Thorium_Summary

Dataset description

Thorium isotope data summaries from AMLR and NBP cruises to the Antarctic in 2006

Cruises

Associated Publications

Brzezinski, M.A., Nelson, D.M., Franck, V.M. and Sigmon, D.E., 2001. "Silicon dynamics within an intense open-ocean diatom bloom in the pacific sector of the southern ocean." Deep-Sea Research Part II 48, pp. 3997–4018

Michiel Rutgers van der Loeff, Manmohan M. Sarin, Mark Baskaran, Claudia Benitez-Nelson, Ken O. Buesseler, Matt Charette, Minhan Dai, Örjan Gustafsson, Pere Masque, Paul J. Morris, Kent Orlandini, Alessia Rodriguez y Baena, Nicolas Savoye, Sabine Schmidt, Robert Turnewitsch, Ingrid Vöge, James T. Waples. "A review of present techniques and methodological advances in analyzing 234Th in aquatic systems" Marine Chemistry, Volume 100, Issues 3-4, 1 August 2006, Pages 190-212

Pike, S.M., K.O. Buesseler, J. Andrews and N. Savoye, 2005. "Quantification of 234Th recovery in small volume sea water samples by inductively coupled plasma mass spectrometry." (PDF) Journal of Radioanalytical and Nuclear Chemistry, 263(2): 355-360.

Willard S. Moore and Ralph Arnold (1996). "Measurement of 223Ra and 224Ra in coastal waters using a delayed coincidence counter." Journal of Geophysical Research, vol. 101, no. c1, pages 1321-1329, January 15, 1996.

Acquisition description

Sampling and Analytical Methodology

Particle sinking rates were determined using the 4 liter measurement of 234Th (Pike et al., 2005). Samples were collected from hydrocasts from a shipboard CTD. The unfiltered 4-liter samples were immediately acidified to pH ~1.5 using concentrated Nitric acid. Samples were shaken vigorously and 230Th added as a yield monitor. The samples were shaken again and allowed to equilibrate for 8 hours. Concentrated NH4OH was subsequently added to each sample to adjust the pH to 8. Extraction of thorium from seawater was then accomplished by co-precipitation via a MnO2 precipitate onto a 25-mm-diameter QMA filter. The filtered samples were air dried and counted on a RISO beta detector (Rutgers van der Loeff et al., 2006). All samples were counted for at least 24 hours or until the counting error was < 3%. Samples were recounted after >150 days (~6 half lives) to determine the sample background. Detector calibration was confirmed with 3000m deep water sample.

Particulate carbon was collected through a McLane WTS-LV in-situ pump and filtered through a 142mm GFF filter. 22mm subsamples were collected, dried and transported back to the WHOI laboratory for CHN analysis on the Flash EA1112. The samples were pelletized in ultra clean tin capsules, combusted at 900oC, separated in a gas chromatographic column, and measured through a thermal conductivity detector. The CHN analyzer was calibrated by using an acetanilide standard. A second subsample was taken and analyzed for biogenic silica (Brzezinski et al 2001). Sodium Hydroxide was added to the filter and heated to 95oC for 45minutes. It was placed on ice and neutralized with hydrochloric acid. After centrifuging, the supernatant is then analyzed for silicate on a Lachat Quickchem 8000.

Processing description

Data Processing

Modifications to original data made to conform to BCO-DMO database convention

Cruise_ID added
Spaces in Sample_ID replaced with dashes for consistency with Radium summary data
empty cells filled with "nd" (no data)
Latitude/Longitude headers converted to lat/lon
date reformatted to YYYYMMDD
time reformatted to HHMM
decimal data values padded to consistent decimal places
spaces, minus signs, and "<"'s replaced with underscores or text in misc data headers
POC/PON used in place of Part Organic Carbon/Nitrogen in headers
"No Sample" values replaced with "nd" in Sample_Ids FA-494, FA-495
"Surface" values in Depth data replaced with "1"

1. Conductivity, Temperature, Depth:

   Shipboard CTD

2. Pump4:

   McLane WTS-LV Large Volume, High Accuracy, Oceanographic Sampling Pump

3. Pump5:

   Ship's clean water intake pump (surface sample)

This document is created from the content of the BCO-DMO metadata database.    2010-03-15  07:02:34