**2. Sources, inventory and levels of 129I in marine and terrestrial environment**

All 129I formed in the primordial nucleosynthesis decayed to stable 129Xe. Two natural processes responsible for natural background levels of 129I are spallation of cosmic rays on

The Potential Of I-129 as an Environmental Tracer 369

10-7, even 10-6−10-4 in the vicinity of nuclear fuel reprocessing plants (Table 4) (Duffa &

Fig. 1. Liquid and atmospheric releases of 129I from NFRP in La Hague and Sellafield for

Atmospheric releases are not plotted, but they are considered in the total amount. Annual atmospheric releases ranged from 1.19 to 9.58 kg 129I with a total amount of 235.5 kg in the

Anthropogenic 129I predominates in marine environment in biosphere and upper layers of the oceans and in terrestrial environment in soil, therefore it can be expected that the isotopic ratio 129I/127I is increasing in these compartments of the ecosystem. Precipitation and seawater are probably the main carriers for 129I exchange among different compartments in marine and terrestrial environment. Data from literature clearly show that 129I levels in marine sediment, marine algae and soil are several times higher than in seawater or precipitation. Meaning that 129I is most probably chemically or biologically

To summarize, different values of 129I/127I isotopic ratios in environment are today envisaged as 10-12 for pre-nuclear era, 10-9 in slightly contaminated regions and 10-9–10-6 in regions affected by the releases from NFRP. The highest ratios were found in the close

transformed to species which accumulate in those compartments (Tables 3 and 4).

period from 1952 to 2000 (compiled by Lopez-Gutierrez et al., 2004).

vicinity of NFRP with values from 10-6 to 10-4 (Hou, 2009).

period from 1952 to 2000.

Frechou, 2003; Frechou & Calmet, 2003).

atmospheric Xe (cosmogenic) in the upper atmosphere and spontaneous fission of 238U (fissiogenic).

Although 129I is produced naturally the main part is a consequence of human nuclear activities (Table 1). In this way the sources can be divided in natural and man-made or in pre-nuclear and nuclear era. From 1945 anthropogenic sources of 129I were nuclear weapons testing, nuclear accidents (Chernobyl) and at present marine and atmospheric discharges from NFRP. Operating plants in Europe are located in England (Sellafield), France (La Hague) and Russia (Mayak), and outside Europe in China, India, Pakistan and Japan (Tokaimura, Rakkasho). 129I is produced during the operation of a nuclear power reactor by nuclear fission of 235U(n, f)129I and 239Pu(n, f)129I. It was estimated that about 7.3 mg of 129I is produced per megawatt day. 129I is released during reprocessing of nuclear fuel – mainly by PUREX process. The fuel is first dissolved with nitric acid and at this step iodine is oxidized to volatile I2 and despite all efforts to trap and collect released iodine some part may be discharged from the NFRP (Reithmeir et al., 2006).


\*NFRP…nuclear fuel reprocessing plant; \*\*Marine discharges are sum discharges from La Hague and Sellafield NFRP, Atmospheric releases are sum releases from La Hague, Sellafield, Marcoul and Karlsruhe-WAK (after Hou et al., 2009)

Table 1. Sources and 129I/127I ratio in environment

Until the beginning of the 1990s the total annual discharges from two European NFRP, La Hague and Sellafield, remained below 20 kg year-1. The discharges increased later considerable – up to 300 kg year-1 and accounted until 2000 for more than 95 % of the total inventory in the global ocean (Fig. 1) (Alfimov et al., 2004; Lopez-Gutierrez et al., 2004). The natural, pre-nuclear 129I/127I isotopic ratio was significantly influenced by releases of anthropogenic 129I to the environment. The estimated pre-nuclear 129I/127I isotopic ratio in marine environment was assessed with analysis of marine sediments and agreed to be 1.5 · 10-12 (Table 2) (Moran et al., 1998; Fehn et al., 2000a; Fehn et al., 2007). For the terrestrial environment – pedosphere and biosphere no agreed data on pre-nuclear ratio exist. Human nuclear activity increased the 129I/127I ratio in marine environment to 10-11 – 10-10 and to 10-8 – 10-5 (Table 3) in the Irish Sea, English Channel, North Sea and Nordic Seas which are influenced by liquid discharges from European NFRP (Frechou & Calmet, 2003; Alfimov et al., 2004; Hou et al., 2007). In the terrestrial environment the 129I/127I ratio increased to 10-9 –

atmospheric Xe (cosmogenic) in the upper atmosphere and spontaneous fission of 238U

Although 129I is produced naturally the main part is a consequence of human nuclear activities (Table 1). In this way the sources can be divided in natural and man-made or in pre-nuclear and nuclear era. From 1945 anthropogenic sources of 129I were nuclear weapons testing, nuclear accidents (Chernobyl) and at present marine and atmospheric discharges from NFRP. Operating plants in Europe are located in England (Sellafield), France (La Hague) and Russia (Mayak), and outside Europe in China, India, Pakistan and Japan (Tokaimura, Rakkasho). 129I is produced during the operation of a nuclear power reactor by nuclear fission of 235U(n, f)129I and 239Pu(n, f)129I. It was estimated that about 7.3 mg of 129I is produced per megawatt day. 129I is released during reprocessing of nuclear fuel – mainly by PUREX process. The fuel is first dissolved with nitric acid and at this step iodine is oxidized to volatile I2 and despite all efforts to trap and collect released iodine some part may be

**Source Inventory/release (kg)\*\* 129I/127I ratio in environment** 

Chernobyl accident 1.3−6 10-8−10-6 (in contaminated area)

European NFRP\* by 2007 5200 10-8−10-6 (North Sea and Nordic

from Hanford NFRP\* 275 10-6−10-3 (in air near NFRP)

\*NFRP…nuclear fuel reprocessing plant; \*\*Marine discharges are sum discharges from La Hague and Sellafield NFRP, Atmospheric releases are sum releases from La Hague, Sellafield, Marcoul and

Until the beginning of the 1990s the total annual discharges from two European NFRP, La Hague and Sellafield, remained below 20 kg year-1. The discharges increased later considerable – up to 300 kg year-1 and accounted until 2000 for more than 95 % of the total inventory in the global ocean (Fig. 1) (Alfimov et al., 2004; Lopez-Gutierrez et al., 2004). The natural, pre-nuclear 129I/127I isotopic ratio was significantly influenced by releases of anthropogenic 129I to the environment. The estimated pre-nuclear 129I/127I isotopic ratio in marine environment was assessed with analysis of marine sediments and agreed to be 1.5 · 10-12 (Table 2) (Moran et al., 1998; Fehn et al., 2000a; Fehn et al., 2007). For the terrestrial environment – pedosphere and biosphere no agreed data on pre-nuclear ratio exist. Human nuclear activity increased the 129I/127I ratio in marine environment to 10-11 – 10-10 and to 10-8 – 10-5 (Table 3) in the Irish Sea, English Channel, North Sea and Nordic Seas which are influenced by liquid discharges from European NFRP (Frechou & Calmet, 2003; Alfimov et al., 2004; Hou et al., 2007). In the terrestrial environment the 129I/127I ratio increased to 10-9 –

Sea water)

10-8−10-6 (in rain, lake and river

10-6−10-3 (in soil, grass near NFRP)

water in West Europe)

(fissiogenic).

discharged from the NFRP (Reithmeir et al., 2006).

Marine discharges from

Atmospheric releases from European NFRP\* by

Atmospheric releases

Karlsruhe-WAK (after Hou et al., 2009)

Table 1. Sources and 129I/127I ratio in environment

2007

Nature 250 ~1 · 10-12

440

Nuclear weapons testing 57 1 · 10-11−1 · 10-9

10-7, even 10-6−10-4 in the vicinity of nuclear fuel reprocessing plants (Table 4) (Duffa & Frechou, 2003; Frechou & Calmet, 2003).

Fig. 1. Liquid and atmospheric releases of 129I from NFRP in La Hague and Sellafield for period from 1952 to 2000 (compiled by Lopez-Gutierrez et al., 2004).

Atmospheric releases are not plotted, but they are considered in the total amount. Annual atmospheric releases ranged from 1.19 to 9.58 kg 129I with a total amount of 235.5 kg in the period from 1952 to 2000.

Anthropogenic 129I predominates in marine environment in biosphere and upper layers of the oceans and in terrestrial environment in soil, therefore it can be expected that the isotopic ratio 129I/127I is increasing in these compartments of the ecosystem. Precipitation and seawater are probably the main carriers for 129I exchange among different compartments in marine and terrestrial environment. Data from literature clearly show that 129I levels in marine sediment, marine algae and soil are several times higher than in seawater or precipitation. Meaning that 129I is most probably chemically or biologically transformed to species which accumulate in those compartments (Tables 3 and 4).

To summarize, different values of 129I/127I isotopic ratios in environment are today envisaged as 10-12 for pre-nuclear era, 10-9 in slightly contaminated regions and 10-9–10-6 in regions affected by the releases from NFRP. The highest ratios were found in the close vicinity of NFRP with values from 10-6 to 10-4 (Hou, 2009).

The Potential Of I-129 as an Environmental Tracer 371

**Sample 129I/127I (10-8) Reference** 

Scotland, Scottish Sea, influence of Sellafield, 2003-

Sweden, Baltic Sea, influence of La Hague and

Denmark (influence of liquid discharges from NFRP) Roskilde Fjord and Bornholm, 1995-1998 (*Fucus* 

Klint, 1986-1999 (*Fucus vesiculosus*, n = 39)

Goury, 1998-1999 (*Fucus vesiculosus*, n = 3) Goury, 1998-1999 (*Fucus serratus*, n = 3) Goury, 1998-1999 (*Laminaria digita*, n = 2)

West and South coastline, *Fucus vesiculosus*

Goury and Dielette, 2003 (*Fucus serratus*, n = 12) Goury and Dielette, 2003 (*Laminaria digita*, n = 8)

East coastline (influence of liquid discharges from

Slovenia, Adriatic Sea, *Fucus virsoides*, September

Croatia, Adriatic Sea, *Fucus virsoides*, October 2006,

2005, five locations 0.086–0.11

locations 0.068–0.15

three locations 0.15–0.31

France (vicinity of La Hague)

NFRP), *Fucus vesiculosus* 

Russia, *Laminaria digitata* 

marine compartments

Japan Sea, Toyama Bay, October 2006 0.0086

Greenland, 1997 (*Fucus distichus*, n = 7) 0.07−0.15

(Utsira), 1980-1995 (*Fucus vesiculosus*, n = 16) 1.88−18.5

Germany, North Sea, 1999 153 Szidat et al., 2000a Greenland, 1999 (n = 5) 0.07−0.24 Hou, 2004

2005 (n = 14) 7.2−336 Schnabel et al., 2007 Israel, Sea of Galilee, June 1998 0.31 Fehn & Snyder, 2000b Israel, Engedi, Dead Sea, June 1998 0.003

Suzuki et al., 2008 Japan Sea, Off Sekine, 2006-2007 (n = 2) 0.0063<sup>−</sup>0.0068

Sellafield, core sample –from 0 to 21 cm, 1997 0.34−1.06 Aldahan et al. 2007

1985, n = 7 1994, n = 7 2003, n = 9

1985, n = 8 1994, n = 7 2003, n = 8

Osterc & Stbilj, 2008 Italy, Adriatic Sea, *Fucus virsoides*, June 2006, five

Table 3. 129I/127I isotopic ratios in nuclear age environmental and biological samples from

Murmansk region, 1966 Murmansk region, 1967 White Sea, 1971 Novaya Zemlya, 1989 Novaya Zemlya, 1993 2.50−9.12

3.54−37.5

1010−1940 930−1210 540−1270

496−1960

0.08−0.73 0.47−6.5 0.21−5.0

4.8−85 0.83−30 24−85

0.016 0.034 0.027 0.48 0.72

Hou et al., 2000a

Frechou et al., 2003

Keogh et al., 2007

Cooper et al., 1998

<sup>349</sup>−960 Barker et al., 2005

England, Irish Sea, near Sellafield 2004-05 (n = 4) 89−820 Atarashi-Andoh et al., 2007

*Sea water*

*Sediment* 

*Seaweed* 

Norway

Ireland

*vesiculosus*, n = 8)


Table 2. 129I/127I isotopic ratios in pre-nuclear age environmental and biological samples
