Multielement analysis of natural waters by neutron activation, group chemical separations, and gamma-ray spectrometric techniques

Abstract

A multielement analytical technique of thermal neutron activation of frozen water samples has been developed and applied to the studies of natural waters. A rapid group chemical separation utilizing ion exchange resins and a precipitation step to reduce 24Na and 42K interferences, followed by ?-ray analysis of the fractions with Ge (Li) and multiparameter NaI (T1) systems, permits the simultaneous measurement of a large number of trace constituents. Samples of river water, rain water, processed sewage water and Greenland ice were analyzed for 19 trace elements -Ag, As, Br, C1, Co, Cs, Cr, Cu, Fe, Hg, K, Mn, Na, Rb, Sb, Sc, Se, U, and Zn. These data have been used in studies of trace element concentration factors in aquatic biota, precipitation scavenging processes, and environmental pollution.

Neutron activation techniques for the measurement of trace metals in environmental samples

“…In addition, quartz contains much higher levels of impurities than polyethylene or polypropylene and is a potential source of contamination. Tanner et al (1972), and Brune and Landstrom (1966) have described a mefihod for neutron irradiating 30 to 80 ml samples of fresh water in a frozen state in polyethylene containers as a means of preserving the samples prior to and during the neutron irradiation.…”

“…Therefore, to measure the short-lived neutron activation products of As, Hg, Cu, Zn, Ba and La, as well as several other elements of geochemical interest, it is necessary to 24 remove the interfering Na. Tanner et al (1972) have described a simple two-step separation scheme which eventually permits the semi-instrumental measurement of about 19 trace elements (see Figure 2). The method simply consists of passing a neutron activated water sample, containing carriers of 0.1 mg each of Na, K, Rb and Cs, through a column of Dowex 1x2 anion exchange resin which has been converted to OH , S and CO^ forms by contacting with IM solutions of NaOH,.Na2S and Na2C03, respectively.…”

“…Without any separations at all it would still be possible to measure Ag, Br, CI,Co, Cr, Cs, Fe, Mn, Na, Rb, Sb, Sc, Se, U, Zn, Ag and occasionally Hg, simply by counting the neutron activated river water samples at several optimum times following the irradiation (approximately 4 hours, 3 days and 20 days). The radiochemical separations permit the measurement of As, Cu, La and K. Table 1 also lists the approximate limits of detection for 20 elements in river water utilizing the method of Tanner et al (1972), and compares these limits with maximum allowable concentrations of some of the more toxic heavy metals in drinking water, as established by the U. S. Public Health Service. As indicated in Table 1, this semi-INAA technique can be used to detect most heavy metal pollutants in fresh waters at concentrations well below maximum permissible limits.…”

“…(after Tanner, Turekian (1969) (b) after method of Tanner et al (1972) Thirty to eighty ml water samples; integrated thermal neutron exposure 2x10^^ n/cm^; count for 10 min., 60 min., and 1000 min, after decay times of 3 hrs, 24 hrs and 23 days, respectively; 20 cc Ge(Li) detector.…”

“…Arsenic can usually be measured in river or lake waters by the semi-INAA method of Tanner et al (1972). However, in some natural waters, particularly precipitation, the As must be preconcentrated from large volumes of water.…”