coverage of the measurements in the oceans were for
some areas not dense enough for accurate calculations.
Another known accident contributing to marine
contamination was the burn-up of a US satellite
(SNAP 9A) above the Mozambique channel in
1964 which released 0.63 PBq
238
Pu and 0.48 TBq
239
Pu; 73% was eventually deposited in the southern
hemisphere.
The Chernobyl accident in 1986 in the former
USSR is the latest major event creating fallout to the
oceans. Two-thirds of the c.100 PBq
137
Cs released
was deposited outside the Soviet Union. The total
input to the world oceans of
137 Cs from Chernobyl is
estimated to be from 15–20 Pbq, i.e. 4.5 PBq in the
Baltic Sea; 3–5 PBq in the Mediterranean Sea,
1.2 PBq in the North Sea and about 5 PBq in the
northeast Atlantic.
Natural Occurring Radioactive Material
Oil and gas production mobilize naturally occurring
radioactive material (NORM) from the deep underground reservoir rock. The radionuclides are primarily
226
Ra,
228
Ra and
210
Pb and appear in sludge
and scales and in the produced water. Scales and
sludge containing NORM represent an increasing
amount of waste. There are different national regulations for handling this type of waste. In Norway, for
example, waste containing radioactivity above 10 Bq
g
À1 is stored on land in a place specially designed for
this purpose. However, there are reasons to believe
that a major part of radioactive contaminated scales
and sludge from the worldwide offshore oil and gas
production are discharged to the sea.
Reported NORM values in scales are in the
ranges of 0.6–57.2 Bq g
À1 226
Ra þ
228 Ra (Norway),
0.4–3700 Bq g
À1 (USA) and 1–1000 Bq g
À1 226
Ra
(UK).
Scales are an operational hindrance in oil and gas
production. Frequent use of scale-inhibitors reduce
the scaling process but radioactive components are
released to the production water adding to its already elevated radioactivity. More than 90% of the
radioactivity in produced water is due to
226 Ra and
228 Ra having a concentration 100–1000 times higher
than normal for seawater.
The discharge of produced water is a continuous
process and the amount of water discharged is considerable and increases with the age of the production wells. As an example, the estimated amount
of produced water discharged to the North Sea in
1998 was 340 million m
3 and multiplying by an
average value of 5 Bq
À1 of
226 Ra in produced water,
the total input of
226 Ra to the North Sea in 1998 was
1.7 TBq.
Discussion
The total input of anthropogenic radioactivity to the
world’s oceans is not known exactly, but a very
rough estimate gives the following amounts: 85 PBq
dumped, 100 PBq discharged from reprocessing and
1500 PBq from fallout. Some of the radionuclides
have very long half-lives and will persist in the ocean,
for example
99 Tc has a half-life of 2.1 Â 10
5 years,
239,240 Pu, 2.4 Â 10
4 years and
226 Ra, 1600 years.
137 Cs,
90
Sr and
228 Ra with half-lives of 30 years, 29
years and 5.75 years, respectively, will slowly decrease depending on the amount of new releases.
In an oceanographic context it is worth mentioning
the differences in denomination between radioactivity
and other elements in the ocean. The old denomination for radioactivity was named after Curie (Ci) and
1 g radium was defined to have a radioactivity of 1 Ci;
1 Ci 3.7 Â 10
10 Bq and 1 PBq 27 000 Ci. Therefore
released radioactivity of 1 PBq can be compared to the
radioactivity of 27 kg radium.
The common denominations for major and minor
elements in seawater are given in weight per volume.
For comparison if 1 PBq or 27 kg radium were diluted
in 1 km
3 of seawater, this would give a radium concentration of 0.027 mg l
À1 or 1000 Bq l
À1
. Calculations like this clearly visualize the sensitivity of the
analytical methods used for measuring radioactivity.
In the Atlantic Ocean for example radium (
228
Ra) has
a concentration of 0.017–3.40 mBq l
À1
, whereas
99
Tc
measured in surface waters off the southwest coast of
Norway is in the range of 0.9–6.5 mBq l
À1
.
Measured in weight the total amount of radionuclides do not represent a huge amount compared
to the presence of nonradioactive components in
seawater. The radioisotopes of cesium and strontium
are both important in a radioecological context
since they have chemical behavior resembling potassium and calcium, respectively. Cesium follows
potassium in and out of the soft tissue cells whereas
strontium follows calcium into bone cells and stays.
Since uptake and release in organisms is due to the
chemical characteristics and rarely if the element is
radioactive or not, radionuclides such as
137 Cs and
90 Sr have to compete with the nonradioactive isotopes of cesium and strontium.
Oceanic water has a cesium content of about
0.5lmg
À1
and a strontium content of about
8000 mg l
À1
. Uptake in a marine organism is most
likely to be in proportion to the abundance of the
radioactive and the nonradioactive isotopes of the
actual element. This can be illustrated by the following example. The sunken nuclear submarine
Komsomolets contained an estimated (lowest)
amount of 1.55 PBq
90
Sr (about 300 g) and 2.03 PBq
RADIOACTIVE WASTES 303
some areas not dense enough for accurate calculations.
Another known accident contributing to marine
contamination was the burn-up of a US satellite
(SNAP 9A) above the Mozambique channel in
1964 which released 0.63 PBq
238
Pu and 0.48 TBq
239
Pu; 73% was eventually deposited in the southern
hemisphere.
The Chernobyl accident in 1986 in the former
USSR is the latest major event creating fallout to the
oceans. Two-thirds of the c.100 PBq
137
Cs released
was deposited outside the Soviet Union. The total
input to the world oceans of
137 Cs from Chernobyl is
estimated to be from 15–20 Pbq, i.e. 4.5 PBq in the
Baltic Sea; 3–5 PBq in the Mediterranean Sea,
1.2 PBq in the North Sea and about 5 PBq in the
northeast Atlantic.
Natural Occurring Radioactive Material
Oil and gas production mobilize naturally occurring
radioactive material (NORM) from the deep underground reservoir rock. The radionuclides are primarily
226
Ra,
228
Ra and
210
Pb and appear in sludge
and scales and in the produced water. Scales and
sludge containing NORM represent an increasing
amount of waste. There are different national regulations for handling this type of waste. In Norway, for
example, waste containing radioactivity above 10 Bq
g
À1 is stored on land in a place specially designed for
this purpose. However, there are reasons to believe
that a major part of radioactive contaminated scales
and sludge from the worldwide offshore oil and gas
production are discharged to the sea.
Reported NORM values in scales are in the
ranges of 0.6–57.2 Bq g
À1 226
Ra þ
228 Ra (Norway),
0.4–3700 Bq g
À1 (USA) and 1–1000 Bq g
À1 226
Ra
(UK).
Scales are an operational hindrance in oil and gas
production. Frequent use of scale-inhibitors reduce
the scaling process but radioactive components are
released to the production water adding to its already elevated radioactivity. More than 90% of the
radioactivity in produced water is due to
226 Ra and
228 Ra having a concentration 100–1000 times higher
than normal for seawater.
The discharge of produced water is a continuous
process and the amount of water discharged is considerable and increases with the age of the production wells. As an example, the estimated amount
of produced water discharged to the North Sea in
1998 was 340 million m
3 and multiplying by an
average value of 5 Bq
À1 of
226 Ra in produced water,
the total input of
226 Ra to the North Sea in 1998 was
1.7 TBq.
Discussion
The total input of anthropogenic radioactivity to the
world’s oceans is not known exactly, but a very
rough estimate gives the following amounts: 85 PBq
dumped, 100 PBq discharged from reprocessing and
1500 PBq from fallout. Some of the radionuclides
have very long half-lives and will persist in the ocean,
for example
99 Tc has a half-life of 2.1 Â 10
5 years,
239,240 Pu, 2.4 Â 10
4 years and
226 Ra, 1600 years.
137 Cs,
90
Sr and
228 Ra with half-lives of 30 years, 29
years and 5.75 years, respectively, will slowly decrease depending on the amount of new releases.
In an oceanographic context it is worth mentioning
the differences in denomination between radioactivity
and other elements in the ocean. The old denomination for radioactivity was named after Curie (Ci) and
1 g radium was defined to have a radioactivity of 1 Ci;
1 Ci 3.7 Â 10
10 Bq and 1 PBq 27 000 Ci. Therefore
released radioactivity of 1 PBq can be compared to the
radioactivity of 27 kg radium.
The common denominations for major and minor
elements in seawater are given in weight per volume.
For comparison if 1 PBq or 27 kg radium were diluted
in 1 km
3 of seawater, this would give a radium concentration of 0.027 mg l
À1 or 1000 Bq l
À1
. Calculations like this clearly visualize the sensitivity of the
analytical methods used for measuring radioactivity.
In the Atlantic Ocean for example radium (
228
Ra) has
a concentration of 0.017–3.40 mBq l
À1
, whereas
99
Tc
measured in surface waters off the southwest coast of
Norway is in the range of 0.9–6.5 mBq l
À1
.
Measured in weight the total amount of radionuclides do not represent a huge amount compared
to the presence of nonradioactive components in
seawater. The radioisotopes of cesium and strontium
are both important in a radioecological context
since they have chemical behavior resembling potassium and calcium, respectively. Cesium follows
potassium in and out of the soft tissue cells whereas
strontium follows calcium into bone cells and stays.
Since uptake and release in organisms is due to the
chemical characteristics and rarely if the element is
radioactive or not, radionuclides such as
137 Cs and
90 Sr have to compete with the nonradioactive isotopes of cesium and strontium.
Oceanic water has a cesium content of about
0.5lmg
À1
and a strontium content of about
8000 mg l
À1
. Uptake in a marine organism is most
likely to be in proportion to the abundance of the
radioactive and the nonradioactive isotopes of the
actual element. This can be illustrated by the following example. The sunken nuclear submarine
Komsomolets contained an estimated (lowest)
amount of 1.55 PBq
90
Sr (about 300 g) and 2.03 PBq
RADIOACTIVE WASTES 303