Abstract:

This dataset includes baseline short-lived radioisotope measurements from sediment cores collected throughout the Gulf of Mexico. Samples were analyzed by gamma spectrometry with High-Purity Germanium (HPGe) gamma-ray detectors (Canberra Coaxial Planar configuration) for total 210Pb (46.5 keV), 214Pb (295 keV and 351 keV), and 214Bi (609 keV) activities. The mean activity of the 214Pb (295 keV), 214Pb (351 keV), and 214Bi (609 keV) was used as a proxy for 226Ra activity and therefore the supported 210Pb that is produced in situ. The reported excess 210Pb (210Pbxs) is the difference of the total 210Pb and the supported 210Pb.

Suggested Citation:

Schwing, Patrick; Hollander, David J.. 2018. Short-lived radioisotope (excess Pb210) measurements from sediment cores collected throughout the Gulf of Mexico from 2010-11-07 to 2017-07-20. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-122c-pa67

Purpose:

The purpose of this dataset was to provide Gulf of Mexico-wide baseline measurements of surface sediment Pb-210 activities in advance of future oil spills. These baseline measurements can be used in the event of future oil spills as a reference to quantitatively assess impact and recovery.

Data Parameters and Units:

Station id, latitude (decimal degrees), longitude (decimal degrees), excess Pb210 (dpm), date of core collection (MM/DD/YYYY)

Methods:

Samples were analyzed by gamma spectrometry on Canberra HPGe (High-Purity Germanium) Coaxial Planar Photon Detectors for total 210Pb (46.5Kev), 214Pb (295 Kev and 351 Kev), and 214Bi (609Kev) activities. Data were corrected for counting time and detector efficiency, as well as for the fraction of the total radioisotope measured yielding activity in dpm g-1 (disintegrations per minute per gram). Detector efficiencies (limit of detection) were all <3% of the total activities measured, determined by similar methods to Kitto et al., (1991). Efficiency calibrations were based on analyzing 12 varying masses (1-50g) of the IAEA-447 standard. By relating the counts measured at variable masses to the known activity of the standard, self-absorption is also included in the efficiency calibrations (Hussain et al., 1996). The Cutshall method (Cutshall et al., 1983) was used on select sediment samples, and results show that the self-absorption and variability is negligible and within detection error. The mean activity of the 214Pb (295 Kev), 214Pb (351 Kev), and 214Bi (609 Kev) was used as a proxy for 226Ra activity and therefore the supported 210Pb that is produced in situ. The supported 210Pb was subtracted from the total 210Pb (measured) to determine excess 210Pb (210Pbxs).

Provenance and Historical References:

Cutshall, N. H., Larsen, I. L., & Olsen, C. R. (1983). Direct analysis of 210Pb in sediment samples: self-absorption corrections. Nuclear Instruments and Methods in Physics Research, 206(1-2), 309-312. doi:10.1016/0167-5087(83)91273-5 Hussain, N., Kim, G., Church, T. M., & Carey, W. (1996). A simplified technique for gamma-spectrometric analysis of 210Pb in sediment samples. Applied radiation and isotopes, 47(4), 473-477. doi:10.1016/0969-8043(95)00319-3 Kitto, M. E. (1991). Determination of photon self-absorption corrections for soil samples. International journal of radiation applications and instrumentation. Part A. Applied radiation and isotopes, 42(9), 835-839. doi:10.1016/0883-2889(91)90221-L

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