Stable and radioactive environmental
isotopes in scientific and industrial
applications.
Adam Porowski
„Science for Industry: Necessity is the mother of Invention”
Warszawa, 20-22.06.2012
Isotopes
Isotopes are atoms (i.e. nuclides) of a single element whose nuclei
contain the same number of protons but a different number of
neutrons.
The number of protons uniquely defines the element, whereas the
number of neutrons defines the isotope of that element.
16O
, 17O, 18O, 1H, 2H
Why environmental isotopes?
The environmental isotopes are naturally occurring isotopes of
elements found in abundance in our environment: H, C, N, O, S principal elements of hydrogeological, geological and biological
systems.
1.isotopic composition of these elements in natural substances is not a function
of time but is caused by physicochemical processes;
2.they are light elements and the relative mass differences between their
isotopes are large, imparting measurable fractionations during physical and
chemical reactions;
- 1H ⇒ mass difference = 100 %
- 12C ⇒ mass difference = 8.3 %
- 16O ⇒ mass difference = 12.5 %
3. serve as tracers of water, carbon, nutrient and solute cycling;
2H
13C
18O
4. the distribution of the isotopes of these elements among different phases
varies primarily as a function of temperature;
Why environmental isotopes?
Isotopic fractionation
Molecules with differences in mass have different reaction rates
which leads to isotope fractionation – i.e. unequal distribution of
isotopes between two coexisting substances or two phases of the
same substance.
Fractionation factor α:
αs− p
 bX 


Rs  a X  s
=
=
Rp  b X 
a 
 X p
 18O 
 16 


O
α 18Owater −vapour =  18  water = 1.0093
 O


 16O 

 vapour
Isotopic fractionation is caused by:
chemical processes (equilibrium and nonequilibrium isotope exchange reactions)
physical processes (i.e. kinetic processes like evaporation, diffusion, dissociation)
biological processes (i.e. may be regarded as special cases of chemical and
physical processes).
αis temperature dependent.
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
1. Tracers of hydrological cycle
- GMWL
- LMWL
- seasonal variation in precipitation
- water balance of lakes
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
2. Identiffication of groundwater origin
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
2. Identiffication of groundwater origin: sedimentary basins
Central Carpathian Synclinorium, Poland
Examples from USA
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
2. Identiffication of groundwater origin
Foresudetic Monocline, copper mine
drainage waters Poland
Upper Silesian coal Basin, drainage waters,
Poland
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
3. Geothermal systems and high temperature water-rock interaction
Scientific and industrial applications:
Oxygen and Hydrogen stable isotopes
4. Isotope geothermometry:
for example: oxygen isotope in H2O – SO4 system
1000lnα
α = 2.88(106 /T2) – 4.1
isotherms after Mizutani and Rafter
(1969a).
Scientific and industrial applications:
Groundwater quality
Stable isotopes of S & N
Scientific and industrial applications:
Radioactive isotopes: groundwater
dating
Young groundwater datind: Tritium
3H
→ 3He + β-
Half-life time of tritium = 12.43 years
Lumped parameter models:
1.Piston Flow Model (PFM)
C out = C in exp( − λτ t )
2. Dispersion Model (DM)
1
C out = C in exp{(
1
)[ 1 − ( 1 + 4 PD λτ t ) 2 ]}
2 PD
3. Exponential Model (EM)
C
out
=
C in
1 + λτ
t
Scientific and industrial applications:
Radioactive isotopes: groundwater
dating
Old groundwater dating:
14 N
7
+
1 n
0
→
Half-life time of
14 C
6
14C
+
14C
1 p
1
= 5730 years
Lumped parameters model + corrections
Thank you for your attention
Adam Porowski
Instytut Nauk Geologicznych PAN
ul. Twarda 51/55
00-818 Warszawa
[email protected]