14.3 Results
The results regarding the radioactivity of the sediments are presented in Table 14.1,
for Cs137 and Table 14.2, for K40.
The results indicated the presence of artificial radionuclide Cs-137, with values
between 0.5 and 10.5 Bq/kg and average 2,1þ/À1,5 Bq/kg. The natural radionuclide K-40 is also present in the range of 55–494 Bq/kg sediment, with average
249þ/À94 Bq/kg. The relative highest deviation at average activity level of the
radionuclides can be explained by small different areas, having some physical and
geological peculiarity.
14.4 Discussions
Analyzing the correlation factor for each transect (MM1 to MM7) from Mamaia
beach, is identified positive correlation between K40 and Cs137 radionuclides
(range between 0,59 and 0,94 for r). One single profile has no correlation (0,11 at
MM7; Table 14.3).
Another set of correlation factors can be obtained between Cs and K radionuclides, by zonal layers (coastal, backshore, swash, surf, nearshore; Table 14.4). In
nearshore zone, without mixing process, the differentiation of sediments lead to
insulation fields and low correlation at zonal level. On the contrary, in areas with
good mix, there is a stronger correlation (0,74–0,94).
Analyzing the correlation factors for main granulometry parameters, in case of
Cs137, different aspects can be observed (positive or negative correlation, as in
Tables 14.5 and Table 14.6). An evident negative correlation of radioactive content
is visible with size (mean diameter), the fine grains having good capacity to
concentrate it (Tables 14.5 and 14.6).
Water movements influence the transport and segregation of sediment (zonal
differences), and their quality (granulometry, content) affecting the fixation of
radionuclides (see the dispersion of the average levels of Cs137 and K40 contents).
Dams and submerged constructions can influence the local and zonal distribution of
sediments, according with the marine currents and wave regime (Diaconeasa 2017).
The external radiological impact of the radioactive content in sand of the
Mamaia beach is at low level. Using the dose coefficient from (UNSCEAR
2000), result an average absorbed dose in air of 10,4 nGy/h for K40, under
worldwide level. Actually the external exposure rates is reported for Romanian
seashore in the Mamaia area at average at 59 nGy/h. This results are confirmed by
in-situ dose rate measurements (Margineanu et al. 2013).
14 Gamma-Ray Radionuclides in Sediments from Mamaia Beach on the Romanian. . .
235
The results regarding the radioactivity of the sediments are presented in Table 14.1,
for Cs137 and Table 14.2, for K40.
The results indicated the presence of artificial radionuclide Cs-137, with values
between 0.5 and 10.5 Bq/kg and average 2,1þ/À1,5 Bq/kg. The natural radionuclide K-40 is also present in the range of 55–494 Bq/kg sediment, with average
249þ/À94 Bq/kg. The relative highest deviation at average activity level of the
radionuclides can be explained by small different areas, having some physical and
geological peculiarity.
14.4 Discussions
Analyzing the correlation factor for each transect (MM1 to MM7) from Mamaia
beach, is identified positive correlation between K40 and Cs137 radionuclides
(range between 0,59 and 0,94 for r). One single profile has no correlation (0,11 at
MM7; Table 14.3).
Another set of correlation factors can be obtained between Cs and K radionuclides, by zonal layers (coastal, backshore, swash, surf, nearshore; Table 14.4). In
nearshore zone, without mixing process, the differentiation of sediments lead to
insulation fields and low correlation at zonal level. On the contrary, in areas with
good mix, there is a stronger correlation (0,74–0,94).
Analyzing the correlation factors for main granulometry parameters, in case of
Cs137, different aspects can be observed (positive or negative correlation, as in
Tables 14.5 and Table 14.6). An evident negative correlation of radioactive content
is visible with size (mean diameter), the fine grains having good capacity to
concentrate it (Tables 14.5 and 14.6).
Water movements influence the transport and segregation of sediment (zonal
differences), and their quality (granulometry, content) affecting the fixation of
radionuclides (see the dispersion of the average levels of Cs137 and K40 contents).
Dams and submerged constructions can influence the local and zonal distribution of
sediments, according with the marine currents and wave regime (Diaconeasa 2017).
The external radiological impact of the radioactive content in sand of the
Mamaia beach is at low level. Using the dose coefficient from (UNSCEAR
2000), result an average absorbed dose in air of 10,4 nGy/h for K40, under
worldwide level. Actually the external exposure rates is reported for Romanian
seashore in the Mamaia area at average at 59 nGy/h. This results are confirmed by
in-situ dose rate measurements (Margineanu et al. 2013).
14 Gamma-Ray Radionuclides in Sediments from Mamaia Beach on the Romanian. . .
235