2
General Features of Radioisotopic Methodology
tions are accompanied by the emission of radioactive radiation in the form of
high-energy particles or hard X-rays. Among the isotopic nuclides, however,
there are a number of specimens in which the nuclei remain stable regardless
of the variation in mass number. These represent the stable isotopes. As an
example, the stable isotopes of natural and stable isotopic nuclides of nitrogen and oxygen can bc given: thc natural element nitrogen r--W and its stable
isotope N~5; the natural element oxygen O~o and stable isotope OAR. Most
radioactive isotopes exist do not neither in nature or present as minor admixtures in natural minerals, such as the long-living 14C-carbon. For experimental
work, they are produced artificially in atomic pools or cyclotrons, in which the
stream of fast neutrons reacts with nuclei of appropriate elements, inducing
their transformation.
Radioisotopes, having the same atomic number z as the natural nuclides
of this element and the same charge of nucleus, have the same chemical properties. The presence of trace amounts of radioactive isotopes in atoms, forming
molecules of living tissues, same as their radioactive disintegrations (radioactivity) induces no biological side effects, except maybe the so-called isotopic
effect - the effect of some retardation in biochemical reactions of small molecules containing a heavier atom of isotopic radionuclide with a larger mass
number (see Sect. 2.3.1). The nuclear transformations of radioactive isotopes
commonly used in hydrobiology as tracers, such as 3H, 14C, 32p, 35S, and 45Ca
result in the emission of l3-rays (Table 1.1). This means that their mass number
a remains the same, but the numbers of protons z in them, and correspondingly their atomic number after emitting the negatively charged particle, rises
by one, so that their nuclides transform to another chemical element. For
example, during radioactive fission, radioactive hydrogen 3H (tritium) transforms to helium: fH ~He +13-rays, radioactive carbon to nitrogen: A 4 c j4N +,
radioactive phosphorus 32p to sulfur: 32p 32S. During such a l3-type nucleic transformation, caused basically by nucleus instability in a given radio nuclide combined with an excess of neutrons in it, one of neutrons in the nucleus (N)
disintegrates in the following way: N -e + +p + an, where: -e is the particle represented by the electron, +p the proton, and an the anti neutrino.
Among the practically important characteristics of radioisotopes which
are in use as tracers in hydro biological studies are: the type of radioactive rays
emitted, their energy, and the half-life of the radioisotope. The corresponding
parameters are given in Table 1.1 and in Fig. 1.1. The basic unit of the intensity of isotopic radiation, radioactivity, is 1 Bequerel (bq), which corresponds
to a rate of one disintegration S-I, or 60 min-I. Correspondingly, the unit of
megabequerel (mbq) is equal to 6010 0 disintegrations min- I (dm), and that of
the gigabequerels (gbg) 601 0 9 dm. Another, older system of radioactivity units
operates with microcuires (/-lCi) which corresponds to 2.22 10 0 dm, millicuries
(mCi) equal to 2.2210 9 dm, and curies (Ci) = 2.2210 12 dm. This means that
1 mbq = 23.03 /-lCi and 1 gbg = 27.03mCi.
Other characteristics of radioactivity important in practical evaluation and
measurements are: the half-life time of a given radioisotope, the concrete
General Features of Radioisotopic Methodology
tions are accompanied by the emission of radioactive radiation in the form of
high-energy particles or hard X-rays. Among the isotopic nuclides, however,
there are a number of specimens in which the nuclei remain stable regardless
of the variation in mass number. These represent the stable isotopes. As an
example, the stable isotopes of natural and stable isotopic nuclides of nitrogen and oxygen can bc given: thc natural element nitrogen r--W and its stable
isotope N~5; the natural element oxygen O~o and stable isotope OAR. Most
radioactive isotopes exist do not neither in nature or present as minor admixtures in natural minerals, such as the long-living 14C-carbon. For experimental
work, they are produced artificially in atomic pools or cyclotrons, in which the
stream of fast neutrons reacts with nuclei of appropriate elements, inducing
their transformation.
Radioisotopes, having the same atomic number z as the natural nuclides
of this element and the same charge of nucleus, have the same chemical properties. The presence of trace amounts of radioactive isotopes in atoms, forming
molecules of living tissues, same as their radioactive disintegrations (radioactivity) induces no biological side effects, except maybe the so-called isotopic
effect - the effect of some retardation in biochemical reactions of small molecules containing a heavier atom of isotopic radionuclide with a larger mass
number (see Sect. 2.3.1). The nuclear transformations of radioactive isotopes
commonly used in hydrobiology as tracers, such as 3H, 14C, 32p, 35S, and 45Ca
result in the emission of l3-rays (Table 1.1). This means that their mass number
a remains the same, but the numbers of protons z in them, and correspondingly their atomic number after emitting the negatively charged particle, rises
by one, so that their nuclides transform to another chemical element. For
example, during radioactive fission, radioactive hydrogen 3H (tritium) transforms to helium: fH ~He +13-rays, radioactive carbon to nitrogen: A 4 c j4N +,
radioactive phosphorus 32p to sulfur: 32p 32S. During such a l3-type nucleic transformation, caused basically by nucleus instability in a given radio nuclide combined with an excess of neutrons in it, one of neutrons in the nucleus (N)
disintegrates in the following way: N -e + +p + an, where: -e is the particle represented by the electron, +p the proton, and an the anti neutrino.
Among the practically important characteristics of radioisotopes which
are in use as tracers in hydro biological studies are: the type of radioactive rays
emitted, their energy, and the half-life of the radioisotope. The corresponding
parameters are given in Table 1.1 and in Fig. 1.1. The basic unit of the intensity of isotopic radiation, radioactivity, is 1 Bequerel (bq), which corresponds
to a rate of one disintegration S-I, or 60 min-I. Correspondingly, the unit of
megabequerel (mbq) is equal to 6010 0 disintegrations min- I (dm), and that of
the gigabequerels (gbg) 601 0 9 dm. Another, older system of radioactivity units
operates with microcuires (/-lCi) which corresponds to 2.22 10 0 dm, millicuries
(mCi) equal to 2.2210 9 dm, and curies (Ci) = 2.2210 12 dm. This means that
1 mbq = 23.03 /-lCi and 1 gbg = 27.03mCi.
Other characteristics of radioactivity important in practical evaluation and
measurements are: the half-life time of a given radioisotope, the concrete