4 Isotope Geochemistry in the Environment
63
members: continental crust and mantle stand at 10-11 and 1.1, respectively and so
this lower ratio must derive from a more primitive source. The only candidate ore
body seems to be the Siberian ores. It could be that Russia has become the
dominant exporter of platinum group elements to the USA. As such information is
difficult to obtain, and the major source of anthropogenic osmium is not known
well enough, the authors do not choose to speculate further. However, the
potential of the heavy metal approach to pollution research is clear.
4.2 Migration of Contaminated River Water into Groundwater
S y s t e m s
The enrichment of various toxic substances in groundwater is a direct result of the
infiltration of contaminated river water. Radon and oxygen isotope analyses
carried out on river and groundwater have made it possible for rates of exchange
between surface and groundwater to be calculated (Siegent1~a~er and Shotterer
1977; Stichler et al. 1986; Hoehn and Gunten 1989).
2_" Rn is a daughter product of the decay series of "--ss U (Fig. 4. I1) with a halflife of only 3.8 days. The enrichment of -'2~-Rn in the upper atmosphere is mainly a
consequence of diffusive emanation from U bearing minerals in granitic rocks, the
rate of emanation being significantly dependent on the microstructure of the rock.
In granular aquifers the intensity of radiation and rate of transport of radon is
strongly influenced by the grain size distribution, weathering of grain surfaces and
porewater content. Since the noble gas radon is almost chemically inert, it can
migrate unhindered and diffuse from particle surfaces into the nannopores
between grains. In water saturated aquifers, radon transport is strongly dependent
on the speed of groundwater currents. Groundwater is particularly enriched,
whereas surface waters are strongly depleted in radon. This concentration
difference permits the determination of infiltration or exfiltration rates using radon
as a natural tracer.
Age dating using radionuclides is based on one hand on the decay of the
radionuclides (equations IV, V; Sect. 1.2), and on the other hand on the increasing
concentration of the daughter product, which will after a certain amount of time
exist in equilibrium with the mother nuclide (N), i.e. secular equilibrium.
Equations (IV) and (V) may produce the following equation for the increase in
amount of the daughter isotope (D):
D = N o ( 1 - e -z')
([)
for radon:
A, - A , ( l - e -a')
(II)
63
members: continental crust and mantle stand at 10-11 and 1.1, respectively and so
this lower ratio must derive from a more primitive source. The only candidate ore
body seems to be the Siberian ores. It could be that Russia has become the
dominant exporter of platinum group elements to the USA. As such information is
difficult to obtain, and the major source of anthropogenic osmium is not known
well enough, the authors do not choose to speculate further. However, the
potential of the heavy metal approach to pollution research is clear.
4.2 Migration of Contaminated River Water into Groundwater
S y s t e m s
The enrichment of various toxic substances in groundwater is a direct result of the
infiltration of contaminated river water. Radon and oxygen isotope analyses
carried out on river and groundwater have made it possible for rates of exchange
between surface and groundwater to be calculated (Siegent1~a~er and Shotterer
1977; Stichler et al. 1986; Hoehn and Gunten 1989).
2_" Rn is a daughter product of the decay series of "--ss U (Fig. 4. I1) with a halflife of only 3.8 days. The enrichment of -'2~-Rn in the upper atmosphere is mainly a
consequence of diffusive emanation from U bearing minerals in granitic rocks, the
rate of emanation being significantly dependent on the microstructure of the rock.
In granular aquifers the intensity of radiation and rate of transport of radon is
strongly influenced by the grain size distribution, weathering of grain surfaces and
porewater content. Since the noble gas radon is almost chemically inert, it can
migrate unhindered and diffuse from particle surfaces into the nannopores
between grains. In water saturated aquifers, radon transport is strongly dependent
on the speed of groundwater currents. Groundwater is particularly enriched,
whereas surface waters are strongly depleted in radon. This concentration
difference permits the determination of infiltration or exfiltration rates using radon
as a natural tracer.
Age dating using radionuclides is based on one hand on the decay of the
radionuclides (equations IV, V; Sect. 1.2), and on the other hand on the increasing
concentration of the daughter product, which will after a certain amount of time
exist in equilibrium with the mother nuclide (N), i.e. secular equilibrium.
Equations (IV) and (V) may produce the following equation for the increase in
amount of the daughter isotope (D):
D = N o ( 1 - e -z')
([)
for radon:
A, - A , ( l - e -a')
(II)