However, in the far western area (stations P39 and P5), where the strong salinity stratification occurred (bottom water was characterized by high salinity of about 13�C16PSU), the water flowing from the east with lower salinity was not able to displace bottom water. This resulted only in increase of activity at the upper layer of halocline.Figure selleckchem MEK162 4Seasonal and spatial variations in 90Sr activity in the offshore profile in the years of 2005�C2010.3.2. Estuary ProfileThe drainage basin of the Baltic Sea covers an area of about 4.3 times larger than the sea itself, bringing large amounts of freshwater to the sea from the rivers [19]. In the Baltic Sea catchment, the least significant source of 90Sr to the land was the atmospheric deposition after the Chernobyl accident.

The total deposition from Chernobyl on land amounted to 10PBq 90Sr and was 125 times more than got directly to the Baltic Sea, because the less volatile isotope was confined to areas closer to the damaged reactor and later washed out with rain and riverine outflow [7]. In the terrestrial environment strontium cations are mobile and easily washed out by rain water to the rivers and lakes [10, 20]. Nowadays, the water of the Vistula contains about 30% less 90Sr than water of the southern Baltic Sea. In the estuary profile (Figure 5) 90Sr activity is determined by two factors: the outflow of the Vistula and the inflow of water from the northern parts of the Baltic Sea. In this profile, which has effect opposite to offshore profile, the activity of 90Sr in water increased with salinity due to the diluting of the riverine water.

The lowest strontium activity was recorded at the station in close proximity to the estuary and the highest one at the station located farthermost from the estuary. This is particularly marked at two measurement stations, located at a distance of ca. 2km (ZN2) and 20km (P110) from the river of Vistula mouth. A strong statistically significant correlation of 90Sr activity with salinity for these stations was found: r = 0.580 (P = 0.0047, n = 24). An exceptional situation was observed in 2010 when, due to heavy precipitation in May, a flood occurred in the Vistula River catchment area, and, as a result, a number of flood crests discharged into the Gulf of Gda��sk [21�C23]. The fresh water outflow into the Baltic Sea during May and June 2010 amounted to 235% and 319%, respectively, of the long-term (1951�C2000) mean.

The correlation of 90Sr and salinity was then characterized by r = 0.639 (P = 0.0642, n = 10). However, the diluting effect of fresh water in the surface water layer of the Gulf of Gda��sk was not so obvious as in previous years because of the relatively high activity of strontium in riverine water, reaching 5.8Bqm?3 (Figure 5). The average activity of 90Sr in surface water at a station of the 20km distance from Anacetrapib the river mouth reached then 6.0 �� 1.6Bqm?3 and it was lower by 15% from the activity determined in near bottom water (7.6 �� 1.