrylic fiber filters (adsorbs Be-7). The efficiency of the fiber for extraction of Be from seawater was determined by adding stable Be atomic absorption standards to a drum containing seawater, pumping the water through an iron fiber cartridge, and at every 100 L measuring the Be content of the cartridge effluent. Based on several trials, it was found that for sample volumes in the range 400-700L, extraction efficiencies are respectively, 82 ± 3% to 76 ± 2%.

All fibers were returned to the lab where they were dried and ashed. Fiber samples were pressed into pellets. All samples were then placed over a low background germanium gamma detector. 7Be has a readily identifiable peak at 478keV. The detector is calibrated for these samples by adding a commercially prepared mixed solution of known gamma activities to ashed fiber and counting in the appropriate geometry.