The234U and230Th radionuclides are highly retarded by factors of 104 to 105 in basalt groundwater (Hanford) and briny groundwaters from Texas, and geothermal brine from the Salton Sea Geothermal Field (SSGF). In basalt groundwaters (low ionic strength), Ra is highly sorbed, while in brines (high ionic strength), Ra is soluble. This is probably because the sorption sites are saturated with Na+ and Cl– ions, and RaCl2 is soluble in brines.210Pb is soluble in SSGF brine, probably as a chloride complex. The234U/230Th ratios in basalt groundwaters and brines from Texas and SSGF are nearly unity, indicating that U is in the +4 state, suggesting a reducing environment for these aquifers.
Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10–4 g/g to 10–10 g/g. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization.
A radiochemical neutron activation analysis using a rare earth group separation scheme has been used to measure ultratrace levels of rare earth elements (REE) in IAEA Human Hair (HH-1), IAEA Animal Bone (H-5), NBS Bovine Liver (SRM 1577), and NBS Orchard Leaf (SRM 1571) standards. The REE concentrations in Human Hair and Animal Bone range from 10–8 g/g to 10–11 g/g and their chondritic normalized REE patterns show a negative Eu anomaly and follow as a smooth function of the REE ionic radii. The REE patterns for NBS Bovine Liver and Orchard Leaf are identical except that their concentrations are higher. The similarity among the REE patterns suggest that the REE do not appear to be fractionated during the intake of biological materials by animals or humans.
We measured 37 elements in six USGS geological camples and one NBS biological orchard leaf (OL) sample, using sequential INAA
and radiochemical group separation coupled with high resolution, high efficiency Ge(Li), and a Ge(Li) with anticoincidence
shields. The elemental concentrations in these samples vary over three orders of magnitude. Our results agree very well with
the reported values. The rare earth values in PCC-1 are 2–4 times lower than the reported values. Precise REE patterns are
defined in USGS samples, which are characteristic of the total rock types. The REE pattern in OL is identical to the mineral
apatite. In addition to the possibility that OL may be contaminated by local soil, it is also possible that the uptake of
REE trace elements by plants from soil is perhaps dominated by accessory mineral such as apatite, or plants take up the REE
from bulk soil in a preferential manner as a smooth function of the REE ionic radii.
Current techniques for determining low levels of dissolved thorium involve chemical separations, generally by coprecipitation with a carrier cation, purification by ion exchange procedures, electroplating and, finally, alpha counting by alpha spectrometry. Similarly, measurements of low228Ra and224Ra activities requires concentration, by coprecipitation with barium sulfate, followed by gamma counting. An improved method for determining radium and thorium from the232Th decay series has been developed which measures the activity of220Rn as an assay of its parents. Although some ingrowth corrections and minor separation procedures for Th are required, the results to date show that the dynamic counting of220Rn via de-emanation and alpha counting by the alpha-scintillation method is a preferable approach for determining these radium and thorium isotopes accurately and efficiently. The method for lower limit detection depends on the emanation rate, which depends on purge-gas flow rate and sample volume analyzed. Using 50-cc and 1000-cc bubblers, and maximum effective purge gas flow rate, a lower limit of detection of 0.4 and 0.06 pCi/L220Rn can be obtained, respectively.
Rare-Earth Element (REE) concentrations in briny groundwaters are very low, and range from ppb to ppt levels. REE can be measured at these low levels using prechemistry to concentrate the REE, postchemistry as an REE group separation following neutron activation, and reactivation for chemical yields. The brine solutions appear to be stable with respect to trace elements (such as the REE) over the four years of sample storage. The brine REE patterns are highly fractionated from light REE to heavy REE, including a negative Eu anomaly. The REE patterns appear to be characteristic of each formation and its source region.
Authors:J. Laul, M. Smith, C. Thomas, P. Jackson and N. Hubbard
Analytical procedures for measuring various radionuclides in the238U and232Th chains in briney waters are described. Using methods such as mass spectrometry, and alpha, beta and gamma spectrometry, the desired measurement sensitivity required for each of the radionuclides is achieved.233U,228Th,208Po,212Pb, and133Ba are used as tracers for chemical yield recoveries. Typical precision of the results range from 5–20%.
The concentrations of seventeen elements in two species of fungus which cause wheat bunt disease,Tilletia caries (DC.) Tul. andTilletia controversa Kühn, were determined by instrumental neutron activation analysis. Differences in the K and Cl concentrations between these
two species of spores are large and therefore can be used as a criterion for distinguishing between the two species of fungus.
Authors:J. Laul, E. Lepel, W. Weimer and N. Wogman
A rare earth group separation scheme followed by normal Ge(Li), low energy photon detector (LEPD), and Ge(Li)−NaI(Tl) coincidence-noncoincidence
spectrometry significantly enhances the detection sensitivity of individual rare earth elements (REE) at or below the ppb
level. Based on the selected γ-ray energies, normal Ge(Li) counting is favored for140La,170Tb and169Yb; LEPD is favored for low γ-ray energies of147Nd,153Sm,166Ho and169Yb; and noncoincidence counting is favored for141Ce,143Ce,142Pr,153Sm,171Er and175Yb. The detection of radionuclides152mEu,159Gd and177Lu is equally sensitive by normal Ge(Li) and noncoincidence counting;152Eu is equally sensitive by LEPD and normal Ge(Li); and153Gd and170Tm is equally favored by all the counting modes. Overall, noncoincidence counting is favored for most of the REE. Precise
measurements of the REE were made in geological and biological standards.
Authors:J. Laul, D. Case, M. Wechter, F. Schmidt-Bleek and M. Lipschutz
A thermal neutron activation analysis technique has been developed for the analysis of terrestrial rocks and stony meteorites
for trace elements. The main emphasis of the method is directed toward minimizing chemical procedures and maximizing the use
of Ge(Li) gamma spectroscopy and computer data reduction. The validity of the technique is demonstrated by presenting data
obtained for synthetic samples, U.S G.S. Standard Rocks and three ordinary chondrite meteorites for the following elements:
As, Au, Co, Cs, Ga, Ge, Hg, Mo, Os, Re, Sb, Sc, Se, Te and Zn.