Dataset: CaCO3_core
Deployment: TT013

   PI:              Margaret Leinen
   of:              University of Rhode Island, Grad. School of Oceanography
   dataset:         Calcium Carbonate concentrations, sediment cores
   dates:           November 07, 1992 to November 29, 1992
   location:        N: 4.0433  S: -4.9605  W: -140.1467  E: -139.4015
   project/cruise:  EqPac/TT013 - Benthic survey
   ship:            R/V Thomas Thompson

Carbonate analysis methodology: Calcium carbonate was determined from inorganic carbon measurements made on a Coulometrics Inc. Model 5011 CO₂ coulometer with a Model 5030 carbonate carbon apparatus. Between 5 and 10 mg of sample were acidified with 2ml 2N HCl to evolve CO₂. The CO₂ gas was bubbled into a titration cell where CO₂ was converted to hydroxyethylcarbonic acid which was automatically titrated with a coulometrically-generated base to a colorimetric endpoint. Grams of carbon in the sample are calculated based on factory standardization of the coulometric titration. Calcium carbonate content was calculated by assuming that all inorganic carbon in the sample was present as calcium carbonate, a reasonable assumption for these biogenic sediments which contain little or no dolomite. The CO₂ coulometer has an accuracy of 0.15 µg carbon. The precision of the complete procedure is ±0.52 wt% calcium carbonate based on the standard deviation of a lab standard of deep sea sediment which we developed from the study area. Duplicate analyses were performed on every tenth sample and an additional analysis was made for every pair which differed by more than 2 wt%.