Secondary radioactive contamination of the Black Sea after Chernobyl accident: recent levels, pathways and trends

Deep-water profiling of 137Cs and 90Sr in the Black Sea: a further insight into dynamics of the post-Chernobyl radioactive contamination

“…Comparison of these surface water values with those found at the same site in May 1986 [3,5] reveals the decrease in 137 Cs and 90 Sr concentration in the upper waters by factor 9.2 and 5.2, respectively. The smaller value for 90 Sr is caused essentially by its additional input with riverine waters in which strontium is well soluble in contrast to 137 Cs [1,2,6]. This additional inflow of 90 Sr has reached a maximum in the late 1990's-early 2000's as seen from the time-trend of activity ratio 90 Sr/ 137 Cs showed by us earlier [6] and updated in Fig.…”

“…The smaller value for 90 Sr is caused essentially by its additional input with riverine waters in which strontium is well soluble in contrast to 137 Cs [1,2,6]. This additional inflow of 90 Sr has reached a maximum in the late 1990's-early 2000's as seen from the time-trend of activity ratio 90 Sr/ 137 Cs showed by us earlier [6] and updated in Fig. 3 with the use of the most recent data given in Fig.…”

“…3). This decrease may be explained by both the reducing of 90 Sr inflow from the rivers due to depletion of mobile fraction of 90 Sr within the watersheds and/or due to remobilization of part of 137 Cs deposited in the Black Sea sediments, primarily in areas adjacent to the river mouths [6]. On the other hand, the increasing of 90 Sr/ 137 Cs ratio in 1995-2005 (Fig.…”

“…At the same time, the essential advantage of this technique is the possibility to check easily the sorption efficiency for each individual sample, which is determined by comparing the 137 Cs activity on the first and second adsorbers [11,13]. Also, the CuFe(CN) 6 -impregnated sorbent does not scavenge dissolved strontium, allowing to use the final filtrate to determine 90 Sr concentration in the same sample by radiochemical precipitation, purification and radiometry via beta activity of its daughter radionuclide 90 Y [14,15]. However, the large volume of samples is undoubtedly the main disadvantage of such methods, that complicates significantly determination of radionuclide concentration in deep-sea waters [16].…”

“…As a result, concentration of these radionuclides in the Black Sea surface water increased sharply, exceeding the levels measured during the pre-Chernobyl period. Besides direct atmospheric deposition, the Black Sea received (and still continues to receive) additional input by river runoff [1,2,6]. For example, Egorov et al (2010) have shown that total inflow of 90 Sr to the Black Sea from the Dnepr and Danube rivers in 1986-1994 was estimated to be 160 ± 28 TBq [3].…”