Salt marsh sediment CHN, bulk density and gamma emission data from sediment cores are provided for calculation of high marsh sediment accumulation and accretion rates in sediments collected during the Fall of 2014 in the Nelson Island Creek marsh, off Stackyard Rd., Rowley, MA.
On October 30th, 2014, four 40 cm deep cores were collected on the high marsh platform within 20-40m of the tall eddy flux tower on the Nelson Isalnd Creek marsh platform. Two cores were collected from stunted Spartina alterniflora marsh and two cores were collected from Spartina patens marsh. Cores were transported to the lab and stored at 4°C before further analysis. Cores were sectioned in 2 cm layers, which were subsequently dried at 60C. Bulk density was determined on the section, which was subsequently ground. Subsamples for CHN analysis (Thermo Scientific Flash 2000 NC Soil Analyzer) were first hydrated and then fumed with HCl to remove carbonates. We used a pure germanium gamma spectrometer (Canberra, GCW3023) to measure gamma emissions of 210Pb (46 keV), 137Cs (661.62 keV), 214Pb (352 keV) and 214Bi (609.32 kev). 214Pb and 214Bi were used to determine unsupported 210Pb, as a measure of 226Ra. Subsamples for radiochemical analysis were sealed for 21 days to ensure equilibrium between 226Ra and 210Pb before counting.
All specific activities except for 137Cs activities are corrected for counting efficiency.
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