About Total Alpha Activity of Underground Water Sources

Artesian wells remain strategically important sources of drinking water for the Kyiv megacity, especially in the vicinity of radioactively contaminated areas of the Chornobyl exclusion zone. The contribution of groundwater to the total volume of drinking water was indicated. The water from 144 artesian wells was investigated in terms of total alpha activity: 67 of them were drilled up to the Cenomanian aquifer of the Upper Cretaceous, 77 - up to the Bajocian aquifer of the Middle Jurassic. Studies have found that the total alpha activity in 39 wells exceeds the regulatory limit, with 37 of the 39 wells supplying water from the Bajocian aquifer. The average total alpha activity of the Cenomanian water is 0.033 ± 0.003 Bq/dm3, the most active water of this aquifer is produced in the Obolon area where the average value equals 0.045 ± 0.004 Bq/dm3. The average total alpha activity of the Bajocian water is 0.115 ± 0.012 Bq/dm3, the most active water of this aquifer is produced in the Obolon and Troyeshchyna areas where the average values equal 0.097 ± 0.010 Bq/dm3 and 0.188 ± 0.018 Bq/dm3, respectively. Therefore, in average, the Bajoian water is 3.5 times more active than the Cenomanian one: the average activity reaches 0.115 ± 0.012 Bq/dm3 against 0.033 ± 0.003 Bq/dm3. GIS mapping of the total content of α-emitters in the groundwater of both aquifers was created. The dynamics of the gross alpha activity of artesian water from both aquifers was monitored for the Obolon area. It was determined that when consuming the Bajocian water, two times more alpha-emitters enter the human body than from the Cenomanian water. The processing of the results through the spline interpolation with the Spatial Analyst Tools module ArcGIS 10.1 made it possible to analyze this trend for the megacity area: geological and tectonic factors such as block movement of the foundation, unequal incision of ancient watercourses into the pre-Bajocian surface and the erosion of sediments had always had the greatest influence on the enhanced alpha activity of the Bajocian water.