Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes ³²P, ³³P around Balaklava Coast

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)₃ obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)₃ with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)₃ with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin ³²P and ³³P were used. Volumetric activity profiles of ³²P and ³³P in particulate and dissolved forms were obtained. Based on ³²P and ³³P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters.