Dataset: Palmer Station Thorium

Salinity and density were measured using a CTD.  4-L Samples for total water-column ²³⁴Th activity were collected using Go-Flo bottles at 7 depths from the surface to 100 m.  Sample volume was determined gravimetrically and then samples were acidified to a pH < 2 with nitric acid and a Th-230 tracer spike was added.  Samples were shaken and allowed to equilibrate for 4 – 9 hours.  Samples were then re-basified with ammonium hydroxide to a pH of 8 – 9, shaken, and allowed to equilibrate for >8 hours.  Samples were then vacuum filtered at high vacuum pressure through a quartz (QMA) filter.  Filters were mounted in RISO planchets and counted on a RISO low-level beta multi-counter at Palmer Station.  Following a background count >6 months later, samples were dissolved in 8M nitric acid / 10% hydrogen peroxide solution and a Th-229 tracer spike was added.  Samples were then shipped to the Woods Hole Analytical laboratory for analysis of the Th-229:Th-230 ratio, which was used to calculate the initial precipitation and filtration yield of Th-234. For additional details, see Stukel et al. (2015) and Stukel et al. (2022).