Envlron. Sci. Technol. 1083, 17, 248-250
-ature Cited Abdel-Rahman, M. S.; Couri, D.; Jones, J. D. J. Enuiron.
Dioxide-CP in Potatoes and Tomatoes”; a report by Olin Research Center, New Haven, CT, 1979. (11) Robson, H. L.Encycl. Chem. Technol. 1949,3,707-716. (12) Pitman, A. L.; McLaren, J.; Davis, F. H.; Groggins, P. H. Chern. Metall. Eng. 1938,45,692-696. (13) Masters, B. J. In “Inorganic Isotopic Synthesis”; Herber, R. H., Ed.; W. A. Benjamin: New York, 1962;pp 215-226. (14) Franson, M. A., Ed. ”Standard Methods for the Examination of Water and Waste Water”, 14th ed.; American Public Health Association: Washington, DE., 1976. (15) Masschelein, W. J. “Chlorine Dioxide: Chemistry and Environmental Impact of Oxychlorine Compounds”;Ann Arbor Science, Ann Arbor, MI, 1979. (16) White, G.C. “Handbook of Chlorination”;Van NostrandReinhold New York, 1979. (17) Dodgen, H.;Taube, H. J. Am. Chem. SOC.1949, 71, 2501-2504.
Pathol. Toxicol. 1980,3,421-430.
Abdel-Rahman, M. S.;Couri, D.; Bull, R. J. J. Enuiron. Pathol. Toxicol. 1980,3,431-449. Ridenour, G. M.; Ingols, R. S. J. Water Works Assoc. 1947, 39,561-567. Ridenour, G. M.; Annbruster, E. H. J. Water Works Assoc. 1949,41,537-550. Benarde, M. A.; Israel, B. M.; Oliveri, V. P.; Granstrom, M. L. Appl. Microbiol. 1965,13,776-780. Roller, S.D.; Oliveri, V. P.; Kawata, K. Water Res. 1980, 14,635-641. Cronier, S.; Scarpino, P. V.; Zink, M. L.; Hoff, J. C., presented at the 77th Annual Meeting of the American Societry for Microbiology, New Orleans, LA, May 1977. (8) Ridenour, G. M.: Innols. R. S.: Armbruster. E. H. Water Sewage Works 1949; 96;279-283. (9) Stevens, A. A,; Seeger, D. R.; Slocum, C. J. In “Ozone/ Chlorine Dioxide Oxidation Produds of Organic Materials”; Rice, R. G., Cotouro, J. A., Ede.; International Ozone Institute: Cleveland, OH, 1978;pp 383-395. (10) Incoviello, S. A.; Thomas, R. J. “MigrationData for Chlorine
Received for reuiew December 22, 1980. Revised manuscript receiued Nouember 8,1981. Accepted December 6,1982. This work was supported in part by National Science Foundation Grant PFR 78-27067.
Application of y-y-Directlonal Correlatlon Measurements for Speclation Studies in Environmental Research Marcel de Bruin” and Peter Bode Interuniversity Reactor Institute, Mekeiweg 15, 2629 JB Delft, The Netherlands
Photons and/or particles emitted consecutively in the decay of a radionuclide exhibit a specific directional correlation pattern. This pattern is subject to perturbations due to interactions between the decaying nuclei and their chemical and physical environment. For molecules in solution, the degree of perturbation depends on the size of the molecule in which the nucleus is incorporated, while the presence of a time dependency of the perturbation is an indication for the occurrence of chemical or physical reactions. The experimental characteristics of perturbed directional correlation (PDC) experiments make the technique very suitable for studies of trace-element behavior in very dilute systems, e.g., that present in biological and environmental systems. This is illustrated with results from a PDC experiment involving trace-element uptake by roots of a tomato plant seedling.
Introduction Most characteristics of nuclear transformations of radionuclides are virtually independent of the chemical and physical status of the decaying atom. As an exception, an influence of the chemical form on the decay constant has been observed for decay through internal conversion or electron capture since in this case the orbital electrons are involved. However, these differences are small and hard to measure. Stronger effects of chemical binding on nuclear decay characteristics can be observed in the directional correlation pattern existing between particles and/or photons emitted in consecutive decay processes. For certain elements (see Table I) the delay time ti between these emissions is such that an appreciable disorientation of the nuclear spin may occur ( I ) , resulting in a perturbation of the directional correlation expressed as the perturbation factor G . The perturbation depends on the 248
Environ. Sci. Technol., Voi. 17, No. 4, 1983
t I I’O
I 1
\
O”
cj
Small Molecules
\
0.4
Very Large Molecules Proteins
0.2 L
0.0
I
I
I
,
!
Correlation time T c Molecular weight
I
___)
Figure 1. Dependence of 0 on molecular weight and associated rotational correlation time ( 6 ) .
chemical and physical status of the decaying atoms such as, e.g., structure and composition of the surrounding of atoms incorporated in solids or size of the molecule the atoms are bound to and viscosity for atoms present in solution (Figures 1and 2). Changes in the chemical status of a radioactive species will be reflected in the effective directional correlation (2-5). For practical applications of perturbed directional correlation (PDC) measurements, the use of y-ray-emitting nuclides is most suitable; the directions of charged particles (p,a)are strongly altered by interactions between these particles and sample or container material. y-y-Directional correlation functions can be measured with the use of two detectors (Figure 3). The viewing angle between the two detectors can be varied, and the number of events detected in coincidence in both detectors is recorded as function of 6. The directional correlation often depends on the time elapsed between the two correlated y-ray emissions. It can be measured as a function of the delay
00113-936X/83/0917-0248$01.50/0 0 1983 American Chemical Society
Table I. Characteristic Properties of Some Radionuclides Suitable for Trace-Element Studies Using PDC Measurements max spec cascade decay y-y cascade, abundmethod of min act., ti,b ns production nuclide half-life mode keV-keV ance: % clcilclg concn, ppb
