4 Isotope Geochemistry in the Environment
49
snow with concentrations of silicate dust and sulfur, which are considered to
approximate fluxes of soil dust and volcanic fall out respectively, which are
considered to be the main sources of natural lead in precipitation.
Zobrist (1983) investigated the fluxes of airborne material in detail. He was
able to show that not only lead but also several other heavy metals including
cadmium, copper and zinc are found in greater concentrations in rain water than
would be expected, considering natural cycles (Fig. 4.2). The input of lead into the
oceans through precipitation is actually greater than the input by way of rivers.
The relative fluxes for ammonium, zinc and copper are about the same for both
fluvial and atmospheric sources. For other substances, atmospheric input is
outweighed by that from flowing surface water.
The transport of undesirable substances in dissolved form or by way of a
colloidal phase is usually dependent upon physico-chemical conditions, e.g. pH.
In the next part, we will discuss the origin, transport and exchange behavior of
heavy metals and other trace elements, from the perspective of isotope
geochemistry, as they make their way into the rivers and groundwaters from both
anthropogenic and natural, geogenic sources, and during migration through the
soil. Although isotope geochemistry has great potential for solving
environmentally orientated problems, this approach has only been applied in a few
specific cases. Isotope geochemistry allows us to characterize element cycling in
the environment, to identify point sources of contamination and to observe
exchange processes between fluid and solid phases. These applications will
undoubtedly become clearer with carefully chosen examples.
4.1 H e a v y M e t a l s in t h e E n v i r o n m e n t
Lead is important when we consider the migration behavior of heavy metals.
There are two reasons for this:
I Our environment is heavily burdened by lead. Since the beginning of
industrialization, the concentration of Pb in the atmosphere of the northern
hemisphere has increased by a factor of one hundred. Today, almost all
atmospheric lead comes from industrial sources. By far the largest contribution
comes from the exhausts of motor vehicles as a byproduct of the combustion of
petrol where lead is used as an anti-knocking agent. As a result of rain, snow or
mist, lead may be rapidly taken up into the atmosphere, making its way into the
soil and surface water and eventually into the biologic cycle.
2. Lead has several isotopes. As industrial lead is likely to have various
characteristic Pb isotopic compositions, depending on how it was produced and
released, industrial contamination can be identified. Mass spectrometry allows us
49
snow with concentrations of silicate dust and sulfur, which are considered to
approximate fluxes of soil dust and volcanic fall out respectively, which are
considered to be the main sources of natural lead in precipitation.
Zobrist (1983) investigated the fluxes of airborne material in detail. He was
able to show that not only lead but also several other heavy metals including
cadmium, copper and zinc are found in greater concentrations in rain water than
would be expected, considering natural cycles (Fig. 4.2). The input of lead into the
oceans through precipitation is actually greater than the input by way of rivers.
The relative fluxes for ammonium, zinc and copper are about the same for both
fluvial and atmospheric sources. For other substances, atmospheric input is
outweighed by that from flowing surface water.
The transport of undesirable substances in dissolved form or by way of a
colloidal phase is usually dependent upon physico-chemical conditions, e.g. pH.
In the next part, we will discuss the origin, transport and exchange behavior of
heavy metals and other trace elements, from the perspective of isotope
geochemistry, as they make their way into the rivers and groundwaters from both
anthropogenic and natural, geogenic sources, and during migration through the
soil. Although isotope geochemistry has great potential for solving
environmentally orientated problems, this approach has only been applied in a few
specific cases. Isotope geochemistry allows us to characterize element cycling in
the environment, to identify point sources of contamination and to observe
exchange processes between fluid and solid phases. These applications will
undoubtedly become clearer with carefully chosen examples.
4.1 H e a v y M e t a l s in t h e E n v i r o n m e n t
Lead is important when we consider the migration behavior of heavy metals.
There are two reasons for this:
I Our environment is heavily burdened by lead. Since the beginning of
industrialization, the concentration of Pb in the atmosphere of the northern
hemisphere has increased by a factor of one hundred. Today, almost all
atmospheric lead comes from industrial sources. By far the largest contribution
comes from the exhausts of motor vehicles as a byproduct of the combustion of
petrol where lead is used as an anti-knocking agent. As a result of rain, snow or
mist, lead may be rapidly taken up into the atmosphere, making its way into the
soil and surface water and eventually into the biologic cycle.
2. Lead has several isotopes. As industrial lead is likely to have various
characteristic Pb isotopic compositions, depending on how it was produced and
released, industrial contamination can be identified. Mass spectrometry allows us