Sediment samples are more consistent on radionuclides and their concentration
can be estimated to an average uncertainty of 20%. As geometries are similar,
trends and distributions can be calculated from this information.
This is not the case for seawater samples where only a few of the radionuclides
can be evaluated with a consistent uncertainty and no distribution or trend analysis
can be performed for the overall set.
13.4 Discussion
The sediment distributions on the western Black Sea shelf follow the sea currents
feature in the area. At the Danube mouths there are two main streams: one from
north to south and the other from south to north. From north to south current flows
near shallow waters (near-shore) on the entire depth with speeds range from 0.33 to
0.47 m/s. The river currents spread fan-shaped with rapid decrease in their speed.
After mixing with the Black Sea waters, the river currents are influenced by the
coastal currents and the river discharge.
In cold season, winter, the sea currents are stable due to the wind intensity and
stability. Current flows from south to north in a compact mass, down to 10 m water
depth and a width of 40 nautical miles and tends to push but to maintain the northsouth current near the coast. The current from south to north has a maximum speed
of 0.47 m/s (Fig. 13.4).
Sediment sample distribution has an expected shape, the shoreline is more
consistent for earth like radionuclides like
226 Ra and
232 Th as the waters a shallow
and the radionuclide behavior is similar the one found in ground sites. Their
concentration decreases with the distance to the shoreline (Fig. 13.5).
These plots can be referenced as natural radioisotopes specific to the soil it’s
composition for the Dobrogea seashore areas while the following radionuclides that
we evaluated can be linked to the presence of human activities (in the case for
137 Cs) or with natural materials for
40 K.
The values are in good concordance with the one previously taken for the Black
Sea (Valeva et al. 2002) (Fig. 13.6).
Average
137 Cs detected concentrations fall under the UNSCEAR (UNSCEAR
2011) reports average for our country and no unusual concentrations were found
within this study. The higher concentrations on the Danube Delta interface to the
Back Sea can be due to nuclear activities at Cernavoda but the detected value is well
less the exception concertation. Concentrations up to 40 Bq/Kg are common to the
Chernobyl event (Blebea-Apostu et al. 2012). Activities for similar studies showing
higher Cs concentrations can be found in literature (Mohammad Reza Abdi et al.
2009) (Fig. 13.7).
Potassium 40 is one key radionuclide associated to both animal and vegetal
concentrations and its distribution can be correlated to such activities or to large
deposits of wood or other construction materials leading to higher concentrations
within specific regions along the shore line. The above picture presents the
13 Radionuclides Assessment for the Romanian Black Sea Shelf
227
can be estimated to an average uncertainty of 20%. As geometries are similar,
trends and distributions can be calculated from this information.
This is not the case for seawater samples where only a few of the radionuclides
can be evaluated with a consistent uncertainty and no distribution or trend analysis
can be performed for the overall set.
13.4 Discussion
The sediment distributions on the western Black Sea shelf follow the sea currents
feature in the area. At the Danube mouths there are two main streams: one from
north to south and the other from south to north. From north to south current flows
near shallow waters (near-shore) on the entire depth with speeds range from 0.33 to
0.47 m/s. The river currents spread fan-shaped with rapid decrease in their speed.
After mixing with the Black Sea waters, the river currents are influenced by the
coastal currents and the river discharge.
In cold season, winter, the sea currents are stable due to the wind intensity and
stability. Current flows from south to north in a compact mass, down to 10 m water
depth and a width of 40 nautical miles and tends to push but to maintain the northsouth current near the coast. The current from south to north has a maximum speed
of 0.47 m/s (Fig. 13.4).
Sediment sample distribution has an expected shape, the shoreline is more
consistent for earth like radionuclides like
226 Ra and
232 Th as the waters a shallow
and the radionuclide behavior is similar the one found in ground sites. Their
concentration decreases with the distance to the shoreline (Fig. 13.5).
These plots can be referenced as natural radioisotopes specific to the soil it’s
composition for the Dobrogea seashore areas while the following radionuclides that
we evaluated can be linked to the presence of human activities (in the case for
137 Cs) or with natural materials for
40 K.
The values are in good concordance with the one previously taken for the Black
Sea (Valeva et al. 2002) (Fig. 13.6).
Average
137 Cs detected concentrations fall under the UNSCEAR (UNSCEAR
2011) reports average for our country and no unusual concentrations were found
within this study. The higher concentrations on the Danube Delta interface to the
Back Sea can be due to nuclear activities at Cernavoda but the detected value is well
less the exception concertation. Concentrations up to 40 Bq/Kg are common to the
Chernobyl event (Blebea-Apostu et al. 2012). Activities for similar studies showing
higher Cs concentrations can be found in literature (Mohammad Reza Abdi et al.
2009) (Fig. 13.7).
Potassium 40 is one key radionuclide associated to both animal and vegetal
concentrations and its distribution can be correlated to such activities or to large
deposits of wood or other construction materials leading to higher concentrations
within specific regions along the shore line. The above picture presents the
13 Radionuclides Assessment for the Romanian Black Sea Shelf
227