Dataset: Radium and thorium radionuclide measurements in coastal marsh sediments from sediment cores in South Carolina collected from 2017 to 2019

Sampling and analytical procedures: 

Sediment cores were collected with the piston corer and immediately cut at 2-6 cm intervals and transferred to Teflon large mouth bottles. Care was taken to minimize settling of cores or loss of pore water prior to sectioning. A portion of approximately 15 grams was taken from each bottle and was charged with 150 ml of 18 Mohm water and stirred to form a slurry. The slurry was sonicated for 5 min. The pH of the slurry was adjusted to 8-9 by the dropwise addition of concentrated NH4OH. Following the pH adjustment, 1.0 ml of KMnO4 solution (3.0 g l-1) and 1.0 ml of MnCl2 solution (8.0 g MnCl2 4H2O l-1) was added to form a suspension of MnO2. The slurry was then filtered onto a 142 mm GF/F filter. The sample was loaded into a modified recirculation chamber (after Cai et al. 2012) for counting of 220Rn and 219Rn on the RaDeCC system.  Samples were taken back to the laboratory for immediate counting to minimize error in the ratio. Samples were re-measured in the same RaDeCC system after two days and 45 days to differentiate between supported and excess 224Ra and 223Ra.

To estimate porosity, after the sample was collected and split into representative slabs, a portion of the homogenized slab (typically 15 grams) was dried to constant mass using an oven at 60℃. Mass measurements were taken until constant mass was achieved.  

Problem Report:
Noted in the data file, there were four samples that had anomalous counts. These counts were excluded from the data set and results recalculated. Both the original data calculation and the recalculation have been included in the data set. The recalculated samples are denoted with CORR at the end of the sample name and commented on. 

Location: 
Folly Island and Marsh, South Carolina, 32.68 N, 79.95 W
Daniel Island creek/marsh, South Carolina 32.89 N, 79.9 W